Related to J.A. Sinton, ‘A Report on the Provision & Distribution of Infective Material for the Practice of Malaria-Therapy in England and Wales,’ Ministry of Health Reports on Public Health and Medical Subjects 84 (London: Ministry of Health, 1938).
Description:

‘In the earlier work on malaria-therapy, the fever was induced by the injection of infected blood. It was recognised, however, that in certain cases there might be serious objections to the method of inducing malarial attacks by the direct inoculation of blood from patient to patient. This would be the case especially if the donor were suffering from general pareisis, under which conditions the risk of transmitting a syphilitic virus, possibly one with neurotropic characters, to a non-infected patient should never be taken.’ (4)

 

‘The laboratory portion of this unit was under the control of Colonel James, assisted by Mr. P.G. Shute and one laboratory assistant (later two) supplied by the Ministry of Health, while Dr. W.D. Nicol, a medical officer at the London County Council’s Mental Health Service was in charge of the clinical side of the work.

The origianal ward consisted of mosquito-proofed wards holding 12 beds, and two small rooms fitted up for laboratory work in connection with the examination of blood and with the infection of mosquitoes. Since that time there has been considerable expansion, necessitated by a steadily increasing demand for the treatment of cases. The special wards now provide for 23 patients (11 males and 12 females), and it is hoped to extend this accommodation in the near future. These wards are used only for the care of patients suffering from the acute stages of malaria, or who are infective to mosquitoes. Patients who have received treatment, who do not require special observation for malaria, and who are no longer infective to mosquitoes, are accommodated in other parts of the hospital. The laboratory unit now consists of five rooms for routine and research work, a special insectary for breeding mosquitoes, and a room (the temperature of which is thermostatically controlled) for the incubation and preservation of infected mosquitoes.’ (5)

 

‘The Ministry of Health’s Malaria Laboratory at Horton is the “official” source of supply of pure strains of malaria parasites for the purpose of malaria-therapy at mental hospitals, general hospitals, nursing homes, etc., in this country generally. Originally it was intended that the only “official” material supplied for this purpose should be infective mosquitoes, but requests for such treatment soon exceeded expectations. [note: ‘The number of hospitals in England and Wales which have been supplied frequently with infected material is 284 at present...’]

The experimental transmission of malaria by mosquito bites necessitates the carriage of teh infected insects and their application to the patient by a trained assistant. In practice this has not been found possible in all cases treated in institutions situated at long distances from the laboratory. [note: ‘In some of the large provincial hospitals... the infection is often transmitted by direct blood inoculation from patient to patient. Every few months, however, the series of blood inoculations is started afresh by means of mosquito inoculation supplied from Horton.’]. (5)

 

‘In all early work, reliance was placed entirely upon infections with benign tertian malaria (Plasmodium vivax). Such infections are relatively harmless provided that the physical state of the patient is fairly good before the inoculation is made, and careful watch is kept on his condition... By the timely administration of appropriate treatment and by careful nursing to keep the temperature within bounds, it is usually possible to hold the infection in check and damp down its severity. Where these precautions are not taken, the case mortality has sometimes been as high as 10-14 per cent. (Meagher, 1929). However, where specialist experience in the care and management of cases of malaria is assisted by organised arrangements for expert laboratory control and experienced trained nursing, the actual death rate directly attributable to benign tertian malaria is seldom more than about 3.4.per cent.

Under the special controlled laboratory and hospital conditions at Horton, it has been possible to investigate with safety the therapeutic possibilities not only of P. vivax, but also of P. falciparum, P. malariae, P. ovale and P. knowelsi. Infection with these other species of Plasmodium have not been found to be useful for routine distribution as has been that of P. vivax... Infections with P. falciparum are usually much more severe than those with P. vivax, and, if not very carefully watched and controlled, may be very dangerous and may quickly lead to fatal results (James, Nicol and Shute, 1932). [note: Infections with the Roumanian strain of P. falciparum, at present in use at Horton, are rapidly controlled by atebrin.’] In the case of P. ovale, the infections produced are usually less severe than those of P. vivax, and are therefore less suitable as a rule for obtaining beneficial results in general paresis. This species is also less easy to transmit by the technique of mosquito infection. While P. malariae may give good and prolonged bouts of fever, it has not been found possible to transmit the infection by mosquito bite... and the disease is liable to become chronic with [6-7] possible deleterious effects to the patient (anaemia, albuminaria). The results obtained by infections with P. knowelsi were too irregular and uncertain to make this parasite suitable for routine use in malaria therapy.

Infections with these other species of Plasmodium have, however, been found very useful in special circumstances. They are suitable for certain patients who have resisted infection with P. vivax... and also for patients who have... developed... some degree of tolerance to infection with P. vivax. P. malariae has proved especially useful under such conditions.’ (6-7)

 

‘Several different strains of P. vivax derived from countries as far apart as India, Roumania and Madagascar, have been tried at Horton in the practice of malaria-therapy. The one selected as the most satisfactory from all points of view is the so-called “Madagascar” strain at present in use. This strain was isolated originally in 1925 from the blood of a lascar working on a ship coming from Madagascar. [note: ‘It is uncertain whether the original infection was contracted in Madagascar or in some other country abroad, but for the sake of convenience it is known as the “Madagascar” strain.’]... [7-8]

This strain has proved itself... to be a reliable and certain therapeutic agent for malaria-therapy, [note: ‘the “Madagascar” strain of P. vivax has been given to workers in many other countries, and has been used in most of the malaria laboratories of Europe for the treatment of general paresis and for experimental purposes. The countries include Austria, France, Germany, Holland, Italy, Roumania and Spain.’] and one which is easy to transmit both by blood and mosquito inoculation. Since it was established, 132 batches of mosquitoes making a total of over 27,000 insects, have been infected with it at Horton.’ (7-8)

 

‘All requests for infective material are received at the Ministry of Health, whence they are passed on to the Malaria Laboratory at Horton, where appropriate steps are taken to fulfil the demand. For patients in the vicinity of London, infected mosquitoes are usually provided, unless the medical officer asks especially for blood. For patients further afield either blood or mosquito infections are used according to the special circumstances.’ (8)

 

‘From the mass of data which has accumulated in the office of the Ministry of Health and in the laboratory at Horton, much very valuable information has been obtained, not only with regard to malaria-therapy generally, but also with regard to malarial immunity and epidemiology, the action of anti-malarial drugs, and many other facts of the utmost importance to malariologists’ (9)

 

‘Since the last detailed descriptions of the methods used at the Horton Laboratory were published about 10 years ago (James and Shute, 1926; James, 1927a), many changes have been made as the result of experience...’ (11)

 

‘Anopheles maculipennis var. atroparvus, an indigenous species of mosquito which breeds freely in captivity, is the insect of choice for the work of malaria transmission in England. The specimens used for routine work belong to an English strain obtained from an area on the Thames Estuary...

In the early work all the insects had to be caught in nature. As the collecting area was about 60 miles distant from Horton, the mosquitoes available had to be used sparingly as was consistent with efficiency. To overcome this difficulty... attempts were made to breed A. maculipennis var. atroparvus on a large scale at Horton. In 1934 a special insectary was constructed and a colony of this mosquito was successfully established. [Note: ‘Details of the construction of this insectary and of the breeding technique have been given by Shute (1936).'] This was derived originally from a single female and has flourished so well that an ample supply of insects is available at all seasons of the year. If, during winter, extra numbers are needed for some special experiments, those available are supplemented with those caught in nature.

When mosquitoes are needed, the usual procedure is to collect 100-200 pupae from the breeding pens in the insectary. These are put into clean water in a glass vessel, which is placed in a breeding cage in the hot room. The insects which have emerged are collected from the cage as required.

It has been found that freshly-hatched females of the species do not feed so greedily as do older ones, and that their first blood meal is commonly a small one. For this reason, as a rule the laboratory-bred insects are not allowed to feed upon an [11-12] infective patient until they have already had one or more blood meals, usually on a rabbit. In our work such specimens were, therefore, about one week old, and possibly in a few instances two, at the time of the first infective feed.

Most of the mosquitoes collected in nature show the remains of a blood meal when captured. Those not required for immediate use are stored in cages in an outhouse, and are allowed to feed on a rabbit at appropriate intervals. When required for transmission work, the insects are placed in the hot room for 48 hours so that any previous blood meal is completely digested, after which they will usually feed readily, especially if they have been deprived of water for 24 hours.’ (11-12)

 

‘When a suitable case is found, a batch of about 100-200 mosquitoes are allowed to feed on it. The jars used for feeding purposes are all cylindrical, of thick glass with a heavily flanged mouth, and measure about 3 ½ inches (9 cms.) in diameter and height. The bottom of each jar is fitted with a disc of dry filter paper to absorb any of the moisture which is liable to accumulate during the process of feeding, especially if the patient has fever or is sweating at the time. Over the mouth of each jar is tied a piece of mosquito netting having an opening in the middle about the size of the diameter of a test-tube. The insects are captured in test-tubes and transferred through the opening into the jar. When about 30 have been inserted, the end is covered with another layer of netting which is tied in position.

[13-14]

The mouths of the netting-covered jars are applied to the outer surface of the patient’s thigh and pressed firmly against the skin. [note: ‘One assistant cannot deal with more than four jars at the same time in a satisfactory manner. If a greater number of jars is being used another assistant is required, and the remainder are applied to the external surface of the opposite thigh.’] If the patient’s skin be cold or the room temperature low, the insects may be stimulated to feed more readily if a hot-water bottle be applied to the skin for about 15 minutes before the insects are allowed to feed. When the insects have been starved for about a couple of days the majority will usually take a blood meal within about 20 minutes.

When most of the mosquitoes seem to have fed, the jars are removed. The insects are then released into a small gauze cage and those which have taken an obvious blood meal are separated from the rest. [note: ‘This is quickly determined by catching each insect separately in a test tube, and holding it close to a strong light, when the bright red blood of the newly ingested meal is easily detected.’] The former insects are released into a storage cage while the latter are either given another opportunity of feeding un the next day or are destroyed. [note: ‘No mosquito which has had an opportunity of making an infective feed is ever placed among the normal insects, because there is always a risk that it may have imbibed a minute, but undetected, blood meal sufficient to infect it. Such insects mixed with normal ones might transmit infection when the latter are being nourished upon a non-infected patient, or might produce a mixed infection as the result of a later feed upon a patient infected with another species of Plasmodium.’]

...[fed again to ensure high infection rates of mosquitoes, large number of infective agents]... [note: ‘James (1926, 1931b) has discussed in detail the factors that may influence the acquisition of transmissible malarial infection in a suitable anopheline host. By the improved laboratory technique which has now been gradually evolved at Horton, it is now possible to avoid most of those difficulties.’]’ (13-14)

 

‘The Conservation of Infected Mosquitoes.

After the insects have received an infecting feed, they are stored in gauze cages at temperatures ranging from 70˚ to 80˚F. (21˚-27˚C.) to allow of the development of the parasite in those that have acquired a plasmodial infection. For experimental purposes, temperatures outside this range have been tried, but for routine work the average now employed is about 75˚F. (24˚F). To ensure that conditions are favourable for the prolonged survival of the insects at these temperatures, a relative humidity of about 80 per cent. or over is maintained. [14-15]

In the earlier work the insects were conserved in ordinary bacteriological incubators kept at a suitable temperature and humnidity. In 1932 a special incubation room was constructed. This has greatly facilitated the routine work and produced much more satisfactory results – a much larger stock of infected insects can now be maintained and the duration of life among them is considerably larger.

The methods that have been employed in this laboratory may be divided, therefore, into two groups – (i) that in which the mosquitoes were stored in ordinary incubators, and (ii) that in which they were kept in the specially heated room. The survival rates are very different in these two groups, that in the former only being about half that in the latter (vide Sinton and Shute, 1938).

A description of these two methods is given below:-

(i) Incubator Group of Insects. – The incubator was heated electrically. The humidity was kept at a high level by inserting a bowl of water and by hanging wet cloths in it. No attempt was made to maintain a constant degree of humidity; the object aimed at was merely to keep it at a high level but below saturation point.

The insects were confined in cages with an end dimension of 8 inches by 8 inches, and a length of 11 inches. The top and bottom of each cage was of wood, while the slides were covered with mosquito-netting, and at one end was a cotton sleeve to allow of the insertion of the insects. A watchglass full of water was placed in each cage to provide facilities for egg-laying (James 1927a).

(ii) Heated-Room Group of Insects. – The room used has a floor area about 11 feet square and a height of about 8 feet. The north side [note: ‘This prevents the marked variations in temperature which may be caused by sunlight beating into the room during the summer months.’] of the room is occupied almost exclusively by a large glass window, which is made in two layers with an air-space between them to minimise the loss of heat.

The room is heated by four electrical heaters, one placed low down on each wall. [note: ‘It is important that a bright reflecting surface be placed above and behind each heater. These reflections should be inclined downwards and outwards so that the heat is thrown towards the middle of the room, otherwise the distribution of the heat may be very unequal.’] These heaters are controlled thermostatically so that the temperature can be regulated at the required level. For ordinary routine work this is between 75˚F and 80˚F. (24-26˚C)

The relative humidity of the room is maintained at about 75-80 per cent. by large pans of water placed on the floor. [15-16] When necessary the humidity is increased by means of damp cloths wetted by a flow of hot water from a tap at a sink in the corner of the room.

The insects are kept in large cubical cages (Figs. 1 and 2 [images of cages with 3 segments – one image includes rabbit in one of the segments. Caption: ‘Figs. 1 and 2 – Cage with mosquito gauze removed to show the animal compartment surrounded by wire netting (A). In fig. 1 the door (B) is closed, while in fig. 2 it is open to show the rabbit, with an area for feeding on its back denuded of hair, resting in the metal tray (D) which is partly withdrawn. The wire (C) on which a damp cloth is hung during the feeding period, is also shown.’]) each side of which measures about 18 inches (45 cms.). The sides and top are covered with mosquito-gauze. The bottom is made of wood, while a thin layer of wood is fixed over the top to protect the gauze, and is in contact with it. The gauze should be tightly stretched to prevent injury by the rabbit or other animal inserted for feeding purposes.

One section of the cage, equal to one-fourth the space, is shut off from the rest by wire netting of ½-1 inch mesh. This provides a compartment for housing a rabbit or other animal. It is closed with a wooden door, [note: ‘Where several species of Plasmodium are being used to infect insects at the same period, the woodwork of the cages is painted a distinctive colour for each species (red for P. vivax; blue for P. falciparum; green for P. ovale; black for P. malariae, and white for uninfected insects). No cage is ever used for any other type of infection except that appropriate to its colour. This ensures that there is no risk of the accidental transmission of a mixed infection because a mosquito has been overlooked in a cage considered to be empty, and so used for the storage of insects infected with another species of Plasmodium.’] and is provided with a metal tray having edges about 3 inches high (Fig. 2). The latter facilities the rapid introduction and withdrawal of the animal, and thus diminishes the risk of insects escaping at this time. At the same end of the cage near the door, a cotton sleeve attached to the mosquito-gauze, opens into the cage and is used for the introduction of mosquitoes. A small earthenware basin filled with water is also placed inside the cage to provide a place for oviposition by gravid insects.

Parallel with and about 1 inch outside the top bar on each side of the cage, is fixed a metal wire. A damp cloth is hung over each of these bars whenever a rabbit is placed in the cage. The increased humidity so produced appears to stimulate the feeding activities of the insects. The cloth should not be in contact with the netting as this would allow the mosquitoes to suck up moisture, an act which is undesirable as it makes the disinclined to take a blood meal for some time afterwards. Contact with the moist cloth also tends to cause premature rotting of the netting.

The cages are arranged on shelves around the sides of the hot chamber.’ (14-16)

 

‘Feeding of Infected Insects.

In the earlier experiments with the incubator, raisins, dates, bananas, etc., were provided for the insects to feed upon [16-17] in the intervals between meals. It was soon found, as noted by numerous other workers, that many of the mosquitoes so fed developed an infection with bacteria and moulds in their gut and tissues. This usually resulted in a heavy death rate. [note: ‘Although no comparative experiments have been made, we formed the impression that such accidents were more frequent among insects stored in incubators than among those kept in large rooms, i.e. where there was a free circulation of air. De Buck and Swellengrebel (1935) have reported very good results with insects fed entirely on sugar-water and stored in a warm room.’]

It was also found that insects which had been allowed to feed on such a diet showed less inclination to take a blood meal subsequently than did insects which had been fed on blood only (Darling, 1910; James and Shute, 1926). This is a distinct disadvantage in the practice of malaria-therapy by mosquito bites, although there was no evidence to show that such a diet had any effect in retarding or preventing the development of the plasmodial infection in insects so fed (James, 1931b). For these reasons, in all the later work blood meals were provided either from man or from rabbits. [note: ‘Mosquitoes usually bite rabbits almost entirely in the region of the nose, so that if many insects are placed with a rabbit, this area may be bitten so frequently that a cankerous sore soon develops. If the hair be removed from the back of a rabbit an admirable feeding place can be exposed (Fig. 2). This is best done by the use of a depilatory paste... The loose hair is cut away roughly with scissors from a large area on the back of the rabbit, and the paste is applied with a wooden spatula. After about 2 minutes the paste is removed and the area thoroughly washed with water and dried.’]

When A. maculipennis var. atroparvus is kept at a temperature of about 79˚F. (26˚C), a large blood meal is digested in about 48 hours, and, unless the insects are fed at least every second day, a high death rate occurs at this temperature.

In the case of mosquitoes kept in the incubator, this meant that they had to be collected into test-tubes, transferred to a feeding jar, and applied to a man or rabbit every time a blood meal was necessary. Many of the insects which only took a small meal, or showed no inclination to bite during the period of application of the feeding jar, were liable to die in the intervals between opportunities for feeding, unless these were given at least once daily. In many instances two daily applications were made, each lasting about one hour. Apart from deaths due to starvation, the very frequent handling of these insects, necessitated by the feeding technique, must have been a factor in diminishing their expectation of life.

The conditions were very different in the case of the insects kept in a warm room. If it were not considered necessary to [17-18] give the insects another infecting meal, a prepared rabbit was placed in the small compartment of their cage every evening, and left there over-night. As mentioned previously, a damp cloth was hung on either side of the cage to stimulate feeding while the rabbit was present in the cage. These insects were only handled when given their original infecting feeds, and not again until they were removed to transmit the infection. Their opportunities for feeding lasted about 16 hours daily as compared with the maximum of 2 hours in the case of the insects stored under incubator conditions.

Every few days one or more mosquitoes devoid of blood were removed and dissected to determine the presence, the rate of development and the intensity of any plasmodial infection acquired.

In the earlier work with the incubators, the mortality among the infected insects was so high that it was necessary to conserve as many of them as possible to meet the demands for such mosquitoes. For this reason when sporozoites had been detected in their salivary glands, the batch of infects insects was stored in a refrigerator at about 5˚C., and removed only when taken out to infect a patient, or for necessary blood meals at long intervals (vide Second General Report of the Malaria Commission, 1927). In this way a single batch of infected mosquitoes could be used for a long period, sometimes for 3 months (James and Shute, 1926).

Because of the survival rates of the infected insects have been nearly doubled since the introduction of the hot room for storage, the necessity of keeping batches of infected mosquitoes for long periods has almost disappeared. This result has been aided by improvements in technique, by the larger numbers of insects available from the insectary, and by the increase in the patients being treated at Horton, which has resulted in the presence of a greater number of suitable cases upon whom to infect insects. At present the mosquitoes are stored continuously in the hot room, and usually remain highly infective for at least one month. At the end of which time, the transmission of infection may become less certain, so a new and more recently infected batch is then employed. Infective insects are only stored in the refrigerator when a very large batch, say 500, have been infected at one time, or for experimental investigations.’ (16-18)

 

‘Transmission of Infection by Mosquitoes.

When a request is received for the transmission of malarial infection by mosquitoes, about 15-20 insects, starved for 48 hours and free from blood, are placed in a feeding jar and taken by a trained assistant to the hospital where the patient is. During transit the feeding jars are packed in a thick leather case, to prevent breakage and thus the escape of infective insects.

The mosquitoes are given an opportunity of biting by applying the gauze-covered end of the feeding jar to the external surface of the patient’s thigh (vide supra). If the patient is residing a distance of several hours’ journey from the laboratory, two batches of insects are often taken, and these are given an opportunity of feeding immediately on arrival, and again a few hours later. To be absolutely certain that the transmission will be effected, an attempt is made to get at least 10 mosquitoes to bite, but with the heavily infected insects commonly used, a much smaller number would be sufficient. [note: ‘On some occasions when the insects have shown little inclination to bite, the infected salivary glands have been dissected out, crushed, and suspended in Locke’s fluid, as described by James, Nicol and Shute (1927). The resultant suspension was then injected intravenously. This procedure is also very useful for experimental purposes, and makes it possible to inoculate a known number of sporozoites (Shute, 1937).’]

After biting, the insects are brought back again to the laboratory. Some of those showing evidence of a blood meal are dissected to confirm the presence of sporozoites in their salivary glands, and so show that infective material had been inoculated during biting. The remainder are replaced in the cage in the incubation room.’ (19)

 

Related to M. Hogg and K.M. Willis, 'Report on Visit to Approved Hospital' [Horton Hospital], 25th May 1938.
Description:

‘For Mental Nursing Committee

9^th June 1938.

Report on Visit to Approved Hospital.

HORTON HOSPITAL, EPSOM.

Purpose of Visit- Routine.

Date of Visit- First visit on 23^rd May 1938 by Miss Willis and Miss Hogg.

Number of Beds ... F.1636, M.542 = 2178 (Males to be increased shortly to 681)

Number of beds occupied on day of visit ... F.1564, M.530 = 2094

Average daily occupation for preceding year ... F.1636, M.545 = 2181.

We visited the above hospital on May 23^rd, 1938, and were received by the Medical Superintendent, Dr. Nichol [sic] and the Matron, Miss Lowman, S.R.N. (West London Hospital), who took us round the hospital.

Buildings- This hospital was built in 1902, and consists of two main administrative blocks, one for males and one for females, and 6 villas – two for admission, and one for G.P.I. , three for convalescent patients. There is an Operating Theatre, adequate, but a new Theatre Unit is to be built this year. This hospital supplies all the injections for Malaria Treatment throughout the country, and has a good Pathological Department. There are two Nurses’ Homes; each Nurse has a comfortable, well-furnished bedroom, the Sisters are allowed to have a patient for cleaning their rooms. The grounds are extensive, but not well kept. There is a very nice Chapel in the grounds.

Class of case- All types of acute and chronic nervous and mental disorders. The beds are graded, there are 24 Female Wards and 6 Male Wards containing 33 to 118 beds in each Ward. The Male patients are under the Matron’s administration, and the Female Nurses all work in the Male Wards with the Male Nurses with a Sister in Charge [sic]. All the Wards lacked finish, and there appeared to be very little Occupational Therapy to keep the patients happy. The Matron said the Male patients would not work in the grounds.

Nursing staff- Matron, 3 Assistant Matrons, all S.R.N., and R.M.P.A. certificate. 2 Night Sisters, R.M.P.A. certificate, R.M.N. by experience, 14 Sisters – 12 R.N.M. by experience and 4 by Examination. 104 Charge Nurses, 13 registered by experience and 5 by Examination. 56 Staff Nurses, all R.M.P.A. certificate. 112 Probationers, (48 Probationers short, 28 married women who have had training in Mental Work filling in the vacancies). Male Staff- 4 Head Male Nurses, 7 Chief Charge Nursees, 20 Charge Nurses, 61 Staff Nurses and Probationers. The Head Male Nurse is R.N.M., and R.M.P.A. certificate, the other trained Nurses- R.M.P.A. certificate. The Nursing Staff appeared to be of a poor type, the Probationers mostly of Elementary School Education. They were all neat and tidy.

There are 5 Resident Medical Officers and 3 non-resident.

Teaching Facilities:

Lectures given by- The Medical Superintendent and Resident Medical Officers, and the two Assistant Matrons, one taking the senior Probationer Classes, and the other the junior. Attendence at lectures is compulsory, and all Nurses have more than six months’ bedside nursing.

Class room accommodation- The Lecture Room is satisfactory with desks and blackboard, but the Charts old, and need renewing. The Practical Class Room a dark room with nothing in it but an old Sterilizer and a large round table. Some equipment kept in a cupboard outside the room.

Equipment-

Is the Equipment satisfactory? Fairly so.

Are the following provided?

Skeleton Yes

Disarticulation Bones Some

Models A brain

Charts and Diagrams Old expect [sic] for one of the Spinal Cord

Ward equipment Some

Reference Library No

Remarks- This hospital lacks finish throughout; the Superintendent said the type of Probationer entering for training was of poor education and unable to cope with the General Nursing Council Examinations.

Recommendation

That a properly equipped Practical Class Room be supplied according to the General Nursing Council’s requirements.

Signature – KATHLEEN M. WILLIS.

MARGARET HOGG.

Date – May 25^th, 1938.’

Related to P.G. Shute, ‘A Simple Method of Rearing and Maintaining Anopheles maculipennis Throughout the Year in the Laboratory,’ The Journal of Tropical Medicine and Hygiene 39 (20) (1936), pp. 233-235.
Description:

‘Most workers when trying to rear Anopheles maculipennis in the laboratory seem to have relied on artificial foods such as dried yeast, hay infusions, dried and crushed insects, piscidin, etc. Adults can be reared in this way, but the results are far from satisfactory. The larval mortality is always very high; the water must be changed almost daily, and the adults which eventually emerge are, as a rule, much smaller than normal for the species. Furthermore, it is my experience that adults reared on yeast and other artificial foods do not readily bite man and animals.’ (233)

 

'During mosquito survey work in England I have observed that when larvae of A. maculipennis are present in lakes and ponds it is along the grassy edges; they are never present in any part of a lake which is devoid of living vegetation. The method of rearing Anopheles maculipennis is based on this simple fact. Unglazed earthenware pans 18-20 in. in diameter are used. Narrow slices of grass sods are cut from a field or hedgerow and put round the inside rim of the pan. A medium sized tuft is placed in the centre and the pan three parts filled with water. Rain-water only is used; in Epsom the tap water is very chalky and quite unsuitable. The rain-water is filtered through muslin to prevent other insect larvae getting in, such as chiromus, culex, etc. No artificial food of any kind is added and usually no attention is required from the time the newly hatched larvae are added until the adults emerge.’ (233)

 

‘It sometimes happens that a scum forms on the surface of the water... Unless this scum is broken up at once most of the young larvae die... If only one or two breeding pans are in use a football is all that is required to aerate the water. A piece of glass tubing is fitted into the mouthpiece of the rubber bladder and a control clip is fixed on the rubber nozzle of the mouthpiece and the air is allowed to bubble out slowly...

While it is important to break up the scum of the breeding pan it is equally important not to continue to aerate the water once the scum has disappeared because the water will become too clear and the larvae will not have sufficient food.’ (233)

 

‘By the above technique a genetically pure strain of the variety atroparvus has been maintained in the insectory for over three years. It has enabled us to study their habits under laboratory conditions and has provided us with large numbers of insects for malaria therapy work during the season of the year when it is almost impossible to collect sufficient numbers in Nature.’ (234)

 

‘During the summer months it is very easy to maintain a large stock... To ensure a constant supply of eggs during the winter months we examine the adults and collect those which show ovary development. Those adults with mature ovaries are separated and each put into a small glass cylinder resting over a Petri dish containing a little water. It is our experience that adults with mature ovaries in large cages do not readily oviposit during

[image: ‘Fig. 2.- A wooden rack which holds eight glass cylinders, each containing one female adult with mature eggs.’]

the winter. By bringing them into very close contact with water they lay eggs readily.’ (234)

 

‘During the winter, although the temperature never falls below 75˚F., most of the females go into a state of semi-hibernation and those which continue to develop eggs do not lay them so readily as in the summer. The difficulty is overcome by isolating each gravid adult and confining it in a small space with a little water.’ (235)

 

‘The continuous breeding of this variety in the laboratory has enabled us to study its bionomics over a long period. We have been able to observe that there is quite a wide variation of the eggs, especially as regards colour... At the same time we have never seen a batch of eggs which would pass for messeae, typicus or labranchiae. This makes one realise how simple the problem of classification of the races of Anopheles maculipennis would be if only the other varieties could be induced to fertilize in the laboratory.’ (234)

 

‘Because egg-laying is prolific during the summer it may be necessary on occasion to skim off some of the eggs from the breeding pans to prevent overcrowding. This, of course, only applies when adults are flying about in the insectory, as is the case at our centre.’ (235)

 

Related to Principles and Methods of Antimalarial Measures in Europe: Second General Report of the Malaria Commission of the League of Nations (Geneva: LNHO, 1927).
Description:

‘We desire [in this report] to refer... to an entirely new field of enquiry which has lately become available in Europe and which, if scientifically tilled and harvested, promises to yield fruitful results. We refer, of course, to the field of enquiry opened up by the use of malaria as a method of treatment. The Commission is unanimously of opinion that, both in the immediate interest of the patients who undergo that treatment and in the ultimate interest of the millions of malaria sufferers in the world at large, it is essential that, in each country where the method is used, there should be central expert control and an officially organised arrangement by which a pure strain of a relatively innocuous organism cultivated in mosquitoes would be available for use. This means that a laboratory shall be established for the continuous provision of infected mosquitoes and that there shall be an official arrangement by which an expert member of the laboratory staff shall take the infected insects personally to the hospitals in which patients are to be treated, and shall have facilities for studying the course of the malarial attacks in those persons. We suggest that, wherever possible, the work in this laboratory should be carried out in close collaboration with the laboratory situated in the same district as the [a] malarious locality which has been selected for continuous routine observations of the natural course of the disease [recommended above] [10-11] among the general population. In this way, the factors concerned in the seasonal onset, course and decline of the natural disease (benign tertian, at least) among the population could be correlated with the more exact records of infection of anopheles month by month in the laboratory and the clinical manifestations of infected patients in the hospital. We can imagine no scheme of enquiry which would be likely to give more profitable results from the practical point of view, and no scheme which, in the present state of knowledge, would better justify the initial and recurring expense involved.’ (10-11)

 

‘Section II.

Arrangements for Studying Malaria

1. The Study of Artificial Infection of Mosquitoes and Man.

In the preceding Section, we stated the Commission’s opinion that the scientific study of malaria in all its aspects must be continuously pursued. To this end we recommended: (1) The establishment in each country of a laboratory for the provision of infected mosquitoes, which could be used, under expert supervision, for the malaria treatment of certain diseases; (2) the establishment in one or two malarious areas in each country an “observation station”, where certain routine epidemiological enquiries should be made at regular short intervals.

We hope that co-ordinated study along these two lines will be pursued continuously in every European country where necessary arrangements can be made. As a guide to those arrangements, we shall describe in this Section two or three of the laboratories and observational stations which members of the Commission visited during their European tours.

We shall begin by giving a brief account of the arrangements which have been made in England for the continuous provision of a supply of mosquitoes for inducing a pure infection in benign tertian malaria in patients to be treated. The work provides an opportunity of studying the clinical and parasitological features of malaria contracted in the natural way, as well as the circumstances governing the infection of mosquitoes and the factors which influence the persistence of the infective virus in those insects. The first results of a study on these lines were the subject of a special report to the Commission, which was published in 1926 as C.H./Malaria/57(1).

The hospital in which the arrangements are installed is in the Horton Mental Hospital at Epsom, near London. It is a hospital accommodating about 1,500 patients, and there are several other hospitals of the same size in the near neighbourhood. Therefore a considerable number of cases of general paralysis and other mental diseases which are to be treated with malaria are always available.

In the grounds of the hospital there is an isolated villa which has been allotted exclusively for the malarial treatment of patients. Fig. 4 is a photograph of this villa. [35-36]

[image of single-storey building – caption:

‘Figure 4. – Pavilion used for Malaria Treatment.

It contains two wards, each with seven beds, and several small rooms each with one or two beds. The total accommodation is for twenty patients. Fig. 5 is a photograph of one of the larger rooms.]

[image of three hospital beds in bright-looking room – caption:

‘Figure 5. - One of the Larger Wards’]

[36-37]

Each ward and small room is completely mosquito-proofed with double doors, as shown in Fig. 6, and with removable mosquito-proof window frames.

[image of covered, box-like structure around ward door – caption:

‘Figure 6. - Doors Protected against Mosquitoes’]

[37-38]

One of the medical officers of the hospital (Dr. Nicol), who is a psychiatrist, with considerable experience in the clinical and pathological study of malaria and in its treatments, devotes himself to the clinical care of the patients who pass through the course of treatment, and to a study of the disease in its clinical aspect and in its effect upon general paralysis and other mental conditions. He has under him a staff of nurses who have been specially trained in the nursing of malaria patients and the manner in which observations relating to the degree of fever and other clinical symptoms should be taken and recorded. Fig. 7 is a photograph of this staff.

[image – group of nurses (made and female) surrounding man in suit (Nicol?) – caption:

‘Figure 7. – Nurses Specially Trained in the Treatment of Malarial Patients.’]

[38-39]

Two small rooms in the building are equipped for the necessary laboratory work (Fig. 8), which is done by a senior laboratory assistant (Mr. P.G. Shute) who has been specially trained for the duty.

[image = corner of a room with shelves, miscellaneous equipment (inc. microscope, small mosquito ‘cages’), large box-like structure with sign above denoting ‘Infective Mosquitoes’ - caption:

‘Figure 8. – Laboratory.’]

The work is concerned only with benign tertian malaria parasite (P. vivax) and with A. maculipennis.

The strain of P. vivax, which has been in use since May 1925, was obtained from an otherwise healthy patient who contracted malaria in Madagascar. Before it was used for the infection of mosquitoes, it was proved to be an unmixed strain by direct blood inoculation into two patients. [39-40]

The mosquitoes (females of maculipennis) which are used are not bred from larvae but are collected in the adult stage from stables and other buildings in a country district where malaria does not occur. They are collected one by one in test-tubes, from which they are transferred to the mosquito cage shown in Fig. 9.

[image of box structure covered by material – caption:

‘Figure 9. – Mosquito Cage with Waterproof Cover’]

When about 300 have been caught, the waterproof cover shown in the photograph is drawn over the cage, which is then taken to the laboratory. After removing the waterproof cover, the cage is placed in the incubator at 23˚C. for 24 hours, in order that the blood in the stomachs of the mosquitoes may be digested quickly and that they may be ready to feed upon the infecting case.

The infecting case must be in the stage of the attack which is represented by the words “mosquitoes fed daily” in the following graphs: [40-41]

[images of malaria patient temperature graphs marked by times of mosquito feeding]

[41-42]

The two essential conditions are that the peripheral blood contains male and female gametes and that the gametes are ripe. The first is ascertained by finding these forms of the parasite in thin films of blood, the second by ascertaining that the male forms

[image of microscopic field with cells and dark patch – caption:

‘Figure 10. – Flagellated Male Parasite Partially Absorbed by a Polymorphonuclear Leucocyte.’]

[Image of male (Shute?) reaching into box covered by mesh – caption:

‘Figure 11. Capture of Mosquitoes in the Cage’]

[42-43]

“flagellate” readily (as in Fig. 10) in a “moist-chamber preparation” of freshly drawn blood.

[image of small jars covered with gauze mesh (mosquito cages) – caption:

‘Figure 12. – Glass Jars Used for Feeding Mosquitoes.’]

When the mosquitoes are to be fed on the infecting case, they are taken from the cage by catching them in a test-tube in the manner shown in Fig. 11. Then they are transferred from the test-tube to the glass jars shown in Fig. 12.

This is done in the following way: Tie a piece of paper over the open mouth of the jar. In this cover cut a half-circle valve of the same size as the mouth of a test-tube. Take the test tube that contains the mosquito and put its cotton-wool plug over the paper valve. Draw away the cotton-wool and at the same time push the mouth of the tube through the valve into the bottle. When the mosquito has flown into the bottle, draw out the tube and at the same time plug the valve with the cotton-wool. Transfer twenty mosquitoes in this way to each of four or five bottles. Then lay a piece of cotton mosquito-netting over the paper which closes the mouth of the bottle. Keep the mosquito-netting in place by laying the palm of the hand over it and carefully draw away the paper, thus leaving the netting as a cover to the mouth of the bottle. Tie the netting on tightly as in Fig. 12. [43-44]

The jars containing the mosquitoes are then placed on the leg of the patient in the manner shown in Fig. 13. A nurse keeps the mouths of the jars pressed closely against the skin during the period allowed for feeding, which is usually about twenty minutes. The mosquitoes bite readily through the netting which covers the mouths of the bottles.

[image of patient’s leg on bed with four mosquito jars resting on it – caption:

‘Figure 13. – Mosquitoes Biting Patient.’]

When the mosquitoes have fed, the jars are placed inside the mosquito cage and the mosquito-netting covers removed. The mosquitoes escape into the cage and the jars are taken out.

The cage is then placed in the incubator. The temperature at which the incubator is kept is 23˚C. By keeping a bowl of water in the incubator and by hanging wet cloths in it, the air is kept as nearly saturated with moisture as possible.

The procedure described is repeated daily, the mosquitoes being fed for at least five days on the infecting case. Afterwards they are fed every day or every other day on a patient who is awaiting treatment.

Some mosquitoes die every day. They are dissected to ascertain the progress of the malaria infection. When sporozoites are present in the salivary glands (which is usually between the tenth and fifteenth day after the first infective feed, but may be as long as the eighteenth or twentieth day) incubation at 23˚C. is discontinued, the group being kept instead either at room temperature or in an ice-box at 5˚ or [44-45] 6˚C. during the periods when the mosquitoes are not required for infecting patients.

In order to infect a patient, four or five mosquitoes are transferred from the cage to one of the glass jars and are allowed to bite the patient in the same manner as was described for the procedure of infecting the mosquitoes. Usually two or three of the mosquitoes bite within a few minutes.

If an infected batch of mosquitoes is kept in an ice-box during the intervals between successive feedings, some individuals will usually remain alive and infective for at least a month and occasionally much longer.’ (35-45)

Related to S.P. James, ‘Some General Results of a Study of Induced Malaria in England,’ Transactions of the Royal Society of Tropical Medicine and Hygiene 24 (5) (1931), pp. 477-525.
Description:

‘Benign Tertian Malaria.- For the purpose of obtaining supplies of mosquitoes infected with Plasmodium vivax, eighty-four batches of Anopheles maculipennis were fed on suitable cases and incubated until sporozoites were present in the salivary glands. The number represents approximately one batch per month during the period of the work... [478-479]

In addition, for various reasons, we have infected a considerable number of patients with P. vivax by direct blood inoculation instead of by mosquito bites.

Quartan Malaria.- In 1928 we obtained from Dr. Kirschbaum, of the Friedrichsberg Hospital, Hamburg, a strain of quartan malaria which we have used for the treatment of forty-five patients, all of them being infected by direct blood inoculation.

Malignant Tertian Malaria.- We have used a tropical strain of P. falciparum for the treatment of twenty patients, all being infected by direct blood inoculation, an Italian strain for the treatment of three patients, of whom two were infected by the bites of infected maculipennis fed upon crescent cases in hospital in Rome, the third by direct blood inoculation, and a Sardinian strain for the treatment of three patients, the infection of one of them being by the bites of maculipennis caught in nature in a house at Posada in that country, and brought by hand to England, and in the others by inoculation of blood from that case.’ (479)

 

‘As long ago as 1901 it was found that, even under what seemed to be the most favourable conditions, certain individual mosquitoes in a successful batch either failed altogether to become infected or became infected very lightly. In 1908, Darling again called attention to the point, and in 1921, Wenyon laid stress on it in recording the results of his feeding experiments in Macedonia. In our first laboratory report we were inclined to attribute the differences to technical circumstances. Yorke and Macfie, in their paper read at a meeting [486-488] of this Society in 1924, attributed the differences to a state of the patient's blood rather than to varying receptivity of different individual mosquitoes of the batch. From the results of many experiments in which we were careful to separate out for subsequent dissection, a number of mosquitoes which had all sucked (as nearly as could be ascertained) the same amount of blood, we are now of opinion that the variations are too great to be attributed to any other reason than that individuals of the same species of anopheles vary greatly in their receptivity to infection. The variations are as marked between individual mosquitoes which have been fed several times on a suitable case as they are in single feeding experiments... Possibly the reason for the wide differences may be that the lining of the stomach wall of some individuals in a batch of mosquitoes is not so permeable to vermicules as is the lining of others. It is suggestive in this connection that in heavily infected insects the zygotes are distributed almost equally over the whole stomach, while in lightly infected insects they are present towards the posterior end only, the infected and the uninfected parts of the wall being often sharply separated by a ring of zygotes. The distribution on some infected stomachs suggests that the lining (cuticula as Grassi called it) is very thin over only a small area of the internal layer of epithelial cells, or is actually ruptured or absent at that spot; for the distribution indicates that the vermicules had found and streamed through that single place of entry to distribute themselves in fan-like fashion or in a cluster among the epithelial cells. (See the plate facing this page). This peculiar distribution suggests a histological rather than a biochemical explanation. If the explanation were to lie in a histological character of this kind, it would give support to the observations of Huff and others, who claim that, by breeding out from particular individual female Culex pipiens which have failed to become infected when fed on the avian parasite, they have succeeded in obtaining a race of which all the members are refractory... But perhaps there is more in the latter aspect of the subject than meets the eye, for we were inclined to think that our own maculipennis of England had become developed into a race refractory to P. falciparum, until, by taking a batch to Italy, we found that 50 per cent. of individuals readily became infected when a "good infector" was available.’ (486-488)

 

'In view of the importance of "domiciliary infection" in the spread of indigenous malaria in England, we have made some experiments to ascertain the period required for maculipennis to become infective (sporozoites in the glands) when, after a single feed on a suitable case of benign tertian malaria, they are kept in the bedroom of a house during the months of July to September. For one of these experiments the readings of the dry and wet-bulb thermometer twice daily are recorded on the accompanying graph. For purposes of comparison similar batches of maculipennis fed on the same patient at the same [488-489] time were kept at a known constant temperature in an incubator. The periods required at bedroom temperature in different experiments were fifteen days in two experiments, and twenty-three days in a third. The time in which the control batches became infective in the incubator at a temperature which did not vary between 76° and 80°F. dry bulb and 74° and 78°F. wet bulb was nine days.’ (488-489)

 

'Theoretically the species of anopheles which suck the largest volume of blood at a meal should be those most often found to be infected and to carry the greatest numbers of zygotes. But in the field this is not the usual finding, and even in experimental work it seldom or never happens that in single feeding experiments the number of zygotes found can be correlated at all with the amount of blood ingested, or that the increased infections resulting from second [489-490] and third feeds bear any obvious relation to the amounts of blood taken in at those feeds. The subject is of interest in connection with endeavours to forecast the probability and amount of infection in mosquitoes fed upon carriers whose blood contains a known number of ripe gametocytes (or exflagellating male forms) per cubic millimetre. The late Dr. Darling worked systematically at this problem... He assumed that half the gametes would be females capable of developing into zygotes in the mosquito's tissues, and therefore that in the above example he ought to be able to find 544 zygotes in mosquitoes fed once, 1,088 in those fed twice, and 1,632 in those fed thrice. In actual experiments, however, the numbers of zygotes found never approached those figures, and from the fact that only fifty zygotes were found in a mosquito when 1,632 were predicted by the formula, he concluded that 97 per cent. of all the female gametes taken into the stomach of a malaria-carrying mosquito fail to develop into zygotes. If this were the general rule, it would indicate not only that anopheles are hardly more successful malaria-carriers than culicines, but that any differences of carrying-power between different species of anopheles would be so small as to be inappreciable.

... We have worked out the predicted number of zygotes in relation to the actual numbers found by dissection in a number of experiments, but... the numbers of zygotes found indifferent individuals of a batch of mosquitoes fed at the same time on a case vary so greatly that a figure representing the usual or average loss would be of little or no service for comparing the relative carrying-power of different species. This is one of the reasons why great caution is necessary in concluding, from the results of comparative feeding experiments, that a particular species of anopheles is a "better malaria carrier " than another.’ (489-490)

 

'Batch 2 was infective from 30th January to 9th February, sporozoites being found in the salivary glands of all mosquitoes dissected during that period. With the mosquitoes of the batch there were nine successes and three failures, two of the failures being with mosquitoes which, by dissection immediately after they had bitten the patients, were proved to [492-493] have sporozoites in their salivary glands at the time of biting. This finding is usually considered to be unequivocal evidence that sporozoites were injected by the mosquito when it bit the patient, and therefore as proving that failure, when it occurs, is due to the patient's insusceptibility to malaria. This was the decision made at first in the two cases mentioned, but we were obliged to reverse it a month later when both patients were successfully infected by mosquitoes of the next batch.

Batch 33 was also one in which, after 13th February, when the batch became infective, all the mosquitoes dissected were found to have sporozoites in their salivary glands. All cases bitten on the 14th and 15th February were successful. On the 16th the batch was taken to Torquay and from there on the 17th to Exeter and Exminster; thence, on the 20th, back to London. The results during this period and later were as follows:-

...[table of results (shows travel of mosquitoes from Torquay-Exter-Exminster-Horton-Harpenden-London)]...

In this group cases 158 to 162 are those about which it has to be decided whether sporozoites were injected or not. None of those patients could be considered "insusceptible" because all were successfully infected a short time after the first failure. It must be concluded that the mosquitoes were responsible for the failures, but the dissection results indicated that all of them had sporozoites in the salivary glands at the time of biting.’ (492-493)

 

‘we are obliged to admit that in our experience the test of finding sporozoites in the salivary glands of a mosquito after biting, is not good evidence that sporozoites were injected by that mosquito when it bit the patient. This observation, unfortunately, adds to the difficulties of experimental work on malaria. Taking it into account, it is obvious that great caution is necessary in coming to a decision that failure is due to the patient being "insusceptible " or "immune." It is preferable, in our opinion, to meet the difficulty of explaining failures such as are recorded in the above [493-494] examples by assuming that a requirement for successful infection is that sporozoites, in addition to being present in the cells of the salivary gland, must be lying free in the common salivary duct of the mosquito at the time of biting. On this assumption it is easy to account for a sequence of failures following asequence of successes, and vice versa, as well as for single failures which appear rather frequently in a scattered manner among the successes in our records.

We are fortified in making this assumption by recalling to mind the complex anatomical structures and interrelated mechanism by which a biting mosquito injects a drop of saliva into the wound before commencing to suck blood, and the difficulty, during die microscopic examination of a dissected salivary gland, of expressing sporozoites from the substance of gland cells into the common salivary duct and salivary cup, and of driving them thence with the saliva into the salivary channel along the hypopharynx. It is easy to imagine that, in the natural act of biting, the suction force of the pump-like mechanism of the salivary cup may not always be sufficient to draw sporozoites, as well as saliva, into the cup.

...

In an earlier paper I mentioned some "failures " among anaemic patients whose state of general health was very poor. This is perhaps a point worthy of study in tropical regions where ankylostomiasis is prevalent and severe. In those regions it may not always be correct to assume that all native children with few or no parasites have acquired an "immunity."’ (493-494)

 

'Patients who have passed through a long attack of benign tertian malaria ending in freedom from fever without being treated by quinine (so-called "spontaneous recovery ") still continue to have parasites in their blood. These are patients whom I have already mentioned as being those in whom the infection has been allowed "to smoulder." Parasites are sufficiently numerous to be found even in thin films for three or four weeks, but later their continued presence can only be ascertained when the patient is subject to some change of habit, such as being allowed to be up from bed and to walk about. At such times parasites can be found again, and often there is a recrudescence of fever. The blood picture and parasite findings in these patients are not different from what is found in many native children in hyperendemic areas.

... That the parasites are still present for many months is proved by the occurrence (usually between the eighth and tenth month after the date of primary infection) of a definite recurrence of fever and reappearance of parasites in the peripheral blood...

... after there has been a recurrence and "spontaneous recovery," endeavours to bring on a fresh attack by reinfection with the same parasite fail.’ (495)

 

‘The question is often asked whether these results assist to explain the immunity problem as it presents itself in untreated native communities in the tropics and, if so, in what manner. The question is not easy to answer, because, so far as I am aware, no one has yet studied immunity among native races except as a mass problem. It is known that among those races the parasite rate percent., the spleen rate per cent., and the average number of parasites per cubic millimetre of blood decrease with advancing age periods, but from these data we can only guess very roughly at what is actually happening to individual members of the community. The next step is not for those who are studying induced malaria in Europe, but for those who are studying hyperendemic malaria in the tropics. Instead of parasite and spleen rates per cent. of populations of different ages, what seems to be needed is an intensive study of individual infants and children in a localised hyperendemic area from the point of view of the kind of results just recorded. Such an enquiry should start with the newly born, and each individual should be under continuous observation until the usual age of naturally acquired immunity is reached.’ (497)

 

‘The graph on page 508 has been prepared to indicate the significance of some of our observations in explaining the peculiar seasonal incidence of benign tertian malaria in Northern Europe and some other countries. It is based on what actually happened in the cases of 107 patients who were under our observation at Horton continuously for more than six months, most of them much longer. For the purposes of the graph, the events have all been brought to the [508-509] same starting point by assuming that the date of primary infection in all cases was the 1st September.

It will be seen that the seasonal clinical incidence is about the same as that of natural benign tertian malaria in Northern Europe, and that the "Spring rise," about which so much has been written, is due to recurrences in persons who had their primary attack in September, together with primary attacks in persons whose infections in September remained latent through the winter... in natural circumstances the occurrence of these cases in the spring is not due to any special climatic or other environmental condition peculiar to that season, but results from the fact that April and May are between thirty and forty weeks after September, which was the month in which infection occurred. If the month of infection had been April instead of September, there would have been a "winter rise" in November and December.’ (508-509)

 

‘Under the heading prophylaxis I mentioned that the results of giving quinine in cases infected by direct blood inocuIation are quite the reverse of those obtained in cases infected by the bites of mosquitoes. For this reason, useful conclusions on treatment cannot be drawn from results obtained in blood inoculated cases. The explanation of the difference may be that by blood inoculation only the forms of the parasite which live in red blood corpuscles are introduced, whilst by the natural method of infection a form of the parasite is introduced which has always lived, not in red blood corpuscles, but in tissue cells. In the mosquito it has lived in the celIs of the stomach wall and of the salivary glands, and it has not been dependent on haemoglobin for nutriment. Evidently quinine has not the same action on a tissue parasite of that kind, as it has on the ordinary red cell forms. Clinically a striking difference between the two classes of case is that true (long interval) relapses, and recurrences are [515-516] not observed (so far as we can ascertain) in inoculated cases, while they occur in 50 per cent. of mosquito-infected cases...

The fact that blood-inoculated cases of malaria are cured permanently by a single short course of quinine has had the unfortunate result of making many believe that induced malaria, even when caused by the bites of mosquitoes, is not comparable with the naturally acquired disease as it occurs in the tropics.’ (515-516)

 

Related to S.P. James, W.D. Nicol and P.G. Shute, ‘Clinical and Parasitological Observations on Induced Malaria,’ Proceedings of the Royal Society of Medicine 29 (1936), pp. 879-894.
Description:

‘It is a matter of common knowledge, which was exemplified during the recent epidemic in Ceylon, that in every malarious country there is a striking clinical-difference between ordinary endemic malaria and the epidemic disease. Why is it that ordinary endemic malaria, whether it is due to the so-called benign species or to the so-called malignant species, is comparatively mild and rarely followed by a fatal issue while epidemic malaria is always serious and is directly responsible for many-deaths? The question is one that is seldom dealt with in textbooks and, when it-is, the severity and fatality are usually attributed to factors other than those relating to the malaria parasite itself and the mosquitoes which transmit it. They are usually attributed to economic stress, hardship, famine, exposure, and other circumstances which sometimes happen to coincide with the epidemic. Reasons of this kind were emphasized by most writers on war-malaria in Eastern Europe and they have been prominently brought to notice in accounts of the recent epidemic in Ceylon. Contrary to this view we think that our work at Horton indicates that a type of malaria closely resembling epidemic malaria can be produced in the absence of any of those adverse circumstances which for this reason must be regarded, in our opinion, as playing only a minor role. We think that the leading role is played by the parasites themselves in the human host and in the mosquito. But in saying that the parasites play the leading role we do not mean that the strains responsible for the endemic disease cause the severe cases met with in an epidemic by becoming more "virulent."... we have no evidence that the inherent virulence of a particular strain can be increased or diminished. The [879-881] change in the parasites which we have observed at Horton (and which we think maybe the change that is responsible for the severity of epidemic malaria) is not an increase of virulence but an increase of physical vigour and vitality, leading to the production of individuals which represent the species in its perfect form... the number of parasites which appear in persons infected with these healthy and vigorous parasites exceeds considerably the number which appear in persons infected with a less active strain. Susceptibility and other factors in the human host being equal, the number of parasites governs the severity of the case, and the result of using a strain which multiplies freely and vigorously is that non-immunes of normal susceptibility who are infected with it develop the severe "epidemic type" of the disease.

At Horton between 1925 and 1930 we succeeded in increasing the physical vigour and activity of an endemic strain of P. vivax from Madagascar to the degree in which it caused this severe "epidemic type" of the disease in 80% of our cases. We did so by using a particular procedure in passaging the strain through the human host and insect vector.’ (879-881)

 

‘Frequent blood examinations must be made to see that the parasites are not becoming too numerous and there must be careful nursing to keep the temperature within bounds. Where these precautions are not taken the case mortality directly due to the malarial attack may be as high as 10 to 14%.’ (881)