Showing papers in "Transactions of The Royal Society of Tropical Medicine and Hygiene in 1960"

Folic acid and vitamin B12. Effects of graded doses in the treatment of tropical nutritional megaloblastic anaemia.

Abstract: 1. 1) Patients with severe nutritional and pregnancy megaloblastic anaemia were treated with combinations of folic acid and vitamin B12 in doses ranging from an ineffective to a presumed fully effective level. 2. 2) The study was designed to determine the separate contributions of the two vitamins to the response to treatment of this anaemia and particularly to detect any interaction (potentiation) between the two vitamins. 3. 3) Folic acid was found to give significant variations in response, but vitamin B12 did not show any effect. No interaction was detected.

Studies on the epidemiology of malaria in New Guinea. Part I. Holoendemic malaria--the clinical picture.

Abstract: Summing up the above data we can say that there is as intense transmission in Maprik as can be found in holoendemic areas of Africa, such as the Sigi Valley ( Davidson and Draper , 1953) and that this results in a clinical picture differing from that in Africa only in the parasite ratio. We feel that Metselaar , (1956a, 1957), is correct in ascribing this to the absence of the sickle-cell gene from New Guinea indigenes, but disagree that the WHO (1951) classification of endemicity cannot be applied here. There is no doubt that transmission is much more intense in Maprik even than in the Nimboran Valley and the lower inoculation rate and higher adult spleen rates found there are accounted for by this. We have attempted to show that there is a grading in New Guinea of the intensity of malaria transmission so that a single survey conducted at random in any part of the country may show anything from the absence of malaria to true holoendemicity. In the next part of these studies we will give the entomological evidence for these statements, and in later parts will make a comparison with the situation in an area of unstable seasonal malaria, i.e. Minj. References in the text will be listed at the conclusion of Part III of this series.

Experimental transmission of Brugia Malayi and B. Pahangi to man

Abstract: 1. 1) An attempt was made to transmit back to man a strain of Brugia malayi originally obtained from man and transmitted through a macaque monkey and thence to a cat. Two volunteers were inoculated with infective larvae of this strain which had developed in Mansonia longipalpis. Neither of these volunteers subsequently developed microfilariae. 2. 2) An attempt was also made to transmit to man a strain of B. pahangi, a species hitherto only known as an infection of animals. Two volunteers were inoculated with infective larvae from Armigeres obturbans which had fed on a cat carrying a strain of B. pahangi originally obtained from a naturally infected civet cat. 3. 3) One of the volunteers inoculated with B. pahangi developed microfilariae 84 days later, and these persisted in small numbers for a further 56 days. The microfilariae resembled B. pahangi morphologically, and the identification was confirmed by mosquito-feeding experiments and by experimental transmission to a cat from which an adult male B. pahangi was later recovered. The other volunteer did not develop microfilariae. 4. 4) All four volunteers suffered from episodes of lymphangitis, lymphadenitis, and oedema in the inoculated limb, starting in each instance about one month after the inoculation. 5. 5) Although there was no true leucocytosis, all four volunteers developed a relative increase in eosinophils with maxima ranging from 18 to 32 per cent. occurring 12 to 13 weeks after the inoculation. 6. 6) All volunteers showed positive complement-fixation tests and skin tests (to Dirofilaria antigen) about 12 weeks after the inoculation. 7. 7) One volunteer from each pair developed subcutaneous nodules in the inoculated arm about 4 months afterwards. 8. 8) The significance of these findings is discussed. B. pahangi must now be regarded as potentially infective to man. The clinical episodes are considered to be reactions to the immature developing worms, whereas the eosinophilia is more probably a response to some product of the adult worms. Subcutaneous nodules do not seem to have been described previously in association with filarial infection.

Stages in the life-cycle of Leishmania donovani.

Abstract: 1. 1) A technique for observing the phenomena associated with the first stages of infection of cells by flagellates of Leishmania donovani is described. In our experience flagellates enter only monocytes and there is a mutual attraction. They enter body first, and once inside the cell move freely, flagellum first. Many flagellates may be killed, death being signalized by formation of a droplet at the tip of the flagellum and vacuole formation and digestion. There may be a relationship between susceptibility of animal species and the frequency of vacuole formation. 2. 2) Cinemicrographic technique was used to record infected spleen macrophages, exflagellating cell-free cultures and rosette formations of flagellates. It might be possible to use the exflagellation stage to study the components of flagellar movement.

Hookworms in the aetiology of tropical iron deficiency anaemia: Radio-isotope studies

Abstract: 1. 1) The relation between hookworm infestation and anaemia was investigated before and after multiple vermifuges by estimating intestinal blood and iron loss with 51 Cr. and 59 Fe. 2. 2) Maximum blood loss was 180 ml. and iron 33 mg. daily for a worm load of 834 A. duodenale and 249 N. americanus . A loss of 30 ml. daily for a load of only 166 worms was encountered. Augmentation of dietary iron absorption that is associated with increased marrow activity and depleted iron stores, is incapable of meeting these excessive losses. Such losses deplete the iron stores and lead to anaemia. There were great variations in the blood losses in different patients, and in the same patient on different days. 3. 3) The amount of iron lost depended on the haemoglobin level of the patient at the time the loss occurred. 4. 4) The blood loss was correlated with worm loads and species and was greater for A. duodenale . Both A. duodenale and N. americanus are found in Kenya, most patients having both. Loads up to 850 adult A. duodenale and 2,400 N. americanus were recorded by counting adult worms after multiple vermifuges. 5. 5) Removal of worms reduced the blood loss to nil, but did not improve the haemoglobin level unless iron therapy was also given. Iron therapy without removal of worms cured the anaemia, but the haemoglobin fell again once iron therapy was stopped, unless the worms were removed. 6. 6) Patients previously infected with hookworms and who had taken vermifuges, but no iron, presented with gross anaemia but no worms; others taking iron, but no vermifuge, had heavy worm loads but no anaemia. Other factors obscuring the relation between hookworms and anaemia are the migratory habits of the worms leaving few or many bleeding points, the situation of the worms whether over a large or small blood vessel, the rapidity with which bleeding points are sealed, etc. When these factors as well as worm loads and species are taken into consideration, there is always a close correlation between hookworms and anaemia. Failure to make allowances for them has led to the mistaken view that hookworms and anaemia are not related. 7. 7) Even multiple vermifuges will not produce egg-negative stools, but by reducing worm loads will cut blood loss to insignificant amounts. 8. 8) N. americanus was shown to be more resistant to all vermifuges than A. duodenale perhaps because of its small size and its location in the intestinal villi where vermifuges may not easily penetrate. 9. 9) There was little evidence that diet was associated directly with hookworm anaemia; an adequate diet will not diminish the chances of infection or reduce blood loss. Low economic status was, however, closely linked with insanitary habits and the less frequent use of footwear, both paramount factors affecting the risks of infection. 10. 10) The specific deficiency in hookworm anaemia is iron, and it will respond to oral iron provided this is given in sufficient amounts to raise the haemoglobin level to normal and replace the depleted iron stores. Inadequate iron therapy is the commonest cause of failure to respond, but untreated intercurrent infections will also prevent a full remission of the anaemia. Parenteral iron has no advantage over oral iron provided the latter is taken. 11. 11) Other sources of iron loss that may aggravate the iron deficiency anaemia are discussed. 12. 12) Vermifuge campaigns, fortification of diet with iron, the use of footwear and improvement in sanitation, are measures that should be adopted to reduce worm loads and the associated anaemia.

A preliminary account of the transmission, maintenance and laboratory vectors of Brugia pahangi.

Abstract: 1. 1) Brugia pahangi occurs naturally in the domestic cat and dog and in several species of forest animals in areas where B. malayi is endemic. 2. 2) Attempts were made to transmit B. pahangi by the direct inoculation of infective larvae to domestic cats, slow loris, macaque monkeys, civet cats, squirrels, tree-shrews and guinea-pigs. Cats, slow loris and civet cats were successfully infected, but no monkeys became infected. 3. 3) The prepatent period in cats varied from 59–83 days. Microfilaria counts rose to high levels and have been maintained for more than 2 1 2 years. 4. 4) The rate of development in the vertebrate host was followed. 5. 5) Feeding experiments with a wide range of mosquitoes showed that Armigeres obturbans is a very efficient host. Mansonia annulatus is also a good host but M. uniformis is less efficient and M. longipalpis is a comparatively poor laboratory host. M. (C.) crassipes, Anopheles barbirostris, A. umbrosus and small numbers of Aedes aegypti and Culex fatigans also supported development to the infective stage. 6. 6) M. longipalpis and M. annulatus were proved to be vectors in nature.

Observations on the amount of virus present in the haemolymph of Aedes aegypti infected with Uganda S, yellow fever and Semliki Forest viruses.

Abstract: 1. 1) An account is given of experiments to determine the amount and time of first appearance of virus in Aedes aegypti infected with three arthropod-borne viruses. 2. 2) In mosquitoes with infections of over one day duration, the virus in the haemolymph represented usually from 0.01 to 1.0 per cent. of the total in the insect. 3. 3) Virus appeared in the haemolymph about 10 minutes after the infective blood meal, disappeared after about 3 hours, and reappeared about 48 hours later. 4. 4) These observations and their bearing on our knowledge of the multiplication of viruses in insects are briefly discussed.

The toxicity and immunological properties of some sea-snake venoms with particular reference to that of Enhydrina schistosa

Abstract: 1. 1) Toxicity tests were made on a number of snake venoms but special attention has been paid to Enhydrina schistosa venom. 2. 2) The toxic fraction of E. schistosa venom is rapidly destroyed by heat and readily passes through a cellophane dialysis sac. 3. 3) The LD50 dose for a variety of laboratory mammals and one species of fish is 40 to 120 μg./kg. For the frog it is 20 μg./kg. 4. 4) Electrophoretic analysis at pH 6.8 showed that the toxic fraction of the venom was more electropositive than the other components. 5. 5) Various methods of producing an antivenom were attempted. Using Freund's incomplete adjuvant, an antiserum was prepared of which 1.0 ml. was required to neutralize 100 mouse LD50 of venom, using an in vitro testing method. 6. 6) Immunoelectrophoretic analysis suggested that the toxic fraction of the venom is less antigenic than the other protein components. 7. 7) By in vitro testing, E. schistosa antivenom afforded significant cross protection against Hydrophis cyanocinctus and Hydrophis spiralis venoms. Antivenoms to krait, cobra and a polyvalent antivenom to Indian cobra, krait, Echis and Russell's viper afforded negligible neutralization of E. schistosa venom.

Papio doguera (Dog Face Baboon), a Primate Reservoir Host of Schistosoma mansoni in East Africa.

Abstract: 1. 1) A prevalence of natural infection with Schistosoma mansoni of 23.9 per cent. was found in 134 Papio doguera (dog face baboons) classified as children or older. These findings were based upon the examination of tissue removed at autopsy from the liver and intestine. 2. 2) The demonstration of natural infection in baboons indicates that P. doguera is a reservoir host for S. mansoni in East Africa.

Malaria in the Pare area of Tanganyika. Part II. Effects of three years' spraying of huts with dieldrin.

Abstract: 1. 1) A sequel to an earlier paper describes the effects, during 3 years, on the vector mosquitoes and on the human malaria of the spraying of huts with the residual insecticide Dieldrin. 2. 2) Typical A. funestus completely disappeared and there were great reductions in the numbers of A. gambiae found alive in huts. The population of A. gambiae was also reduced, except in places where there were opportunities for extensive feeding on cattle. There were no changes in the host choices of A. gambiae. In many dissections for sporozoites the only infected mosquitoes found were from inadequately sprayed places. 3. 3) The action of Dieldrin was studied. Although it caused some irritation and its lethal action was slow, Dieldrin, in the dosages used, was found to cause a high mortality amongst A. gambiae coming into contact with sprayed surfaces, and this effect was very persistent. No change in susceptibility to Dieldrin occurred in A. gambiae, but this was found in other arthropods. 4. 4) There was a considerable fall in all human malaria indices, but evidence from several sources suggested that a low degree of malaria transmission continued throughout. 5. 5) Possible reasons for this are discussed, with the causes of persistent parasites in older children.

Studies on the transmission of Kyasanur Forest disease virus by Haemaphysalis spinigera newman

Abstract: 1. 1) Four batches of larvae of the tick Haemaphysalis spinigera were infected with Kyasanur Forest disease virus by feeding on four young White Leghorn chicks circulating the virus. Larvae from all batches ingested the virus. Nymphs emerging from the larvae and adults emerging from the fed nymphs were shown to be infected. 2. 2) The titre of the suspensions of unfed nymphs after storage at −50°C. varied from 5.0 to 6.8. Titre of the virus in adult tick suspensions after storage at −50°C. varied from to 6.0. Infection rates in adults from the four batches varied from 25 per cent. to 70 per cent., the average being 52 per cent. Forty-two per cent. of the males and 61 per cent. of the females were found to be infected. Virus was recovered from adults up to at least 176 days after the infecting feed as larvae. 3. 3) Virus isolated from the nymphs as well as the adults was shown to be identical with KFD virus. 4. 4) Nymphs from all four batches transmitted the infection to young White Leghorn chicks by bite. Of 33 chicks tested, definite evidence of transmission was obtained in 25 (76 per cent.). Partially fed nymphs were shown to be capable of transmitting the infection to clean chicks whilst feeding to repletion. Single nymphs transmitted the infection. 5. 5) A young buffalo calf, on which infected adults fed, circulated virus and developed neutralizing and low III antibodies, but not CF antibodies, to KFD virus. 6. 6) In a second chick-tick-chick cycle, clean H. spinigera larvae fed on a chick that had acquired the infection following the bite of an infected nymph. Nymphs emerging from the larvae transmitted the infection to clean chicks. The virus isolated from nymphs and adults of this batch was identified as KFD virus.

The isolation of viable schistosome eggs by a digestion technique

Abstract: A method is described of isolating viable eggs of Schistosoma mansoni from the liver and gut of infected hamsters by digesting away the unwanted tissue with trypsin and pepsin. The final washing by centrifugation is regulated so that most of the dead eggs are removed in the supernatant. Using this method, at least 100,000 eggs can be obtained from five hamsters. About one-third of the eggs are mature and show active flame cell movement; they hatch readily in fresh water and the miracidia have been successfully used to infect snails. Eggs prepared in this way are suitable for use in the circumoval precipitin test.

Skin histopathology in fatal jellyfish stinging

Abstract: 1. 1) The histopathology of the skin lesion is studied in two cases of fatal jellyfish stinging in north Queensland. Details of the circumstances, the clinical observations preceding death and subsequent postmortem reports are given. 2. 2) Sections of the skin appropriately stained and examined showed numerous nematocysts on the surface of the skin, the threads of which had penetrated through to the dermis. The stratum corneum appeared oedematous with its layers separated. The Malpighian layer was thinned and its cells degenerate, with pyknotic nuclei. There were no obvious changes in the deeper layers. 3. 3) The surface nematocysts were demonstrable by suitable illumination, or by silver impregnation as in reticulum techniques. They were identified as microbasic mastigophores. These were unusually large and with a distinctive elongate capsule. They matched accurately the principal nematocysts on the tentacles of the Cubomedusae (“sea-wasps” or “box-jellies”) Chironex fleckeri and Chiropsalmus quadrigatus. Further identification of the species of jellyfish on nematocyst structure has not as yet proved possible. 4. 4) The Portuguese man-of-war, Physalia, has no nematocysts which match those of the fatalities. It has no microbasic mastigophores, and its nematocysts (haplonemes) are spherical. The role of other medusae as possible agents for fatalities is discussed. As in Physalia there is no good evidence to support possible claims of other medusae as lethal species. 5. 5) The nature of the skin reaction in the weal is considered to be purely toxic; there is no histological evidence that the reaction is anaphylactic. 6. 6) The possible medico-legal significance of these results is discussed. It is considered that histopathological study and examination of the attached nematocysts in skin weals will be of medico-legal help in persons suspected of having died from a jellyfish sting.

Cultivation of the African sleeping sickness trypanosomes from the blood and cerebrospinal fluid of patients and suspects.

Abstract: 1. 1) The method described made it possible to cultivate T. gambiense and T. rhodesiense readily from patients. 2. 2) Cultures were established with equal ease from blood or from spinal fluid. 3. 3) The method proved to be sensitive, detecting blood and spinal fluid infections ignored by current diagnostic procedures. Thus, approximately 20 per cent. of “negative suspects” from an epidemic area were shown to be infected. Conventional methods were particularly poor for cerebrospinal fluid examination, detecting only 10 per cent. of those obtained by culture. 4. 4) The method is reliable. We have no evidence that trypanosomes failed to grow in pure culture. However, under African field and hospital conditions, many cultures were inconclusive because of contamination. 5. 5) An independent means for estimating the accuracy of conventional diagnostic methods is now provided. It is clear that these conventional methods are often in error, and that the error is always in one direction: that of underestimation. Accordingly, certain earlier investigations require re-evaluation, since failure to detect trypanosomes signifies not that the micro-organisms were absent, as was supposed, but only that the limit of sensitivity of the method had been reached. 6. 6) The culture method should prove to be a useful tool for the investigation of a number of problems which have hitherto resisted analysis.

Experimental infection of mice with Madurella mycetomi

Abstract: 1. 1) Following Borelli's (1957) observations, the production of granulomata and typical grains by Madurella mycetomi in peritoneal structures of the white mouse has been studied. 2. 2) Most regular grain production follows intraperitoneal injection of a mixture of 4 mg. or more of M. mycetoma , strain L20, and 4 mg. or more of killed Mycobacterium tuberculosis . 3. 3) Grains are also produced, but less regularly, by multiple intraperitoneal injections of the fungus alone.

The Biology of a Newly Isolated Strain of Plasmodium berghei in a Rodent Host and in Experimental Mosquito Vectors.

Abstract: 1. 1) A strain of Plasmodium berghei , Kasapa S.P. 7307, recently isolated from the Belgian Congo, has been cyclically transmitted through Anopheles quadrimaculatus, Anopheles aztecus , and young white rats three successive times. Sporozoites from crushed oocysts of heavily infected mosquitoes were used as inoculum. 2. 2) The newly isolated “passage” strains were designated as N.Y.U. 1 , N.Y.U. 2 , and N.Y.U. 3 Strains of P. berghei (New York University Strains). 3. 3) The pre-patent period in four sporozoite infected young rats were: 71 hours, 96 hours, 8 days, and 10 days. 4. 4) Parasites found in the peripheral blood at the early “flooding” period of 71 hours after sporozoite inoculation are described in detail. 5. 5) A description is given of the different developmental stages of the sporozonic cycle as observed in the newly isolated strains, under experimental conditions.

Studies on the epidemiology of sleeping sickness in East Africa. III. The endemic area of Lakes Edward and George in Uganda

Abstract: 1. 1) The endemic of Trypanosoma gambiense sleeping sickness in Busongora, in south western Uganda, started at the beginning of the century as an eastward extension of a long standing endemo-epidemic on the Semliki River in the Belgian Congo, which was brought to a fierce epidemic outbreak between 1915–1923 through Belgian administrative measures, and finally controlled by the evacuation of the whole valley in 1924–1925. The reasons for this outbreak, carried by Glossina palpalis, are described. 2. 2) In 1910 a severe but local epidemic was decimating the fishing and salt trading communities of Lakes Edward and George and the Kazinga channel, so the evacuation of the surrounding populations into the southern Ruwenzori foothills was undertaken in 1913–1914. 3. 3) The important salt trading centre of Katwe, on Lake Edward, was preserved and protected by clearings and regular inspections for sleeping sickness. 4. 4) Infection remained at a very low but persistent endemic level until 1932, when a sharp epidemic developed among the resettled population in Busongora, on the Ruwenzori slopes 12 miles north of Lake Edward. The outbreak was reduced, by clearing G. palpalis-infested rivers and by the treatment of cases, to a very low level within 3 years, but in 1942 a second epidemic occurred and spread rather more widely than the first. Again control was established by clearing and treatment so that the status of the disease here since 1949 has been that of a low endemic with two to four cases a year, and no cases since 1955. 5. 5) The endemics in Busongora were restricted to a very small area, 12 miles long by 3–4 miles wide, in which a concentration of the population and the distribution of G. palpalis on many small streams brought about such close man-fly contact as to present ideal conditions for the transmission and spread of trypanosomiasis. The 1942 epidemic started from an even more restricted endemic focus on one stream, the Bukangara, and ended up in the same small focus within which the few cases from 1953–1955 all occurred. 6. 6) Periods of very low endemicity, sometimes with no cases recorded just before the epidemic outbreaks, can be explained by the mildness of the disease and tendency to relapse to an infective state providing unsuspected sources of infection for the tsetse at these times, and by inaccuracies in the recording and detection of cases leading to underestimation of the true incidence. 7. 7) Nevertheless the present is certainly a period of very low incidence, with infections up to 1955 concentrated in one small focus on the Bukangara River. Experimental spraying on that river in 1955 effected complete though temporary disappearance of G. palpalis, and no cases have occurred in 1956 and 1957. If a careful watch on this area for a year or two more, establishes that trypanosomiasis has indeed disappeared, this incident will provide a most valuable example of the eradication of sleeping sickness during its narrowly focal endemic state with a minimum of effort.

Studies on the epidemiology of malaria in New Guinea Part IV. Unstable highland malaria—The clinical picture

Abstract: 1. 1) Malaria in the highlands is highly unstable and severe seasonal epidemics are usual following the main rainy season. During such epidemics up to 25 per cent. of the community may be infected with plasmodia and 5 per cent. may be infective to mosquitoes. Even higher rates occur in some highland localities at about 5,000 feet when over 70 per cent. of the community may be infected, and 1 to 2 per cent. die. In the dry season parasite rates fall to about 5 per cent., and gametocyte rates to about 1 per cent. 2. 2) P. vivax is about three to four times as common as P. falciparum and P. malariae , but the actual proportions vary with the seasons. P. falciparum and P. malariae become relatively more common during epidemics. 3. 3) A low degree of premunity is present in at least the older age-groups particularly to P. vivax . It is possible that infants under 4 months of age are relatively tolerant to P. falciparum parasitaemia. This may be related to the presence of foetal haemoglobin at this age. 4. 4) The presence of Anophelism sans malaria in some highland localities requires detailed study, as the basis of such situations is still obscure.

Observations with the Ultropak microscope on microfilariae of Litomosoides carinii circulating in the liver of a cotton-rat, before and after the administration of hetrazan

Abstract: Microfilariae of L. carinii were observed circulating in the peripheral capillaries of the liver of an infected cotton-rat by means of the Leitz Ultropak microscope. The mf. could be clearly seen as white snake-like organisms, offering little resistance to the blood flow. After intravenous administration of Hetrazan, the majority of mf. adhered, generally by their tails, to the capillary walls and sometimes a leucocyte was also found attached to the tail.

The mechanism of malarial hepatomegaly and its relationship to hepatic fibrosis.

Abstract: 1. 1) In malarial hepatomegaly, sinusoidal dilatation is the most important factor contributing to the enlargement of the organ. 2. 2) Reticulo-endothelial hyperplasia and hypertrophy provide a minor contribution only. 3. 3) Chronic malaria provokes a slight degree of periportal fibrosis which, in the absence of liver cell damage, does not penetrate further into the substance of the lobule.

II. Ecological aspects of the evolution of mosquito-borne virus diseases

Abstract: 1. 1) The evidence suggests that the mosquito-borne viruses assumed their present form in their arthropod vectors. 2. 2) This process may be presumed to have accompanied and been related to the evolution of methods of utilizing the blood meal for the maturation of the eggs. 3. 3) It is a reasonable assumption that the mosquitoes originally evolved during the latter part of the Mesozoic in relation to the evolution of their vertebrate hosts and of the angiospermous plants. 4. 4) The general pattern of host-parasite relationships in the mosquito-borne diseases suggests that the virus diseases originated in relation to avian hosts and mosquitoes of the genus Culex s. str. 5. 5) The picture of primate evolution during the early Tertiary presented by the fossil record suggests an origin during the Eocene in Europe and North America. This was followed by expansion into the Old and New World tropics and isolation there consequent on progressive climatic deterioration. The same may be true of the birds, but these have not been studied in the present connection. 6. 6) The hypothesis, based on pathological and serological evidence, that West Nile is the most primitive of the Group B viruses is consistent with paras. 4 and 5, and with current ideas regarding the zoogeography of the mosquitoes. 7. 7) The mosquito-borne viruses appear to have achieved the passage from eastern Asia into North America, but they are replaced in the central Eurasian steppes by closely related acarine-borne viruses. This is probably associated with the fact that the dominant steppe mosquitoes belong to the genus Aedes and hibernate in the egg. Similar considerations probably account for the exclusion of Aedes -borne viruses from subtropical areas where the only vectors are Culex spp. hibernating and aestivating as adults. 8. 8) The foregoing consideration strongly suggests that the basic ecological factors affecting the evolution of the Group B viruses have been those relating to hibernation and aestivation. It also suggests that, whatever local alternatives may exist, the mosquito vector has provided the only site of hibernation and aestivation of the virus of sufficient importance to have affected the broad evolutionary picture in the subtropics. In the tropics adaptation to particular vertebrate hosts may have been of prime importance. 9. 9) The ecology of West Nile virus is insufficiently understood. It may involve arboreal vectors. St. Louis, Japanese B and Murray Valley, appear to be swamp viruses. The evolution of other Group B viruses may be pictured as having accompanied the exploitation of new habitats, swamp forest (Ntaya, Ilheus), veldt with temporary pools (Wesselsbron) and the forest canopy (yellow fever, ? Zika). 10. 10) This has been accompanied by the transfer to aedine vectors in the tropics and acarine vectors in the steppes. 11. 11) Dengue-1 and -2 may have become independent of all but their secondary vectors. Bat salivary gland virus may have achieved independence of arthropod vectors altogether. 12. 12) The picture presented here is based on the current assumption that West Nile is the most primitive of the Group B viruses. If evidence were to be produced to the effect that the Russian SS group are more primitive this would lead to a reorientation of our approach and many interesting questions would become pertinent. The point is an important one, but it is one for the virologists.

Part II. holoendemic malaria—the entomological picture

Abstract: The main vector of the Maprik area is A. punctulatus which maintains a high population density throughout most of the year. The natural daily survival rates of this and the related A. farauti and A. koliensis are higher than formerly estimated, and this in turn permits the development of high sporozoite rates. All members of the A. punctulatus group spend at least part of the night indoors, and the actual length of time may depend on their respective peak biting times. In Part III of this series the data accumulated so far will be analysed and interpreted in relation to the possibilities of malaria control. References will be given at the conclusion of Part III.

Clinical trials with entamide furoate and related compounds. I. In a non-tropical environment.

Abstract: 1. 1) In a non-tropical environment where reinfection can be discounted, three derivatives of dichloroacet-4-hydroxy-N-methylanilide (Entamide), the benzoate, piperazine sulphate and the furoate have been tried in human infections with Entamoeba histolytica . 2. 2) Entamide benzoate, 40 mg./kg. body weight daily for 10 days resulted in disappearance of parasites from the stools in an average of 3.6 days, and of 15 patients passing cysts who were followed-up after treatment there were two relapses. 3. 3) Entamide piperazine sulphate, 30 mg./kg. body weight daily for 10 days resulted in disapperance of parasites from the stools in an average of 4 days, and of 14 chronically infected, treated and followed-up, one relapsed. Two patients having acute amoebie dysentery were treated of whom one relapsed. 4. 4) Entamide furoate, 20 mg./kg. body weight daily for 10 days resulted in disappearance of parasites from the stools in an average of 3.4 days, and of 30 in whose faeces cysts were present and who were followed-up after treatment one relapsed. Three patients with acute amoebic dysentery were treated of whom two followed-up did not relapse.

Clinical trials with entamide furoate, entamide piperazine sulphate and emetine bismuth iodide: II. In a tropical environment

Abstract: 1. 1) In a field trial in Nigeria, Entamide furoate, Entamide piperazine sulphate and emetine bismuth iodide were used in the treatment of patients having intestinal amoebiasis. 2. 2) The failure rate as assessed by the number of patients found to have the infection as revealed by an average of 2.4 examinations at 2-monthly intervals after a full course of each drug was 10 per cent. in 71 patients treated with Entamide furoate, and 25.3 per cent. in 55 patients treated with emetine bismuth iodide. 3. 3) Entamide furoate appears to be an effective amoebicidal drug in the case of cyst-passers, and can be used for out-patients; but it is less effective in the treatment of acute amoebic dysentery. 4. 4) A survey of the incidence of various intestinal parasites in Nigerians shows that E. nana, T. trichiura, A. lumbricoides , hookworms, E. coli and E. histolytica are all common.

Relative increase in the prevalence of Plasmodium falciparum some years after the beginning of a house-spraying campaign in Netherlands New Guinea.

Abstract: 1. 1) Following residual spraying in Netherlands New Guinea, it was observed that in areas where transmission could be stopped, P. falciparum was reduced most rapidly in the human-host reservoir, followed by P. vivax and P. malariae. This is in accordance with theory. 2. 2) In areas where the degree of transmission was only diminished, P. falciparum, after an initial fall, came to the fore again, and this species was responsible for a high proportion of the malaria cases which came for treatment. 3. 3) The explanation probably lies in the increased production of gametocytes which was most marked in P. falciparum infections, and may be due to the rapid loss of immunity of the human host to this species, as soon as the number of infections is diminished.