For the purpose of testing culicifuges numbers of Stegomyia fasciata (the Yellow Fever mosquito), bred in incubators, were placed in cages kept in the laboratory. The efficiency of the preparations was tested by coating the forearm with a definite quantity of one or other of them and exposing in a cage, each test being controlled by inserting after a short interval the other and untreated arm in the same cage, the number of bites being compared in each case. By this procedure it was hoped to obtain a measure of the relative protection which the culicifuges might be expected to afford when used under practical conditions against Anopheles mosquitoes.

In the first series of trials conducted within 15 minutes of application, eight preparations out of a total of 22 tested gave satisfactory results. Their active ingredients were (1) Oil of Cassia and Camphor, (2 a) Oil of Cassia and Peppermint, (5) Oil of Eucalyptus and Citronella with Phenol, (9 a) Crude Naphthalene (coke oven) and Camphor, (10) Crude “Parasitox,” (15 a) Light Wood Oil, (21) Oil of Turpentine, (22 a) “Lawson's Anti-mosquito Compound.” These preparations were then tested to ascertain for what period their protection could be depended upon. Preliminary trials indicated that this period was not likely to extend for more than two hours between treatment of the arm and exposure in the cage. None of the preparations gave complete protection in this series of trials; the most efficient were Nos. 1, 21. 2 a, 15 a and 9 a, over a two hours period.

It appeared, however, that the two experimenters were unequally attractive to the mosquito. Making allowance for this, preparations 2 a. 1, 15 a, and 21 were almost on a parity, followed by 9 a, 10 and 5 in order. A series of experimental trials based on this element of preference on the part of the mosquito was confirmatory of the factor of preference and showed a ratio of attraction of about the order of G. T. 3, A. B. 2.

Observations on the behaviour of the mosquitoes during the tests suggest that the protection afforded does not result from a dislike of the insects to the culicifuge but to its obscuring the attractiveness of the human odour.

Regarding the make up of the essential ingredients it was found that fluid preparations were inconvenient and tended to be wasteful in application. Soap preparations, unless very soft, are apt to be difficult of economic use and in either case are more readily dissipated by perspiration than waxy or greasy ones. Culicifuges prepared with grease are more easily applied but are not so lasting as those put up with wax. Soft wax preparations, correctly adjusted to the temperature in which it is proposed to use them, are most suitable for out of doors use, especially in the case of troops. The retarding of volatilisation caused by the admixture of the active ingredients with wax or grease is a distinct advantage, but care must be exercised in respect of the relative proportion of active substance to the base. The golden rule is to use as much of the active constituent and as small a quantity of the inert base as is consistent with convenient application and the prolonging of the period of efficiency, not, as most proprietary compounders appear to think, as little as possible.

In choosing a culicifuge for use. the human factor of choice in regard to pleasing and unpleasing odours should be as little disregarded as consistent with efficiency. Where large quantities are needed cost is an important consideration, but must not be allowed to endanger the willing co-operation of the individuals it is desired to protect.

1. Mehlis's gland secretion in trematodes and pseudophyllidean cestodes may be a lecithin-like phospholipid.

2. After enzymic degradation of the lecithin into lysolecithin the release of egg-shell precursors from the vitelline cells is effected.

3. Soon after the completion of the egg-shell the lysolecithin may be reconverted into lecithin in vitelline cells of Penetrocephalus ganapatii, thus accounting for the periodic acid-Schiff positive reaction.

1. Anagrus atomus (L.) Hal. is a mymarid parasite of the eggs of Erythro-neura pallidifrons Edwards.

2. The parasite is parthenogenetic, at any rate for the greater part of the year.

3. Two larval stages are described.

4. More than one egg may be laid in a single host egg and these eggs may hatch, but only one of the Anagrus larvae reaches maturity.

5. The development of Anagrus atomus takes about sixteen days.

6. The species is multi-voltine.

Observations have been made on the ultrastructure of objects identified as ovarian balls from female Moniliformis after 1, 3, 5, 7 and 9 days in the rat. Similar objects are present in the body cavity of female cystacanths from cockroaches. The ovarian balls from 1-day-old worms are formed of several cells which are enclosed within a surface coat. During development, the ovarian balls increase in size and cell number and the internal organization appears to become more complex. After 9 days of development in the rat, the surface coat of the ovarian balls can no longer be observed and microvilli are present. It also appears that the supporting syncytium has been formed by this time.

By employing a combination of sub-stage heating and supra-vital staining with eosin or neutral red it was found that viable and non-viable hydatid scolices could be distinguished microscopically. Using this technique a study of the effect of heat in vitro on hydatid scolices has shown that death resulted from exposures at 50° C. for 70 min. and at 55° C. for 30 min.

Experiments on the effect of boiling in destroying the contents of fertile cysts embedded in sheep liver showed that when offal was added directly to boiling water destruction of scolices was complete after 40 min. boiling. When the infected liver was placed in cold water brought to the boil, scolex death was assured only after 30 min. subsequent boiling.

Ultra-violet radiations of 2537 A. did not kill scolices under the conditions adopted. Although this wave-length would apparently be ineffective as a scolicicidal agent in surgery of the human hydatid cyst, irradiation of hydatid fluid containing scolices might offer a simple method for initial sterilization of scolex culture media.

The author wishes to acknowledge many helpful suggestions and loan of the Hanovia lamp by Dr G. M. Richardson of the Virus and Immunology Research Department, Otago Medical School.

Recent studies on parasite communities have considered the factors which contribute to variability in parasite infections among populations of one host species. This paper examined parasite assemblages of crucian carp (Carassius carassius) in a natural set-up of two distinctive environments inhabited by the same host species and differing in respect to composition of other fish species: ponds, where extreme conditions prevent other fish species from occurring and lakes, where crucian carp coexist with other fish species. Our aim was to evaluate the significance of parasite exchange, environmental conditions and host suitability for the depauperate parasite assemblages observed in pond crucian carp. As predicted, crucian carp had more diverse parasite species composition in lakes, which supports the hypotheses of increased opportunities for parasite exchange with other fish species and better environmental conditions for the parasites. However, for instance, diplostomids were found only from few fish individuals in very low numbers. Experimental exposure trials with the eye fluke Diplostomum spathaceum in the laboratory indicated that crucian carp were totally resistant to infection, which is exceptional and suggests that the low number of these parasites in crucian carp was due to physiological unsuitability of the host. To obtain a better understanding on the mechanisms underlying the formation of parasite assemblages in these fish, further studies on the relationships between the unique physiology of crucian carp and infection success by other parasite species are needed.

During autumn and winter, separate pasture plots were seeded with Ostertagia ostertagi eggs produced by worms which had persisted in the host over summer as inhibited larvae, or which had developed directly from larvae acquired from pasture in late summer. Successive groups of parasite-free calves grazed the plots in spring for 14 days at 4-week intervals and were killed for worm counts 14 days after removal from pasture. The proportion of inhibited early 4th-stage larvae was substantially greater in calves which grazed the plot carrying the progeny of previously inhibited worms. This finding is more easily reconciled with differential survival on pasture over spring and summer of inhibiting and non-inhibiting morphs, than with the concept of a physiological switch from inhibiting to non-inhibiting behaviour in individual larvae.

An attenuated line of Leishmania major (L. major H-line) has been established by culturing promastigotes in vitro under gentamicin pressure. A modification of the previously described method for the generation of attenuated L. major is described, giving rise to attenuated parasites after 8 rather than 12 subpassages. No lesions developed in BALB/c mice infected with L. major H-line, whereas L. major wild-type (WT) induced a Th2 like response with progressive lesions. Analysis of splenocyte IFN-γ and IL-4 production following stimulation with promastigotes shows that the L. major H-line preferentially induces Th1-like responses and possibly down-regulates Th2 responses in BALB/c mice. L. major H-line parasites remained localized in the skin and draining lymph node, whereas L. major WT parasites disseminated into the visceral organs of BALB/c mice. Mice infected with L. major H-line acquired some resistance against L. major WT. These results show that the attenuated cell line of L. major is not only avirulent but that it may also modulate the host immune response.

The in vitro development of the pentastomid Porocephalus crotali from the infective, seventh (VII) instar, dissected from the tissues of rat intermediate hosts, to the adult male (X) and female (XI) instars, normally resident in the lung of rattlesnake definitive hosts, is described. The culture medium comprised washed human blood cells, resuspended in bovine serum (50[ratio ]50, v/v), with 20% minimum essential medium and antibiotics. Two batches of approximately 100 pentastomids, maintained at a density of 2 worms/ml, were cultured in 500 ml bottles in an atmosphere of 5% CO2 in air at 28°C. Culture bottles were rotated slowly on a Rollacell system and the medium was replenished every 2–3 days. Growth was monitored at various intervals by weighing worms, measuring cast cuticles with attached moulted hooks recovered from the medium, and by dissecting worms for measurements of various organ systems. Three moults separated the infective and adult male instar, whereas 4 moults were necessary in the case of females. In both cultures natural mortality was about 10% over a 160-day period, by which time 33–51% of females and 62–70% of males had reached the terminal instar. Some males attained full sexual maturity with seminal vesicles loaded with viable sperm: such males were indistinguishable from males recovered from naturally infected rattlesnakes. However, females never achieved full size, even after 200 days, and although copulation did not occur in vitro, some females became patent.

Cercaria vaullegeardi develops in daughter sporocysts within the digestive gland of the prosobranch Gibbula umbilicalis. On emergence into the host mantle cavity the cercarial body retracts into the cystophorous tail, the ‘encysted’ cercaria being then shed into the sea. The encysted cercaria is described at the ultrastructural level for the first time and developmental stages are redescribed. The cercarial body has no penetration or cystogenous glands: a single type of sub-tegumental secretory cell produces vesicles containing neutral mucopolysaccharides which pass into the tegument at encystment. The immotile cystophorous tail consists essentially of a fibrous caudal cyst and 8 appendages including a delivery tube. Scanning electron micrographs show the surface of tegumental membranes enveloping the caudal cyst to be covered with a honeycomb pattern of indentations derived from electron-lucent vesicles produced by the caudal gland. The fibrous-walled delivery tube comprises proximal and distal sections and a modified terminal end-piece.

This epidemiological study assesses the occurrence of enteric parasites in 4303 patients attended at two public hospitals in Ankara (Turkey) during 2018–2019. Microscopy was used as a screening test. Giardia duodenalis was also identified using a commercial ELISA for the detection of parasite-specific coproantigens. Giardia-positive samples by microscopy/ELISA were confirmed by real-time PCR and characterized using a multilocus genotyping scheme. Blastocystis sp. was genotyped in a sample subset. Blastocystis sp. (11.1%, 95% CI 11.4‒14.8%) and G. duodenalis (1.56%, 95% CI 1.22‒1.96) were the most prevalent pathogens found. Cryptosporidium spp., Entamoeba histolytica and intestinal helminths were only sporadically (<0.5%) found. For G. duodenalis, sequence (n = 30) analyses revealed the presence of sub-assemblages AII (23.3%), discordant AII/AIII (23.3%) and mixed AII + AIII (6.7%) within assemblage A, and BIII (10.0%), BIV (3.3%) and discordant BIII/BIV (23.3%) within assemblage B. Two additional sequences (6.7%) were assigned to the latter assemblage but sub-assemblage information was unknown. No associations between G. duodenalis assemblages/sub-assemblages and sociodemographic and clinical variables could be demonstrated. For Blastocystis sp., sequence (n = 6) analyses identified subtypes ST1, ST2 and ST3 at equal proportions. This is the first molecular characterization of G. duodenalis based on MLG conducted in Turkey to date.

The availability of genome sequence data has facilitated the development of high-throughput genetic screening approaches in microbial pathogens. In the African trypanosome, Trypanosoma brucei, genome-scale RNA interference screens have proven particularly effective in this regard. These genetic screens allow for identification of the genes that contribute to a particular pathway or mechanisms of interest. The approach has been used to assess loss-of-fitness, revealing the genes and proteins required for parasite viability and growth. The outputs from these screens predict essential and dispensable genes and facilitate drug target prioritization efforts. The approach has also been used to assess resistance to anti-trypanosomal drugs, revealing the genes and proteins that facilitate drug uptake and action. These outputs also highlight likely mechanisms underlying clinically relevant drug resistance. I first review these findings in the context of what we know about current drugs. I then describe potential contributions that these high-throughput approaches could make to the development and implementation of new drugs.

Teneral Glossina morsitans centralis were fed on the flanks of African buffalo, N'Dama or Boran cattle infected with Trypanosoma vivax IL 2337. The infected tsetse were maintained on goats and on day 25 after the infected feed, the surviving tsetse were dissected to determine the infection rates. The mean mature infection rates (% ± S.E.) in the tsetse fed on buffalo, N'Dama and Boran cattle were 34·3 ± 9·9, 33·7 ± 13·4 and 58·9 ± 7·1, respectively. Logistic regression analysis indicated that infection rates in the labrum and hypopharynx of the tsetse were significantly lower when fed on the infected buffalo or N'Dama than Boran cattle. Similarly, the risk of infection was significantly lower in male than female tsetse. When teneral G. m. centralis, G. pallidipes, G. p. gambiensis, G. brevipalpis and G. longipennis were fed simultaneously on either the buffalo cow, the N'Dama bull or the Boran steer infected with T. vivax IL 2337, the mature infection rates were higher in the two morsitans group than the two fusca group tsetse, whilst G. p. gambiensis was relatively refractory to the infection, irrespective of the host species on which they fed. Logistic regression analysis indicated that the infection rates in the labrum and hypopharynx were significantly different amongst the five tsetse species for each of the three infected host animals. Nevertheless, the trypanotolerant African buffalo and N'Dama cattle may serve as reservoirs of T. vivax infection as can trypanosusceptible Boran cattle.

Host immunity will result in increased homozygosity at immunogenic loci if they encode products that elicit allele-specific immune responses. This increased homozygosity can be detected by comparison to ‘neutral’ (i. e. unselected) loci in the same genome which act as controls for the various epidemiological factors, such as biting rate, which affect homozygosity. Numerical results suggest that homozygosity should be 20 to 500 % higher at immunogenic loci, a result which is robust to changes in host death rate and the degree of linkage between the immunogenic and neutral loci. The same logic applies to loci which encode drug resistance: treated individuals with resistant infections will transmit zygotes homozygous for the resistance allele. It is argued that this increased homozygosity at putative immunogenic loci can act as a diagnostic feature to test using field data. The method also serves as a potentially very powerful method of identifying immunogenic and drug-resistant loci in laboratory studies of species such as the murine malaria Plasmodium chabaudi.

In continuation of our investigations on the relationship between the various Coccidia living in man and carnivorous animals (dog, cat, fox, etc.), we have had the opportunity of examining the intestines of several badgers, Meles taxus, which died in the Zoological Gardens, Budapest. These examinations revealed in a number of cases the occurrence of Coccidia belonging to both Eimeridae and Diplosporidae. In order to eliminate the possibility of these coccidial infections having been derived from other animals (fox, dog, cat), kept in close proximity with the badgers, it was found necessary to determine whether such infections also occur in badgers living under natural conditions. With the kind help of Prof. Raitsits, head of the ambulatory clinics of our College, we succeeded in obtaining a young specimen of Meles taxus, which not only harboured Coccidia, but subsequently served as an experimental animal for various cross-infections.

Longitudinal muscles in adult male Schistosoma mansoni appear to remain in almost all respects functional after tegumental disruption by Triton X-100. Responses to high K+, ouabain, low temperature, praziquantel and neurotransmitters are still present. Muscle membrane potentials remain near those of control animals and lanthanum nitrate is still excluded from the muscle after the Triton treatment. Although muscle contractility remains after tegumental disruption, sodium and calcium levels, as measured by plasma emission spectroscopy, increase by 20–30% while potassium and magnesium levels decrease by 15%. 45Ca2+ accumulation is double that of control animals. Upon exposure to a bathing medium lacking Ca2+, Triton-treated animals lose responsiveness to high K+, ouabain, low temperature and praziquantel more rapidly than do control animals. D-600, which effectively blocks the high K+ response in control animals, has no measurable effect on the high K+ response in Triton-treated animals, suggesting that voltage-dependent Ca2+ channels are present in the tegument.

The morphology of the mucosal surface of samples from the small intestine of young protein-deficient pigs was examined by scanning electron microscopy. Three pigs had been infected with Ascaris suum for at least 58 days while 1 had remained uninfected; all pigs were housed and maintained under the same conditions, at the same time. The tissue samples collected at post mortem examination from pigs which contained A. suum showed varying degrees of villous atrophy and fusion. In addition, unusual small craters and as yet unidentified objects were observed at the surfaces of the enterocytes of Ascaris-infected pigs. These changes in mucosal morphology were not seen in the tissue taken from the uninfected pig. The possible association between the mucosal lesions and lactose maldigestion in young, protein-deficient pigs infeceted with A. suum is discussed.

With the recent global spread of a number of mosquito-borne viruses, there is an urgent need to understand the factors that contribute to the ability of viruses to expand into naïve populations. Using dengue and chikungunya viruses as case studies, we detail the necessary components of the expansion process: presence of the mosquito vector; introduction of the virus; and suitable conditions for local transmission. For each component we review the existing modelling approaches that have been used to understand recent emergence events or to assess the risk of future expansions. We identify gaps in our knowledge that are related to each of the distinct aspects of the human-mosquito transmission cycle: mosquito ecology; human–mosquito contact; mosquito–virus interactions; and human–virus interactions. Bridging these gaps poses challenges to both modellers and empiricists, but only through further integration of models and data will we improve our ability to better understand, and ultimately control, several infectious diseases that exert a significant burden on human health.

The intraperitoneal inoculation of chickens with 100–170 mg of Statolon, an artificial interferon inducer in mammals, induced the production of a virus interference factor in the serum. Chickens, 3 and 5 weeks old given 40–170 mg Statolon i.p. produced significantly fewer oocysts after infection with E. maxima than untreated chickens.

Only three serum samples (from a large number examined) taken from chickens 1, 4 or 6 days after E. tenella infection or 6 h and 6 days after E. maxima infection showed slight but significant antiviral effects.

Most of the nine species dealt with in this paper were collected before the outbreak of World War II. Library facilities in Ceylon, meagre enough even in normal times, were altogether unavailable during the war years owing to the removal of the Colombo Museum Library to safe areas inland. It was only after the library was brought back to Colombo at the beginning of 1947 that this paper could be got ready for publication. Hence it appears 10 years after the last contribution in the series.