Groups of five 3-kg Kenyan monkeys, Cercopithecus aethiops, were exposed individually to 150,600 or 1500 Schistosoma mansoni cercariae per monkey. Three monkeys died soon after the infections became patent and the survivors were autopsied 4 months after exposure. Mortality and most haematological, parasitological and pathological sequelae of infection were dose-related, but not the white cell response or changes in the levels of serum proteins or fibrinogen. No gross liver fibrosis was seen. Comparison of this study with earlier ones on related cercopithecine monkeys suggests that the vervet closely resembles the baboon in its response to S. mansoni infections. Difficulties in managing and maintaining vervets can be overcome by using colonybred or properly adapted feral animals. Thus, the vervet provides a cheaper, more readily available primate model for experimental S. mansoni studies. A prolonged infection, sufficiently heavy to permit reliable parasitological monitoring without undue mortality, should be provided by 150 S. mansoni cercariae per kg body-weight, using the Kenyan strains of vervet and parasite.

The intestinal morphology or rats given one, 10 or 100 cysticercoids of Hymenolepis diminuta was examined by scanning electron microscopy. The presence of this tapeworm causes extensive villous atrophy and fusion. The most extreme changes in mucosal architecture were observed adjacent to the mature proglottides of the worm and in these areas the villi were reduced either to flattened plate-like structures or to low irregularly shaped undulations. The presence of one large H. diminuta resulted in more severe pathological damage than caused by several smaller worms. Colonization of the upper region of the ileum by long filamentous bacteria was also observed in rats infected with H. diminuta.

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entering the value of s/X in a chi-square table.

The multiplicity of soluble esterases in Raillietina tetragona, R. echinobothrida and R. cesticillus was studied by use of slab polyacrylamide gel electrophoresis. Five fractions of esterase activity were observed in R. tetragona, seven in R. echinobothrida and three in R. cesticillus. The various fractions of esterase activity of closely related species of Raillietina showed differential behaviour towards various chemicals. Based on the inhibitory effect of inhibitors p-CMB, EDTA, malathion, silver nitrate and eserine sulphate, the various esterases have been classified into arylesterase, carboxylesterase, acetylesterase and cholinesterase.

The response of the free-living stages of Nippostrongylus brasiliensis, Nematospiroides dubius, Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia ostertagi to a wide variety of antiparasitic agents in vitro was investigated.

All the major broad spectrum veterinary anthelmintics showed good activity against each of these worms with EC30 values varying from about 00002mg/1 for certain benzimidazoles and ivermectin to about 6–5 mg/1 for febantel. Of 22 known narrow spectrum anthelmintics useful only against H. contortus and/or helminths other than trichostrongyles, only 10% showed good activity at concentrations equal to or less than 100mg/1. Further, only one of 15 antiprotozoal agents showed good activity in these tests at the 100mg/1 level.

A new fasciolicide, triclabendazole, tested at single oral dose rates of 5 and lOmg/kg body-weight, proved to be highly effective (>99%) against chronic field infections of Fasciola hepatica and F. gigantica in sheep. The Performance of the new drug compared favourably with niclofolan at the recommended dose. Neither product was effective against Dicrocoelium dendriticum and Paramphistomum spp.

The microfilarial level in the peripheral blood of Mastomys natalensis infected with the filarial parasites, Litomosoides carinii, Brugia pahangi, B. malayi and Dipetalonema viteae was monitored at two-hour intervals for 24 hours. The microfilariae of B. pahangi and B. malayi exhibited nocturnal and diurnal subperiodicity, respectively; no such periodicty was seen in L. carinii and D. viteae infections.

The level of B. pahangi and D. viteae microfilariae in peripheral blood was significantly increased when the host was anaesthetized with diethylether or pentothal sodium. Ether-induced anaesthesia had no effect on tne level of B. malayi microfilariae but pentothal was most effective. The peripheral blood count of L. carinii microfilariae tended to decrease in the anaesthetized animals but the reduction was not statistically significant.

Of the 2,652 Lymnaea truncatula collected from sites in Cumbria and Gwynedd during 1973–75, when the Prevalence of fascioliasis in the primary host was low and declining, only 123 were infected with Fasciola hepatica. Dissection of these snails revealed that the proportion infected, the mean redial burden and the Proportion of mature rediae in each snail increased with shell length.

The results are compared with a similar data set acquired when the prevalence of infection in both the Primary and intermediate hosts was uncharacteristically high. Although the results are qualitatively similar, there are important quantitative differences. The mean redial burden of infected snails at times of high disease Prevalence was generally twice as high as that reported in the present study. It is suggested that differences in habitat microclimate could not account entirely for the observed differences in redial burden and the role of multiple miracidial infection is discussed.

To test the ability of cells and/or serum from jirds (Meriones unguiculatus) infected with Litomosoides carinii to transfer the ability to retard development of challenge larvae, a series of transfer experiments were done. Groups of jirds received larval challenge preceded by one of eight preparations: spleen cells and/or serum from 10-day-patent infected jirds; normal spleen cells and/or normal serum; primary larvae; challenge larvae only.

No significant differences in size or numbers of larvae recovered were found among groups receiving either cells or serum only. However, significant differences in larval size were found between groups receiving both cells and serum from infected donors and those receiving normal cells and serum. These comparisons indicate that the ability of infected jirds to retard development of challenge infection larvae can be transferred with cells and serum together but not separately.

In the desert city of Beersheba, Israel, a survey was made of the infection rate of Toxocara canis in dogs. 3.0% of dogs destroyed at the municipal dog pound had intestinal T. canis. 7% of faecal samples gathered from day care centres throughout the city were shown to contain T. canis eggs. This low rate of infection could possibly be explained by the hot, arid climatic conditions which may render eggs non-infective or by the sandy soil in the area that may cover faeces containing T. canis ova and make the eggs unavailable to other dogs.

Medium in which T. canis larvae had been cultured was applied to a Sephadex G-25 gel column and four fractions (Fr. 1-Fr. 4) were isolated. Each fraction was administered to mice by implanting a mini-osmotic pump into the peritoneal cavity and the subsequent peripheral blood eosinophilic counts were recorded. Mice given Fr. 1 showed a markedly greater eosinophilic response than did those given the other fractions. Complement activation by each fraction was investigated using normal human serum. Fr. 1 and Fr. 3 had a capacity to activate complement. The results suggest that Fr. 1 may be not only antigenetic and allergenic but also could induce eosinophilia and activate complement.

The four species of the genus Strongylus Müller, 1780, namely, S. equinus, S. edentatus, S. vulgaris and S. asini were examined with the scanning electron microscope (SEM). The buccal cavity of each species was cut transversely and longitudinally and the scanning electron micrographs illustrate the shape of the buccal cavity and the dorsal gutter. The micrographs also show the presence of denticles near the oral rim of the buccal cavity of S. edentatus and the shape of the teeth in the buccal cavity of S. equinus, S. vulgaris and S. asini. The bursa of the four species has three symmetrical lobes, one dorsal and two lateral. The length of the three lobes in relation to each other varies between the species. The genital cone has a single large ventral papilla, a pair of dorsal raylets, a median dorsal cuticular appendage and a variety of cuticular appendages lateral and ventral to the cloaca. The development and arrangement of these components differs between the four species of the genus and can be used as a supportive character for specific identification.

Ancylostoma ceylanicum is a new introduction as an experimental hookworm model. Information on the biology of this parasite in its laboratory host—the golden hamster, is meagre. Its infectivity, longevity and fecundity were studied to obtain relevant information especially on vulnerable points in the maintenance and continuation of the infection. 100% infectivity was obtained with an inoculum of 60 larvae per animal. Maximum numbers of parasites were harboured from day 15 to day 18 after infection and thereafter gradually declined. Approximately 10% of the worms were still present at the end of the third month of infection. The in vitro release of eggs in a 24-hour period by one female nematode peaked from day 25 to day 39; a second rise occurred on day 70 after infection.

Histopathological studies of Neoechinorhynchus hutchinsoni infection in Nemacheilus kashmirensis show partial or complete damage of the host intestinal wall, depending upon the degree of penetration. Increased number of goblet cells are seen at the site of unperforated wounds but where the intestinal wall is completely perforated the goblet cells were undifferentiated. The parasite destroys the mucosa, lamina propria, muscle layer and serosa leading to perforation. This report of perforation by Neoechinorhynchus hutchinsoni is the first in the genus Neoechinorhynchus.

Non-specific and specific phosphatases have been histochemically localized in the tissues of Avitellina lahorea, an intestinal parasite of sheep and goats. Large quantities of acid phosphatase, alkaline phosphatase and adenosine triphosphatase were observed in almost all organs except the parenchyma where there were moderate amounts of acid phosphatase and no alkaline phosphatase; the reproductive ducts contained moderate amounts of alkaline phosphatase. 5-nucleotidase was observed only in the uterus, egg pouches and eggs and glucose-6-phosphatase activity was restricted to the tegument. The probable functions of these moieties at different sites are discussed.