The tissue reactions in mice, experimentally infected with normal and irradiated cercariae of S. incognitum were studied. The lesions observed in the skin, liver, lungs and the intestine of mice infected with normal cercariae are briefly described, and compared with those observed with cercariae irradiated at 3000 r of gamma rays. In general, the reactions in mice exposed to normal cercariae were more intense than in those infected with irradiated cercariae. The severity of the reactions appeared largely due to the deposition of eggs in the tissues of the mice infected with normal cercariae. The experimental evidence suggested that most of the flukes from the irradiated cercariae are destroyed in the liver by tissue reaction.

Enzyme-linked immunosorbent assay (ELISA) double antibody technique was standardized for detecting S. mansoni Polysaccharide and protein antigens in serum of infected mice. Anti-sera specific for either worm components were obtained in sheep and peroxidase conjugates prepared from each serum. The immunoenzimatic test for protein could detect as little as 6μg/ml antigens, and the test for polysaccharides 3 μg/ml.

Both bisexual and unisexual male worm low infections were produced, and studied for as long as 27 weeks post-exposure. Worm components were found in serum from both types of infections and in progressively higher percentages of animals until the end of the 27 weeks observations period. For unisexual male infections this percentage reached from about 50% to 60% of mice, and 100% for bisexual infections. Significantly higher antigen concentrations in serum were found at 27 weeks for bisexual infections, no antigen increase being detected in relation to starting egg secretion, which occurred at 5 week infections.

S. bovis is an economically important parasite of cattle and possibly of sheep and other domestic stock in many African and Mediterranean countries. Control of this infection by chemotherapy and mollusciciding is impractical and this has stimulated interest in vaccination. Previous work in sheep with the Central and South African species S. mattheei has led to the development of an effective vaccine which incorporates irradiated schistosomula produced by artificial transformation of cercariae. In the present experiments a similar S. bovis vaccine has been used in sheep. Fifteen 5 month old Border Leicester × Suffolk crossbred wethers were divided into three groups, two were vaccinated with either 10000 or 20000 6 krad irradiated S. bovis schistosomula, and the third kept as unvaccinated controls. All sheep were challenged with 6700 normal S. bovis cercariae.

Worm recoveries and tissue egg counts at necropsy showed that vaccination with 10000 irradiated schistosomula produced a reduction of 71% in the mean worm burden resulting from challenge of the controls and the mean densities of eggs in the tissues were reduced by 75–82%. Immunization with 20000 irradiated schistosomula was not more effective. Histopathological observations showed that both groups of vaccinated sheep had much milder lesions in the intestines than the non-vaccinated controls. There was also a clear reduction in the severity of liver lesions in 4 of the 5 sheep given the lower dose of irradiated schistosomula but the livers of sheep vaccinated with 20000 irradiated schistosomula had severe and widespread lesions due mainly to a massive accumulation of eosinophils and other inflammatory cells around the vessels.

The combined use of complement fixation (CF) and latex agglutination (LA) tests is reported on sera from 6328 patients with suspected hydatid disease; 191 were confirmed positive at operation (‘known positives’). Results by LA are related to CF titres.

Both tests were negative in 90% of specimens. Nine patients were subsequently found infected of whom 3 became positive in tests after operation.

Of sera positive in both tests, 75% were from ‘known positives’. The remainder were almost certainly from infected patients.

Half the patients whose sera were La positive/CF⋜¼ were follow-up ‘known positives’ in whom CF titres had waned; 2 were early infections.

Only 3% of the cases with an LA negative/CF titre of ⋝1/16 were ‘known positives’ and 6% where the CF titre was 1/8. The remaining CF results in the group were false positives and accounted for 1.2% of all sera tested. Findings show that a CF titre ⋝1/8 with positive LA indicates past or present infection; a negative CF test with positive LA usually indicates past infection; rarely, infection is present when a CF titre is ⋝1/8 and LA is negative. A rising CF titre and positive LA indicates current infection; reliable prognosis following treatment is given by CF.

Various stages of Angiostrongylus cantonensis recovered from the brain of experimentally infected mice were transplanted intracranially into rats. Third and fourth-stage worms recovered 2–7 days postinfection were able to develop normally after transplantation into recipient rats. The fifth-stage worm obtained 14–15 days postinfection would enter the brain tissue of rats but died shortly afterwards. However, the same stage of worms recovered from rats, after a similar transplantation, were found to develop normally in the recipient animal. Young fifth-stage worms, from the subarachnoid space of rats, which were ready for the pulmonary migration were also transplanted into rabbits but the worms failed to reach the lungs. In the control rat-to-rat transplantation, the worms successfully completed the pulmonary migration. The morphogenesis and initial growth rate of A. cantonensis were similar in both mice and rats but in the former host the worms started to grow at a markedly slower rate after the last moult and gradually degenerated.

Schistosoma intercalatum and from Cameroon and Zaire each have their specific snail intermediate host. Hybridization experiments between S. intercalatum from Cameroon and Zaire have resulted in viable miracidia for only two generations. If the two strains are of the same species, cross breeding should be possible for several generations. This paper presents a comparison of the characteristics of the two strains of S. intercalatum in experimental infections in mice.

Worm return, male-female worm ratio, growth rate, number of testes in male adult worms are compared. The quantitative distribution of eggs in the tissues of the mice is recorded. A comparison of the size and shape of the parasite eggs is described as are the changes in the weight of the liver and spleen of the infected mice.

It is considered that the differences observed between the two strains of S. intercalatum do not necessitate a division of the two strains into two separate species.

Schistosoma mansoni cercariae labelled with 75Se-methionine were used to study host-finding capacity by determining the radioactivity of exposed mouse “target” tails. Possible interfering effects of some aquatic vertebrates and invertebrates, plants and algae and secretions and excretions of aquatic organisms were examined.

A marked interferent effect due to predatory behaviour was produced by Cyclops strenuus (Copepoda), Daphnia pulex and D. longispina (Cladocera), Notodromas monacha and Cypria ophthalmica (Ostracoda) and Lebistes reticulatus (guppy). Bufo bufo (Amphibia) and Planaria lugubris (Turbellaria) interfered significantly, presumably by secreting cercaricidal toxins. Several other organisms apparently produced no interference. The interferent effect of the plant species Ceratophyllum demersum, Elodea canadensis, Lemna minor, Ranunculus aquaticus, Holcus lanatus (grass) and Botryococcus braunii was particularly pronounced when they were confined to the surface layer of the water. Several other species did not interfere with host-finding.

Sixty-one serum samples selected on the basis of reactivity in the complement fixation (CF) and latex agglutination (LA) test, were further examined for sensitivity and specificity by indirect haemagglutination (IHA), enzyme linked immunosorbent assay (ELISA) and defined antigen substrate spheres (DASS). Twenty sera from healthy Europeans and 48 samples from patients with either schistosomiasis or trichinosis were also tested. Comparable levels of sensitivity were found between the CF and LA positive sera and IHA, ELISA and DASS. Of the CF positive LA negative group of sera, many were positive by DASS but only a few reacted in IHA and ELISA. Some cross reactivity was also observed in the schistosomiasis sera tested by IHA and ELISA.

The susceptibility of Bulinus truncatus, B. tropicus, B. natalensis, B. coulboisi, B. globosus, B. cernicus and B. wrighti to Schistosoma haematobium from Egypt were examined. Eighteen different populations of B. truncatus were investigated.

A new method of measuring the compatibility between schistosomes and the intermediate snail hosts, the total cercarial production per 100 exposed snail, is introduced.

All B. truncatus populations became infected and could be divided in four groups according to the total cercarial production per 100 exposed snails. In the first group the cercarial production varied from 250 000 to 500 000 and in the last group between 5000 and 20 000. The first group had a high infection rate of 62 to 100% and a low mortality of approximately 10% and the last group showed a very low infection rate and a high mortality.

B. globosus (Rhodesia), B. cernicus and B. wrighti became infected, while B. globosus (Zaire), B. coulboisi, B. natalensis and B. tropicus were refractory.

The shortest prepatent period was 26 days at a room temperature of 26°C. The maximum cercariae production for one snail in one day was 600 and the longest duration of infection was 200 days.

Experimenting with different doses of miracidia, 5 to 50 per snail, resulted in a one hundred per cent infection and a low mortality of 10%. There was only a slight variation in the cercarial production.

The relationship between Schistosoma haematobium from Sudan, Zaire and Zambia and various species and strains of Bulinus, has been investigated. The main emphasis was placed on evaluating the total cercarial production per 100 exposed snails as an index of the compatibility between snail and schistosome. The observations confirmed the results of previous compatibility studies which showed that there two groups of S. haematobium, truncatus-borne from Sudan and Zaire, and africanus-borne, from Zambia. They also revealed that this division was not absolute, as some overlapping occurred. However, if the cercarial production was taken as an indication of compatibility, instead of the infection rate, there was a more definite division between the two groups.

The observation that there is a truncatus-borne strain of S. haematobium present in Zaire extends the area where there is a mixture of truncatus-and africanus-borne strains farther southwards.

22 antigenic components of Taenia saginata proglottides were detected by immunoelectrophoretic (IEP) study. Cross-absorption of the Hyperimmune serum, raised in rabbits against T. saginata, with heterologous and host antigens showed that two thirds of these components were not specific for the cestode. Among the calves experimentally infected with T. saginata eggs, 3 precipitation patterns in IEP were identified depending on the evolutionary stage of the infection. The hydrosoluable extract of T. Saginata was used as antigen. A short precipitating arc present near the antigen well and appearing 3 to 4 weeks post-infection of the calves and a long precipitating arc extending towards the anodic end of the slide and appearing in later stages of infection were found of high diagnostic value. No false-positive reaction or cross-reaction were found. Among the calves harbouring less than 50 cysticerci, false-negative reactions were seen.

Uptake and serosal transfer of the vitamins thiamine, riboflavin and folic acid have been studied in vivo in normal and parasitized rats infected with Hymenolepis diminuta (Cestoda).

Regional differences in intestinal uptake of all three vitamins in both uninfected and parasitized animals were not statistically significant.

In the parasitized intestine mucosal uptake and serosal transfer of thiamine were significantly inhibited, with increased mucosal accumulation of the vitamin as luminal thiamine concentration increased.

Apparent increased riboflavin mucosal uptake in parasitized animals, was not matched by the reduced serosal transfer, suggesting adsorption of the vitamin in the unstirred aqueous layers.

Mucosal uptake of folic acid increased in the parasitized gut; serosal transfer and mucosal accumulation were not affected.

These results, indicating vitamin malabsorption associated with infection by H. diminuta, are consistent with the parasite inhibiting mucosal passive transport mechanisms. This conclusion is supported by the changes in net water fluxes associated with vitamin uptake in the parasitized intestine.

3 × 10−6M praziquantel fails to completely paralyse miracidia and cercariae in a short time but they are not infective when maintained in the solution. 3 × 10−5M praziquantel prevents infected snails shedding cercariae but does not kill daughter sporocyts or developing cercariae. As the action of praziquantel on adult worms is not blocked by 10−2M mecamylamine, pempidine or carbachol, but is reduced by calcium deplection, it is suggested that praziquantel may act by permitting calcium influx to muscle cells causing them to contract.

Moaciria chondropythonis sp. n., from cysts in the wall of the oesophageal/stomach junction of Chondropython viridis originally from New Guinea but kept in captivity at the Zoological Society of London for three months is described and figured. It is distinguished from the other species of the genus by the number and arrangement of the caudal papillae and by its larger size.

Xenopodistomum xenopodis Macnae, Rock and Makowski, 1973 was recovered from the gall bladder of Xenopus laevis laevis imported from the Cape Peninsula, South Africa, during 1967 – 1978. The overall incidence amongst 396 toads was 2.8%, and while the maximum intensity was 8 worms per host, most carried single infections. The parasite was not represented in 570 specimens of 8 other Xenopus taxa from East, Central and West Africa. The internal anatomy of X. xenopodis is of a plagiorchild type, but the adult body form is unusual with marked division into a slender very extensible neck and a broad oval hindbody. Although apparently confined within the gall bladder, the parasite can extend its neck along the bile duct and into the duodenum: host gut contents or intestinal epithelium may therefore supplement the diet of bile fluid. The original description and generic diagnosis have been amplified and amended. X. xenopodis apparently lacks close affinities with other known genera, a characteristic common to many of the parasites which infect the clawed toads.

The effects of some extrinsic factors on the lipid (energy) reserves and longevity of third-stage larvae of the cat hookworm Ancylostoma tubaeforme, were investigated under controlled laboratory conditions. In non-stressful microenvironmental conditions, larval longevity was directly related to the rate of utilisation of the lipid reserves. The effects of the various environmental stresses on longevity could also be explained largely on the basis of their deleterious effects on the lipid metabolism of the larvae.

The alterations of mast cell counts induced in the gut of swiss albino mice by infection with Ancylostoma caninum larvae have been studied, both in single and multiple infections. It was found that mast cell rise was greater in females than males. In singly infected animals, mast cell increase was influenced by the infective dose of inoculated larvae. In case of repeatedly infected mice, mast cell counts were decreased because of their earlier degranulation.