Measurements were made of gravid worm lengths, scolex diameter, rostellum diameter, sucker diameter, and large and small rostellar hooks of adult Taenia hydatigena, T. multiceps, T. ovis and T. pisiformis obtained from dogs in North Wales. Values recorded agreed closely with published values. None of these characters could be used to differentiate reliably between the species except that, of the worms examined, those with large rostellar hooks greater than 228 μim were T. pisiformis and those with large hooks less than 168 μm were T. multiceps. The range of hook lengths of the different species overlapped considerably.

Reliable identification required examination of mature proglottis morphology of specimens which were relaxed before fixation. Relaxed mature proglottides often showed a characteristic shape.

Lengths of rostellar hooks of scolices from T. multiceps coenuri followed the same frequency distribution as adult worm hooks. A strong correlation was shown between coenurus volume and the number of scolices on the coenurus membrane, with a poor correlation between coenurus age and volume.

Cercariae of Schistosoma bovis, S. intercalatum and S. haematobium were radiolabelled by individual exposure of their respective host snails to 75Se-methionine in 1 ml water for a period of 20 hours. Maximum cercaria-bound radioactivity was obtained four to seven days after labelling of snails, but detectable levels of radioactivity incorporation were obtained with all three species for a period of 32 days. The radiolabelling procedure did not interfere with the production of cercariae or with the biological characteristics of the labelled larvae. The described research opens the way for the application of various radioisotope tracer systems in studies on host-parasite relationships between cercariae and schistosomula of terminal-spined species of schistosomes and the final host.

A survey revealed that Onchocerca tarsicola Bain & Schulz-Key, 1974 is a widespread parasite among reindeer in northern Finland. Of 407 animals studied from 12 reindeer herds, 124 (30·5%) were infected. There was a marked difference in infection levels between different reindeer herds and the frequency as well as the intensity of infection was highest in old animals whereas the parasites were rare in yearlings.

A comparative biochemical study was performed on adult and cystic stages of Echinococcus granulosus. Basic quantitative differences in metabolism were apparent between the cystic forms of sheep origin from the UK and Kenya which suggest that each may represent a different geographical strain or sub-strain.

The biochemistry of the human and sheep forms from Kenya was very similar, which probably reflects a certain close affinity between the two. The fact that the cattle, goat and camel forms of E. granulosus, from that country, were distinct biochemically, both from each other and from the sheep and human types, suggests the existence of an unusually complex strain picture there, and that these organisms are either noninfective or only poorly infective to man.

The differences in biochemical composition and metabolism observed between adults produced experimentally and those obtained from naturally infected dogs, may have been as a result of their original hydatid source and/or their differing stage of development.

The life span and the pathogenicity of amphistomes developing from Cercariae indicae XXVI (Paramphistomum epiclitum) were considerably reduced when the metacercariae were gamma-irradiated at 2krad or 3krad. The higher irradiation dose resulted in the complete absence of the flukes in infected animals. Single vaccination of lambs and kids with 3000 metacercariae irradiated at 2 krad or 3 krad stimulated a significant degree of resistance against challenge with 5000 non-irradiated metacercariae. The resistance was more pronounced in the group vaccinated with metacercariae irradiated at 3krad.

The rate of uptake of H3 tyrosine by unisexual females in vitro was accelerated by 22% when male worm extract was added to the culture medium. Pairing of unisexual females with mature male worms in vitro resulted in a similar acceleration of H3 tyrosine uptake. As tyrosine is avidly taken up by the vitelline gland for the formation of egg shell protein the change in the rate of H3 tyrosine uptake can be employed as a sensitive quantitative criterion for assessing its development following stimulation.

Paradistomoidella cerberi n.g, n.sp. and Paracanthostomum cerberi from Cerberus rhynchops, Xenopharynx pyriformis and Allopharynx mehrai from Ptyas korros, Neopronocephalus orientalis from Geoemyda spinosa, and Duthiersia expansa from Varanus salvator are all reported from the area of Kuala Lumpur, Malaysia. Paradistomoidella cerberi most closely resembles members of Paradistomum and of Paradistomoides but is characterized by relatively short caeca, a cirrus sac containing a bipartite rather than sinuous internal seminal vesicle, and unevenly-sized suckers. Kuala Lumpur is a new locality for Paracanthostomum cerberi, X. pyriformis, A. melvrai, and D. expansa. Ptyas korros is a new host for X. pyriformis and G. spinosa is a new host for N. orientalis.

A. A comparative study of a simplified radioimmunoassay (RIA) technique with the indirect haemagglutination (IHA) test in the diagnosis of 72 patients with hydatid disease indicated the greater sensitivity of the former. Both methods had an equal specificity in 60 control patients. RIA will serve as a useful addition to tests already available in hydatid serology.

B. A comparison of the (RIA) technique with the fluorescent antibody test (FAT) in the diagnosis of 33 patients with early, active trichinosis and 30 healthy controls indicated an equal sensitivity and specificity of both methods. The adoption of RIA as an easier method is recommended.

This study of a simplified radioimmunoassay technique for the diagnosis of hydatid disease and trichinosis in man is presented in two sections.

A substantial resistance to a heterologous challenge with Fasciola hepatica was demonstrated in calves harbouring primary patent Schistosoma bovis infections of an age of 10 weeks at challenge, the mean worm burden being reduced by 29·9% (p < 0025) in calves primarily infected with S. bovis as compared with that of the challenge control group. The heterologous resistance was also evidenced by less pronounced liver tissue damage and lower serum gammaglutamyl-transpeptidase values in the S. boms-infected animals compared with the challenge control group.

The karyotypes of two hermaphroditic trematodes, Megalodiscus temperatus and Philophthalmus gralli, were described and compared as to chromosomal morphology and constitutive heterochromatin constitution. The haploid number of chromosomes for both species is 10 and both karyotypes are composed mainly of acrocentric chromosomes. Constant heteromorphism of the No. 10 chromosomes was found in M. temperatus. The heteromorphic chromosomes differ is size and heterochromatin constitution. The possible mechanisms of chromosomal dimorphism in M. temperatus and its significance in the evolution of sexchromosome differentiation in trematodes are discussed.