The innate resistance of the unnatural rat host to the mouse tapeworm Hymenolepis nana is cortisone sensitive but thymus independent. When congenitally athymic nude rats were orally given eggs, cysticercoids, or adult worms of H. nana, no lumenal adults were established except when they were treated with cortisone acetate during the expected lumenal development. The effect of cortisone to promote adult maturation in the rats was compared in nude and normal rats given eggs of H. nana. The fecundity of the worm (assessed by the fresh worm biomass and the number of infective eggs produced) was much higher in cortisone-treated nude rats than in cotrisone-trated norml rats. When the nude rats recostituted with thymocytes were given eggs and treated with cortisone, the fecundity of H. nana dropped to the same level as in cortisone-treated normal rats. It is strongly suggested that the unnatural rat host has thymus-independent cortisone sensitive resistance to an intial infection (which is the main component of the innate resistance and blocks the lumenal establishment of this parasite) and thymus-dependent resistance (which suppresses the established worm' fecudity and may be ascribed to acquired resistance to the ongoing infection).

The two-dimensional patterns (isoelectrofocusing-IEF/polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate-SDS) of S3 fractions of muscle larvae of four Trichinella isolates were compared. The comparative study concerned six groups of polypeptides. It was observed that the Garkavi isolate of Trichinella pseudospiralis was clearly different from the other isolates, and it showed the simplest IEF/SDS polypeptide pattern. The C-76 isolate of T. nelsoni had only four of the six groups, distinguishing it from the GM-1 isolate of T. spiralis and the Boev isolate of T. nativa that showed all the indicated groups.

Heterophyes heterophyes, H. aequalis and H. dispar showed distinct zonation in the small intestine of different definitive hoste. The flukes were found in their appropriate zone within four to six hours after infection. It appeared that their position shifted posteriorly during their life and that the shift proceeded more rapidly in unsuitable hosts. Hisgological sections revealed that the flukes are not deeply embedded in the host's mucosa.

Four Presbytis cristata were treated with oral ivermectin at the same time as the subcutaneous inoculation of 100 infective larvae monthly for three months. Two animals given 0·2 mg/kg monthly and two others given 0·3 mg/kg monthly as well as three control animals became patent for microfilaraemia. However, only 1% of the infective dose was recovered as adult worms from animals in the higher drug dosage group compared to 8·2% and 6·2% in the lower dosage and control groups respectively.

Chromosomes of Nigerian Onchocerca volvulus were compared with those of Guatemalan O. volvulus. Both parasites had basically the same chromosomal construct (2n=8, XY type). Autosomes consisted of a pair of large and two smaller pairs. Sex chromosomes were made up of medium sized X chromosome and very small Y chromosome. It was not possible to infer the position of the centromeres.

The activities of the enzymes superoxide dismutase (E.C.:1.15.1.1) and catalase (E.C: 1.11.1.6) were studied in purified extracts of four nematodes: Ascaris suum, Toxascaris leonina, Toxocara canis and T. cati adult males and females. No catalase activity was found in any of the extracts. The results reveal that the SOD activities of the four parasites presented species differences and also sexual differences within each species. Polyacrylamide gel electrophoresis pattern analysis confirmed that the mobilities, widths and band intensities varied according to the species and sex of the parasite from which the enzyme was obtained.

The surface antigens of oncosphere, cysticercoid, adult scolex and adult strobila (other than scolex) of Hymenolepis nana differ critically from one another. When the oncosphere of H. nana undergoes differentiation and development into the mature tapeworm, the infected mouse first produces anti-oncosphere antibody, followed by anti-cysticercoid, anti-adult scolex and finally anti-strobila (other than scolex region) antibodies of IgG, IgM and IgA isotypes as detected by indirect immunofluorescent antibody test. The parasite changed its surface antigens throughout its differentiation and maturation, and all developmental stages were recognized by the infected mouse host. However, there appeared no further changes in surface antigens during aging after maturation. The antibody responses were always delayed compared with the differentiation and maturation of the parasite.

A total of 21 amino acids were detected in the present investigations on three species of Gangesia (Cestoda: Proteocephalata) viz. G. bengalensis Woodland, 1924, G. hanumanthai Seth & Capoor, 1982 and G. sanehensis Malhotra et al., 1981. The study was conducted in a sub-humid region around Allahabad, India. The implications of amino acid utilization in metabolic activities of fish tapeworms have been discussed.

Five lambs were each sensitized with 400 metacercariae of Fasciola gigantica irradiated at 3 kr gammarays. Eight weeks later, they were each challenged together with 5 controls with 500 non-irradiated metacercariae. Eight weeks later, all of the animals were necropsied and the worm burdens determined. The lambs which received the sensitizing infections had 80% less worms than the controls. The sensitized lambs also showed less hepatic damage compared with the controls as indicated by lower levels of the serum enzyme glutamate dehydrogenase. The blood indices showed insigicant reductions in the sensitized lambs whereas marked reductions were found in the erythrocytes, packed cell volume and haemoglobin values of the challenge controls. Bilirubinaemia was also evident in this latter group.

Infections of the common limpet, Patella vulgata were investigated along the coast of the Ards Peninsula, Co. Down. Samples were taken from around Portavogie, a small fishing port where seabirds aggregate to feed on fish offal, and from 14 sites along a 15 km transect. A new method of removing larval digeneans from the visceral hump of snails is described. The bulk of the parasite material was rediae of Cercaria patellae. The stage of development of these rediae varied significantly between hosts. Prevalence of infection was substantially greater close to Portavogie. The volume of parasite material recovered was greater for limpets close to rock pools than for those on rocks free from surface water at low tide. Among the latter limpets, the volume of parasite material in the visceral hump increased with increasing height on the shore. The greater part of the variation in parasite volume recovered from snails was determined by the size of the snail. The presence of larval digeneans was associated with progressive deterioration of host gonadal tissue and discolouration of the foot, mantle and digestive gland.

The oxidative metabolism of Gastrothylax crumenifer mitochondrial fractions was assayed polarographically at 30°C in the presence of various substrates. Succinate was most readily oxidized, malate and pyruvate were oxidized at subsantially lower retes. The spcific inhibitors such as malonate, KCN, NaN3, oxaloacetate, salicylhydroxamic acid and oligomycin effectively affected the mitochondrial oxygen consumption. The results indicate the presence of oxidative phosphorylation and cytochrome systems. Mitochondrial ATPase was found to be active.

Living, intact protoscoleces of the British horse and sheep strains of Echinococcus granulosus were subjected to surface radioiodination procedures using 125I and Iodogen and 125I-Bolton Hunter reagent. Subsequent combined electron microscopy and autoradiography revealed specific surface membrane labelling with the Iodogen procedure, but significant tegumental labelling with the Bolton-Hunter reagent. The two parasite strains yielded different profiles of electrophoretically separated labelled proteins; the Iodogen method, not surprisingly, resulted in a less complex pattern of labelled polypeptides than the Bolton and Hunter reagent.

A survey of Angiostrongylus cantonensis was carried out to investigate the mode of transmission from molluse to rat in a fixed study area of Yoron Island from 1979 to 1982. Rattus rattus was found to be infected with a small number of worms in spite of heavy infection with third-stage larvae in Achatina fulica and an abundance of this snail in the area. Natural infection and/or susceptibility with A. cantonensis were confirmed in three small snail species. Bradybaena circulus, Fruticicola despecta and Luchuena reticulata. Young A. fulica was found to be infected with fewer third-stage larvae than mature A. fulica. It was concluded that molluscs which were infected with a small number of third-stage larvae of A. cantonensis play an important role in maintaining the life cycle of A. cantonensis. The percentage of rat stomachs containing molluse tissue was relatively low, and the incidence and infection was low in rats. Infection with A. cantonensis did not occur very often in R. rattus in nature.

The in vivo efficacy of monensin against Fasciola hepatica was determined in the albino rat. The results were variable, with monensin generally showing greater activity against juvenile (two-week-old) than adult (12-week-old) fludes. Significant (p<0·005) reductions in worm burdens were obtained only following treatment of adult flukes with 2×10 mg/kg monensin (52·9% efficacy), and of juvenile flukes with 1×10 mg/kg (42·4% efficacy) and 2×10 mg/kg (56·23% efficacy). Monensin administered in the diet (200 ppm) had a negligible effect on juvenile and adult fluke burdens. Prophylactic treatment of rats with monensin (100 ppm) produced a 45·5% efficacy, but this was not statistically significant. At doses of 1×5 mg/kg and 2×2·5 mg/kg, monensin had little effect on egg output by F. hepatica. No clear relationship was established between egg output and worm burden, and so faecal egg counting was not a reliable indicator of fluke burdens in the rat.

The indirect immunofluorescent technique was used to determine the occurrence of IgA, IgM and IgG1 immunoglobulin-containing cells in local intestinal mucosal immune responses to Hymenolepis citelli, H. diminuta and H. microstoma infections in mice. In the intestinal lamina propria of H. citelli and H. diminuta infected mice there was no increase in the mean numbers of immunoglobulin-containing cells when compared with uninfected control mice, but there was in H. microstoma infected mice. The numbers of IgG1 – positive cells in both infected and uninfected mice were very small relative to IgA and IgM immunocytes. The distribution of immunocytes in the lamina propria of infected and uninfected mice was essentially similar and the localization of isotypes in duodenal sections showed no immunoglobulins in the villous epithelial cells. There was also no marked difference between primary and secondary infections indicating that immunoglobulin-containing cells play no major role in functional immunity against hymenolepid infections in the mouse. The presence of IgA and IgM was also demonstrated on the tegument of the tapeworms, although the distribution was patchy and more abundant on H. microstoma than on H. diminuta or H. citelli. The time of appearance of both isotypes was latest on H. citelli.

Gastrothylax crumenifer haemoglobin was isolated, purified, chromatographed, and its molecular weight determined on a calibrated Sephadex G–100 column as well as by sodium dodecyl sulphate by the former and 16 500 by the latter method. The oxygen affinity of the pigment (P50O2) was found to be 6·1 mm Hg at pH 7·4.