On the basis of esterase localization the complete nervous system has been visualized in Olveria indica Thapar & Sinha, 1945, a paramphistome from the rumen of cattle, recorded for the first time from the north-east region of India. The basic number of posterior longitudinal nerves (i.e., 3 pairs) is the same as in other paramphistomes; four pairs of anterior longitudinal nerves are present, there being an extra pair of pharyngeal nerves. Conspicuous differences in the innervation patterns were observed, mainly in the innervation of the genital atrial region and acetabulum. The presence of prominent longitudinal connections, joining the anterior and posterior dorsal nerves and the anterior and posterior ventral nerves on either side, is a feature not hitherto found in other paramphistome species. The details of the course of all the nerves and their branches are discussed.

The hydrolysis of various oligopeptides in solution by intact Moniliformis moniliformis was examined using paper chromatographic analysis of the incubation medium. In the presence of transport inhibitors, the respective peptide sub-units and/or amino acid residues accumulated in the bathing medium. Only peptides with serine, methionine, leucine or alanine at the NH2-terminal end of the peptide were hydrolysed. There was no hydrolysis when these amino acids were located internally or at the COOH-terminus indicating genuine aminopeptidase activity of the class, α-aminoacylpeptide hydrolase. Hydrolysis was negligible when the NH2-terminus was arginie, aspartic acid, glutamic acid, glutamic acid, glycine, histidine, lysine, phenylalanine, proline, tryptophan, tyrosine, or valine. In separate experiments, mediated uptake of 0.1 mM3H-leucine by the worms in 2 min was inhibited 100% by 5 mM unlabelled leucine or tri-serine, but only partially inhibited by 5 mM Ser-Gly (66%), 10 mM Ser-Gly (74%), 5 mM Leu-Leu (69%), 10 mM Leu-Leu (70%), 5 mM Leu-Gly (58%) or 5nM Met-Met (69%). Bacause the inhibitions produced by 5 mM Leu-Leu plus 5 mM Met-Met (79%) or 5 mM Leu-Leu plus 5 mM Ser-Gly (76%) were not additive, a single enzyme is indicated. The name serine aminopeptidase is proposed because of its preference for serine.

The pathogenesis of unirradiated, 3 krad-irradiated and 20 krad-irradiated metacercarial infections was compared in zebu calves studied over a 10-week period. Calves exposed to 1000 unirradiated metacercariae (mc) became hypoalbuminaemic, and showed elevated serum concentrations of liver enzymes, whereas neither of the other groups was significantly affected. At slaughter, a mean of 332 flukes was recovered from the 0 krad group, while only 23% and 12% of this number were recovered from the 3 krad and 20 krad groups, respectively. All the worms recovered from the 20 krad group were stunted, and found in biliary ductules, but a mean of 13% of the flukes recovered from the 3 krad group were large, and dwelling in main bile-ducts. Liver lesions typical of acute fascioliasis were present in the 0 krad group, but lesions in the other groups, and particularly the 20 krad group, were far less severe. Judged on clinico-pathological criteria, a single vaccination of calves with 1000 3 krad-irradiated mc induced partial resistance to a challenge with 1000 normal mc eight weeks later, but the reduction in worm recovery was not statistically significant. There was less evidence of protection when two vaccinating doses of 3 krad mc were given within four weeks, with challenge at week 8, and a single vaccination was ineffective aganist a challenge four weeks later. However, when the irradiation dose was increased to 20 krad, a high level of resistance (69% worm reduction) was induced by a single vaccination, given eight weeks before challenge, and liver pathology was strikingly reduced in the vaccinated animals.

Evidence has been presented showing two kinds of acidic protease activities in adult Schistosoma mansoni, Dirofilaria immitis, Angiostrongylus cantonensis and Ascaris suum. A haemoglobinolytic activity without adding any SH-containing compounds was maximal at pH 3.5, 2.5, 30 and 3.5 in S. mansoni, D. immitis, Angiostrongylus cantonensis and Ascaris suum respectively. The inhibitor studies demonstrated that this activity is ascribable to carboxyl protease(s). In the presence of dithiothreitol, activity on Azocoll (azo-dye coupled hide powder) was maximal at pH 4.6, 4.6, 3.5 and 5.6 in S. mansoni, D. immitis, Angiostrongylus cantonensis and Ascaris suum respectively. The effects of inhibitors demonstrated that this activity belongs to the thiol protease class. The intraspecific distribution of the protease activities was studied in some of the nematodes from which the organs could be anatomically separated. The distribution patterns of the haemoglobinolytic and azocollytic activities were quite different in An. cantonensis and much the same in As. suum. Based on the present results, acidic haemoglobinolytic activities reported in adult S. mansoni by other authors are thought to be due to carboxyl and thiol protease(s) respectively.

Although lightly homogenized three-week-old Schistosoma mansoni incubated in Mistuhashi and Maramorosch insect tissue culture medium or the medium of Weller and Wheeldon produced adherent cell layers, continued growth of these cells did not occur. Non-adherent cells obtained by trypsinization also failed to produce long term cell cultures even after the addition of a range of growth factors. The possibility of producing tumour-like schistosome cells by the use of the mutagen ethyl methane sulphonate was therefore examined. Four-hour exposure of three-week-old schistosomes caused in some worms (a) large fluid filled ‘ballooning’, which also occurred in adult males, (b) enlargement of the gut, (c) increase in numbers of large round cells within the worms and (d) tissus outgrowths. It is suggested that these effects of mutagen offer new approaches to obtaining permanent schistosome cell cultures.

The life-cycle of Syphacia muris is described in primary infections of Wistar rats. The life-cycle of S. muris is completed within seven days and no moults were discovered inside the egg. Instead each of two moults were observed outside the egg up to 24 and 40 hours after infection, and TEM studies suggest a third moult occurs up to 64 hours. The development and maturation of the larval stages are described for the first time using both light and electron microscopy. Differences in the size and growth of female S. muris compared with previously published figures could be due to differences in the strains of rats used.

The biochemistry and histochemistry of Pegosomum egretti have been studied using standard techniques. Phosphatases were analysed colorimetrically; the optimum pH for acid phosphatase activity was 5·0 and for alkaline phosphatase was 10·0. The results were compared with those of other trematodes. Histochemical localization of acid and alkaline phosphatases revealed differences in enzyme activity in various tissues. These differences in the site and pattern of distribution of the two enzymes have been discussed in relation to transport of raw materials and the metabolism of the cell concerned.

In the Tambool area (Central eastern Sudan) a survey was made of the infection rate of Echinococcus granulosus in dogs. From the total of 49 dogs shot by the police authority, 25 (51%) had E. granulosus in their intestines. The range of worm recovery was 7 to 28,400. These high infection and recovery rates could be explained by the rate of infection in the intermediate host (camel) slaughtered in the area.

Cytochemical localization of the enzyme phenol oxidase in Neomurraytrema tengra has been studied. Results reveal that the enzyme reacts with substrates such as catechol, hydroquinone, pyrogallol, dopa, doparmine, epinephrine and tyramine, but not with tyrosine and protocatechuic acid. Thus it shows activity with a wide range of phenols, aminated, mono and diphenols and also with deaminated and decarboxylated, di- and polyphenols. The maximum activity of the enzyme occurs between 40°C and 50°C with a pH optimum of 6–6.

Haematological, biochemical and pathological changes were investigated in 214 sheep naturally infected with Fasciola gigantica in an endemic area in the Sudan together with 82 uninfected controls. Infected animals showed a clear decrease in erythrocyte counts, haemoglobin concentration and packed cell volume, a normochromic, normocytic anaemia, leucocytosis and eosinophilia. Serum concentrations of the enzymes glutamate dehydrogenase, sorbitol dehydrogenase and glutamate oxaloacetic acid transaminase were also elevated in the infected group, indicating hepatic damage. This was confirmed by histopathological changes, which comprised degenerative and necrotic changes in hepatocytes associated with haemorrhage, fibrosis, increased lobulation of the liver, mononuclear cell infiltration with haemosiderin deposition in fluke tracks and portal areas and the formation of granulomata around fluke eggs and fluke remnants. In the infected group there was slight hyperglobulinaemia and a marked hypoalbuminaemia, with a decrease in A/G ratio. A slight rise in the level of serum bilirubin was also observed.

A schistosome infection, cf Gigantobilharzia sp., is recorded from a South African coastal bird, Larus dominicanus, for the first time. The histological response to the presence of the worms and their eggs was considered to be unusually mild. These eggs were all immature and were found only in the mucosa of the gut wall. This raises questions about the oviposition behaviour of the female worm.

The development of Trichobilharzia australis Blair & Islam, 1983 in the intermediate host, Lymnaea lessoni Deshayes and in experimental definitive hosts, Muscovy ducks is described, 24 hours after entry into the snail, miracidia had lost their cilia, epidermal plates and lateral processes and became young mother sporocysts. They were located in the tissues of the head-foot organ of the snail and were oval in cross section but still retained the shape of a miracidium, and measured 0·058–0·66 × 0·041–0·049 mm. From the seventh day onward young mother sporocyts were tubular, thin-walled, irregular in shape and were in the tissues of the lung and kidney of the snail. On the 24th day mature mother sporocysts and young daughter sporocysts were found in the digestive gland. Between the 24 th and 29th day mature daughter sporocysts with fully developed cercariae ready to emerge, or already emerged, could be seen in the digestive gland of the snail. Cercariae emerged from the snail from the 29th to 46th day after exposure at 25°±1°:C. The prepatent period of T. australis in the Muscovy ducks was 22 to 42 days after the beginning of exposure to cercariae.

The present paper presents the results of an analysis of the inorganic elements detected in Ternidens deminutus from human and baboon hosts. It reports on the presence of Zn, Fe, P, Ca, Cu, Mg, mn and K in the worms and notes especially that worms from humans contained a higher percentage of body weight of Zn than those from baboons, a finding in agreement with an earlier EDAX analysis of the pigment granules of this species.

Using the local strains of Schistosoma bovis and Fasciola gigantica, it was shown that Sudanese zebu calves with mature primary infections of F. gigantica were highly resistant to challenge with S. bovis cercariae, and vice versa. Liver enzyme tests showed that, in both cases, the primary infections had caused some liver damage. Primary infection with irradiated S. Bovis cercariae, which did not cause significant liver damage, did not protect significantly against challenge with F. gigantica.

In different areas of the world, strains of Echinococcus granulosus have been described which appear to vary in their infectivity, and laboratory primates have been used as indicators of their infectivity to man. This phenomenon was evaluated in Kenya for hydatid material of human, camel, cattle, sheep and goat orgin. Viable eggs, produced by experimental infections in dogs with larval material from all the above intermediate hosts, were fed separately to four baboons (Papio cynocephalus) in each case. Baboons were autopsied between 373 and 501 days following infection and the liver, lungs, heart, spleen and kidneys were thoroughly inspected. Hydatid cysts were recovered from two baboons in each of the camel, sheep and goat groups, three baboons in the cattle group and none of the baboons in the human group. Fertile cysts were found in the cattle and goat groups and it is suggested that the baboon could be used as an experimental model for this parasite.

Jirds were vaccinated by three to five subcutaneous (SC) injections of infective larvae of Brugia pahangi which had been irradiated at 25, 45 or 90 krads from a 60Co source. They were challenged either SC or intraperitoneally. Vaccination with four doses of 50 larvae irradiated with 25 krads produced 49·3% resistance to IP challenge worms and 39·8% against SC challenge worms. Five doses of larvae irradiated with 45 krads produced 62% resistance to SC challenge. Three doses of larvae irradiated with 90 krads produced 74·9% resistance to SC challenge and five doses produced 76·2% resistance. The reasons why irradiated larvae produce resistance whereas normal larvae do not are discussed.

The physiological responses of well-nourished rats to primary infection with the intestinal nematode Nippostrongylus brasiliensis were examined. Infected rats fed ad libitum were compared with uninfected control rats fed ad lib. and also with uninfected rats which were pair-fed to the infected rats. Following infection with N. brasiliensis rat food intake was reduced from day 2 post infection (pi) and there were two periods of minimal food intake (day 2 to 3 and 8 to 9 pi). The water intake of infected rats was only reduced on days 2, 3 and 9 pi and not to the same extent as food intake. Muscle catabolism in infected rats was more severe than could be explained on the basis of their food intake reduction. The rectal temperature and rate of oxygen consumption per g body-weight of rats was not significantly altered by the infection. Host responses to N. brasiliensis are compared with those seen in microbial infections and some of them are found to be considerably different.