This study compares the morphology, anatomy, physiology and histochemical distribution of two key enzymes (AcPase and ATPase) in the intestinal trematode Ganeo tigrinum recovered from hibernating and non-hibernating Rana cyanophlyctis and R. tigrina. It has been shown that the torpid state of the host influences its worm so severely that it produces untanned and low quality eggs, the sperm population falls, the rate of worm infection is decreased and the worms do not grow.

AcPase has been shown to undergo significant changes during hibernation, especially in the gut, where extraordinarily high activity seems to be responsible for the autophagy of certain gastrodermal cells. ATPase similarly reveals a decrease in activity in most of the parasite tissues during hibernation. However, its high activity in the parenchyma has been related to the quick transportation of metabolites, representing the threshold concentration necessary for survival and egg production.

Parasitological and clinico-pathological aspects of Schistosoma intercalatum infection in sheep were studied after exposure to 5000 cercariae per animal. It was shown that the infection, in spite of relatively high tissue egg counts, only gave rise to low-grade clinico-pathological manifestations with almost unaffected blood parameters. The parasites were mainly located in the lower part of the intestinal tract, and the number of eggs being passed in faeces was very low.

Homogenates of the metacercariae of Clinostomum complanatum showed two peaks for the hydrolysis of p-nitrophenyl phosphate at pH 4·5–5·0 and 11·0; specific activity at pH 5·0 was 0·017 µmol p-nitrophenol/mg protein/min and 0·0049 µmol p-nitrophenol/mg protein/min at pH 11·0 at 37°C. Maximal activities of acid and alkaline phosphatases were observed at 50° and 40°C respectively. Both enzymes reached maximal rates after 50 min of incubation. Linearity in enzyme activity was noticed with increasing homogenate concentrations for both enzymes. The Km for p-nitrophenyl phosphate was 1·1 mM with a Vmax of 0·018 units/mg protein for acid phosphatase and 1·6 mM with a Vmax of 0·0052 units/mg protein for alkaline phosphatase. Sodium arsenate and sodium fluoride inhibit and Mg++ and Co++ stimulate both enzymes. Polyacrylamide gel electrophoresis showed one cathodic band each for both the enzymes.

Infection of a dog with Strongyloides stercoralis filariform larvae resulted in a persistent infection. Patent infections were not seen in rabbits, guinea-pigs, rats and 11 inbred strains and one outbred strain of mice. Manipulation of factors known to influence S. ratti infections in mice, such as age and sex of the host and the route of larval presentation, did not facilitate the appearance of rhabditiform larvae in the stools. Administration of immunosuppressive doses of corticosterioids to rabbits, guinea-pigs and C57B1/6 mice did not permit complete development. Similarly, the course of infection was not altered in T cell-deficient hypothymic (nu/nu) mice. The fate of filariform larvae applied to the skin of mice was ascertained; filariform larvae were observed to migrate from the skin via the lungs to the muscles within several days of infection. Although S. stercoralis does not develop to maturity in the small intestine of mice, this system does allow in vivo studies of the actions of anthelmintics against filariform larvae as well as a number of aspects of the immune response to this parasite.

Resistance to challenge infection with Trichostrongylus colubriformis was studied in an outbred strain of guinea-pigs. Resistance was conferred by previous infections of 50 or 100 infective larvae and by intraperitoneal, intramuscular and subcutaneous administration of dialysed transfer factor prepared from guinea-pigs infected with T. colubriformis, by intraperitoneal administration of transfer factor prepared from the blood of sheep infected with T. colubriformis and on one of three occasions using transfer factor prepared from guinea-pigs which had not been infected with T. colubriformis. No significant resistance was transferred by administration of antigen prepared from adult T. colubriformis, or by non-dialysed transfer factor, or by dialysed transfer factor prepared from T. colubriformis-infected guinea-pig tissue which had been stored for several months at −20°C.

Mature hens were induced to moult and were subsequently found to be resistant to both primary and secondary infections of Raillietina cesticillus, whereas non-moulting birds that continued to lay were susceptible to primary and secondary infections.

The migration of infective larvae of Strongyloides ratti has been examined in C57B1/6 mice after percutaneous infection of the anterior abdominal wall. Lateral migration of larvae through the skin and subcutaneous tissues was not seen. Large numbers of larvae were recovered from the muscles between 2 and 24 hours after infection and larvae were seen in the cerebrospinal fluid 24 and 48 hours after infection. Insignificant numbers of larvae were seen in the blood, serosal cavities, liver, spleen, kidneys, brain or nasopharynx. Larvae arrived in the lungs between 24 and 72 hours after infection and worms were first noted in the small intestines at 48 hours. It is concluded that larvae migrate preferentially to the muscles and CSF before passing to the lungs, but the exact mode of travel is uncertain.

The presence of vitelline cells in male Schistosoma mansoni from both mixed and single sex infections in mice is described.

Ultrastructurally these vitelline cells resemble the mature, Stage 4 cells from normal female worms. As yet no developing vitelline cells (Stages 1 to 3) have been found. The cells do not appear to form complete lobules as in the female.

Laboratory ferrets (Mustela putorius furo) were each inoculated with 500 larvae of a strain of Trichinella spiralis that had been passaged in mice for many generations. The recovery of adult worms from ferrets on Days 4 and 7 of infection represented a mean of 32% of the inoculum, with most of the worms being in the anterior three quarters of the small intestine. Larvae subsequently became encysted in the ferret musculature, with the diaphragm alone yielding as many as 5,750 larvae upon digestion.

For comparative purposes, mice were each inoculated with 200 T. spiralis from the same batch of larvae. The recovery of adult worms from mice represented a mean of 54% of the inoculum. An abrupt decline in worm population, typical of infections in the mouse, was observed in both mouse and ferret hosts; in neither species had the decline begun on Day 7 of infection, but it had clearly begun by Day 11 and was essentially ended by Day 14.

The gross morphology and histological and cytological architecture of the lymph system of Orthocoelium scoliocoelium were studied. Each main vessel, near the intestinal bifurcation forms a spindle-shaped sinus. Lymphocytes, similar to the primitive blood cells, have been seen to form aggregates in certain regions of the lymph system. In addition, detailed histochemical observations were made on the localization and distribution pattern of various phosphatases, esterases and dehydrogenases. It is suggested that the lymph system, in addition to the functions already known, may also selectively reabsorb certain important outgoing higher fatty acids from the excretory system. Furthermore, the lymphocytes may also be involved in the defence mechanism of the worm. The nature and function of fine granules in the lymph remain speculative.

Infective larvae of Wuchereria, Brugia, Breinlia, Dirofilaria and Setaria species from an experimental vector, Aedes togoi, are compared. The distinctive bubble-like caudal papillae of Wuchereria bancrofti are readily distinguishable from the protuberant ones of Brugia spp; the ‘ear-like’ papillae of Breinlia are distinct from the ‘knob-like’ ones of Dirofilaria or the ‘thorn-like’ terminal papilla of Setaria.