The lymph system of three amphistome parasites from buffaloes, Gigantocotyle explanatum, Gastrothylax crumenifer and Srivastavaia indica was studied using light microscope histochemistry and electron microscopy. In each case the system comprised a single pair of main longitudinal vessels which gave rise to numerous sub-dividing lateral branches. Although the finer lymph channels associated with most internal systems, they did not penetrate the basement membrane of any organ. The lymph vessels were delimited by a unit membrane and separated from adjacent cells by interstitial material. The lymph fluid consisted of an amorphous proteinaceous, lipid-rich matrix, containing naked nuclei and granules of various sizes. Complexes of endoplasmic reticulum were frequently associated with the nuclei. No distinct Golgi bodies or mitochondria were evident. The granules noted throughout the lymph morphologically resembled autophagosomes and lysosomes. Autophagy within the lymph system presumably mobilizes amino acids for subsequent transport to tissues undergoing active protein synthesis. The lymph channels displayed an intimate relationship with the general parenchyma. In particular, numerous protrusions of lymph occurred into the cytoplasm of certain specialized parenchymal cells surrounding the pharynx. Within these ‘juxtapharyńigeal’ cells autophagic degradation of sequestered lymph cytoplasm apparently occurred. In the three species of amphistome studied, the lymph system appears to function in storage and mobilization of amino acids and possibly lipids. It may also serve to distribute other small molecules throughout the body. The detection of haemoglobin in the lymph system of G. crumenifer and S. indica, but not in Gigantocotyle explanatum, suggests a further role in oxygen storage and transport.

The susceptibility of various mammals to infection with Fasciolopsis buski has been studied. Mice, rats, monkeys and dogs were completely refractory. Guinea-pigs were only partially susceptible. However, young rabbits (6 to 8 weeks old) were found to be susceptible and can be used as an animal model for experimental work on this parasite.

The comparative efficiency of the percutaneous and per-oral routes of infection was studied in goats experimentally infected with Schistosoma bovis. The heaviest infection was obtained by the percutaneous route, but a relatively high parasite load was also achieved by the per-oral route, i.e., where goats were allowed to drink a cercarial suspension, volume of 0·9 to 1·7 litre per animal. Studies using radio-isotopically labelled cercariae were designed to clarify the cercarial penetration sites following uptake by drinking. Radioactivity could be demonstrated in the outer lips, buccal cavity, oesophagus and the reticulum, omasum and rumen. Highest counts were recorded in outer lips, reticulum and rumen constituting 41·2, 22·1 and 20·6%, respectively, of total radioactivity recovered. It is concluded that the per-oral infection route may play a larger role than hitherto anticipated in infection of ruminants, and possibly also in other mammals, with schistosomes. The epidemiological implications of the present findings are discussed.

The in vivo efficacy and ultrastructural effects of mitomycin C were determined against alveolar hydatid disease in experimentally infected animals and compared to mebendazole treatment. Mitomycin C inhibited tne mean cyst mass of treated versus control animals by 84·1% which was statistically significant at the α=0·01 level. Mebendazole given daily inhibited the mean cyst mass by 80·1%, while mebendazole administration on the same treatment schedule as that used for mitomycin C inhibited the mean cyst mass by 74·4% Ultrastructurally, mitomycin C was not observed to affect the tegumental microtriches (microvilli) or ine microtubular system. However, an increase in the number and accumulation of round to oval electronaense vesicles was observed within the subtegument. These inclusion bodies became vacuolated, osequently degenerated, and formed myelin-like figures. Mitomycin C, like mebendazole, was only cystistatic in its effects on the cyst stage of Echinococcus multilocularis as evidenced by the growth of treated cyst material following inoculation into helminth-free animals.

Chemotaxonomic patterns in the distribution of amino acids of Hymenolepis palmarum (Jouri, 1956) and other hymenolepidids revealed the common presence of β-aminoisobutyric acid, lysine, phcnylalaninc and tyrosine but 3,4 dihydroxyphenylalanine and norleucine were exclusive to H. palmarum. Both qualitative and quantitative differences in amino acids have been recorded.

Infective larvae of Bunostomum trigonocephalum exposed to gamma-irradiation at 60 kr failed to develop in the lamb. At levels of 20 and 40 kr, the infectivity of the larvae was reduced and fewer worms developed with a predominating female population. The worms developing from the irradiated larvae were smaller and the sex organs were ill developed. The females developing from larave irradiated at 40kr were functionally sterile with atrophied uterus devoid of eggs.

A number of in vitro culture systems were tested for their ability to support the development of Dirofilaria immitis infective larvae to the fourth larval stage. In cultures of medium ML-15 containing a feeder layer of Dog Sarcoma (DS) cells larvae successfully moulted and showed a small but significant increase in length. Ultrastructural observations demonstrated that the fourth-stage cuticle was synthesized in vitro and in some larvae was fully formed by 60 hours of culture. The hypodermis of moulting larvae contained numerous multi-vesicular bodies. It is concluded that the moult in vitro is a true moult and not an atypical response of the larvae to the conditions of culture.

Three sheep were vaccinated with two doses of 3 Krad-irradiated cryopreserved Schistosoma bovis schistosomula containing 20,000 and 17,000 organisms respectively, injected intramusculary 23 days apart after storage in liquid nitrogen for between 9 and 46 days. A challenge of 5360 S. bovis cercariae was administered percutaneously approximately four weeks after the last vaccine dose to these animals and to three controls. Post-challenge the vaccinated animals gained significantly more weight (27%v.9%), produceed fewer eggs in their facces, showed a smaller reduction in PCV values (–18%v, –27%) and were over-all in better condition than control animals . At perfusion 49·1% fewer adult worms were found in the vaccinated sheep than in controls. The tissue egg burdens were similar in both groups. Histopathologically both groups were similar except that fewer and smaller egg lesions were observed in the livers of vaccinated animals.

Twenty-one mice were injected intramusclarly with 2000 Schistosoma mansoni schistosomula irradiated at 20 Krad and cryopreserved; three mice were killed on each of days 0, 2, 5, 9, 19, 28 and 44 days after infection and muscle from the site of injection in the left hind leg, the lungs and livers removed for histological examination. Schistosomula were seen in sections from the leg muscle from days 0 to 19 inclusive, in the lungs from day 2 to day 28 inclusive and in the livers from days 9 to 28 inclusive. Most schistosomula were seen in sections of the leg muscle with considerably fewer parasites occurring in the lungs and especially the livers. Granulomatous reactions comprising cosinophils, polymorphs, plasma cells and macrophages were first seen in the leg muscle on day 2, in the lungs on day 5 and in the liver on day 19. The peak infiammatory reactions appeared to occur between days 5 and 9, 9 and 19 and 28 and 44 respectively in the three tissues. The pathology is discussed in relation to the dose of irradiation required to attenuate the schistosomula for optimal immunogenicity.

Samples of wild rabbits were collected each month over the six-year period 1977–82 and their intestines and abdomens examined for helminths. Three species of nematode, four of cestode and one trematode were found, Graphidium strigosum was recorded in 33% of the 786 rabbits, Trichostrongylus retortaeformis in 79%, Passalurus ambiguus in 14·2% Cittotaenia Pectinata in 37%, C. denticulata in 11%, Coenurus pisiformis in 3%, Cysticercus serialis in 0·1% and Fasciola hepatica in 0·1%. G. strigosum and P. ambiguus infections were greatest in the older heavier animals whereas juvenile rabbits had the heaviest T. retortaeformis nematode burdens. Seasonal fluctuations were observed in G. strigosum, T. retortaeformis, P. ambiguus and Cittotaenia denticulata. The sex and reproductive state of the female rabbit did not have any significant effect on either the nematode or cestode worm burdens. Myxomatosis was shown to significantly increase the worm burden of T. retortaeformis and raise that of P. ambiguus. No nematode or cestode from domesticated animals were recovered and it was concluded that since F. hepatica was found only once rabbits did not constitute a serious hazard to the farm animals grazing the area.

The production of excretory-secretory antigens by encysted muscle larvae of Trichinella spiralis has been investigated immuno-histochemically using an antiserum raised by infection in rabbits and purified both before and after conjugation by ion-exchange chromatography. The specificity of the antibody for excretory-secretory products was demonstrated by the pattern of staining of live worms in vitro and the failure of the labelled antibody to stain dead, non-metabolizing worms. Using this labelled antibody, and unlabelled antibody in the immunoperoxidase system, the presence of parasite antigen-bearing cells in close proximity to encysted muscle larvae has been demonstrated. This is believed to be the first demonstration of antigen production by encysted muscle larvae in vivo. The implications of this observation to current concepts of immunity to Trichinella spiralis are discussed.

Haemonchus longistipes specimens were collected from experimentally infected Sudanese goats and camels for morphological studies. The specimens from goats were much smaller than those from camels, but their infectivity to camels was not affected by their passage in goats. Goats inhabiting the same areas as camels in the Sudan were found to be naturally infected with H. longistipes, but sheep were not and were resistant to experimental infection.

Experiments were carried out to define the haematological changes taking place during the first six weeks of a primary infection with Nematospiroides dubius. The general pattern of changes was observed to comprise a rapid increase in circulating leucocytes (4 to 5-fold increase) which consisted of a neutropl a, lymphocytosis, monocytosis and an eosinophilia. However, in strong responder NIH mice leucocyte counts returned to normal more rapidly than in other strains (by day 28). In contrast, in weak responder C57BL/10 mice the leucocyte counts whilst falling significantly relative to day 7 did not return to normal within the experimental period. Mice infected with irradiated larvae did not experience as high a leucocytosis as did mice given an identical number of normal larvae. The peak lymphocytosis, neutrophilia and monocytosis were all lower. The removal of adult worms from infected animals by treatment with pyrantel on days 9,11,13 and 16, also significantly altered the pattern of leucocytosis. The neutrophilia which was evident on day 7 returned rapidly to normal, whereas in mice which had retained their worms a peak neutrophilia was observed on day 14. These haematological changes were discussed and related to the failure of hostprotective immunity to operate effectively during the early stages of a primary infection with N. dubius.