Three Jersey bull calves were immunized by subcutaneous injections of sonicated Onchocerca lienalis microfilariae suspended in phosphate buffered saline, and three control animals were injected with medium only. All calves received booster injections 27 days later, and were challenged with live microfilariae 44 days after the booster. Following challenge, only the immunized animals developed an elevated level of circulating eosinophils. When necropsied ten days after challenge there was a 97% reduction in recoveries of microfilariae from immunized animals compared to challenge controls. In human onchocerciasis it is the microfilariae which are the principal cause of pathology, and we believe that studies on O. lienalis in both the natural bovine host and in inbred rodents provide a promising model to investigate immunity to Onchocerca microfilariae.

In lambs under six months of age infected with 10,000 H. contortus third stage larvae two effects were observed as a result of the treatment regimes administered: 1. Reduced adult worm burdens, indicating protection, occurred in the animals treated with combined transfer factor, adult parasitic antigen and precipitated immunoglobulin whereas other treatment combinations produced no significant effects. 2. Defined patterns of histological changes in the abomasa were associated with each treatment and cumulative effects were recognized when combined treatments were given. The responses induced by transfer factor treatment suggest the development of a hypersensitivity reaction outwith the changes seen in primary H. contortus challenge.

The effects of infection with plerocercoids of Spirometra mansonoides on tissue glycogen deposition of rats was determined. Hypophysectomized rats infected for two days had higher liver glycogen concentrations than controls and this effect was greatest after one week. Elevated liver glycogen associated with plerocercoid infection was observed in fed animals both at the beginning and at the end of the light period as well as after an overnight fast. Glycogen phosphorylase (1,4αD glucan: orthophosphate α glucosyltransferase EC 2.4.1.1.) was inhibited but glucose-6-phosphatase (EC 3.1.3.9) was unaffected in the livers of infected hypophysectomized rats. While this effect is similar to actions of both growth hormone and insulin, plerocercoid infection had no influence on glycogen of cardiac or skeletal muscle at any time. Plerocercoid infection had no effect on the glycogen concentration of any tissue of intact rats.

This project investigated the influence of the age and sex of the host and the level of infection with Nematospiroides dubius on the establishment and duration of a primary infection in the jird. It was found that 30 to 35% fewer worms matured in jirds than in mice and that this proportion was unaffected by the level of infection or by the sex of the host. In contrast the age of the jird was found to be critically important in determining the number of adult worms recovered 14 days after infection. Thus, maximum susceptibility to infection was observed when jirds were 18 to 22 days old. In older jirds susceptibility declined until 30 days after birth and thereafter, when approximately 70% of the infective larvae matured (relative to the number of worms maturing in mice).

The duration of a primary infection in jirds was similar in both sexes but was influenced by the level of infection and by the age of the host at infection. Heavier infections (500 larvae) lasted about 10 days longer than low level infections, and expulsion of the parasite occurred even when the host was infected with only five larvae. The duration of a primary infection was markedly prolonged in neonatal jirds, faecal egg counts remaining positive for 54 to 56 days after infection of 12-day-old jirds.

These results supply some further baseline data for future work on the biology of N. dubius in the jird and they provide support for the involvement of immunological processes in the termination of primary infections of this parasite in mature jirds.

Metacestodes of Taenia crassiceps were cultured in laboratory rats and mice, washed in glycine/hydrochloric acid (Gly/Hcl) buffer pH 2·4 and phosphate buffered saline (PBS) pH 7·2 and a soluble extract of the metacestodes (SEM) was prepared from larvae washed in both buffers. The SEM and the original washings were examined for host IgG and a common host antigen (CHA). CHA was present in both the SEM and Washings but IgG only in the washings and, in metacestodes from mice only in the Gly/HCl washings). Metacestodes washed in Gly/HCl were not viable.

Metacestodes were also maintained in vitro in a peptide nutrient agar and 0·9% saline at 37°C and a SEM was prepared from these; metacestodes from mice had neither host IgG nor CHA but those from rats had CHA but not IgG. SEM prepared from ‘normal’ metacestodes showed that the CHA consisted of at least two entities, only one having a common identity with the IgG. These results suggest that molecules of both host IgG and a common host antigen are present on the tegument of these parasites.

The prevalence Angiostrongylus cantonensis, a metastrongylid lungworm of rats, was investigated in three common species of rodents in the Greater Bombay area, namely, Rattus rattus, R. norvegicus and Bandicota bengalensis. In all, 737 R. norvegicus, 100 R. rattus and 100 B. bengalensis were examined and the presence of A. cantonensis infection was noticed in R. norvegicus (1·62%). About 800 slugs (Laevicaulis alte) were examined and were found to harbour third-stage larvae of Angiostrongylus.

In a study of the morphology of the posterior ends of O. tricuspis, it could firstly be recognized that not only the adult females but also the LII to LIV possess five cusps. They have apparently been partly overlooked by microscopic examination because of their appearance in different optical planes.