Mice infected with Nematospiroides dubius show non-specific immunodeprcssion (NSID) of immune responses to concurrently administered antigens. This project investigated the factors influencing the response of oxazolone (T-dcpcndcnt antigen) and LPS (T-indcpcndent antigen) in infected mice. Depressed responses to both antigens were observed in mice infected with N. dubius, although the pattern of immunodeprcssion was influenced by both the level and the relative timing of infection and antigen presentation. Consistent NSID was only achieved when the mice were given the higher levels of infection and there was some evidence that NSID was more severe when infection preceded the administration of antigen by 14 days.In general, although NSID was significant, the degree of immunodepression was not considerable. It was concluded that the underlying mechanism of NSID was likely to be different from that enabling the parasite to survive in the intestine of the chronically infected host, and that altered physiology and host's modulation of the immune responses in heavily infected animals may have given rise to a general weakening of the immune system. It was suggested that future work should investigate NSID and parasitespecific immunodeprcssion locally in the intestine where parasite survival is likely to be determined by events at the nnicosal surface.

TPase and SDII activities were studied in various tissues of Ceylonocotyle scoliocoelium maintained in vitro in medium A for 15 days, using standard histochemical techniques. Results were compared with the normal activities of these enzymes in the tissues of worms freshly collected. Low ATPase and SDH enzyme activities in the tissues of cultured flukes indicated their low metabolic rate. Intensity of enzymatic reactions was also found to be tissue specific. The suitability of culture medium ‘A’ for the in vitro cultivation of amphistomes is discussed.

A new fasciolicide, triclabendazole, tested at single oral dose rates of 5 and lOmg/kg body-weight, proved to be highly effective (>99%) against chronic field infections of Fasciola hepatica and F. gigantica in sheep. The Performance of the new drug compared favourably with niclofolan at the recommended dose. Neither product was effective against Dicrocoelium dendriticum and Paramphistomum spp.

Elevated serum lipids are associated with infections of laboratory rodents with plerocercoids of Spirometra mansonoides. The effect of infection with these larval tapeworms on triglyceride degradation and hepatic de novo fatty acid synthesis was investigated in Syrian hamsters. Serum lipoprotein electrophoresis revealed a consistent elevation in very low density lipoproteins in the infected animals. Lipoprotein lipase activity was enhanced in the infected animals. After seven days of plerocercoid infection the activity of acetyl-CoA carboxylase (E.C. 6.4.1.2) was significantly elevated after 6,12 and 18 hours of fasting. Fatty acid synthetase was significantly increased after 0,6,12,18 and 24 hours of fasting. Therefore, a chronic insulin-like activity on lipid metabolism of hamsters is associated with plerocercoid infection.

The host-parasite interaction at the site of attachment of the adult hookworm, Ancylostoma ceylanicum, to the small bowel mucosa of the dog has been examined by transmission electron microscopy. The lamina propria around the heads of the worms showed intense infiltration with neutrophilic and cosinophilic leucocytes, and plasma cells were also prominent. Erythrocytcs were cxtravasatcd within the lamina propria while the portions of mucosa engulfed into the buccal cavities of the worms were nccrotic and included aggregates of collagen fibres. Within the lumina of the worms were erythrocytcs in varying stages of lysis together with other nccrotic debris.The mucous membrane adjacent to the heads of the worms was ulcerated while more distant cntcrocytcs were small, distorted and displayed various degrees of microvillar loss. Many mucosal blood vessels had platelet aggregates within their iumina but no fibrin deposition was observed. Vessels were often seen in the bases of the ulcers and were prone to rupture. Erythrocytcs and leucocytes were seen in the dog intestinal lumen in close proximity to the bodies of the worms.

Extracts of Dirofilaria immitis adults and microfilariae cause the dcgranulation of mast cells in rat mesentery when applied in vitro and also cause increased vascular permeability in guinea-pigs and rabbits. Adult worms DUt not microfilariac are able to activate complement in vitro and both stages contain a plasminogen activator. No protcolytic activity or hacmolysins could be detected in cither stage. The possibility that these factors may be important in the pathogencsis of dirofilariasis and in the adverse drug reactions that may follow treatment of microfilaraemic animals with dicthylcarbamazine is discussed.

The microfilarial level in the peripheral blood of Mastomys natalensis infected with the filarial parasites, Litomosoides carinii, Brugia pahangi, B. malayi and Dipetalonema viteae was monitored at two-hour intervals for 24 hours. The microfilariae of B. pahangi and B. malayi exhibited nocturnal and diurnal subperiodicity, respectively; no such periodicty was seen in L. carinii and D. viteae infections.

The level of B. pahangi and D. viteae microfilariae in peripheral blood was significantly increased when the host was anaesthetized with diethylether or pentothal sodium. Ether-induced anaesthesia had no effect on tne level of B. malayi microfilariae but pentothal was most effective. The peripheral blood count of L. carinii microfilariae tended to decrease in the anaesthetized animals but the reduction was not statistically significant.

New host and geographical records and new morphological data are reported on three monogeneans: Encotyllabe spari YAMAGUTI, 1934, Choricotyle hysteroncha (FUJII, 1944) and Pseudotagia cupida (HARGIS, 1956).

The establishment, growth, survival and distribution ol Hymenolepis muris-sylvaticae m different laboratory animals (Wistar rats, golden hamsters, CFLP and NMRI mice) after oral infection and surgical transplantation were determined.

Worms that establish in CFLP and NMRI mice grow exponentially but are rejected at different times p.i. depending on the strain of mice and mode of infection. Only in golden hamsters will H. muris-sylvaticae develop to a mature worm; in rats there is no growth at all. Worms of all sizes are found in the posterior half of the small intestine in rats and both strains of mice; in hamsters the worms are recovered more anteriorly.

Counter current Immunoelectrophoresis was used to detect porcine cysticcrcosis and water soluble extracts of scolex and of scolex with cyst wall were used as antigens. Serum samples from 40 pigs infected with Cysticercus cellulosae, five infected with C. tenuicollis and five with hydatid cysts, and 15 healthy pigs were tested. A sharp and thick concave precipitin band was observed at the point of interaction of antigen and antibody within 90min in 39 sera from infected pigs (97–5%). The precipitin reaction was better in barbitone buffer of pH 8–6 with the well distance at 6 mm. No false or cross reaction were found and the test was rapid and sensitive.

Of the 2,652 Lymnaea truncatula collected from sites in Cumbria and Gwynedd during 1973–75, when the Prevalence of fascioliasis in the primary host was low and declining, only 123 were infected with Fasciola hepatica. Dissection of these snails revealed that the proportion infected, the mean redial burden and the Proportion of mature rediae in each snail increased with shell length.

The results are compared with a similar data set acquired when the prevalence of infection in both the Primary and intermediate hosts was uncharacteristically high. Although the results are qualitatively similar, there are important quantitative differences. The mean redial burden of infected snails at times of high disease Prevalence was generally twice as high as that reported in the present study. It is suggested that differences in habitat microclimate could not account entirely for the observed differences in redial burden and the role of multiple miracidial infection is discussed.

Twelve amino acids were detected in six davaincid ecstodes, Davainea hewetensis Dhawan & Capoor (1972) collected from one Gallus gallus domesticus L. at Allahabad, India. Chemotaxonomic studies within the family Davaineidac have shown the presence of cystine and hydroxyproline only in D. hewetensis, although phenylalanine and proline occur in all species examined previously.

Acquired immunity to Nematospiroidcs dubius was studied in the jird. It was found that a primary infection comprising one or two worms was highly immunogenic and the animals were resistant to challenge infection. Abbreviated infections in which the adult worms were eliminated by treatment with pyrantel also elicited strong resistance to challenge indicating that larval parasites as well as adults were involved in acquired immunity. A small proportion of adult worms completed their development in immune jirds and was recovered 11 days after the challenge infection. However, these worms were rapidly eliminated and few survived to day 16. Trickle infections in which the jirds were exposed to very low numbers of worms at regular intervals were unsuccessful in prolonging the duration of a primary infection. It was concluded that the remarkable sensitivity of the jird to infection with N. dubius should enable small quantities of fractionated parasite derived material to be screened for immunogenicity in this host.

Three adult male greyhounds have been repeatedly infected with Toxocara canis by oral administration of 100 to 200 infective ova. Each infection has become patent as shown by the presence of eggs in faeces. Anthelmintic treatment between 7 and 14 weeks after infection yielded an average of 25% of the inoculum as adult worms. These dogs have continued to be fully susceptible to infection despite repeated exposure to this parasite, and despite the presence of scrum antibody to both parasite surface and secreted antigens. These findings imply that adult dogs may not always be immune to toxocaral infection and may therefore contribute significantly to the problem of environmental contamination with T. canis ova.

To test the ability of cells and/or serum from jirds (Meriones unguiculatus) infected with Litomosoides carinii to transfer the ability to retard development of challenge larvae, a series of transfer experiments were done. Groups of jirds received larval challenge preceded by one of eight preparations: spleen cells and/or serum from 10-day-patent infected jirds; normal spleen cells and/or normal serum; primary larvae; challenge larvae only.

No significant differences in size or numbers of larvae recovered were found among groups receiving either cells or serum only. However, significant differences in larval size were found between groups receiving both cells and serum from infected donors and those receiving normal cells and serum. These comparisons indicate that the ability of infected jirds to retard development of challenge infection larvae can be transferred with cells and serum together but not separately.

Cotugnia digonopora consumes, in 24 hours, glucose equivalent to 38% of its body-weight and converts it into metabolites. The Krebs' cycle is insignificant in the breakdown of glucose because very little CO2 is formed. Ether-cxtractablc acids account for most of the consumed sugar, confirming that metabolism is predominantly anaerobic. Glucose is assimilated as glycogen rather than as nucleic acids, lipids and proteins.

Niclosamidc, praziquantel and mebendazole strongly inhibit uptake of glucose by the parasite. A considerable increase in the production of lactic acid over that of ether-soluble and volatile acids under the influence of these drugs, suggests a rhange in the catabolism of sugar towards homolactate fermentation.