The efficacy of eight anthelmintics against Ancylostoma caninum larvae in the skeletal muscles of mice was evaluated. Levamisole (5 × 40 mg kg), thiabendazole (5 × 400mg kg), oxfendazole (5 × 100mg kg), albendazole (5× 1OOmg kg), flubendazole (5 × 200 mg kg), benacil (5 × 200 mg kg) and phenacizole (5 × 200mg kg) showed marked larvicidal activity (98 to 99%). Sch 18099 did not show larvicidal activity even at 5×400 mg kg.

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.

From May 1982 until September 1983 samples of soil and herbage were collected from a paddock grazed from May to October 1982, and for two short periods between May and July 1983, by sheep infected with gastro-intestinal nematodes. Few infective larvae were recovered from the soil although appreciable numbers of larvae were recovered from the herbage. Infective larvae of Trichostrongylus vitrinus in faeces buried in the soil of grass plots, at a depth of 10cm, each month from April 1982 until March 1983, migrated on to the herbage at all times of the year, few remaining in the soil. The significance of the soil as a reservoir of infective larvae is discussed.

The cercarial emergence of Schistosoma japonicum from Oncomelania quadrasi was observed under outdoor conditions in Leyte, Philippines. Nocturnal periodicity of the emergence within 24 hours was recognized. Peak emergence usually occurs between 18:00 and 20:00 and occasionally between 8:00 and 10:00. The peaks were usually synchronized with a sudden lowering of water temperature and light intensity and occasionally with their increase. As the nocturnal periodicity of the emergence was observed in the dark and outdoors, it was suggested that emergence might be dependent on temperature, which is secondarily influenced by photoperiodicity and light intensity.

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.

The fourth-stage larvae and adults of Ascaris suum were studied as they developed in the pig intestine from 11 to 22 days after infection. This is a period of rapid growth, in which both sexes increase approximately ten-fold in body length. Further examination of females showed the length increase to be positively allometric with respect to body diameter. The genital primordium in early fourth stage is at the same relative position along the length of the body as it is in the newly hatched larva. During development from fourth stage to adulthood the greater growth of the posterior part of the worm causes the relative position of the developing vulva to shift anteriad.

Mice, CBA/HT6T6 and C57BL/10, were vaccinated with 1 × 350 or 1 × 500 Schistosoma mansoni cercariae or schistosomula attenuated with 20 or 56 krad 60Co irradiation and challenged with 200 cercariae. Protective resistance against homologous strain challenge was compared using the Winches Farm Field Station (WFFS) and Naval Medical Research Institute (NMRI) strains of S. mansoni. Maximal resistance to challenge was obtained in both strains of mice with cercariae or schistosomula of either WFFS or NMRI strain attenuated with 20 krad. Protection using organisms attenuated with 56 krad was significantly lower. Since previous studies with the two parasite strains have shown that the biological effects of irradiation are similar, the difference in the immunogenicity of the 56 krad-irradiated NMRI strain in this study from earlier studies must be due either to different local conditions for irradiation or to adaptation of the NMRI strain to a new laboratory environment. This finding may have important implications for vaccination studies and investigations of the mechanisms of immunity where radiation-attenuated parasites are used.

Eosinophil infiltrations were observed in the intestine and the muscle of both Trichinella spiralis-infected (WBxC57BL/6)F1-W/Wv mice and their littermates, WBB6F1−+/+, +/W, +/Wv, almost to the same extent. W/Wv mice did not show infiltration of subepithelial mast cells and globule leucocytes in response to T. spiralis infection. Increased numbers of these cells were observed in their littermates. Worms in W/Wv mice were retained for longer periods than those in littermates. Also, no difference was noted in the production of specific serum antibodies between W/Wv mice and their littermates, as determined by passive cutaneous anaphylaxis (PCA) for specific IgE and by indirect haemagglutination (IHA). These results suggest a possible participation of SMC, GL and eosinophils in the expulsion of adult T. spiralis.

The response of hamsters to Ancylostoma ceylanicum was studied between days 13 and 200 after infection. The infected hamsters showed signs of anaemia, particularly between the 13th and 60th days. A significant loss in body-weight in the infected animals was also observed during this period. Serological studies with agar gel-diffusion, counterimmunoclectrophoresis and indirect hacmagglutination tests revealed positive reac tions between the 20th and 60th days followed by a negative response in the latent period between the 60th and 200th days of infection, counterimmunoclectrophoresis test remained positive for a period of 150 days in this experimental model.

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.

Toxocara canis larvae were cultured in vitro in medium containing [35S-]methionine for six days. The medium and the larval tissues were analysed for biosynthetically labelled polypcptides by sodium dodecyl sulphate polyacrylamide gel electrophoresis and autoradiography. Immunoprecipitates with positive and negative human antiserum were similarly analysed, using Staphylococcus aureus to absorb immunocom plexes. The larvae secrete biosynthctically labelled polypeptides into the medium, with three major polypcptides of molecular weights between 99 and 110 x 103 the major constituents. Both of these react strongly with human IgG in human positive scra. Many polypeptidcs become labelled in the larval tissue, but only one polypeptidc with similar molecular weight to the ES antigens, strongly reacted with human IgG.

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.

Snails, provisionally identified as Bulinus tropicus, on the basis of chromosome number, egg protein profile, AcP and 118DH enzymes of the digestive gland, and radular morphology, from Lochinvar National Park, Zambia have been demonstrated to transmit Schistosoma margrebowiei naturally. The identification of the unpaired male schistosomcs was confirmed by PGM and AcP analyses. The observations confirm earlier epidemiological predictions, and add another species of mollusc to the two, B. forskalii and B. scalaris, known to be natural intermediate hosts of S. margrebowiei.

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.

Pylorus and bile-duct restrictions did not prevent the anteriad migration of Hymenolepis diminuta in rat small intestine after food feeding. However, migration was inhibited when the common bile-duct was occluded. The results indicate that pancreatic secretion is the migratory cue for Hymenolepis diminuta in rats.

Fifty-five warthogs [Phacochoerus aethiopicus (Suidae: Artiodactyla)] from the Kruger National Park, Republic of South Africa, were examined for parasites. Adult filarial nematodes were found in lymphatic vessels adjacent to peripheral and visceral lymph nodes, and microfilariae were found in lymph nodes and circulating blood. Both the adult parasite and the microfilaria are described. Specific identification is pending confirmation and recovery of intact adult specimens and microfilariae identical to those described herein.