The percentage composition and spatial distribution of embryogenic stages in the uteri of female Dirofilaria immitis were examined at various times after treatment with a microfilaricidal dose of ivermectin and compared to nontreated parasites. Worms sampled 42 days post-treatment (PT) exhibited an increased proportion of stretched microfilariae in the distal portion of the uterus. A decreased proportion of developed embryos was noted in the mid body region of worms sampled 42 days PT, and these forms were completely absent from the proximal area of the uterus. Relative numbers and spatial distribution of other stages remained virtually identical to controls. Radical changes in the composition and spatial distribution of embryogenic forms were noted in the uteri of a single worm sampled 80 days PT. Unlike nontreated parasites and worms sampled 42 days PT, stretched crofilariae constituted the predominant form in the distal uterus of this worm, and these stages were found in decreasing numbers throughout the proximal segments. Also, the intermediate embryogenic stages were either rare or absent.

The model of Onchocerca lienalis microfilariae (mf) injected into inbred CBA/Ca mice was studied for its usefulness as an additional primary/secondary drug screen for onchocerciasis. Invermectin, DEC, suramin, flubendazole, mebendazole, levamisole, Mel W, furapyrimidone, metrifonate, amoscanate and the new Ciba-Geigy compounds CGP 6140, CGP 20'376 and CGI 17658 all significantly reduced levels of mf at a dose of 5x100 mg/kg or less. An early dosing protocol, on days 3–7 after infection, was found to be generally more effective than dosing on days 11–15, followed by necropsy on day 18. In some cases there were important differences in levels of drug activity depending on whether the drug was administered by the subcutaneous or oral route, indicating that new compounds should be tested via both routes. Ivermectin was by far the most active compound examined, virtually clearing mf from the skin at a dose of 5x0.0063 mg/kg and producing a significant mf reduction (63.5%) at 5x0.008 mg/kg following subcutaneous administration. In comparison, DEC was much less active, producing a 32.4% mf reduction at 5x25 mg/kg ranging up to a maximum of 72% reduction at 5x100 mg/kg. CGI 17658 was the most active compound examined next to ivermectin, almost 100% effective against skin mf at a dose of 5x6.25 mg/kg via the oral route while being less effective via subcutaneous administration (65% reduction). The lowest effective dose examined was 5x3.13 mg/kg (per os) which reduced mf levels by 64%. CGP 20'376 was also very active, resulting in a 46% (subcutaneous) and 62% (per os) reduction at a dose of 5x6.25 mg/kg. This mouse model has clearly identified all the known microfilaricides examined and also, to a lesser extent, those compounds considered to be principally macrofilaricides. We believe it has value as an additional drug screen for onchocerciasis, which will enable the evaluation of novel compounds against skin-dwelling Onchocerca mf at the primary/secondary level, providing complementary information to new in vitro screens using adult Onchocerca.

Use was made of seven FITC labelled lectins as tools to investigate the surface of Onchocerca lienalis larvae as they develop through to the infective third-stage in a natural vector, Simulium ornatum. The lectins were derived from Canavalia ensiformis (Con A), Lens culinaris (lentil), Triticum vulgaris (wheat germ), Arachis hypogaea (peanut), Helix pomatia, Phaseolus vulgaris (kidney bean) and Tetragonolobus purpureus (asparagus pea). Between 70 and 100 living parasites were examined for each developmental stage; i.e. skin microfilariae, late first-stages, second-stages, preinfective third-stages and infective third-stages isolated from the mouth parts of the flies. None of the lectins used bound to the surface of the microfilariae. However, progressive binding to the cuticle of the first- and second-stages was observed using Con. A, lentil lectin and wheat germ agglutinin (WGA). Following moulting to the third-stage, binding of these three lectins declined. Furthermore, as these lectins decreased, peanut and Helix pomatia lectins progressively increased in their binding, despite the fact that they showed little or no binding to the first- and second-stages; stages at which Con A, lentil and WGA were at their maximum. Asparagus pea and kidney bean lectins failed completely to bind to any of the larvae examined. Carbohydrate inhibition tests showed that the lectin was indeed binding specifically to glycoconjugates on the parasite surface. WGA binding was not inhibited by prior incubation with N-acetyl-D-glucosamine, even at high concentrations, but neuraminic acid did completely inhibit its binding. Judging from the patterns of binding on the nematodes themselves, the carbohydrates may not be vector in origin, but derive from the worms. The lectin specificities indicate that initially mannose/glucose type derivatives are present on the surface. Following moulting to the third-stage these are progressively replaced, or overlaid with galactosamine type derivatives, also present on the infective third-stage as it enters the bovine host. The availability of these surface glycoconjugates to attack mediated by natural insect lectins may be of importance in the parasite regulatory mechanisms of the blackfly. Variability in these surface carbohydrates, and in the response to them could well be a contributing factor in the cytospecific variation in S. damnosum susceptibility to geographical variants of O. volvulus.

The possibility of safe immunization of chicks at an appropriate age with a double-dose irradiated Ascaridia galli vaccine given orally at two weeks interval was explored. Chicks immunized at 7 or 10 days of age were not affected adversely since they did not develop any clinical signs and there was no worm establishment after challenge infection. Immunization also elicited detectable circulating antibody titres, with IHA and the conglutinating complement absorption test having a tendency to be enhanced after the booster dose.

Seasonal density fluctuations of Bulinus nasutus populations with accompanying Schistosoma haematobium infection rates in relation to rainfall and habitat water volumes were studied at Ukiriguru, Mwanza, Tanzania. Alongside the snail investigations, 50 school children initially negative for urinary schistosomiasis were examined regularly to determine seasonal incidence rates for the infection. Of the 17 646 B. nasutus collected in 2 years, 156 (0.88%) were found shedding cercariae. Snail populations fluctuated seasonally as influenced by rainfall through its effects on habitat water volume. Monthly snail infection rates ranged from 0.09% to 3.19% and were highest in February and March, at the time of the short dry period. Monthly incidence of S. haematobium in school children ranged between 2.6% and 12.5%, being highest in April and May. There was a significant linear association between monthly snail infection rates and S. haematobium incidence rates in school children ( in 1983/84) suggesting that the maximum transmission period for urinary schistosomiasis in the area occurs during the short dry period, sometime in February/March so that most of the infections in the community would be detected in April/May.

Rhabditis axei, the free living nematode, was detected in the faeces of a chicken maintained in a clean cage in the parasitology laboratory, Zagazig University, Egypt. The source of these worms and the method of their transmission to the laboratory was discussed. The experimental inoculation of 3 chickens with R. axei demonstrated that their survival after passing through the intestine was not possible. Free living nematodes could be confused easily with Strongyloides sp. during routine faecal examination.

Experiments were carried out to explore the survival of 14-day adult H. polygyrus following transplantation to mice of four strains, immunized by various protocols. Adult worm establishment and survival was unimpaired in CFLP mice which were totally refractory to larval challenge. Transplanted adult worms were also successful in NIH mice immunized by the 9-day abbreviated infection regime. However, NIH mice exposed to irradiated larvae or subjected to the divided primary infection, expelled transplanted adults. The 9-day abbreviated infection was further examined in SJL and (C57 Bl10 X NIH) F1 mice which expel adult worms during a primary infection and although this regime was unsuccessful in causing NIH mice to reject adult worms, expulsion of adult worms was accelerated in SJL and F1 mice. The survival of adult H. polygyrus was discussed in the context of stage-specific immunity and the delicate balance between the immunogenic stimuli from developing larvae, the immunomodulatory activities of adult stages and the host's genetically determined capacity to respond to these opposing signals.

Adult trematodes identified as Galactosomum ussuriense Oshmarin, 1963 were recorded from the intestine of Sterna hirundo and Larus brunnicephalus from Visakhapatnam, India. The occurrence of metacercaria of this species in inshore and offshore fishes is discussed in relation to the ecology of the snail intermediate host.

A cysticercus of a possibly undescribed species of Taenia which occurs commonly in Taiwan aborigines was used to establish an experimental infection in a human volunteer. Symptomatic effects attributed to the infection included diarrhoea, upper abdominal pain, and increase or loss of appetite over a four-month period. After an expelled proglottid was observed 122 days post-exposure, eggs and proglottids were found continuously until the patient was treated with anthelmintics. Antibody titres measured by enzyme-linked immunosorbent assay and levels of eosinophilia seemed to correlate with symptoms. Haematological analyses revealed an abnormal lipid metabolism during the entire symptomatic period.

The incidence of haemonchosis in sheep and goats in Sierra Leone showed a seasonal variation with a high peak in the dry season (October to January) and a low one from March to May. Mean relative densities were significantly higher in young hosts and showed two peaks, a high one from August to December and a low one from April to June while the mean relative densities of old hosts were low and exhibited an irregular seasonal pattern with no defined peaks. The peak seasons in young hosts coincided approximately with the dry and rainy seasons. Male hosts showed an overall higher but not a significant mean relative density than females but for most of the months mean relative densities of infection of female hosts were not significantly higher than those of males. The roles of climatic conditions and arrested development (hypobiosis) and self-cure and host age immunity on Haemonchus contortus worm burdens are discussed.

The effect of the immunomodulatory fungal metabolite cyclosporin A (CyA) on the course of Paragonimus miyazakii infection in rats was studied. Administration of CyA 15 to 19 days post-infection resulted in a significantly lower recovery rate of worms and cyst formation in the host's lungs than in controls. Administration of CyA − 1 to + 3 days post-infection enhanced the growth and maturation of P. miyazakii, expressed as weight of worms and the number of worms with eggs in uteri with respect to control values. This study shows that administration of CyA to rats affects the host-parasite relationship, depending on the time of administration of the drug.

The possibility was examined of using a haemoglobinase released during in vitro incubation of adult Fasciola hepatica for immunodiagnosis of fascioliasis. By SDS gel electrophoresis the enzyme appeared as two closely migrating bands with a molecular weight of approximately 27 000 daltons. After Western blotting the bands reacted with serum from rats infected with F. hepatica and mice infected with Schistosoma mansoni. The enzyme was therefore not a good antigen for immunodiagnosis.

A study of larval development of Schistosoma haematobium in the snail Planorbarius metidjensis infected by transplanted sporocysts showed that some embryos in daughter sporocysts have characters intermediate between cercariae and sporocysts. These embryos are interpreted to be nearly mature cercariae that have partially reverted to be secondary sporocysts. If this explanation is correct, it would mean that the embryos which develop within trematode daughter sporocysts can differentiate either into cercariae or into a new generation of sporocysts, but originate from a single type of germinal cell.

The laboratory study of dracunculiasis has suffered from the lack of a suitable, readily available animal model. We have been able to experimentally infect ferrets, Mustela putorius furo, with the North American dracunculid, Dracunculus insignis. Ferrets were inoculated with 75 to 100 infective larvae and were necropsied 90 to 240 days later. Guinea worms were recovered from 10 (56%) of 18 ferrets. A total of 44 worms were recovered, for an average of 4.4 worms per infected ferret. Gravid female worms were recovered as early as 128 days postinoculation. Thirteen (87%) of 15 gravid female worms were recovered from the extremities. Living male worms were recovered at 200 days of age, indicating that not all male worms die shortly after mating. First-stage larvae recovered from gravid females as early as 200 days of age were found to be infective to the copepod. Acanthocyclops vernalis. These observations suggest that the ferret is an excellent laboratory animal for dracunculiasis research.