A preliminary parasitological and malacological survey was effected in rural communities of some Local Government Areas (LGA) in Plateau State, Nigeria, to estimate the prevalence of urinary schistosomiasis and identify active transmission foci. Out of 2888 persons examined in six LGAs, 1381 (47.82%) were excreting eggs of Schistosoma haematobium in their urine. Prevalence rates did not vary significantly (P > 0.05) between the LGAs: Pankshin (62.4%), Shendam (40.2%), Qua'an-Pan (22.9%), Langtang South (45.4%), Langtang North (58.8%) and Wase (50.0%). Infection rates were significantly different (P < 0.001) between the sexes. Many water bodies in the study communities were colonized by infected Bulinus snails. Snail infection rates varied significantly (P < 0.001) between the dry and wet seasons. A positive correlation was observed between snail infection rates and the prevalence of S. haematobium.

The effect of zinc deficiency on the response of CBA mice to infection with the intestinal trematode Echinostoma caproni was examined. Young CBA mice were allocated to one of three dietary groups: a group fed a zinc deficient diet ad libitum, a control group pair fed a zinc sufficient diet and a control group fed a zinc sufficient diet ad libitum. The mice on the zinc deficient diet gained significantly less weight than the pair fed controls. In primary infections with six E. caproni metacercariae followed over a period of 128 days, zinc deficiency delayed worm expulsion. In addition, zinc deficiency resulted in a prolonged IgM response, a delayed IgG response and an increased IgA response towards the end of the experiment. Resistance to challenge infection day 21 following a primary infection with 25 E. caproni metacercariae was slightly, but not significantly, affected by zinc deficiency.

The tegument of Postorchigenes gymnesicus has been studied by scanning and transmission electron microscopy. The general body tegument is spinous and contains mitochondria, biconcave disc-shaped vesicles bounded by an unitary membrane and displaying a protein content, and scarce spherical bodies. The tegument covering specialized body regions is aspinous. Few vesicles were evident in the tegument covering the suckers and oesophagus, being more abundant in the metraterm and cirrus where the tegument is thicker. Laurer's canal has a thick tegument with sparse vesicles, mostly arranged close to the apical membrane. A direct association was evident between the basal lamina underlying the spines and the muscular subtegumental fibres, suggesting a motile character for the spine.

Seven free-living houbara bustards (Chlamydotis undulata macqueeni) wild-caught in the United Arab Emirates (UAE) were examined for helminth parasites. Of five birds investigated post mortem, one was free of gastrointestinal helminths. Two other birds expelled worms following clinical examination and anthelmintic treatment. This is the first report of the parasites of free-living, as opposed to captive, houbara bustards in the UAE. In infested wild birds, fewer species of helminths were recovered than had been found in captive birds and those species present had also been found in captive houbaras. Despite heavy worm burdens, the infested birds were in good condition. Two species of cestodes (Otiditaenia conoideis, Hispaniolepis falsata), two of acanthocephalans (Centrorhynchus lancea, Mediorhynchus taeniatus) and two of nematodes (Hartertia rotundata, Allodapa sp.) were recovered. Histopathological examination of tissue samples from the intestine of three birds revealed no significant pathological changes attributable to the presence of parasites but only localized responses at the sites of parasite attachment.

The successful colonization, establishment and spread of Pomphorhynchus laevis in a small, isolated, Devon river 128 km from the parasite's nearest focus in Dorset was followed over 11 years from 1985. The parasite was first detected in Anguilla anguilla and Platichthys flesus in 1988: by 1995 it had attained prevalence levels of 22.6% in A. anguilla and 43.6% in P. flesus and also occurred in 100% Salmo trutta, 50% Cottus gobio and Noemacheilus barbatulus. As judged by prevalence, abundance, proportion of females gravid and weight of gravid females, S. trutta was the preferred definitive host although C. gobio was a suitable host and may play a role in cycling the parasite: the other three species were unsuitable hosts. The intermediate host was the freshwater Gammarus pulex: the euryhaline G. zaddachi was not infected. On biological grounds, the P. laevis could be assigned to the English freshwater strain and was almost certainly introduced to the river by anthropochore stocking of S. trutta from a Dorset hatchery. The findings demonstrate conclusively that the English strain of P. laevis can colonize and establish in a new locality from which Leuciscus cephalus and Barbus barbus, its normal preferred hosts, are absent and use S. trutta instead. The results also confirm that P. laevis is a poor natural colonizer and appears always to be introduced to new localities by anthropochore transfers of fish. The implications of these conclusions for understanding the present distribution of P. laevis are discussed and it is considered that they provide direct evidence in support of the hypothesis that P. laevis was introduced to Ireland from England and subsequently adapted to use of S. trutta and G. duebeni there.

The ability of Hymenolepis nana oncosphere extract to induce eosinophil chemotactic response was examined in vitro and in vivo. The extract showed a chemotactic activity specific for eosinophils but not for neutrophils. Partially purified eosinophil chemotactic factors (ECFs) from the oncosphere extract showed apparent molecular mass from 5.5 to 9.6kDa and 30 to 40kDa. These were resistant to heating and proteinase K digestion but sensitive to periodate oxidation. Peritoneal injection of the crude extract or partially purified ECFs to mice resulted in a preferential eosinophil infiltration. The chemotactic activity for eosinophils was not separable from the adhesion molecule expression or oxygen radical-inducing activity by means of chromatography or chemical treatments. Furthermore, histological examination demonstrated a marked tissue eosinophilia around H. nana larvae in the intestinal lamina propria of both humoral and cell-mediated immunodeficiency mice. The present findings suggest that H. nana oncosphere-derived molecules facilitate in vivo the intestinal eosinophilia during the infection.

Adults of Echinostoma paraensei grown in mice were exposed to 3-H-tyrosine and transplanted to uninfected mice singly or with unexposed worms. The presence of sperm labelled with the radioactive tyrosine in the seminal receptacles of labelled and unlabelled worms recovered after 5 days indicated the mating pattern of this species. Of nine isolated, labelled worms recovered, four had self-inseminated (44%). Of the 39 unlabelled found with eight labelled worms, only eight exhibited labelled sperm for a cross-insemination rate of 21%. Six of these eight labelled worms had self-inseminated (75%) in addition to the cross-insemination. This pattern of mating is termed unrestricted, unlike the restricted mating seen in three species of eyeflukes, which will not self-inseminate in groups. In contrast to the other species of echinostomes investigated, very little sperm was found in the seminal receptacles of the serially sectioned E. paraensei. Adults were always found in the duodenum, even when transplanted in the ileum.

The activities of selected enzymes of the respiratory chain system in Onchocerca fasciata (Filarioidea: Onchocercidae) have been investigated histochemically. Thus, the localization and distributions of NADH dehydrogenase (EC 1.6.99.3), succinate dehydrogenase (SDH) (EC 1.3.99.1) and cytochrome oxidase (EC 1.9.3.1) were investigated in various tissues of the adult female worm by employing MTT, Nitro BT (dehydrogenases) and DAB (cytochrome oxidase). Different tissues varied considerably in their enzymatic activities. The hypodermis and reproductive tissues showed strong and identical localization of NADH and SDH dehydrogenase activities reflecting high metabolic rates. Little or no dehydrogenase activities were observed in the intestine and cuticle. In contrast to the two dehyrogenases, no activity was observed for cytochrome oxidase in any of the tissues in adult or embryonic stages of the worm. The significance of these results with respect to the energy metabolism of the worm is discussed. It is suggested that O. fasciata lacks a classical, mammalian-type respiratory pathway and that oxidative phosphorylation is of no importance as an energy generating pathway in this essentially anaerobic parasite.

The behaviour and infectivity of the infective juveniles (IJs) of two species of entomopathogenic nematodes, Steinernema carpocapsae Weiser and Steinernema feltiae Filipjev (Rhabditida: Steinernematidae), were determined after exposure to two neuroactive pesticides, oxamyl and fenamiphos, widely used against plant parasitic nematodes. Oxamyl (50 μg ml−1) initially stimulated non-sinusoidal movement in S. feltiae but had no appreciable effect on IJs of S. carpocapsae, while fenamiphos (10 and 50 μg ml−1) increased and sustained non-sinusoidal movement in both species over an observation period of 48 h. The two pesticides reduced the infectivity of both nematode species against late instar larvae of the wax moth, Galleria mellonella L. in a sand-tube bioassay when compared with controls. Infective juveniles of S. feltiae showed limited body waving behaviour on the sand surface whereas S. carpocapsae showed the full range of nictation movements, including body waving, stationary straight postures and leaping. Oxamyl had no significant (P>0.05) effect on the number of IJs of S. carpocapsae which nictated except when the IJs were pre-incubated with this compound for 24 h (P<0.05). In contrast, fenamiphos completely suppressed all nictation and body waving behaviour in both species. Nictating IJs of S. carpocapsae exposed to late instar G. mellonella for 12 h in a filter-paper bioassay were found to be more infective compared with non-nictating IJs. Treating IJs of S. carpocapsae with oxamyl (50 μg ml−1) increased the infectivity of non-nictating IJs compared with controls but reduced infectivity of nictating IJs when exposed to G. mellonella for 12 h. The work is discussed in relation to proposals to use these or other pesticides to enhance the activity and infectivity of IJs of entomopathogenic nematodes.

Live adult and cercarial stages of Sanguinicola inermis Plehn, 1905 (Trematoda: Sanguinicolidae) were maintained in vitro in the presence of carp (Cyprinus carpio L.) leucocytes. Cells and parasites were fixed at intervals from 0.25 to 48 h and examined using light microscopy, SEM and TEM. Within 12 h of exposure, leucocytes were found attached to cercariae although, by 24 h, fewer cells were found attached to postcercarial, juvenile adult stages that had shed their tails. Neutrophils and macrophages were found attached to the damaged tegument of cercariae that had not transformed by 48 h. Few cells were attached to the tegument of adult flukes that were alive when fixed. However, there was extensive tegumental damage and numerous cells were attached to adult flukes that had died before fixation. The results are discussed with reference to parasite survival within the vascular system of the host.

A sandwich antibody ELISA was employed for the detection of circulating filarial antigen in patients with bancroftian filariasis. Wuchereria bancrofti recombinant antigen-derived polyclonal and monoclonal antibodies were successfully used as the revealing antibodies and their efficiency was compared. All the microfilariae (mf) positive (by finger prick and examination of 20 μl of blood under the microscope) individuals tested showed the presence of circulating antigen(s). Among the antigen positive endemic normals (mf negative by the finger prick method), 43% showed microfilariae by a sensitive parasitological method viz. membrane filtration of the night blood samples. A significant correlation was observed between the parasite antigen levels and the blood microfilaria counts among the mf carriers. This information on the parasite antigen levels could be an ideal monitor to indicate the degree of active infection and in the follow up of chemotherapy.

Fresh stool samples from 300 subjects presenting at out-patient clinics in two major hospitals in Port Harcourt were analysed for the prevalence and intensity of gastrointestinal (GI) nematode infections and 85.3% were found to carry at least one of the four species of GI nematodes recognized during the study. The most common species was Ascaris lumbricoides (54%), followed by Trichuris trichiura (43.7%) and Necator americanus (42.7%) and lastly Strongyloides stercoralis (33%). Peak prevalence for A. lumbricoides was among the ≤9 years age cohorts, whilst those for the remaining species all coincided among the 15–19 years age cohort. The frequencies of single, double and triple-species infection categories, across the species and within most of the specific combinations were lower than the expected frequencies calculated from overall prevalence data for each species. Observed cases of non-infected individuals and those carrying all four species were higher than expected, suggesting that a greater than expected subset of the population was free from infection, particularly among subjects ≥30 years old and another subset more prone to infection by all four species, predominantly among the age cohorts ≤29 years. N. americanus and T. trichiura were more commonly encountered among multiple species infection combinations than expected, but the intensity of the former declined as the number of other concurrently infecting species increased. In contrast, the intensity of infection with S. stercoralis increased as the number of other species increased. Positive associations between A. lumbricoides and T. trichiura, N. americanus and S. stercoralis, and T. trichiura and N. americanus were identified in respect of greater than expected co-occurrence of these combinations and significant positive correlations between their respective intensities of infection. These were related to specific age cohorts which were identified as particularly prone to multiple infections.

Freeze fixation-dehydration was used for the first time in the preparation of attached Gyrodactylus for SEM viewing. The technique provided instant immobilization of specimens before death and negligible shrinkage throughout the fixation-dehydration process. Comparisons of sample means of two linear measurements of attached opisthaptors showed 20% more shrinkage of Gyrodactylus fixed using 10% neutral buffered formalin than those which were freeze fixed. Freeze fixation-dehydration was excellent for the study of gross external morphology of attached Gyrodactylus. However, the freeze fixation-dehydration process may cause disruption of intracellular structural components making delicate tissues brittle and more prone to damage during subsequent manipulation.

In order to detect intraspecies differences among isolates of Schistosoma mansoni from different geographical regions, soluble egg antigens (SEAs) of three isolates were characterized using SDS-PAGE. SEAs were prepared from eggs of a South African (SA), Eastern Caprivian (EC) and Puerto Rican (PR) isolate, separated by SDS-PAGE, stained and the molecular masses of constituent polypeptides determined. Protein profiles differed for all three isolates with the number of polypeptides varying from 25 for the PR isolate to 27 for the EC and SA isolates. Molecular masses of the polypeptides fall within the range of 12.0 kDa to 97.9 kDa. The EC and SA isolates shared ten common polypeptides, the PR and SA isolates five and the PR and EC isolates two. Only a 30.8 kDa and a 12.0 kDa polypeptide were common to all three isolates. These differences may, to some extent, account for regional variations in the morbidity of intestinal schistosomiasis reported for different geographical isolates of S. mansoni.

Female ICR mice, 5 to 6 weeks old, were exposed by stomach tube to 25 metacercarial cysts of Echinostoma caproni per mouse. At 14 days post-exposure, mice were fed by stomach tube clorsulon (1000 mg/kg, 500 mg/kg and 100 mg/kg) or rafoxanide (50 mg/kg, 25 mg/kg and 5 mg/kg) dissolved in dimethylsulphoxide (DMSO) carrier and mebendazole (1000 mg/kg and 500 mg/kg) or arprinocid (100 mg/kg and 50 mg/kg) suspended in a 2:1 polyethylene glycol (PEG)/DMSO carrier. All drugs were obtained from Merck Inc. (Rahway, New Jersey, USA) and only single dose regimes were used. Experimentally infected mice that served as controls received either DMSO or 2:1 PEG/DMSO carriers or were not given the carrier. Mice were necropsied 15, 16, 18 and 20 days post-exposure to worms. Doses of 100 mg/kg of clorsulon and 50 mg/kg of rafoxanide were 100% effective in eliminating the echinostomes on day 1 post-administration of the anthelmintics. Mebendazole and arprinocid were ineffective in eliminating worms at 1 or 2 days post drug administration.