Four muscle groups are responsible for the eversion and retraction of the apical denticles and enlarged pseudolabia in Skrjabinoptera goldmanae (Nematoda: Physalopteridae), which occurs in the lizards Chlamydosaurus kingii, Pogona spp. and Varanus gouldii in Australia. These muscles enable the nematode to bury its anterior portion in the gastric submucosa of its hosts. They comprise three sets which are derived from the somatic musculature and are inserted in the oesophagus and associated organs, and a fourth set of muscles which appears to be derived from the muscular oesophagus itself. These accessory muscle groups are described and illustrated, and from this their mode of action in everting and retracting the pseudolabia is derived. Possible selection pressures which led to their evolution are reviewed.

Steinernema feltiae is the most effective nematode for controlling sciarid species but S. carpocapsae does exert some control. S. feltiae is less effective at 30°C than at 22°C. S. anomali, S. riobravis and two Heterorhabditis spp. gave better control at the higher temperature. All six sciarid species tested were susceptible to S. feltiae but there was some variation in the level of infection. UK isolates of S. feltiae were more effective against UK sciarids than the nematode isolates from other European countries which were tested. Adult sciarids are infected by S. feltiae and can disperse nematodes to nematode-free compost.

The cyst wall of the metacercaria of Gynaecotyla adunca (Microphallidae: Digenea) was subjected to comprehensive histochemical analysis. At the light microscope level, a uniformly thick, bipartite cyst wall, probably wholly of parasite origin, was evident. Structural modification of the cyst wall to provide an escape aperture was not apparent. The thicker, inner layer was comprised of phospholipid and glyco- and/or mucoproteins, possibly similar in structure to collagen. The outer layer was highly proteinaceous and contained additional amounts of acidic and neutral mucosubstances. The results are discussed in the context of previous observations regarding the excystment requirements of this microphallid species.

Natural populations of the freshwater gastropods Bithynia tentaculata, Gyraulus convexiusculus, Helicorbis coenosus, Indoplanorbis exustus, Lymnaea acuminata, L. luteola and Vivipara bengalensis, were examined from October 1985 to September 1986 at seven transmission sites for paramphistomiasis, fascioliasis and other gastropod-borne infections in Aligarh, northern India. Gastropod diversity and the type and abundance of vegetation were highest at sites containing permanent water bodies. The distributions of H. coenosus and L. acuminata were positively correlated with the type and abundance of vegetation at these sites. Ephemeral water bodies contained B. tentaculata, I. exustus and L. luteola which were resistant to desiccation during the hot season. Aestivation in these gastropods preceded pronounced breeding activity which began with the onset of the monsoon season. Multivariate analysis (by principal components) was used to investigate relationships between each species of gastropod, their site of occurrence and levels of infection with larval helminths. Seasonal variations in numbers and size class structure in these gastropods were found to influence their prevalences of infection with larval helminths. Metacercarial and cysticercoid infections were more prevalent in smaller size classes of B. tentaculata and V. bengalensis, whereas larval paramphistomes were more prevalent in larger size classes of G. convexiusculus, I. exustus and L. luteola. Attempts were made to equate these findings with seasonality in egg shedding by certain species of adult paramphistomes occurring in domestic ruminants.

Since Ireland is the only country in which Pomphorhynchus laevis (Acanthocephala) uses brown trout (Salmo trutta) as its preferred definitive host, the population biology of the parasite in this host was investigated thus enabling a comparison to be made with data collected on P laevis from other hosts, particularly the cyprinids, chub and barbel. Over a period of 12 months, 549 brown trout were caught from two lakes, Lough Feeagh and Bunaveela Lake, in the Burrishoole River system, Co. Mayo, Ireland. The parasite component community was dominated by a single species, P laevis. Fifty eight percent of the trout sample were infected with the acanthocephalan and the mean abundance (± SD) was 3.1 ± 5.1. The relationships between the prevalence and abundance of P laevis and season and site of host capture and host age and sex were explored. As single factors none of these parameters emerged as significant contributors to changes in parasite abundance although some interaction terms proved to the significant. A random sample of over 700 P laevis parasites were subjected to further investigation and their size, position in the intestine and maturity status are described. Parasites attained an average weight of 7 mg and occupied the posteriad positions within the fish intestine (77%). Parasites from this sample of Irish brown trout attained a similar average size to those found in chub and barbel from England. 42.3% of the total parasites examined contained ovarian balls only and 17% contained fully mature acanthors. Therefore only a moderate proportion of female worms contained mature acanthors in these trout whereas the majority of worms recovered from a sample of chub were gravid. Utilizing a logistic regression model, parasite size, season, and site of host capture emerged as particularly significant factors which contribute to whether a parasite contains mature eggs.

Baboons vaccinated intramuscularly with three times 9000 20 krad irradiated Schistosoma haematobium schistosomula at monthly intervals were exposed percutaneously to either a single mass challenge of 3000 (VMC) or ten, weekly trickle challenges of 300 (VTC) normal S. haematobium cercariae. Unvaccinated mass (MCC) or trickle (TCC) challenge controls were exposed simultaneously. Faecal and urine egg production was delayed in the vaccinated groups which also had reduced adult, particularly female, worm recoveries. Total faecal, urine and tissue eggs were lower in the vaccinated groups, as also were the size of granulomata and the gross pathology and severity of inflammatory responses in the bladder and ureters, except for an increased proportion of tissue eggs in the livers of vaccinated animals. Differences in pathology between groups were less marked in the other organs. Most indices were reduced in the trickle versus the mass challenge control groups. Some of these trends were statistically significant, mostly in the trickle vaccination group (VTC), but others were not. Compared with the appropriate unvaccinated controls, the percentage reduction for the trickle challenge (VTC) group (73%) was three times greater than that of the mass challenge (VMC) group (23%). Overall, the protective effect of vaccination was more clearly demonstrated in the trickle than in the mass challenge groups. This conclusion is based on a single experiment. Nevertheless, because trickle infections probably approximate more closely to what humans receive naturally, it is recommended that they should be used for future testing of all potential vaccines in baboons.

We have previously shown that it is the lung stage schistosomulum which is both the inducer and the target of immunity in rats vaccinated with irradiated cercariae but that rats can also be partially protected by immunization with detergent extracts of mechanically-transformed schistosomula. In the present study we therefore compared the immunogenicity of these and intermediate schistosomular stages. In the first experiment low levels of protection (13–24%) were induced by extracts of mechanically-transformed schistosomula cultured for 3 hours or 2 days but not by extracts of lung schistosomula. In a repeat experiment insignificant levels of protection were induced by extracts of 3 h schistosomula and lung schistosomula were again non-protective. Nevertheless, high levels of anti-schistosomula antibodies were demonstrated and sera from actively immunized rats conferred significant passive protection in five out of six trials. The levels of protection conferred by passive immunization (26–51%) were in each case higher than the levels of protection demonstrated in the respective serum donor groups, showing that some form of immunological blockade suppression is operating to prevent expression of protective immunity in the actively immunized rats.

To investigate antigenic differences between the developmental stages of Anisakis simplex, somatic, excretion–secretion and detergent-solubilized surface antigen preparations of third- and fourth-stage A. simplex larvae, and a somatic antigen preparation of adults, were characterized by SDS–PAGE and immunoblotting using mouse immune serum containing antibodies against the two larval stages. Excretion–secretion and surface antigen preparations from thirdstage larvae behaved very differently from those of fourth-stage larvae, in both SDS-PAGE and immunoblotting; this suggests that certain excretion–secretion and surface antigens are highly stage-specific. By contrast, somatic components of third- and fourth-stage larvae were found to have very similar banding patterns, suggesting conservation of these components during the development of the parasite in mice. The SDS-PAGE and immunoblotting results for adult somatic components seem to support this hypothesis

A total of 549 brown trout were caught from two lakes, Lough Feeagh and Bunaveela Lake, in the Burrishoole system, Co. Mayo, Ireland. Seven species of metazoan parasite were detected but only four species occurred in ≥10% of the sample. The parasite community of the trout was dominated by a single species, Pomphorhynchus laevis, with a prevalence of 58%. Only one allogenic helminth species was recorded from the trout, Diphyllobothriurn ditremum, with the community mainly comprising autogenic species. Few differences were found between the two lakes, although the larger lake, Lough Feeagh, did contain some trout which harboured more parasite species and had, on average, fish with higher numbers of individual parasites. Measures of species richness and diversity were very low, indicating an impoverished helminth community with little potential for interspecific interactions. Host age was found to significantly influence these indices of infracommunity structure.

Studies were carried out to determine the predilection sites of Trichinella nativa muscle larvae in arctic foxes (Alopex lagopus) caught in Greenland. The highest number of larvae per gram of tissue was found in the muscles of the eyes and the legs. With regard to predilection sites no significant differences were demonstrated either between age groups or between foxes with high and low total parasite burdens. Predilection sites were comparable with those recorded earlier in experimentally infected caged foxes and in other carnivorous species. Hypotheses on predilection sites of Trichinella muscle larvae are discussed.

A simple technique using modified Mallory stain in the transferral of Gyrodactylus specimens from ammonium picrate-glycerin to a permanent mountant is described. Hamuli, their connecting bars and the penis sclerites are well defined by the technique as are muscles and tendons, cell nuclei, tegument and gland cells. As well as being useful in the study of general anatomy, the technique enhances the observation of the taxonomically important ventral and dorsal bars. In order to show this, improved illustrations of the dorsal and ventral bars of G. turnbulli are given along with explicit demonstrations of differences in morphology of the ventral bars of G. bullatarudis and G. rasini - two easily confused species.

Migration success (i.e. the proportion of worms that reach the thorax) of Onchocerca lienalis microfilariae (mf) in the haemocoel of Simulium vittatum was studied by inoculating mf into the posterior abdomen, and recording their distribution in the blackfly body at predetermined time points. Mf arrive into the thorax by active locomotion rather than by drifting in haemolymph currents. Migration into the thorax was completed by 12 h post inoculation (pi) but was not continuous throughout this period. Migration proceeded in two phases; the first occurred 0–2 h pi and the second at 6–12 h pi. Overall, migration success 12–24 h pi was only 36%, indicating thata substantial number of mf failed to reach the thorax, either because they were eliminated by the fly's defensive response or because they remained in the abdomen. Migration success was density independent Mf that arrive into the thorax within 2 h pi did not differ in their migration potential from mf that remained in the abdomen at this time. In flies where more mf migrated successfully there was lower mf loss, indicating that migration success was linked to mf loss. Moreover, the proportion of mf in the thorax was not correlated with mf loss, suggesting that mf loss affected the number of mf that migrated successfully, rather than the reverse causal relationship.

This investigation deals with the evaluation of the in ovo technique for the cultivation of trematodes. The technique has previously been used for the maturation of digenetic flukes and the establishment of life cycles in the laboratory but it was not known if the adult flukes produced were morphologically comparable to those found in their natural hosts. Three species of microphallids, Microphallus similis, M. pygmaeus and Maritrema arenaria were used. Metacercariae of each species were inoculated into fertile hen's eggs which were incubated at 41°C for 120 hours. The adult flukes recovered were stained and mounted and morphonietric measurements obtained were compared to definitive descriptions of the three microphallid species. The results showed that the in ovo technique provided adult flukes which were indistinguishable from those occurring in natural hosts.

Protective immunity against Brugia pahangi was examined after adoptive transfer of immune spleen cells. Spleen cells obtained from gerbils at 8 weeks post-infection (p.i.) with 100 infective larvae (L3) of B. pahangi were transferred into naive recipients, and then 24 h later, they were infected with 100 L3 of B. pahangi. The recipients given normal spleen cells and infected by the same manner served as controls. Microfilarial counts in the circulation were monitored at designated times after infection and worm burden and the size of individual female worm were determined at 16 weeks p.i. to evaluate the effects of adoptive immunization. In addition, eosinophil responses and serum antibody titres were examined during the course of infection. In the control group, microfilariae first appeared in circulation at 9 weeks p.i. and continuously increased in number throughout the course examined. In contrast, microfilaraemia was almost completely suppressed in the group given immune spleen cells. Although worm burden was comparable between the two groups, the average size of female adult worms recovered from the adoptively immunized group was significantlysmaller than that from the control group. Eosinophil response was hastened and enhanced by adoptive transfer of immune spleen cells in the early stage of infection. Parasite- specific antibody response was also hastened by adoptive immunization. These results suggest that immune spleen cells could confer protective immunity mainly directed against adult B. pahangi.

Adults of Echinostoma caproni, F. paraensei, and E. trivolvis were processed for starchgel electrophoresis. Ten enzyme systems representing 12 structural loci were examined using three different buffer systems. E. paraensei and E. caproni were found to be genetically inbred as indicated by the lack of heterozygosity in individual worms. All three taxa showed fixed differences indicating they are distinct species. Fixed differences were found between E. paraensei and E. caproni in six enzyme systems, between E. paraensei and E. trivolvis in five enzyme systems, and betweenE. trivolvis and E. caproni in five enzyme systems. Phenic relationships among the three species showed E. caproni was genetically more similar to E. trivolvis than to E. paraensei.

In 1988, 1989 and 1990 second year grazing heifers, naturally infected with gastrointestinal nematodes, were separated into two groups, one of which was treated orally with albendazole. In 1988 and 1989 treatment was administered immediately after parturition (February), and in 1990 during the last term of pregnancy (December). Both treated and control animals were grazed on separate plots in a rotational system. Maximum faecal egg counts were observed amund parturition, except in 1990, when treatment was given at the end of gestation. The main genera identified were Cooperia, Trichostrongylus, Ostertagia and Oesophagostomum. The number of Ostertagia larvae in the treated groups increased from 1989 to 1990, while the others decreased. Pasture contamination with third stage larvae (L3) was lower on the piots grazed by treated heifers. Maximum numbers of L3 were found in autumn, at the end of winter, and at the beginning of spring. Mean serum pepsinogen concentrations were significantly higher in the untreated groups. This concurs with the pattern for L3 on pasture. The trial shows that if a single treatment against gastrointestinal nematodes is carried out, and the animals remain on contaminated pastures, the parasitic load tends to level out after 4–5 months under favourable climatic conditions. However, the percentages of nematode genera occurring in the new populations may differ from those in the original infection.

The ultrastructure of the reproductive organs of adult female T. spiralis was described on the basis of extensive observation under an electron microscope. The organisms were recovered from the host intestine 7 days after oral infection. The organs consisted of a single ovary, seminal receptacle, uterus and vagina, confirming the reports described by previous authors at light microscopical level. All the organs were surrounded by a basal lamina and epithelial cells, and were bathed in haemolymph. Ova were formed in a germinal zone on the ovary wall exhibiting a half-moon shape, and spread to other sides of the ovary Mature ova exhibited a smooth cell surface, cuboidal shape, prominent cytoplasmic polysomes, a clear nucleus and a well-developed nucleolus. Embryos in early stage of development consisted of numerous small cells and were surrounded by a sheath.As they matured they shed the sheath and left a pool of sheaths in the uterus. During oogenesis and embryogenesis of adult worms in normal development, there occurred lipid droplets and the degradation of embryos; reportedly signs of worm damage.

The total DNA of two morphologically similar cestode species of the genus Proteocephalus parasitizing coregonid and salmonid fish, P. exiguus La Rue, 1911 and P. neglectus La Rue, 1911, was compared. The methods of DNA analysis involved digestion of the total DNA with restriction endonucleases and Southern blotting hybridization with the ribosomal DNA probes pSM 889, pSM 389 and pSM 890. No inter-specific variation was found between the two proteocephalid species. Distinct differences in RFLP patterns were recorded between two geographically distinct population of P. neglectus after BspRI digestion; after EcoRI digestion and following hybridization with the 32P-labelled probe pSM 890 and after BamHI digestion and hybridization with the 32P-labelled probe pSM 889. The high degree of genetic similarity revealed in the two Proteocephalus spp. could be a further argument for the conspecifity of both taxa.

From April 1992 until June 1993, the seasonal dynamics of Rhabdochona hellichi (Šrámek 1901) in its definitive host, the barbel (Barbus barbus), was studied in the Jihlava River (the Danube basin), Czech Republic. The parasite occurred in barbel throughout the year (overall prevalence 93% and intensity of infection 1–1384 [mean 78] nematodes per fish), but there were distinct seasonal fluctuations in prevalence and mean intensity values associated with the parasite's seasonal cycle of maturation. Prevalence was very high (usually 100%) during most months of the year, while lowest values were recorded in August and October. The highest values of mean intensity occurred in April. Both prevalence and mean intensity values increased with the body length of the hosts. The parasite exhibited a distinct annual cycle of maturation with egg-producing females present only fmm June until August, whereas larvae occurred in barbel mostly from September until April of the next year. Trichopteran (caddis-fly) larvae of the genus Hydropsyche (H. angustipennis and H. pellucidula) were found as natural intermediate hosts of R. hellichi (prevalence 4%, intensity 1–10 nematode larvae). The strictly seasonal maturation of this nematode may be associated with the temperature regime in the locality and seasonal cycles of maturation of its intermediate hosts.

The effect of temperature on infection, development and reproduction of five Heterorhabditis isolates was examined in Galleria mellonella larvae. Infectivity was examined at six temperatures (5,10, 15,20,25 and 30°C). The proportion of Galleria infected remained relatively constant, only dropping at extremes of the temperature range tested. However, the mean number of nematodes per host produced a different trend, with each isolate displaying optimal infectivity at 25°C. The temperature range over which the juveniles could infect differed between the isolates. This is thought to be related to the geographic origins of the species. Development and reproduction occurred over a slightly narrower temperature range than that allowing infection to occur. Differences between the isolates at which development and reproduction occurred were noted. There were also differences in the mean number of juveniles produced per cadaver following either infection in sand (10 nematodes/larva) or the injection of one juvenile per larva, suggesting that reproduction is tightly regulated by density-dependent constraints.