The prosobranch snail Clypeomorus bifasciata in Kuwait Bay was examined for digenean infections over a one year period during 1994/1995. A total of 1500 snails was examined and 567 (37.8%) were found to harbour nine digenean species. The prevalence of a microphallid species was 33.9% while each of the others occurred in less than 1.2% of the snails. The prevalence of infection increased with shell size. Multiple infections were observed in only five of the infected snails and the microphallid was involved in all of them. Snails were infected with the microphallid throughout the year and there appeared to be two peaks in the proportion of infected snails shedding cercariae, a winter peak from November to January and a summer peak from June to August. The crab Xantho exaratus collected from snail sampling sites was heavily parasitized by microphallid metacercariae of the genera Longiductotrema and Microphallus. This is the first report on microphallid metacercariae in crabs in the Arabian Gulf region.

Sera from patients with clinical characteristics of toxocariasis were assayed using the ELISA method and larval excretory-secretory antigen. Four hundred and seven samples of Toxocara serology were received at the laboratory of ‘Ciudad Sanitaria Juan Canalejo’ Hospital of Corunna, Spain, from 1984 to 1989. Of these, 30 were from adults, 332 from children and 45 from patients of unknown age, resulting in Toxocara seroprevalences of 23.3%, 32.8% and 17.7% respectively. The reasons for these serological differences in the rural and urban areas of Galicia, Spain are discussed.

This study deals with the formation of the metacercarial cysts of four microphallid trematodes, Maritrema subdolum, M. arenaria, Levinseniella brachysoma and Microphallus claviformis. The first observable cyst was present around Maritrema arenaria 18 h p.i. (post-infection). The other species had not developed a cyst by day 8 p.i. but their cysts were apparent by day 16 p.i. These were bi-layered and that of M. subdolum was thicker than those of L. brachysoma and Microphallus claviformis of the same age. The structure of older cysts varied substantially between the four species. Microphallus claviformis and Maritrema subdolum cysts were fully formed at 30 days p.i. Like those of M. arenaria they were bi-layered, the outer layer (up to 3 μm thick) being electron-dense and the inner one (up to 7 μm thick) being less electron-dense. The cysts of fully formed L. brachysoma metacercariae were much more complex, composed of four layers, one of which was divisible into three sub-layers. It was concluded that the outer cyst layer was the product of secretory granules which were previously identified in cercarial tegument. The inner, thicker layer was derived from several sources. These included small tegument vesicles produced over the entire surface of the metacercariae, larger fragments of tegument released from the anterio-ventral region and material liberated from the metacercarial excretory bladder. This heterogeneous material accumulated in the cyst lumen for some time before becoming polymerized to form the thick inner layer or layers of the metacercarial cysts.

The trichostrongyloid nematode Ostertagia nianqingtanggulaensis K'ung & Li, 1965, previously recorded only from sheep in Tibet, is redescribed and is shown to be a common parasite of both sheep and goats at higher altitudes in the Himalayan foothills of western Nepal. Herbage examination indicated that infective larvae can overwinter on snow covered slopes. Use of tracer animals confirmed that migratory flocks are exposed to infection when grazing on alpine pastures during the summer months. In contrast, nearby non-migratory flocks kept at lower altitudes did not harbour O. nianqingtanggulaensis and tracer animals grazed with these flocks did not become infected with this species.

A comparative analysis has been carried out between two populations of Schistosoma haematobium using the same intermediate snail host, Bulinus truncatus, but originating from two distinct ecological areas of Algeria: Khemis-El-Khechna in a sub-humid mediterranean zone and Djanet in a saharan bioclimatic zone. Four parameters have been studied: the growth rate of adult worms, size and shape of the eggs, chronobiology of cercarial emergence and the compatibility with the intermediate host. Results showing divergences for all the characters studied are discussed for the origin of this intraspecific polymorphism of S. haematobium in Algeria.

The composition and diversity of total and intestinal helminth component and infracommunities were determined in eels Anguilla anguilla from four shallow coastal lagoons near Rome. The lagoons differed principally in respect of their salinity. Only Lake Burano still received an input of freshwater, and both freshwater and marine helminth species were found in eels. In the other three lagoons all helminth species were marine or euryhaline and communities were dominated by digeneans. At component community level these three lagoons were far more similar to each other than to Lake Burano, but this distinction almost disappeared at infracommunity level. Species richness and diversity declined with increasing salinity at component community level but not at infracommunity level. Despite the changes and differences in helminth community composition, intestinal helminth infracommunity structure was very similar in all four lagoons and to that in eels from freshwater localities in Britain. The findings thus provide further and unexpected support for the view that some factor(s) other than supply side ones must be operating to produce the fundamental structural similarity in helminth communities in eels.

The desiccation survival and ability to control water loss during drying of individual infective juveniles (IJs) of populations of Steinernema feltiae and Heterorhabditis megidis from Greece and the UK were examined at different relative humidities. Survival at all relative humidities was for minutes only and there was no evidence of enhanced survival of the populations of either species from Greece compared with those from the UK. The survival of individuals of both populations of H. megidis was superior to that of S. feltiae and the rate of drying of H. megidis was significantly slower. The sheath surrounding the IJs of H. megidis appears to be involved in slowing the rate of water loss of the enclosed nematodes.

The interactions between Khawia sinensis (Cestoda: Caryophyllidea), a pathogenic tapeworm of carp, and host leucocytes has been investigated in vitro by monitoring blastogenesis in pronephric, splenic and thymic lymphocytes and apoptosis of pronephric leucocytes. Both parasite homogenate and excretory/secretory (E/S) products were found to suppress lymphocyte blastogenesis at high concentrations (346.6–98.8 μg ml−1) whilstcell stimulation occurred at low concentrations (49.4–19.8 μg ml−1). This differential affect on leucocyte activity may not be associated with apoptosis in vitro as the parasite E/S products did not significantly affect programmed cell death as monitored by acridine orange and DNA analysis. The parasite effect on leucocyte activity is discussed and its relationship to host susceptibility is evaluated.

Female mice of nine inbred strains (A, AKR, BALB/c, C3H, C57BL/6, C57BL/10, CBA, DBA/1 and DBA/2) and H-2 congenic B10.D2, at 9–10 weeks of age, were infected with larval Echinococcus multilocularis by trans-portal injection of hydatid homogenate. Parasitized livers were histologically examined 9 or 13 weeks after infection. Hydatid development was quite different among mouse strains. Multivesiculation was prominent in C57BL/10, DBA/1, C57BL/6 and BALB/c. Protoscoleces were well developed in DBA/2, AKR, DBA/1 and CBA. H-2 congenic B10.D2, which has the background genes of C57BL/10 except for the H-2d gene of DBA/2, resembled C57BL/10 in prohibiting the development of protoscoleces. These data suggest that the qualitative difference in hydatid development may be regulated by non-H-2 gene(s).

Faecal pellets were collected from uninfected rats and rats infected with Hymenolepis diminuta, and analysed for caloric value, lipids, carbohydrates, glucose, amino acids, and proteins. Faeces from infected rats contained significantly more lipid and less carbohydrate and glucose than faeces from control rats. The total free amino acid content of faeces from infected and control rats did not differ, but there were significant differences in the amounts of individual free amino acids. The data support the hypothesis that the nutrient composition of faeces from infected and control hosts differ. Beetles that serve as the intermediate host for H. diminuta may be able to detect these differences, and this may explain why beetles preferentially ingest faeces containing the tapeworm's eggs.

Differences in in vitro vesicular development (microcyst formation) in three Spanish strains of Echinococcus granulosus (sheep–cattle, horse and pig–goat) are reported. Microcyst formation occurred in 19–37 days (sheep strain), 9–18 days (pig strain) and 35–47 days (horse strain). Comparing these results with those from human samples (microcyst formation in 24–38 days), it is possible to consider the sheep strain as the most likely source of human infections in Spain.

Early third-stage larvae of Gnathostoma spinigerum were cultured in RPMI-1640 supplemented with 25mM NaHCO3,100 units/ml penicillin G, 100 μg/ml of streptomycin, 5 μg/ml of amphotericin B and 10% foetal calf serum at 37°C under 5% CO2 in air for 60 days. After 3 days of cultivation, the larvae moulted. Body sizes increased from 0.49 ± 0.09 × 0.07 ± 0.01 mm in length and width to 4.08 ± 0.48 × 0.32 ± 0.04 mm after 60 days of cultivation. The maximum body length and width of these larvae were 4.94 mm and 0.35 mm, respectively. The survival rate (67.5 %) of the worms was observed at the end of cultivation. The addition of foetal calf serum was found to be essential for growth and development.

RAPD technique was used to differentiate individuals of Anisakis simplex obtained from Merluccius merluccius, Phycis blennoides, Conger conger and Lepidorhombus boscii, from the North Atlantic Ocean. The amplification patterns of the host DNA controls were markedly different from those obtained for the parasitic material. No variation within the same host was detected. The amplification patterns for larvae obtained from fish of the same genus were somewhat different. The amplification patterns of A. simplex isolates from M. merluccius, P. blennoides, C. conger and L. boscii, were different. These results suggest the possible existence of two populations with a considerable high genetic variability and a different adaptation to different host species.

Primers for polymerase chain reaction to amplify genomic DNA of both Toxocara canis and T. cati were constructed by adapting cloning and sequencing random amplified polymorphic DNA. The primers are expected to detect eggs and/or larvae of T. canis and T. cati, both of which are known to cause toxocariasis in humans.