The effects of a high protein diet on the host-parasite relationship of Echinostoma caproni in ICR mice were studied. The customized high protein diet (CHPD) contained 64% casein as a source of protein. The control diet consisted of a standard laboratory diet containing 23% casein as a source of protein. Mice were each fed 25 cysts of E. caproni by stomach tube and necropsied 2, 3, 4 and 5 weeks postinfection. The weight of mice on the CHPD did not differ significantly from mice on the control diet. Worm recoveries were also unaffected by the high protein diet. There was a significant decline in worm dry weight, body area and uterine egg counts in worms from mice on the CHPD compared with those on the control diet. Worms from hosts on the CHPD were located more posteriad in the gut than those recovered from mice on the control diet. Changes in the mouse diet adversely affected E. caproni maturation and growth, possibly by altering the immediate host mucosal environment and making it less conducive to worm development.

The breed differences in post-parturient rise (PPR) in faecal egg counts in lambing ewes of different breeds naturally infected with Haemonchus contortus were compared. The ewes of Nali, 50% Nali × 50% Russian Merino/Corriedale and 37.5% Nali × 62.5% Russian Merino/Corriedale were treated with fenben-dazole while ewes of the above three breeds as well as 25% Nali × 75% Russian Merino/Corriedale, were kept untreated. Observations from 3 weeks before lambing to 12 weeks post-lambing at weekly intervals revealed that in treated ewes, egg counts of Nali did not differ significantly with 50% Nali whereas 37.5% Nali had significantly higher egg counts than those of Nali and 50% Nali. In untreated ewes egg counts of 50% Nali were significantly higher than that of Nali on some occasions, while 25% Nali had significantly higher egg counts than the other three breeds. None of the ewes from the Nali breed showed signs of haemonchosis, whereas few lambing ewes of the three Nali crosses (50%, 37.5% and 25% Nali) showed signs of haemonchosis and one ewe of the latter breed died.

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.

The subchronic effect of cadmium on selected immunological parameters was studied in guinea pigs with experimental ascariasis. Cadmium chloride given orally for 28 days caused a considerable suppression of T- and B- cells in the lymphoid organs of intoxicated animals, of the metabolic activity of their peritoneal macrophages and a moderate decline in the level of complement CH50 and AH50 from day 1 to day 28 of the experiment, in comparison with the initial value. After a subsequent infection of the subchronically intoxicated guinea pigs the values for both the cell populations and the macrophage metabolic activity remained considerably suppressed, compared with infected control animals. The phagocytic and metabolic activity of macrophages as well as the CH50 and AH50 level, however, increased conspicuously for a short time after application of heavy metal and after infection but it did not reach the level of the infected group. The level of specific circulating antibodies was not affected by intoxication. Compared with the controls, the mean intensity of infection with Ascaris larvae migrating in the lungs of intoxicated animals increased by 20%. The results have established the negative effect of cadmium on the immunological parameters of the cellular immunity and humoral immunity studied and the impairment of the organism's response to the antigenic stimulus after an A. suum infection.

The migratory pathway of Toxocara canis larvae was determined by infecting mice with a low, medium or high dose of embryonated T. canis eggs and determining numbers of larvae present in the brain, liver, lungs, kidneys and muscle on days 5, 14 and 26 post infection. Variation was seen in the numbers of larvae recorded in the organs of mice which had received the same number of eggs and were at the same stage of infection. This variation was particularly marked in the brain indicating that, for the purposes of behavioural studies, the actual numbers of larvae found in the brain rather than the number assumed from the dose would have to be taken into account when analysing the behaviour of infected mice.

In order to characterize GATA transcription factors in Echinococcus granulosus, a PCR-based cloning strategy was developed. Degenerate oligonucleotides were designed for the most conserved sequence in GATA proteins that include 20 amino acids of the zinc domain. A 60 bp fragment was isolated that had high homology among this sequence and those reported in other species. An analogous sequence was obtained by performing the same procedure with DNA from the free living platyhelminth Dugesia tigrina. High stringency Southern blotting experiments confirmed the presence of this sequence in the parasite genome.

A rapid and reliable method based on immuno-affinity chromatography and preparative high pressure liquid chromatography was used for extraction and purification of cAMP from the two trematode species Gastrothylax crumenifer and Explanatum explanatum. The purified cAMP was quantified by electrospray tandem mass spectrometry in an amount of 44 and 83 picomole/g fresh weight of Gastrothylax crumenifer and Explanatum explanatum respectively.

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.

The occurrence of specimens in a laboratory strain of Trichostrongylus vitrinus exhibiting unusual spicules resembling those of T. minor and T. angistris is reported and the abnormal spicules described. The specimens include individuals with one spicule typical of T. vitrinus and the other spicule of the abnormal type. Possible reasons for the occurrence of such abnormalities are discussed.

C3H/HeN mice were each infected with 40 Echinostoma trivolvis metacercarial cysts on day 0, given intramuscular injections of dexamethasone (DEX) daily for 30 days, and necropsied on days 5, 8, 12, 15, 20 and 30 p. i. Control mice were each infected with 40 echinostome cysts on day 0, but were not treated with DEX and necropsied on the same days as the DEX-treated mice. DEX treatment caused an inhibition of worm expulsion and suppressed the increase in goblet cell numbers that peaked around day 12 p. i. in the untreated control mice. Increase in the number of mucosal mast cells and eosinophils in the control mice that peaked around day 15 and 12 p. i., respectively, was also suppressed by the DEX treatment. The mean body area of the worms from the DEX-treated mice was about the same as that of the control worms on day 5 p. i., and then significantly greater than the control worms on days 8 and 12 p. i. The worms in the treated mice continued to grow until the end of the experiment, on day 30 p. i. Enzyme-linked immunosorbent assay (ELISA) showed that serum IgM from the treated and control mice increased from day 12 p. i., peaked on day 15 p. i., and then decreased. An IgM titre of the treated mice was slightly higher than that of the controls. No marked rise in IgG and IgA titres occurred throughout the experiment in both groups.

Different types of proteoglycans (PGs) from adult worms of Schistosoma haematobium, were sequentially extracted using chaotropic agents under associative conditions (0.5 M GnCl), dissociative conditions (4 M GnCl) and detergents (Triton X-100 and SDS). The extracts were designated Fl, F2, F3 and F4, respectively. The highest amount of uronic acid and carbohydrate was detected in the associative extract (Fl) while the highest amount of protein was detected in the SDS extract (F4). Agarose polyacrylamide gel electrophoresis (A-PAGE) indicated the presence of a different PG in each extract with different electrophoretic mobilities. Agarose gel electrophoresis of glycosaminoglycan (GAG) separated from GnCl, associative and dissociative extracts, and the residue suggested the presence of dermatan sulphate in the two extracts and the residue, in addition to a GAG-like material found in the associative extract only. This glycosaminoglycan showed resistance to digestion with all mucopolysaccharidases and nitrous acid treatment. Gel filtration chromatography of associative extract on Sepharose CL-6B indicated the presence of three main uronic acid peaks (P1, P2 and P3). Chondroitin sulphate was the main GAG that could be detected in peak one (P1). Peak two (P2) contains carbohydrate and uronic acid but has no protein or absorbance at 280 nm. P2 has two types of GAGs: dermatan sulphate and a GAG-like material. The role of this PG in helping the adult schistosomes in evading immobilization by the host blood clotting cascade is discussed. Antibodies to peak one and peak two were detected in hamster sera infected with S. haematobium and S. mansoni using the ELISA test. The specificity of peak two was found to be evident in its low cross-reactivity (18.9%) when confronted with S. mansoni infected sera.

Chromosomes of Acanthocephalus lucii (Muller, 1776) were observed using conventional staining techniques. The number of chromosomes in females and in their developing eggs (2n = 8) as well as the mean (La) and relative length (Lr) of the chromosomes and the localization of the centromere (Ic) were determined. Peculiarities in the behaviour of the chromosomes are also described.

Field investigations were carried out over a 4-year period in three farms of the Haute-Vienne department (France) in order to determine the prevalence of Fasciola hepatica infection in the annual generations of Lymnaea truncatula. Infection rates found in March were significantly lower than those recorded in July or in September (0.8% to 2.2% compared to 5.7% to 13.5% and 4.4% to 9.3%, respectively). They were always lower in overwintering snails than in other snail generations (summer generation in 1989,1990 and 1991; spring and summer generations in 1992). Experimental infections of L. truncatula by F. hepatica were performed to evaluate the characteristics of Fasciola infection with reference to snail generation and snail activity. Survival of summer generation snails at day 30 postexposure was significantly lower in snails collected in September than in those collected in May and June. In the winter generation of L. truncatula, snail survival was significantly higher in snails collected from December to March than in those from November. The prevalence of infection was significantly lower in snails collected in September (summer generation) than in those collected from December to March (winter generation). The duration of the prepatent period was significantly delayed in snails collected from January to March (a mean of 54.2 to 58.2 days instead of 43.1 to 49 days in the other groups), whereas that of the patent period was significantly shorter (5 to 9.3 days instead of 18.3 to 40.3 days, respectively). In snails collected from January to March, the number of metacercariae was significantly lower than that found from other snail groups (a mean of 21.5 to 42 metacercariae instead of 72.8 to 151.4 cysts, respectively). Fasciola infections of L. truncatula originating from spring and summer generations were more efficient than those from the winter generation of snails.

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.

In vitro pairing studies on rediae of Echinostoma trivolvis, E. caproni, Zygocotyle lunata, Ribeiroia sp. and sporocysts from a species of armatae cercaria were undertaken at 22°C in a Petri dish bioassay containing an agar substratum and a Locke's 1:1 overlay. Pairing was arbitrarily defined as larvae in contact or within 1 mm of each other. Intraspecific and interspecific pairing occurred in the bioassay using several larval combinations initially placed 5 or 10 mm apart. Intraspecific pairing occurred with the rediae of Ribeiroia sp. and interspecific pairing was seen between E. trivolvis or E. caproni and Ribeiroia sp. A previous study documented intraspecific and interspecific pairing between rediae of E. trivolvis and E. caproni. Armatae sporocysts did not pair intraspecifically or interspecifically when matched with either E. caproni or E. trivolvis rediae. Intraspecific pairing of Z. lunata or interspecific pairing between Z. lunata rediae and echinostome rediae did not occur. The significance of redial pairing remains unclear.

This study compares the metacercariae of a ‘pygmaeus’ microphallid discovered in Littorina saxatilis from the coast of Northern Ireland with the metacercariae of Microphallus piriformes and M. pygmaeus from the same species of gastropod mollusc from Arctic Russia. Light and scanning electron microscopy were used to provide morphometric and surface details for descriptions of the organisms concerned. Comparison and statistical analysis of the results established that the species from Northern Ireland was M. piriformes and not M. pygmaeus as had previously been assumed. It dearly indicates the need for critical assessment of the accuracy of literature dealing with the occurrence of ‘M. pygmaeus’ in both intermediate and final hosts.