Rapid freezing and substitution with fixative prior to scanning electron microscopy was used to demonstrate the pattern of beat and recovery of the cilia of free swimming miracidia of Fasciola hepatica. There were stages of dexioplectic metachronal co-ordination and the power stroke was approximately 15° anticlockwise from the anterior–posterior axis. Around the circumference of the body of the miracidia there were approximately 12 metachronal waves of power and recovery. Free-swimming cercariae were recorded by time-lapse photography and, after conventional fixation, by scanning electron microscopy. Cercarial tail-beats were to the posterior of the body in the lateral plane at a rate of 8 Hz. The tail has paired lateral ridges positioned to act as leading edges. There is an array of 32 sensory papillae on the mid-ventral surface of the tail. The tegument of the most distal part of the tail is described: it is free of sensory endings and the surface shows a spiral pattern.

The composition and diversity of the total and intestinal component and infra-communities were determined in eels Anguilla anguilla from three shallow lagoons on the Adriatic coast of Italy to determine whether the helminth communities would differ in composition and structure from those in eels from lagoons on the Tyrrhenian coast. The lagoons differed in respect of their management regimes and the extent of freshwater influx. Both freshwater and marine species of helminths were found in the eels in all three lagoons, but the freshwater component was richer in Valle Figheri. A suite of three digenean eel specialist species occurred in all three lagoons, of which any two members dominated each community. This conferred a high degree of similarity between the communities of the three lagoons. The same three species also dominated helminth communities in eels in lagoons along the Tyrrhenian coast of Italy, and compositional similarity levels were similar within and between western and eastern groups. Species richness was higher in the component communities of the eels of the Adriatic lagoons when compared to the Tyrrhenian ones, but diversity and dominance indices were of a similar order of magnitude and range. Intestinal helminth communities were richer and more diverse in two of the Adriatic lagoons because the proportion of eels with zero or one helminth species was, unusually, in the minority. It was nevertheless concluded that infracommunity structure was similar in eels from both western and eastern lagoons and that the hypothesis that it would differ in Adriatic lagoons could not be supported. The findings provide further evidence of the similarity in composition and structure of helminth communities in eels from coastal lagoons throughout Europe.

The tegument of adult Saccocoelioides godoyi Kohn & Froes, 1986 (Digenea: Haploporidae), specimens of which were collected from the intestine of the freshwater fish, Leporinus friderici (Bloch, 1794) (Anostomidae) from the reservoir of Itaipu Hydroelectric Power Station, Parana State, Brazil, was studied by transmission electron microscopy. The tegument comprises an external anucleate layer, covered by a surface plasma membrane and associated glycocalyx. The surface layer is bound by the basal plasma membrane and contains spines, two types of inclusion bodies and mitochondria. Tegumental cell bodies are located beneath the surface musculature and contain a single nucleus, cytoplasm with rough endoplasmic reticulum, mitochondria, ribosomes, and inclusion bodies similar to those found in the external layer. Cytoplasmic strands connect the cell bodies to the external surface layer, suggesting that the inclusion bodies are produced in these cells and pass up into the syncytium, as is known for other digeneans from experimental evidence.

Outbred LACA mice and inbred NIH mice were administered low (100 ova), medium (1000 ova), high (3000 ova) and trickle (4×250 ova) doses of Toxocara canis ova and the effect of infection on activity was examined with respect to: (i) the dose of ova administered and (ii) the number of larvae recovered from the brain. Larval recovery from the brain was significantly reduced in NIH mice compared to LACA mice for the 1000, 3000 and trickle doses. Mice from each strain were divided into larval intensity groupings based upon the number of larvae recovered from their brain. Activity for each mouse was measured pre- and post-infection by observing its behaviour in the home cage. Activity was assessed by monitoring six different independent categories of murine behaviour – ambulation, grooming, rearing, digging, climbing and immobility. Within each behavioural category, the duration of time spent at each behaviour per mouse within one thousandth of a second, the number of short bouts performed and the number of long bouts of behaviour performed were recorded over a 20 min period. Activity of LACA and NIH mice differed prior to infection. LACA mice spent more time immobile compared to NIH mice, which ambulated and climbed more. Variations in activity were also observed between groups of mice prior to infection. The effect of infection differed by strain, by dose and by larval intensity. Post-infection LACA mice became more immobile and ambulated less. NIH mice showed reduced immobility, but while ambulation decreased digging and climbing increased post-infection. Short bouts of activity remained unchanged among LACA mice post-infection but showed an increase for some behaviours in NIH mice.

Outbred LACA mice were administered low (100 ova), medium (1000 ova), high (3000 ova) and trickle (4×250 ova) doses of Toxocara canis ova and the effect of infection was examined with respect to the number of larvae recovered from the brain and their behaviour. Recovery of larvae from the brain was generally low with the % recovery expressed in terms of the total dose administered being highest for the 3000 dose (6.1%) and 1000 dose (6%), followed by the 100 (4.4%) and trickle (3.5%) doses. The variation in larval recoveries was large between individual mice receiving similar doses. The level of infection in the brain was lower in mice receiving a multiple as opposed to an equivalent single dose of ova. Mice were then divided into three larval intensity groupings based upon the number of larvae recovered from their brain. The ranges for the groups were as follows: low intensity group, 0–15 larvae; moderate intensity group, 27–55 larvae; high intensity group, 66–557 larvae. Three behavioural tests were carried out on control and infected mice. Exploration and response to novelty was examined using a ‘T’ maze and learning was investigated by means of a water-finding task. Anxiety was measured using an elevated plus maze apparatus. Infected mice were less explorative and less responsive to novelty in the ‘T’ maze and this was particularly pronounced for the heavily infected mice. In the elevated plus maze, infected mice displayed reduced levels of anxiety to aversive and exposed areas of the maze, particularly in the case of the moderate and high intensity mice. There was evidence for impaired learning ability in the water task apparatus for moderate and high intensity mice. In general, the effects of infection on behaviour were more pronounced in the moderate and high intensity groups compared to the low intensity group.

Adult Fasciola gigantica are leaf-shaped with tapered anterior and posterior ends and measure about 35 mm in length and 15 mm in width across the mid section. Under the scanning electron microscope its surface appears rough due to the presence of numerous spines and surface foldings. Both oral and ventral suckers have thick rims covered with transverse folds and appear spineless. On the anterior part of the ventral surface of the body, the spines are small and closely-spaced. Each spine has a serrated edge with 16 to 20 sharp points, and measures about 20 μm in width and 30 μm in height. In the mid-region the spines increase in size (up to 54 μm in width and 58 μm in height) and number, especially towards the lateral aspect of the body. Towards the posterior end the spines progressively decrease in both size and number. The tegumental surface between the spines appears highly corrugated with transverse folds alternating with grooves. At higher magnifications the surface of each fold is further increased with a meshwork of small ridges separated by variable-sized pits or slits. There are three types of sensory papillae on the surface. Types 1 and 2 are bulbous, measuring 4–6 μm in diameter at the base with nipple-like tips, and the type 2 also have short cilia. Type 3 papillae are also bulbous and of similar size but with a smooth surface. These sensory papillae usually occur in clusters, each having between 2 and 15 units depending on the region of the body. Clusters of papillae on the lateral aspect (usually types 1 and 2) and around the suckers (type 3) tend to be more numerous and larger in size. The dorsal side of the body exhibits similar surface features, but the spines and papillae appear less numerous and are smaller. Corrugation and invaginations of the surface are also less extensive than on the ventral side of the body.

Oesophagostomum bifurcum larvae, cultured from human stools collected in northern Ghana, were used to establish experimental infections in monkeys. A patent infection was established in a rhesus monkey (Macaca mulatta) and this infection was used to generate larvae to inoculate additional monkeys. In all, 17 animals were inoculated. Thirteen of 15 animals developed antibodies to the infection between 19 and 62 days post inoculation (PI); two animals had a positive response before inoculation. Four of ten animals developed patent infections between 88 and 134 days and passed eggs in the faeces. Egg shedding was consistent in only one animal, but at low levels of one or two eggs per 2 mg direct smear, and extended over a 400 day period. In the other three animals, egg shedding was sporadic and of only 2–4 weeks duration. In seven animals necropsied between 19 and 22 days PI, one to 17 early fourth-stage larvae were recovered from nodules in the bowel wall; in an eighth animal examined at 314 days, six immature adult worms (early fifth stage) were recovered from nodules in the bowel wall. The morphological features and growth of these recovered larvae are described. Three animals were inoculated with larvae that had been dried for one week at 28°C; two animals began shedding eggs at 128 and 134 days PI, respectively. The present results suggest that the parasite obtained from humans is poorly adapted to lower primate hosts, and supports the concept that Oesophagostomum bifurcum found in humans and monkeys in the same geographical region of northern Ghana and Togo are distinct and that the infections in humans are not likely to represent zoonotic infections acquired from monkeys.

A preliminary purification has been carried out by continuous elution electrophoresis of a 49.5 kDa protease of crude extracts from Dicrocoelium dendriticum eggs. The enzyme showed a high capacity to degrade the collagen derivative azocoll at acidic pH. Although it is necessary to carry out further experiments to confirm any physiological role, this protease could be implicated in penetration mechanisms.

A unique human case of alveolar echinococcosis was described in 1979 from the Klatovy district of the Czech Republic. However, there were no previous epidemiological studies in this area focusing on detection of the source of infection – Echinococcus multilocularis adults producing eggs. During the period June 1997 to April 1999, 29 out of a total of 46 (63.3%) red foxes (Vulpes vulpes) in the Klatovy district and one of four foxes (25.0%) in the Pilsen South district were found to be infected with adult worms of E. multilocularis. No E. multilocularis adults were found in other animals from the Klatovy district (i.e. three specimens of Martes martes, two Martes foina, one Mustela erminea, two Meles meles and one Felis catus f. domestica). An examination of faecal samples from 55 dogs (Canis familiaris) from the Klatovy district resulted in the detection of E. multilocularis DNA in one (1.8%) sample. The present results support the possibility that human alveolar echinococcosis previously described in the Czech Republic had the character of an autochthonous infection. There are also indications of a potential risk of infection to humans.

The genetic diversity within the genus Trichinella was studied using cleavage fragment length polymorphism (CFLP) analysis. The CFLP method generates specific fingerprints based on single nucleotide mutations. By this method the amplified intergenic regions of the 5S rRNA genes of the eight different genotypes of Trichinella were analysed. The CFLP pattern of T. spiralis was completely different compared with the sylvatic species T. britovi, T. nativa, T. nelsoni, and the genotypes Trichinella T5, Trichinella T6 and Trichinella T8. The T. pseudospiralis intergenic region can be differentiated by size from the other species of Trichinella.

Peroxynitrite (ONOO-) is a cytotoxic anion, produced by interaction between nitric oxide and superoxide in vivo in some inflammatory cells. This study investigated its effects on Fasciola hepatica and Dicrocoelium dendriticum isolated from ovine livers and kept in bile at room temperature. Peroxynitrite was synthesized using a quenched flow reactor and assayed spectrophotometrically. It was applied at different concentrations (10-3.5 to 10-2.3 M) to the flukes kept in bile. The viability of the peroxynitrite-treated flukes was compared with a control group (n=5–7 per group). Control F. hepatica and D. dendriticum lived for 226±11 and 208±14 min, respectively. Life times were decreased by peroxynitrite at all concentrations used (P<0.001). At the highest concentration of peroxynitrite, F. hepatica and D. dendriticum lived only for 6.1±0.4 and 4.1±4.1±0.2 min, respectively. Correlation between peroxynitrite concentration and parasite viability was significant in the case of F. hepatica (r=-0.842; P=0.0035). A single application of peroxynitrite can decrease the life span of ovine liver flukes. A failure in the activation of hepatic macrophages in infected animals may lead to a decreased production of free radicals and, thus, peroxynitrite. Such a failure is likely to deprive the body of a defence tool against multicellular parasites.

The effects of a diet deficient in the B vitamins on infectivity, growth, and distribution of Echinostoma caproni in ICR mice were studied. The vitamin-deficient diet (experimental) was isocaloric to the control diet but lacked the B vitamins. Thirty-six female, 6- to 8-week-old ICR mice were each infected with 25 metacercarial cysts. From the day of infection to the day of necropsy, 18 mice were fed the experimental diet and the remaining mice received the control diet. Equal numbers of experimental and control mice were necropsied at 2, 3 and 4 weeks postinfection (p.i.). Mice on the experimental diet showed a significant loss in body weight between 2 and 4 weeks p.i. There was no significant difference in worm recovery at 2 to 4 weeks p.i. from mice on either diet. Worms from hosts on the experimental diet were more dispersed and located more posteriad in the small intestine than those from mice on the control diet. Worm dry weight was significantly less in hosts on the experimental diet at all weeks p.i. compared with that of hosts on the control diet. The body area of worms on the experimental diet was significantly less at 2 and 3 weeks p.i. than that of worms on the control diet. An isocaloric diet deficient in the B vitamins had a detrimental effect on the growth of E. caproni in ICR mice.

Steinernema longicaudum Shen & Wang is redescribed based on a comparative morphological study of specimens from the type isolate from China, and two other isolates recovered from Korea and the USA. For the first and second generation female, the location of the vulva, shape of the vulval lips, and shape and length of the tail were newly observed diagnostic characters. A more detailed description of the morphology of the male spicules and gubernaculum, and the arrangement of the genital papillae is included. A description, based on scanning electron microscopy observations, of the lateral field pattern of the third-stage infective juveniles is also provided. Additionally, restriction fragment length polymorphism profiles based on the internal transcribed spacer region, and cross-breeding tests supplement the description of this species.

Studies on the seasonal population dynamics of Neoechinorhynchus qinghaiensis (Acanthocephala: Neoechinorhynchidae) in its fish host Gymnocypris przewalskii przewalskii in the Qinghai Lake, China, were carried out with samples taken in May 1991, August 1992, November 1992 and February 1993. Prevalences were higher than 44% in all seasons. The mean intensity of infection was above 124 worms per fish. The maximum intensity of worms recovered from a single fish was 1402 in the autumn of 1992. Differences in the mean abundance, mean intensity and prevalence are not statistically significant relative to season and this is likely to be related to the stable temperatures recorded at the bottom of Qinghai Lake. Over-dispersed distributions of N. qinghaiensis in the host population, due to heterogeneity and feeding habits, were observed in all seasons. The size composition of both sexes of N. qinghaiensis showed males to be less than 3.5 mm and females between 0.5 and 4.25 mm, with the main recruitment phase in the worm populations occurring in the autumn, extending through winter and spring with the lowest recruitment occurring in the summer. The maturation and copulation of worms were mainly focused in the summer season. The sex ratio of female to male was both high in winter (1.51:1) and spring (1.48:1). The higher proportion of females and the change in the worm sex ratio in winter can be attributed to the reduced longevity of male worms. As immature male worms exhibit a higher proportion of the worm population than females in all seasons, further studies are needed to determine if such a situation compensates for the shorter life span of males.