The quantitative assay of mitochondrial monoamine oxidase (MAO) activity revealed a higher enzyme level in Explanatum explanatum than Gastrothylax crumenifer. The specific MAO inhibitors, chlorgyline, pargyline, deprenyl and nialamide produced different degrees of interspecific inhibition. The differential effects on enzyme activity of chlorgyline and deprenyl suggests the possible existence of polymorphic forms of the enzyme, MAO-A and MAO-B, in amphistomes. These specific inhibitors also had a differential influence on the in vitro motility of amphistomes, further indicating the involvement of different forms of MAO in the oxidative deamination of biogenic monoamines which might be partly responsible for neuromuscular coordination in amphistomes. The experimental procedures used in this study could be conveniently used for quick screening and evaluation of some of the qualitative effects of anthelmintic drugs under in vitro conditions.

A survey of parasites was conducted on 258 Symphodus ocellatus (Teleostei: Labridae) collected in Corsica National Park (west Mediterranean). In addition, the total length, sex and social status were recorded for each individual fish. Three species of trematodes were found in the digestive tract. One of the parasites, Genitocotyle mediterranea, was only present, with one exception, in males of large size, and principally in the individuals that had the highest status and that were involved in nest construction. Two hypotheses are suggested to explain this particular distribution of a parasite: the immunocompetence handicap and the changing trophic behaviour as the fish grows.

The effect of praziquantel (PZQ) on the strobilar development of the cyclophyllidean cestode Mesocestoides corti was explored. Mesocestoides corti larvae were cultivated under conditions reported to favour their differentiation to the adult stage. Parasites were exposed to 0.1 μg ml-1 PZQ for 16 h and subsequently transferred to drug-free medium. The ocurrence of segmentation — an early event of the larval somatic differentiation to the adult worm — was considered as quantitative data. This phenomenon was evidenced earlier in worms transiently exposed to PZQ with respect to control cultures. Moreover, the rate of segmentation of drug-treated worms at the end of the experiment almost doubled that of control worms. To date, no similar effect on any cestode developmental process has been reported for an anthelmintic drug. In the light of the existing knowledge and understanding of PZQ mechanisms of action, the proposed experimental approach could contribute to the elucidation of pathways and mechanisms involved in cestode strobilar development.

A total of 140 trout were examined from four lakes in north west Ireland, Loughs Craghy, Waskel, Meela and Owennamarve. Eleven species of metazoan parasite were recorded, ten of which were of freshwater origin and Anisakissp. was the only marine species. No acanthocephalan species were found. Diphyllobothrium ditremum, D. dendriticum and Anisakissp. were the only allogenic species. Lough Owennamarve had the largest component community with nine species recorded. Lough Meela, the only brackish water lake had the smallest component community with six species recorded. Lough Waskel and Craghy had intermediate component community values. Lough Meela showed the lowest levels of similarity to any of the other lakes. Values for the Shannon-Wiener diversity index were highest for Lough Owennamarve and lowest for Lough Meela and intermediate for the other two lakes. Lough Meela had the highest values for the Simpson's dominance index and the Berger-Parker index. Lough Owennamarve had the highest Brillouin's index and Lough Meela had the lowest. The use of multiple regression techniques to control for the potentially confounding effect of geographical distance as a predictor of community similarity was discussed. No parasite species found could be considered as regionally and locally abundant and therefore described as a core species. The helminth community appears to have some degree of predictability, but chance colonization events are also important.

Gastrointestinal helminths were collected from pademelons of the genus Thylogale (Marsupialia: Macropodidae) in eastern Australia and Papua New Guinea. Examined were 12 Thylogale stigmatica stigmatica and 13 T. s. wilcoxi, the latter subdivided into eight specimens from the northern limit of their distribution and five from southern areas, all from eastern Queensland, Australia, one T. s. oriomo from Papua New Guinea and ten T. thetis from southeastern Queensland and northern New South Wales, Australia. Six species of cestodes and 40 species of nematodes were found. The helminth community of T. s. stigmatica was similar to that found in northern specimens of T. s. wilcoxi, while differences from the helminth community present in southern T. s. wilcoxi could be accounted for by parasites acquired from sympatric T. thetis. Thylogale thetis harboured a community of helminths distinct from but related to that in T. stigmatica. The evidence suggests that all subspecies of T. stigmatica examined share a common helminth community, but that in areas of sympatry, T. stigmatica and T. thetis share some of their parasites.

The lung fluke, Paragonimus westermani (Kerbert, 1878), is widely distributed in Asia, and exhibits much variation in its biological properties. Previous phylogenetic studies using DNA sequences have demonstrated that samples from north-east Asia form a tight group distinct from samples from south Asia (Philippines, Thailand, Malaysia). Among countries from the latter region, considerable molecular diversity was observed. This was investigated further using additional DNA sequences (partial mitochondrial cytochrome c oxidase subunit 1 (COI) and the second internal transcribed spacer of the nuclear ribosomal gene repeat (ITS2)) from additional samples of P. westermani. Phylogenies inferred from these again found three or four groups within P. westermani, depending on the method of analysis. Populations of P. westermani from north-east Asia use snail hosts of the family Pleuroceridae and differ in other biological properties from populations in south Asia (that use snail hosts of the family Thiaridae). It is considered that the populations we sampled can be divided into two species, one in north-east Asia and the other in south Asia.

Mature specimens of Cucullanus heterochrous Rudolphi, 1802 (Nematoda: Cucullanidae) were obtained from the intestine of the flounder, Platichthys flesus, from Danish waters. Eggs embryonate in seawater but do not hatch. Fully developed larvae pressed out of eggs are 430 μm long with amphids and dereids and enclosed within the cuticle of a previous larval stage. Infective larvae are believed to be in their third stage. Experimental studies showed that the polychaetes, Nereis spp., Scoloplos armiger, Brada villosa and Capitella sp., may act as intermediate hosts. In N. diversicolor the larvae increase their length to 1 mm within four weeks (15°C) without moulting. Experimental infections showed that larvated eggs are not infective to fish, whereas >550 μm long larvae from polychaetes survived in 4–24 cm long flounders and plaice, Pleuronectes platessa. Third-stage larvae 550 μm to 1.1 mm long were found in the submucosa of the intestine one week post infection. At a length of about 800 μm to 1.4 mm they moult to fourth-stage larvae. Fourth-stage larvae, immature and mature worms occur in the intestine and rectum. Fourth-stage larvae and adults survived experimental transfer from one flounder to another. Similar developmental stages survived for two weeks in the intestine of experimentally infected cod, Gadus morhua.

The ectoparasite fauna of two damselfishes, Stegastes nigricans and Dascyllus aruanus, from Moorea Island in French Polynesia was investigated. Gills of these damselfishes were infected with congeneric Monopisthocotylea Monogenea belonging to the genus Haliotrema. Stegastes nigricans were found to harbour a guild of three Haliotrema species whereas only one species inhabited D. aruanus. Microhabitat distribution, inter- and intraspecific competition and interspecific associations on the gill were studied. Observations on site preference revealed no spatial segregation between the three congeneric species inhabiting the gills of S. nigricans. Juvenile and adult monogeneans of that guild occurred on the same microhabitat. The dominant species Haliotrema sp. 1 did not expand on the microhabitat when the intensity of infection increased. Interspecific association tests revealed positive and negative associations. Haliotrema sp. 4 expanded its distribution on the gills of Dascyllus aruanus when the intensity of infection increased suggesting the likelihood of intraspecific competition. Juvenile and adult monogeneans of Haliotrema sp. 4 appeared to segregate as a result of intraspecific competition. This competition may exist to enhance resource availability when the gill habitat is limited. Overlaps between niche breadth and species microhabitat were revealed for monogenean species inhabiting S. nigricans. Interspecific competition did not appear to play an important role in the distribution of S. nigricans congeneric ectoparasites. Reinforcement of reproductive barriers may have led to the avoidance of hybridization.

An analysis is made of the community structure of the helminth parasites of the tuna Euthynnus affinis collected off the coast of Visakhapatnam, Bay of Bengal. The helminth fauna comprised 23 species, consisting of two monogeneans, 18 digeneans, one larval cestode, one nematode and one acanthocephalan. Didymozoids, represented by 14 species, were the dominant members of the parasite spectrum. The parasite assemblage is characterized by species richness as well as a high diversity. Most of the parasites found, the didymozoids in particular, were host specialists, exhibiting a high degree of host specificity. The fauna comprised three core species, four satellite species and many secondary species, with no potential for interaction among them but the degree of predictability is high in that each infracommunity comprised two or three core species superimposed by a few secondary species. Many host factors such as the varied diet, high vagility, long life span and endothermy appear to have contributed to the development of the species rich and diverse parasite communities in the tuna. There was evidence for a decrease in parasite density and an increase in diversity with increase in host size, indicating that host size has a profound influence on the component community structure.

A total of 110 cattle were examined in an area endemic for Bancroftian filariasis for the prevalence of infection of the bovine filarial parasite Setaria digitata. About 12.5% of cattle were found to harbour both adult worms in the peritoneum and microfilariae (mf) in circulation; 70% of the cattle were amicrofilaraemic but with an adult worm infection. A third group of cattle (16.5%) was free of detectable mf and adult worms. The presence of adult worms and/or mf did not influence the antibody levels to any of the four antigen preparations of S. digitata. However, there was a significant inverse relationship between the presence of antibodies to microfilarial sheaths and the absence of circulating mf as shown by the immunoperoxidase assay. Cattle immunoglobulin containing high titres of anti-sheath antibodies cleared circulating microfilariae very effectively in Mastomys coucha thus demonstrating the protective nature of anti-sheath antibodies in eliminating circulating microfilariae in vivo.

The ingestion of soil in parks and public places containing eggs of Toxocara may constitute a significant health risk, particularly to children. To determine the most efficient method for extracting eggs from experimentally contaminated soil, two consecutive studies were undertaken. Four techniques, including washing, sieving, vacuum, and the one recommended by the World Health Organization, were evaluated. Recovery rates of over 85% were recorded with both washing and sieving methods. Using the washing technique, all combinations of the four pre-treatment solutions, distilled water, acetoacetic solution pH 5, 0.1 N sodium hydroxide and 1% Tween 20, and seven flotation fluids with different specific gravities (S.G.) ranging from 1.20 to 1.35 were assayed. The association of distilled water and saccharose solution with an S.G. of 1.27 showed the best results, with a recovery rate of 99.91%.

The effect on the pasture contamination level with infective trichostrongylid larvae by feeding the nematode-trapping fungus, Duddingtonia flagrans at two dose levels to first time grazing calves was examined in Lithuania. Thirty heifer-calves, aged 3–6 months, were divided into three comparable groups, A, B and C. Each group was turned out on a 1.07 ha paddock (a, b and c). The paddocks were naturally contaminated with infective trichostrongylid larvae from infected cattle grazing the previous year. Fungal material was fed to the animals daily during a two month period starting 3 weeks after turnout. Groups A and B were given 106 and 2.5×105 chlamydospores per kg of live weight per day, respectively, while group C served as a non-dosed control group. Every two weeks the heifers were weighed and clinically inspected. On the same dates, faeces, blood and grass samples were collected. From mid-July onwards, the number of infective larvae in grass samples increased markedly (P<0.05) on paddock c, whereas low numbers of infective larvae were observed on paddocks a and b grazed by the fungus treated groups. However, the results indicate that administering fungal spores at a dose of 2.5×105 chlamydospores per kg live weight per day did not significantly prevent parasitism in calves, presumably due to insufficient suppression of developing infective larvae in the faeces. In contrast, a dose of 106 chlamydospores per kg lowered the parasite larval population on the pasture, reduced pepsinogen levels (P<0.05), and prevented calves from developing parasitosis.

A total of 301 blue whiting, Micromesistius poutassou Risso, 1826, ranging in length from 17 to 28 cm, from Motril Bay (Mediterranean coast, south Spain) were examined for anisakid nematodes, as these fish are common items in the Spanish Mediterranean diet. Three anisakid species were morphologically identified with a total prevalence of 10.63%. Anisakis simplex s.l. Rudolphi, 1809 had a prevalence value of 6.65%, compared with 2.66% for A. physeteris Baylis, 1923 and 2.33% for Hysterothylacium aduncum Rudolphi, 1802. Variations in prevalence values with season and host size are discussed. Allozyme markers (leucine aminopeptidase-1) were used to identify anisakid nematodes assigned to the A. simplex complex and all examined larvae were found to correspond genetically to A. pegreffii Nascetti et al., 1986.

High performance thin-layer chromatography (HPTLC) was used to analyse the neutral lipids in the rediae, cercariae, and encysted metacercariae of Echinostoma caproni from Biomphalaria glabrata snails. Visual observations of the chromatograms showed that the most abundant lipid fraction in all stages was free sterol. Quantification of the free sterol revealed mean weights of 2.7 ± 0.64 ng per redia, 0.53 ± 0.023 ng per cercaria, and 0.081 ± 0.0098 ng per encysted metacercaria. Oil Red O staining of the larval stages confirmed the presence of lipids within the rediae and cercariae but did not show lipids in the encysted metacercariae. The dimunition in neutral lipids from the cercarial to the encysted metacercarial stage does not support a previous observation that fat increases in successive phases of the digenean life cycle.