The in vitro effect of Khawia sinensis on leucocyte activity in carp (Cyprinus carpio)

Influence of Triaenophorus nodulosus plerocercoids (Cestoda: Pseudophyllidea) on the occurrence of intestinal helminths in the perch (Perca fluviatilis)

Concurrent infections of helminths in vertebrates are widespread and may demonstrate synergistic, antagonistic or negligible levels of interactions between species that share a common site. However, indirect interactions between species that occur in different organs of a host are poorly documented, particularly in fish. Plerocercoids of Triaenophorus nodulosus are common liver infections of European perch (Perca fluviatilis). These larval cestodes cause extensive liver damage, resulting in systemic pathologies that include alteration of the physiochemical environment of the intestine. Perch harbour a wide range of intestinal helminths whose occurrence may be potentially influenced by the concurrent presence of T. nodulosus plerocercoids. The present study, using an existing dataset, investigated the effects of T. nodulosus on the infection levels of four common perch helminths - Acanthocephalus lucii, Camallanus lacustris, Proteocephalus percae and Bunodera luciopercae. The prevalences of A. lucii and C. lacustris were significantly reduced in fish infected by T. nodulosus, although the mean intensity of infections remained unaffected for any helminth species, while the mean abundance of C. lacustris was significantly reduced in plerocercoid-affected perch. Differences in site selection and individual interactions between the four helminth species in the intestine of T. nodulosus-infected and non-infected perch were rarely observed.

Effects of a chemically polluted discharge on the relationship between fecundity and parasitic infections in the chub (Leuciscus cephalus) from a river in southern England

In fish there is a close association between endocrine and immune function that during seasonal changes in reproductive status can affect the fishes susceptibility to parasitic infection. The effects of endocrine-disrupting pollution on this association are not known. The present study investigates the effects of a chemically polluted (ammoniacal nitrogen, zinc, bromide) discharge in Cranleigh Waters, a river in southern England, on the fecundity and parasitism of chub, Leuciscus cephalus, over an 18-month period. In the polluted site, the gonado-somatic index (GSI) of fish was lower in females and higher in males compared to an unpolluted upstream site, indicating an androgenic effect on reproduction. Parasite species richness, especially the intestinal helminths Proteocephalus torulosus and Pomphorynchus laevis, was increased in fish in the polluted site. However, the occurrence of the two most common parasite species in the river-Myxobulus sp. 1, a gill myxozoan, and Diplostomum sp., a trematode found in the eye-was unchanged between polluted and unpolluted river sites. Nevertheless, there was a significant relationship between GSI and the prevalence of these two parasite species in the unpolluted site but not the polluted site suggesting that endocrine disruption of reproduction did not lead to an increase in host susceptibility. The reasons for this are discussed.

Tapeworm Khawia sinensis: review of the introduction and subsequent decline of a pathogen of carp, Cyprinus carpio

The Asian tapeworm Khawia sinensis Hsü, 1935 (Cestoda: Caryophyllidea) is a large-sized (body length up to 11.5 cm) monozoic (unsegmented) parasite of common carp (Cyprinus carpio L.) that may cause mortality of young fish (fry). Since the 1960s, this cestode successfully colonized a large part of Europe, including the British Isles, North America and Japan. However, a review of published records provides evidence that the tapeworm K. sinensis, invasive parasite of carp, has become less common during the last two decades. Decline of K. sinensis may have been related to the recent introduction of another invasive tapeworm, the caryophyllidean Atractolytocestus huronensis Anthony, 1958 to Europe. Other factors that may have caused that K. sinensis is much less common than previously are also briefly discussed. A comparison of K. sinensis from feral and cultured carp, published to date, with those recently found for the first time in wild populations of carp in Slovakia did not reveal any marked differences in their morphology or measurements.