Includes bibliography.

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Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 117-134).

Lernaea spp. was identified as a widespread problem in West Malaysia and various aspects of the parasite were studied. A survey of the distribution of Lernaea spp. in West Malaysia revealed its presence in all the 8 government owned fish breeding stations, 104 privately owned farms and 4 out of 5 consignments of imported fingerlings. The Lernaea spp. present in these ponds were identified as L. piscinae and L. cyprinacea "Asian" form (=b.elegans) and its morpha forms, L. ctenopharyngodonis and L.guadrinucifera. The life cycles of L. cyprinacea and L. piscinae were determined under laboratory conditions. Infection of ~. auratus with the offspring of L. cyprinacea "Asian" form produced adult females similar to the maternal form and another form identified as b. ctenopharyngodonis. A. nobilis, infected with L. cyprinacea "Asian" form and L. piscinae produced only species identical to the maternal form. A high degree of polymorphism was revealed and was further investigated. Morphometric studies on the larval stages and adult female parasites were investigated and reliable characteristics for the identification of Lernaea is discussed. The distribution frequency of b. cyprinacea on 3 host species and L. piscinae on A. nobilis in aquarium tanks was goodness of tested for/fit with the theoretical negative binomial distribution. The bases of fins were found to be the preferred site of infection for both species. studies on growth performance of A. nobilis infected with L. piscinae in ponds, revealed a significant reduction in Specific Growth Rates. Infected fish had a higher mortality than uninfected fish. A decrease in parasite infection on the body surface after 3 months was associated with its appearance in the eye. A challenge infection did not establish and the fish were suspected of being immune. Histopathological studies showed a typical inflammatory response with the formation of a granuloma. Eosinophilic granular cells, lymphocytes, and club cells which were identified in the hosts immune to the infection, were believed to play an important role in the rejection of parasites.

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No description available.

Natural selection should favour host defenses that reduce a host’s exposure to parasites or reduce their negative effects. One strategy that resolves the substantial costs of host immunity and/or tolerance is to avoid infective stages altogether. For fish, behavioural avoidance is well-known for defense against aquatic predators, but it is poorly known for defense against parasites. I used a model system that is amenable to experimental manipulation to test the behavioural avoidance hypothesis for fathead minnows exposed to the larvae of two of their common flatworm parasites. First, I showed that minnows exposed to a liver encysting trematode, Ornithodiplostomum sp. showed an increase in lipid peroxidation, an indicator of oxidative stress, persisting through worm development. Three lines of evidence provided support for the behavioural avoidance hypothesis. First, shoal area decreased in groups of minnows exposed to O. ptychocheilus cercariae compared to those exposed to cues from other aquatic threats. Second, average worm numbers were 50 % lower in fish confined to artificial shoals compared to non-shoaling minnows, indicating that shoaling reduces risk of exposure. The third experiment showed that minnows within the centre of shoal reduced their risk of infection by 67%. Taken together, these results demonstrate a cost of trematode infection on minnows, that minnows can detect infective larvae within the water column, and that social living reduces a hosts’ risk of exposure. / xi, 84 leaves : ill. ; 29 cm

The relationships among parasite growth, responses to infection and host genetic factors were examined in rodents infected with Echinococcus multilocularis. Mongolian gerbils, cotton rats and C57L/J mice were relatively susceptible to the infection, whereas five other inbred strains of mice, and hybrids and backcrosses between C57L/J and C57BL/6J mice were more resistant. In mice, susceptibility to E. multilocularis was controlled by multiple, non-H-2-linked genes, as were pathological, inflammatory and specific (antibody) responses to the infection. These responses were also affected by the degree of parasite growth in individual hosts. Antibodies, natural killer cells and hematological responsiveness were ruled out as contributing to resistance to E. multilocularis. Studies on peritoneal leukocytes from infected animals suggested that infections with E. multilocularis were controlled by cells in two phases: an acute phase involving neutrophils and mononuclear cells and a chronic phase involving eosinophils and mononuclear cells.

The ecology of Protocalliphora parasitism was studied for a two-year period in two species of cavity nesting passerine birds breeding in southwestern Quebec, the eastern bluebird (Sialia sialis Linnaeus) and the tree swallow (Tachycineta bicolor Vieillot). Both species occupied next boxes in open field habitats. Nests were parasitized primarily by Protocalliphora sialia Shannon and Dobroscky. / The relationship between the number of Protocalliphora larvae per nest and selected nesting variables was examine for the two species. The variables included hatching date of the host young, nest material volume, number of fledglings, and percent canopy cover above the nest box. In bluebirds, the number of larvae per nest was significantly correlated with nest material volume in 1989 and number of fledglings in 1990. In tree swallows, the number of larvae per nest was significantly correlated with hatching date and number of fledglings in 1989. / Information on reproduction in Protocalliphora was obtained. Gravid flies were captured in active nests up to the last end of the second week of the nestling period. P. sialia was determined to be at last bivoltine through mark, release, and recapture studies. It was determine that nulliparous P. sialia can complete egg development within 9 or 10 days after eclosion. The practicality of a new Protocalliphora trapping technique and a mark, release, and recapture technique was demonstrated. (Abstract shortened by UMI.)

The rate of recombination and parasite load of species of anuran from Peruvian Amazonia were examined to test the idea that recombination functions to diversify progeny in order to resist the continual counter-adaptation of parasites. The anurans were found to be hosts to over 32 species of macroparasite, as well as a wide variety of protistan and moneran parasites. It was found that a combination of three variables (diet, habitat, abundance), together with host body size accounted for a substantial proportion of the variation in mean parasite richness and parasite species distribution among host species. The relationship between parasites and ecology was found to be independent of host phylogeny. The demonstration of substantial environmental heterogeneity in parasitization predicates that a positive relationship between parasite richness and recombination should be found in this case. This prediction was supported by the data: highly parasitized species of anuran had higher rates of recombination. This is the first study to demonstrate a direct positive relationship between recombination (rather than sex) and parasites.