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The spontaneous expulsion of low-level Echinostoma revolutum infections was markedly impaired in mice harbouring 4-week-old Schistosoma mansoni infections at the time of infection with the echinostome.
Members of the genus Trichobilharzia are parasitic in visceral or nasal body parts of their avian hosts. The examination of water snails in South Bohemia revealed a schistosome infection in Radix peregra snails. The experimental infection of ducklings (Anas platyrhynchos, Cairina moschata) confirmed that a new Trichobilharzia species--T. regenti n. sp.--was found. The adults, eggs and larvae (miracidia and cercariae) of the species were morphologically characterized. The adult occupy the nasal blood vessels where they lay the eggs; the miracidia hatch from the eggs directly in the tissue and leave the host during drinking/feeding of the infected birds.
Bunodera sacculata (Trematoda: Allocreadiidae) infected 65 (54%) of 120 yellow perch collected in 1997 and 40 (50%) of 80 perch from Silver Creek in 1998. and 17 (30%) of 56 perch in 2000 from Silver Lake in lower Michigan. Gravid B. sacculata occurred in the pyloric ceca and anterior intestine. There were differences in monthly trends (July through August) in prevalences, mean intensities, and mean abundances of B. sacculata in Silver Creek between 1997 and 1998. The mean intensity +/- SD (8.2 +/- 9.1) and mean abundance (4.1 +/- 7.8) of B. sacculata were significantly higher in 1998 than in 1997 and 2000. An additional 20 perch (0+ in age) collected from the creek in July 1998 were all infected and had the highest mean intensity of 21.3 +/- 14.1.
Infections by metacercariae of Clinostomum (Leidy, 1856) species adversely affect aquacultured fish and are potentially transmissible to humans. Molecular methodologies are efficient tools, which enable diagnosis of all life-history stages of trematodes in their diverse hosts. The small subunit of ribosomal DNA genes of adults of the Old World Clinostomum complanatum (Rudolphi, 1819) and the New World Clinostomum marginatum (Rudolphi, 1819), obtained from a little egret Egretta garzetta (Linnaeus, 1766) and the great blue heron Ardea herodias (Linnaeus, 1758), respectively, were amplified, sequenced, and aligned. The resulting alignment was used to develop a genetic assay to differentiate between these species.
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Density-dependent constraints on parasite growth, survival or reproduction are thought to be important in preventing the unchecked increase in parasite numbers within individual hosts or host populations. While it is important to know where, and with what severity, density dependence is acting within the parasite life-cycle, interpretation of data from natural infections is difficult. In this paper, we present a Monte Carlo simulation technique for examining such data for evidence of density dependence. We also describe how this technique may be used to distinguish among mechanisms hypothesized to generate density-dependent phenomena.
The reproductive kinetics of Protopolystoma xenopodis primary and secondary infections in Xenopus laevis were monitored in a 3-year study. Thirty-five naïve, lab-raised, full-sib X. laevis from 1 spawning were each exposed to 30 P. xenopodis eggs. The course of infections at 20 degrees C was monitored by screening isolated hosts for parasite egg production. Ninety-four percent of toads supported the development of gravid parasites. Infections became patent 9-19 weeks p.i., lasted 3-30 months and produced estimated totals of 1-7152 eggs/host. Variation in primary infection characters was discontinuous: a subgrouping of hosts (16%) was characterized by extended infection duration and low reproductive rate. In order to test the effect of long-term infection history on a subsequent challenge, each host was re-exposed to P. xenopodis infective stages (30 eggs/host) 6 months after the loss of its original infection. Establishment of patent infection was significantly lower (15%), and pre-patent period (12-28 weeks) longer, than in primary infections of the same hosts, and than in concurrently exposed naïve controls (contemporary full-sibs of the primary/secondary infection group, maintained in parallel; n = 28). There was no relationship between primary infection characteristics and secondary infection outcome. Overall reproductive output per initial infective stage for the primary exposure exceeded that for the secondary exposure by a ratio of 15:1. Results suggest that primary infection with P. xenopodis can elicit strong, long-term protective immunity against re-infection in X. laevis.
Sera from cattle with single or mixed infections of Fasciola gigantica. Dicrocoelium hospes, Schistosoma bovis and paramphistomes were examined for fluorescent antibodies. Cross-reacting antibodies of the heterologous flukes were easily detected by using cryostat sections with whole-fluke-antigen of all three flukes. The presence of F. gigantica antibodies in a cattle herd was tested at two monthly intervals in order to establish the occurrence of chronic fascioliasis. The lack of significant differences in antibody levels of infected, treated and uninfected cattle however showed that herd antibody levels are not very useful to detect chronic Fasciola infections.
Hepatic trematodiasis caused by Cyclorchis campula was diagnosed in a juvenile Ganges River dolphin that had been in captivity at an aquarium for approximately 1 year. Histopathologic findings were severe chronic suppurative cholangitis, hyperplasia of the bile duct epithelium, and periductal fibrosis associated with fluke infection of the large bile ducts.
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