Publications by authors named "Gerald W Esch"

Disseminated visceral coccidiosis (DVC) is a widely distributed intestinal and extraintestinal disease of cranes caused by eimeriid coccidia and has lethal pathogenicity to several crane species. Here, feces of 164 black-necked cranes collected in Dashanbao Black-necked Crane National Nature Reserve, China, were examined to determine the prevalence of coccidial oocysts. Of the 164 fecal samples, 76 (46.

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Sheep (Ovis aries) are intermediate hosts for at least six named species of Sarcocystis: S. tenella, S. arieticanis, S.

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Rapid losses of biodiversity due to the changing landscape have spurred increased interest in the role of species diversity and disease risk. A leading hypothesis for the importance of biodiversity in disease reduction is the dilution effect, which suggests that increasing species diversity within a system decreases the risk of disease among the organisms inhabiting it. The role of species diversity in trematode infection was investigated using field studies from sites across the U.

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Water buffalo (Bubalus bubalis) is the intermediate host for at least four species of Sarcocystis: S. fusiformis, S. buffalonis, S.

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Williamson's mouse deer, Tuagulus williamsoni (Kloss), is one of the smallest ungulates among tragulid species found in northern Thailand, and Yunnan Province, China. Here we describe Sarcocystis menglaensis n. sp.

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Digenetic trematodes have complex life cycles involving multiple hosts and free-living larval stages. Some species have 2 lar-val stages that infect snails, with miracidia and cercariae using these molluscs as first and second intermediate hosts, respec-tively. Although both larval stages may infect the same snail species, this is accomplished using different chemical cues and may be influenced by different biotic and abiotic factors.

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The microhabitats in which hosts live can potentially influence the ability and success of parasites in finding and infecting these hosts. The infection dynamics of both digenetic trematode parasites and a nematode parasite (Daubaylia potomaca) infecting a pulmonate snail, Helisoma anceps , were observed in a small North Carolina lake using 3 different classifications of substratum type based on percent coverage by leaves and debris. There were no differences in snail site occupancy or density between substratum types, but small-scale differences in microhabitat impacted parasite prevalence and intensity in their gastropod hosts.

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Numerous species of Sarcocystis have been reported from wild ruminants, but none has been from Williamson's mouse deer (Tuagulus williamsoni). Here, we describe a new species, Sarcocystis tuagulusi, infecting five of 12 Williamson's mouse deer from southwest China. Mature sarcocysts are microscopic, up to 2280-μm long.

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Auto-infection is a life history strategy used by many parasitic organisms, including digenetic trematodes. The process of autoinfection most frequently involves the transfer of a life cycle stage of the parasite from one site to another inside the same host, usually accompanied by morphological transformation. Moreover, among trematodes, the stage being transferred may also move from one host to another in completing the life cycle, i.

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The infection patterns of parasites are often tied to host behavior. Although most studies have investigated definitive hosts and their parasites, intermediate host behavior may play a role in shaping the distribution and accumulation of parasites, particularly the larval stages. In an attempt to answer this question, more than 4,500 pulmonate snails were collected from 11 states in the mid-Atlantic and Midwestern United States in the summer of 2012.

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Fifty-six oriental voles, Eothenomys miletus (Thomas), were collected in Anning prefecture of Yunnan Province (China) between March 2012 and December 2013 and examined for the presence of sarcocysts. Sarcosysts of a new species, Sarcocystis eothenomysi n. sp.

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Daubaylia potomaca is a nematode parasite that exhibits an unusual direct life cycle in planorbid snails in which adult females are the infective stage, after being shed from a definitive host. The present study examined the shedding patterns of this nematode to determine what cues or mechanisms might lead to the parasite leaving its host. A correlation was found between host death and the frequency and number of D.

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Hemophagocytic syndrome is a rare disease that is often fatal, despite treatment. An immunocompetent patient was presented with fever, hepatosplenomegaly, cytopenias, hypertriglyceridemia, hypofibrinogenemia, and hyperferritinemia, which conformed to a hemophagocytic syndrome diagnosis. Despite broad antibiotic treatment, the patient's clinical condition rapidly deteriorated and he died within 8 days of admission.

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Daubaylia potomaca is a parasitic nematode that exhibits a direct life cycle using planorbid snails as their only host. Within the snail host Helisoma anceps , all developmental stages of the parasite are present at any given time. The nematode has an unusual life cycle, with the adult female being the infective stage rather than the third-stage larvae (L(3)), as is commonly the case in many other parasitic nematode life cycles.

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Many biotic interactions can affect the prevalence and intensity of parasite infections in aquatic snails. Historically, these studies have centered on interactions between trematode parasites or between trematodes and other organisms. The present investigation focuses on the nematode parasite Daubaylia potomaca and its interactions with a commensal, Chaetogaster limnaei limnaei , and a variety of trematode species.

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Daubaylia potomaca is an unusual parasite for several reasons. Specifically, it has a direct life cycle in which it uses a planorbid snail, Helisoma anceps , as the definitive host. In addition, adult females have been shown to be both the infective stage and the only stage documented to be shed from a live, infected host.

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The effects of autogenic-allogenic status on the species-area relationship and the relationship between geographic distance and intercommunity dissimilarity were investigated in macroparasite communities of the bluegill sunfish Lepomis macrochirus. Rank correlation analyses were used to examine the relationship between pond surface area and species richness of all species collectively and of autogenic species and allogenic species separately. A positive relationship was found for allogenic species, whereas there was no association for all species, nor was there an association when the study was restricted to autogenic species.

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Rates of community similarity decay were examined among parasite communities of the bluegill sunfish from isolated populations located throughout the midwestern and southeastern United States. Rates of decay were compared for assemblages composed of all species, autogenic species only, and allogenic species only. Rates of similarity decay were calculated by regressing a matrix of intercommunity distance against a matrix of intercommunity Sorenson similarity for each group of species.

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A positive relationship between distribution and local abundance is often observed among species in a community. The resource-breadth hypothesis suggests that this pattern is the result of differential abilities among species to utilize available resources, such that generalists are widely distributed and locally abundant, and specialists are narrowly distributed and locally sparse. This hypothesis was tested in a community consisting of 22 species or morphospecies of parasites infecting members of 18 species of fish among 14 sites in 7 small streams in the Appalachian Mountains of North Carolina.

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Traditionally, the field of parasitology has dealt with eukaryotic animals, to the exclusion of viruses, bacteria, fungi, etc., which is the way it will be approached here. The focus of the present paper will be on certain ecological aspects of the life cycles and life-history strategies employed by the Digenea, a diverse group of platyhelminths that includes some 25,000 species.

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