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Publication Date


Document Type

Honors Project


Biological Sciences


Metagenomics, Molecular biology, Gastrointestinal system, Strongylida, Helminthiasis, Horses, Equine


Horses require constant anthelmintic drug treatment in order to prevent infection by a group of parasitic nematodes called cyanthostomes, or small strongyles. Clinically, this group of parasites rarely proves to be fatal with many horses not showing strong symptoms when infected; however, in some cases infection can lead to serious health problems. Because horses are commonly dosed so frequently with anthelmintic drugs, there is a serious risk of the parasites becoming immune to the drugs or for serious health problems to develop due to a lack of parasites. This study attempts to begin to discover the possible effects of infection by parasitic nematodes, as well as the effect of anthelmintic drug treatments on the highly sensitive microbiome of the equine gastrointestinal tract using metagenomic methods. Fecal samples from four horses were collected four days before an anthelmintic drug treatment and then for four days after treatment. Two tests, bacterial fingerprinting and massively parallel sequencing, were used to explore the changes of the microbiome in order to provide both a broad and a detailed view of the environment within the gastrointestinal tract. The bacterial fingerprinting test revealed that the microbiome among horses was found to be highly variable, solidifying the idea that each individual has its own specialized microbiome in the gastrointestinal tract. Furthermore, no species were found to be present in all four horses across both treatment periods, suggesting that there is no core set of bacterial species present in all horses. On average 50% of bacterial species were found to be conserved from day-to-day and an average of 102 species appear to make up the microbiome of the equine gastrointestinal tract. The removal of parasites does not significantly affect the microbiome, while the treatment with the anthelminthic drug appears to have a slight effect.




58 p. : ill. (some col.) Honors project-Smith College, Northampton, Mass., 2012. Includes bibliographical references (p. 43-44)