Brugia Malayi - Clark Science Center - Smith College

Metagenomic Study of the Equine Gatrointestinal Tract before and after
Treatment with the Antihelminthic Medication, Ivermectin
Rachael Sirois
Horses require constant antihelminthic treatment in order to prevent infection by a range of parasitic nematodes. Infection by
parasitic nematodes can lead to a variety of symptoms, including retarded growth, weight loss, anorexia, anemia, recurrent colic,
digestive disturbances, general weakness, and in severe cases, death. Many antihelminthic treatments work by interfering with the
nervous system and muscle function of the parasite, but they may also eliminate other organisms, such as natural gut bacteria and
fungi. The ideal way to study this process while better understanding the equine gastrointestinal tract is to conduct a metagenomic
study of the gastrointestinal tract microbiome. 1 This study will be performed with the purpose of addressing two specific aims:
1) identify the approximate genetic composition of samples isolated from the equine gastrointestinal tract, thereby providing an
accurate representation of the microbial community, and 2) track individual species throughout the duration of the treatment cycle
using high-throughput sequencing.
The central hypothesis is that the presence of these parasitic nematodes, or the drugs used to treat them, may cause changes
in the balance of the gastrointestinal tract microbiome and, in turn, adversely affect the health of the horse. DNA samples will be
isolated from equine fecal samples throughout the duration of pre-treatment, treatment, and post-treatment with the antihelminthic
medication, Ivermectin. After determination of sample genetic composition through use of the Automated Ribosomal Intergenic
Spacer Analysis (ARISA) method, 2 genomic DNA samples will be sequenced using the high-throughput sequencing technology,
Ion Torrent by Life Technologies, which is to be provided by New England Biolabs in Ipswich, MA. The proposed research is
significant because it addresses the need for a better understanding of the equine GI tract microbiome, a valuable field that is
highly underrepresented in the biology sphere.
Two fecal samples, Pre-treatment with Ivermectin and Post-treatment with Ivermectin, were appropriately prepped for
sequencing on the Ion Torrent, which included end-repair of the samples and adapter ligation. The Ion Torrent generates
relatively shorter reads, ranging from 170-200 base pairs and thus, bioinformatics will be an important component to this project.
Sequencing of the pre-treatment samples generated 986 contigs comprised of 394,376 base pairs. The next stage for this project
will be to decide on a data analysis program, such as Geneious or Galaxy, to analyze the data from both Pre-treatment and Posttreatment
samples. This will be the aim for my research going into the 2012-13 academic year and will be the focus of my master’s
thesis to be presented at the end of the spring semester. (Supported by Blakeslee Fund in Biological Sciences)
Advisor: Steven Williams
References:
1 Santos, A. S., et al. “Understanding the Equine Cecum-Colon Ecosystem: Current Knowledge and Future Perspectives.” Animal 1.1 (2010): 1-9. Print.
2
Popa, R., et al. “Limitations and Benefits of ARISA Intra-Genomic Diversity Fingerprinting.” Journal of Microbiological Methods 78.2 (2009): 111-8. Print.
2012
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