Who Will Catch Johne’s Disease?

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Gina Geiselman works with DNA samples in the Genetics Lab.

Gina Geiselman works with DNA samples in the Genetics Lab.

Wild animals can be endangered for many different reasons, most of them related to habitat loss, poaching, climate change, and pollution. However, disease outbreak in wild and captive animals has also been a factor of major concern to conservationists. Diseases such as Johne’s (pronounced yo-nees) disease have been reported in hoofed mammals at the San Diego Zoo and San Diego Zoo Safari Park, jeopardizing valuable animals designated to specific breeding programs or exhibits. This disease is a bacterial infection that causes wasting and chronic diarrhea, eventually leading to death.

Because of the potentially disastrous effect of Johne’s disease on captive wildlife health and conservation, it is vital to identify those individuals at higher risk or more susceptible to the disease and prevent mortality. This summer, I had the opportunity to work in the Genetics Division of the San Diego Zoo Institute for Conservation Research exploring genetic markers potentially associated with species susceptibility to Johne’s disease in various hoofed mammals in our collection, including springbok, water buffalo, and various goat species.

Above is sequenced white-tailed gnu DNA from the gene SLC11A1.

Above is sequenced white-tailed gnu DNA from the gene SLC11A1.

I examined genetic variation in genes that have been used to study Johne’s disease in cattle and a similar disease in humans, Crohn’s disease. These so-called “candidate genes” for Johne’s disease did not show evidence of being associated with susceptibility to Johne’s, as patterns of genetic variation were not correlated with levels of incidence across species. This result was disappointing but somewhat expected, given that genes associated with disease susceptibility are typically very hard to identify, especially among animals in managed care with small population size and related individuals.

Nonetheless, this study was a great opportunity for me to learn new genetic techniques. It opened up a new possibility for evaluating more genes and also additional animals in future studies. Animal care and well-being is a San Diego Zoo Global priority, and using genetics as a tool may help improve the management of these precious and endangered animals.

Gina Geiselman is a 2014 summer fellow at the San Diego Zoo Institute for Conservation Research.

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