Saving Species with Math

Ruminants like this Indian gaur are susceptible to Johne’s disease.

Emerging diseases are a threat to both wildlife and human health. Recently, disease has been implicated in a variety of significant conservation problems, such as the global decline of amphibians, the loss of Hawaii’s native birds, and dramatic population decreases of Tasmanian devils. Veterinarians and physicians use the modern technology of vaccines, drugs, and quarantine to fight disease, but sometimes these modern tools just aren’t enough. Organisms may evolve more rapidly than vaccines can be developed, bacteria can become resistant to drugs, and pathogens may be spread too quickly through the global movement of people and animals to be contained by quarantine.

What if math could be used to stop a deadly outbreak? Often people dislike math in school, but it may be the key to addressing many challenges we face today. Simple pieces of information, such as the contact rate between animals (or people), the number infected, how long an infection lasts, and how quickly it is transmitted can be translated into elegant equations. The joining of these equations gives rise to mathematical models that can describe how disease is spread, help identify the most effective points of intervention, and even predict the severity of an outbreak.

Today’s epidemiologists, mathematicians, and computer experts are using mathematical models to fight disease. Human health researchers have recently used models to understand the factors driving the worldwide spread of H1N1 influenza. San Diego Zoo Global uses such models to help us understand transmission and intervention strategies for Johne’s (pronounced Yo-nees) disease, thanks to support from the Ellen Browning Scripps Foundation. This disease of ruminants (e.g., goats, sheep, deer, and antelope) is an incurable bacterial infection of the intestines. Although we do not lose very many animals to Johne’s disease, it requires constant and challenging surveillance methods to ensure that our animal populations have not unknowingly acquired this infection. We have constructed a mathematical model that is helping us identify the best points of intervention and the optimal disease surveillance strategy. The outcome is better disease response capabilities for us and better health for the animals in our care.

Who would have thought that math would be so useful in our mission to save species!

Carmel Witte is a researcher and Bruce Rideout is the director of the Wildlife Diseases Laboratories of the San Diego Zoo Institute for Conservation Research. Read Carmel’s previous post, Cutting-edge Science in Historical Surroundings.

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