Zoonoses: The War between Domestication and Disease


A recent outbreak of Ebola in West Africa has killed 101 people out of 158 suspected cases, according to a World Health Organization (WHO) report released April 10. There are no known treatments or vaccines for this disease, and the fatality rate differs widely, from 25 to 90 percent. According to WHO, Ebola transmission among humans occurs via direct contact of bodily fluids and tissues as well as contact with infected animals. The disease is zoonotic, meaning it can be transmitted from animals to humans.

In fact, more than half of all human pathogens are zoonoses. Ebola may seem like a distant threat, but zoonotic diseases such as H1N1 (swine flu), West Nile Virus, and HIV/AIDS are much closer to home. All of these diseases highlight the importance of understanding zoonoses in the context of human health.

The Saint Louis Institute for Conservation Medicine (ICM) conducts research projects to investigate zoonotic disease using the concept of One Health, an emerging model that bridges animal and human health research. The institute was established by the Saint Louis Zoo in order to research diseases that affect the conservation of threatened and endangered species.

In a report on zoonotic disease and One Health, the World Bank said many countries’ current “public health systems (both their human and veterinary systems) are often the weakest links in preventing the spread of disease in their animal and human populations, to their neighbors and to the rest of the world.” Through research done at institutions such as the ICM, this link may be strengthened.

Sharon Deem, Director of the ICM, said conservation medicine is a way “to better understand the health of animals, humans and the ecosystems that support all life on earth.” Conservation medicine and the concept of One Health can supplement our knowledge about zoonotic diseases and help combat their negative effects—for both animals and humans.

The ICM is currently exploring the effect of pathogens in unpasteurized camel milk on the health of both wildlife and humans. In Northern Kenya, around 10 percent of people drink unpasteurized camel milk, exposing themselves to zoonotic pathogens. By studying the diseases present in the milk and the mechanism of their transmission to both humans and wildlife, the ICM hopes to minimize disease exposure and decrease the use of wildlife for protein.

The study found a higher prevalence of pathogenic bacteria in camel milk than in sheep and cattle milk. In Kenya, this increased risk corresponds with an increased use of camels as domesticated animals. This, in turn, augments the number of camels that can infect other animals. The study is still in its early stages, but the ICM considers it “a first step to better understand potential impacts that camel production may have on the health of humans and wildlife in the region.” Therefore, the problem is one of both public and environmental health.

“It’s important not to put the wildlife as the bad guys,” Deem said. “The intimacy and the contact has changed why these pathogens that have natural reservoirs are spilling over into humans.”

study published in Nature shows that decreased biodiversity often causes an increase in the rate of transmission. Additionally, “almost half of the zoonotic diseases that have emerged in humans since 1940 resulted from changes in land use, from changes in agricultural or other food production practices, or from wildlife hunting.”

WHO reports that outbreaks of Ebola usually occur in remote villages near rainforests and that the natural reservoir is fruit bats. In an effort to slow the Ebola outbreak, Guinea has banned the sale and consumption of bats, a local delicacy.

However, very little is known about whether bats directly infect humans or if there is a bridging animal. By looking more closely at the animal-human disease interface for Ebola, we could discover possible ways to avoid transmission of the disease in the future.

The ecosystem we live in and the prevalence of zoonotic diseases are intricately linked. Public health as well as long-term conservation and research efforts can work together to reduce the prevalence of pathogenic diseases and to promote biodiversity.


How can YOU get involved in conservation medicine?


The ICM conducts studies on wildlife preservation and human health in both the United States and abroad. Strictly conservational research includes a study on box turtles in Forest Park and Galapagos turtle movement ecology. In addition to the dromedary camel project, there is also a current study researching lemur and human health in Madagascar. Additionally, a study researching the effects of zoos on mental health has begun this spring.


If you are interested in working on conservation medicine, check out the ICM at http://www.stlzoo.org/conservation/institute-for-conservation-medicine!

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