Social Network Analysis Provides Insights for Predicting Infectious Disease Risk

julierushmoreAs part of DugDug’s ongoing series on leading researchers in animal ecology, we have had the unique privilege of interviewing Dr. Julie Rushmore, who just completed her Ph.D. in the Odum School of Ecology and is now working towards a veterinary degree at the University of Georgia. Her recent paper, titled Social network analysis of wild chimpanzees provides insights for predicting infectious disease risk. was published in the journal The Journal of Animal Ecology. The paper studies infectious disease risk in chimpanzee networks.

Please tell me very briefly about your own background and research interests and what led you to do this type of research study?

My long-standing research interests and experiences center on the ecology of infectious diseases and the conservation of threatened species, especially non-human primates. As an undergraduate at Duke University, I performed independent research and an honors thesis in primate behavior at the Duke Lemur Center. Prior to graduate school, I assisted researchers in Madagascar, where I recorded wildlife census data, helped trap and immobilize wildlife, and collected samples for diagnostic work. Through this field experience, I witnessed the devastating effects that infectious diseases can have on endangered species. As human encroachment and contact with wildlife intensifies, opportunities for pathogen transmission from domesticated animals and humans into wild animal populations will increase. I thus realized that to better understand pathogen transmission and control in animals, veterinary researchers that have both clinical skills and a deep understanding of the scientific process are urgently needed. This ultimately led me to pursue a PhD in wildlife disease ecology, with plans to later acquire a DVM.

What were some of your findings?

We found that the most connected individuals in the chimpanzee social networks – that is, the individuals with the most social contact – were the high-ranking adult females and their juveniles. Our results suggest that these individuals were highly connected within in the community because they frequently formed ‘nursing parties’ in which two or more family units (a mom and her juveniles) would spend time together. To a lesser extent, high-ranking males were also more connected relative to other community members. Previous modeling and field studies have demonstrated that highly connected individuals tend to be more likely to transmit and acquire infectious diseases than less connected individuals. Thus, targeting these highly connected individuals for disease intervention could help us develop more impactful and cost-effective vaccination or treatment campaigns for wildlife populations.

How can these findings be used?

For several human diseases, modeling studies have shown that targeting highly connected individuals for vaccination is often significantly more effective in preventing outbreaks than randomly vaccinating individuals. Thus, network models can help identify the minimum number of highly connected individuals that should be vaccinated to reduce outbreak sizes. We are currently using infectious disease models to simulate pathogen transmission on our observed chimpanzee networks to assess the effectiveness of different intervention strategies in slowing pathogen spread. This work is already underway, with results from these simulations showing that for moderately contagious pathogens (such as influenza), infections starting in the most connected individuals are likely to generate significantly larger outbreaks than infections starting in less connected individuals.

What do you plan to do next with these findings?

In addition to publishing this work in academic journals, I’m also very interested in communicating this information to the wildlife managers that directly work on great ape conservation in Africa. To this end, in July 2013 I met with Ugandan government officials and wildlife veterinarians in Uganda to discuss how results from this work can be incorporated into future plans for great ape pathogen control. It was really exciting to share this information with the professionals that are on the ground and responsible for implementing great ape health interventions. It was also wonderful to get their feedback on follow-up projects that could further benefit great ape conservation.

What are ways to increase awareness around this?

We often hear in the news that diseases can spread from wildlife (e.g., chimpanzees and gorillas) into human populations, but what’s talked about less frequently is that humans can also spread their germs to wildlife populations. Great apes did not evolve with many of our diseases, which is why a virus responsible for the common cold in humans can be deadly for a wild chimpanzee. Understanding how, why, and when human diseases spread to wild ape communities can help us better conserve these endangered animals.

Please tell us a little more about your department

I conducted this research at the University of Georgia’s Odum School of Ecology (http://www.ecology.uga.edu/). The Odum School is the first standalone ecology school in the world, and the research done here spans a range of ecological topics including infectious diseases, ecosystem ecology, watershed ecology, evolutionary ecology and sustainability.