Many wildlife species are social and live in groups, which provides benefits critical to survival. Group living and cooperation between individuals improve group performance by enhancing reproduction, improving foraging success, and increasing the ability to defend against predators. However, it is also known that the relative size of the group matters. If the number of individuals in a group decreases, the benefits also may decrease, potentially threatening group persistence. This phenomenon is referred to as the Allee effect: a population or group is at an increased risk of extinction when the number or density of individuals falls below a certain threshold due to either ecological or genetic factors (or a combination of the two). On the other hand, increased populations and increased population densities also can be problematic because they enhance group vulnerability to infectious disease. Allee effects have been widely studied and are known to have important implications for wildlife ecology but the connection between Allee effects and disease emergence is much less well understood. Understanding how group size and Allee effects drive infectious disease interactions is critical, however, to the conservation and management of endangered social species as well as to the control of emerging diseases that infect group-living species and threaten both human and animal health. In the research funded by this award, Dr. Kathleen Alexander (Virginia Polytechnic Institute State University) and her team will take an innovative approach to address this critical knowledge gap. They will integrate empirical field studies with mathematical modeling to investigate and identify principles and processes that influence disease transmission in group-living species. They also will establish international scientific networks linked to a comprehensive postdoctoral and graduate student-training program to produce multidisciplinary scientists with skills in international emerging infectious disease research, an area of increasing need. Other education components of the project include a structured K-7 educational program to foster interest and increase understanding of infectious disease ecology in children in the study region. The research project will also establish a foundation to foster collaborative learning between Botswana youth and undergraduate minority students in the United through interactive lectures and contemporary learning media including podcasts and social media. This program will link students from Botswana, where infectious disease deaths from HIV/AIDS and tuberculosis are common, and the United States where pandemic infectious disease is rarely experienced. Students will explore disease causation and control on a broad level with a focus on the common global need. This approach is directed at strengthening cross-cultural understanding and international leadership capacity in minority-driven scientific discovery in the ecology of emerging infectious disease. To study the connection between Allee effects and infectious disease emergence, Alexander and her team will build on their long-term study of banded mongoose (Mungos mungo) in northern Botswana. The highly social banded mongoose is threatened with a novel, emerging tuberculosis (TB) pathogen, Mycobacterium mungi. This pathogen is closely related to the human TB pathogen, M. africanum, and causes high levels of mortality among banded mongoose, threatening the persistence of smaller social groups. The research team will take an integrated methodological approach that links molecular genetic studies of the host and pathogen with population biology and behavioral ecology studies of mongoose social groups that occur across both protected and unprotected areas of the landscape. They will use this empirical study system to investigate and identify dominant factors, processes, and thresholds that determine the outcome of the interaction between infectious disease and Allee effects. Research results will be used to develop a conceptual framework and advance knowledge and theory that can be used to determine if and when Allee effects should be included in models of infectious disease in group-living species and how these interaction should be computationally characterized. Results will be important to the management of social wildlife species involved in transmission of infectious diseases of importance to both animal and public health as well as to the conservation of endangered group-living species.


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