Vanessa Ezenwa

Vanessa Ezenwa is an associate professor at UGA with joint appointments in the Odum School of Ecology and the Department of Infectious Diseases, College of Veterinary Medicine. Dr. Ezenwa received a PhD in ecology and evolutionary biology from Princeton University, and then worked at the United States Geological Survey in Reston, Virginia as a National Research Council Postdoctoral Fellow before joining the faculty at the University of Montana, Missoula in 2005. She moved to the University of Georgia in 2010.

Dr. Ezenwa’s research focuses on the ecology of infectious diseases in wild animal populations, and she teaches courses in infectious disease ecology and evolution and behavioral ecology to graduate and undergraduate students, respectively. Her work combines field studies with laboratory work and theory to address questions about the causes and consequences of interactions between hosts and their parasites. Since infectious disease threats to human and animal populations are on the rise, as are strategies to control and manage these diseases, one stream of research in Dr. Ezenwa’s lab focuses on understanding the ecological and evolutionary consequences of these types of intervention strategies in natural populations.

For example, because parasitic worm infections are widespread in human populations, and can exacerbate the outcome of some viral and bacterial infections, worm treatment (i.e. deworming) is often discussed as a potential tool for indirectly combating microbial pathogens, such as HIV and tuberculosis. Worm infections are as common in wildlife as in humans, and might worsen the outcome of microbial infections in some populations, so focusing on African buffalo in Kruger National Park, South Africa, Dr. Ezenwa and colleagues examined how gastrointestinal worm infections affected the susceptibility of these animals to bovine tuberculosis (bTB), and the severity of disease once they become infected. Buffalo are the major reservoir of bTB in southern Africa and are responsible for the spillover of infection to livestock and other wildlife, including lions which can contract bTB from consuming infected buffalo. By tracking experimentally dewormed animals over a multi-year period, Ezenwa found that worm treatment reduces the severity of bTB in buffalo, but because infected animals survive better without worms they have more opportunities to pass bTB on to other individuals, exacerbating the spread of the disease. These results show that on one hand, treating for worms has positive outcomes in terms of the survival of individual animals that contract bTB, but this comes with the potential cost of increased disease transmission. Thus, managing one type of infection can have complex and counterintuitive effects on other diseases. Dr. Ezenwa believes that understanding these complexities will help us design more effective intervention strategies in the future.

Dr. Ezenwa, and students and postdoctoral researchers in her lab, are also interested in understanding the consequences of disease management strategies other than drug treatment. For example, for wildlife diseases where effective drug treatments and vaccines are rarely available, management strategies such as culling are sometimes used to manage disease spread. As an example, in Hluhluwe-iMfolozi Park (HIP), South Africa where bTB prevalence in buffalo is reported to be as high as 73% in some herds, a test and cull program has been ongoing since the mid-1990’s to help control the spread of the disease. Using this system as a case study, work spearheaded by a postdoctoral researcher in Dr. Ezenwa’s lab investigated the impact of this bTB control effort on buffalo genetics. Focusing on a gene associated with immune defense to bTB, the study found evidence that culling is reducing immunogenetic diversity in the HiP buffalo population. Since the erosion of immunological diversity may have important consequences for how animals can respond and adapt to future disease threats, this work suggests that there may be unintended, evolutionary consequence of some forms of disease management.

Infectious diseases are an ongoing threat to animal health, human health, and wildlife conservation. Dr. Ezenwa believes that studies of infectious diseases in natural systems, including studies on how management actions feedback on the ecological and evolutionary dynamics of both hosts and parasites can contribute key insights into how to better control and manage infectious diseases and protect animal and human health.