July 2016

The Zoo Matrix

In 2016, West Nile Virus (WNV) is a household name. But just a handful of years ago, very little was known about the virus in the Western Hemisphere. Tracey McNamara, DVM, DACVP, and Professor of Pathology in the College of Veterinary Medicine at Western University of Health Services played an integral role in bridging the knowledge gap. Her path to discovery began in the summer of 1999 when McNamara was working as the lead pathologist at the Bronx Zoo when she discovered a rising number of dead crows near zoo grounds.

Worrying about the potential spread of an illness to her animals, McNamara began performing dissections on the crows, dissections which revealed symptoms consistent with viral encephalitis. Shortly thereafter, a number of exotic birds at the zoo died and human encephalitis cases in the region began to surface in the New York area. Still, no link could be established between the two outbreaks. Largely through McNamara’s persistence, collaborative efforts were established between academia, the US Army, and the Centers for Disease Control (CDC) to help identify the virus as (WNV).

Initially, the CDC proved hesitant to get involved with McNamara’s discoveries since its mission strictly focuses on human illnesses and her investigation was focused on dead crows. As a result, McNamara called upon a personal relationship she had with a pathologist with the US Army, which helped establish the connection between the crow illness and the human illness, and CDC became involved.

In the years following McNamara’s discovery, WNV continued to spread rapidly throughout the Western Hemisphere. From 1999 to 2015, there were 43,822 reported cases of WNV and 1,884 deaths in the United States*. As a result, efforts focused on educating the public on the virus and creating mosquito abatement programs.

Looking back on the experience, McNamara says, “The work I performed surrounding West Nile Virus was the most exciting and gratifying work of my career as it was a true validation of the role pathology plays.” McNamara continues, “Had it not been for recognizing the trends in encephalitis among the crows, we would not know that West Nile is a cross-species virus.”

As the world learns more about the Zika virus with each passing day, it is vital to look back on McNamara’s work. According to McNamara, WNV and Zika are similar in the sense that affected communities were taken by surprise despite work by the CDC, along with other agencies, to get ahead of the next emerging disease threat. McNamara maintains that mosquitoes are a real threat to public health and that global warming exacerbates their potential.


Confirmed cases of locally acquired dengue in Monroe County, Florida, in 2010.


Cases of locally acquired dengue in Monroe County, Florida, since 2010.