Mosquito Diversity, Arboviral Risks, and Blood Feeding Patterns at the Nashville Zoo at Grassmere

Abstract

The epidemiological triad is a framework to conceptualize interactions between the environment, a disease agent, and wildlife/human hosts that result in disease transmission. Zoological parks provide a unique opportunity to study the epidemiological triad because they are areas where exotic animals, free-roaming native animals, humans, and mosquito habitats are located in close proximity. The Nashville Zoo at Grassmere in Tennessee previously experienced arboviral transmission, and as such, became a prime research site for the increasing knowledge of arboviral disease transmission dynamics within a zoo setting. I sampled mosquitoes over four months in 2020 within and outside of the Nashville zoo using four mosquito trap methods and 12 sampling locations. Mosquitoes were identified to species, Culex mosquitoes were analyzed for arboviruses, and engorged mosquitoes were preserved for host feeding analysis to determine zoonotic feeding risk. I captured over 9,000 mosquitoes representing 24 different species, including a new species record for Davidson County, TN (Cx. nigripalpus). Minimum infection rates (MIR)s for WNV, SLEV and FLAV were 0.79, 0, and 4.14, respectively. Host DNA from 60 engorged mosquitoes was matched to 18 host species, including four species belonging to the zoo. Overall, wild birds were the preferred host species. Northern cardinals, which are competent reservoirs of WNV, were the most commonly fed upon wild bird. Further research is needed to determine if the northern cardinals are serving as zooprophylaxis for WNV transmission in the zoo or if the presence and utilization of these competent reservoirs present a higher risk of infection to the zoo animals. These results collectively demonstrate the utility of zoological parks as sentinels for both emerging pathogens, human and wildlife risk, and vector diversity.