What term refers to an animal that maintains a disease organism in nature (e.g., birds for WNV and EEE)?

• A. Bridge Vector
• B. Pathogen
• C. Reservoir Host
• D. Larva

Answer: (C)

A reservoir host is the animal that keeps a disease organism alive in nature. For vector-borne diseases like West Nile virus and Eastern equine encephalitis, birds serve this role by harboring the virus and maintaining it through time. When mosquitoes bite these infected birds, they pick up the virus and can transmit it to other animals or humans, helping the pathogen persist in the ecosystem even when outbreaks aren’t occurring. Humans and many other mammals often serve as incidental or dead-end hosts, meaning they don’t effectively pass the pathogen back to mosquitoes. A bridge vector would be a mosquito that transmits the pathogen from the reservoir to incidental hosts, the pathogen is the disease-causing agent, and a larva is just an immature life stage not relevant to this concept.