Chapter 7 : Diseases Transmitted by Birds

Abstract:

Infectious diseases can be transmitted to humans from birds by one of several mechanisms ( Table 1 ). In group 1 infections, birds are the natural reservoirs for the infectious agent, which causes illness among them. The diseased birds then disseminate the infectious agent into the environment, and humans become infected as accidental hosts. Examples of such infections include psittacosis, Newcastle disease, avian influenza, and yersiniosis. In group 2 and 3 infections, birds are the natural reservoirs for the infectious agent but do not become ill themselves. The infectious agents of group 2 infections (for example, salmonellosis and mite infections) disseminate from the colonized birds into the environment directly, and the agents of group 3 infections (for example, eastern equine encephalitis [EEE], western equine encephalitis [WEE], St. Louis encephalitis [SLE], and Japanese B encephalitis [JE]) disseminate by means of arthropod vectors and involve humans as accidental hosts. With group 4 infections, birds are not the natural reservoirs, but they facilitate growth of the organisms in the environment by means of their fecal matter. Examples of infections of the last category include the fungal diseases histoplasmosis and cryptococcosis.