Ecology and impacts of vector-borne disease on native birds: California avian communities
Presence of disease in birds, both wild and captive, has been recognized and documented since the dawn of recorded human history. There is growing recognition of ecological importance of disease-causing agents (pathogens) and their effects on physiological, behavioral, and ecological states of well-being (“health”) in free-ranging animals and their ecosystems. With the embrace of principles and methods of wildlife microbiology, pathology and infectious disease epidemiology, as well as diverse ecological methods, examinations of the host-disease agent/vector-environment triad are beginning to tell us how disease can have local and far-reaching impacts in birds and their ecosystems. Main categories of infectious agents of importance to birds include viruses, bacteria, protozoa, helminths, and fungi. Routes of disease transmission can include direct (bird to bird; through coughed droplets or fecal-oral spread as examples), vertical (parent to offspring prior to hatching), and a route of our research focus, vector-borne. For wild birds in California, we were interested in determining rates of exposure for vector-borne pathogens and investigating habitat relationships. Our approach was to apply serological, blood smear, and PCR diagnostic methods, as well as interrogate data bases of dead bird diagnostic data, and evaluate spatial and temporal ecological relationships among species and pathogens.
Avian taxa investigated in our laboratory have spanned a spectrum from hummingbirds to hawks. Most recent work includes assessment of Haemosporidian blood parasites (protozoa), West Nile virus, and Avian Poxvirus in hummingbirds. To date, the Haemosporidium Haemoproteus was detected in 18% of the hummingbirds tested, with differences evident among species and ecosystem characteristics. We provide a foundation and synthesis with our previous work in other species and pathogens to evaluate community- and ecosystem-scale effects and impacts of diseases in birds.