Human Health Risks from Nesting Waterbirds on Alcatraz Island: A Preliminary Assessment

Sullivan, Heather; Huyvaert, Kathryn; Bentler, Kevin; McLean, Robert; Hutcheson, H; Franklin, Alan

In addition to being an historical site, the natural history of Alcatraz Island offers visitors an opportunity to observe a variety of native and cultivated plants as well as eight species of nesting seabirds. The western gull (Larus occidentalis) is the most abundant bird species on Alcatraz Island with approximately 1033 breeding pairs (data from GGNPC 2006). Gulls (Larus spp.) are of particular interest to human health because of their large populations and their close contact with humans on Alcatraz Island. Several recent studies document the presence of pathogenic bacteria in feces deposited by gulls (Steele et al. 2005, Reed et al. 2002, and Palmgren et al. 2005). Fecal material collected from gulls has also been documented to contain significant numbers of fecal coliform per gram of feces (3.68 x 108) (Alderisio 1999). It has also been suggested that seabirds may be responsible for the transhemispheric exchange of Lyme disease (Reed et al. 2002). In addition, gull species are susceptible to high pathogenic avian influenza H5N1 (HPAI) (Brown et al. 2006). Our objectives were to conduct preliminary surveys to initially identify, describe and measure the frequency and intensity of wildlife diseases that could pose a threat to local human health. In particular, we focused our attention on HPAI virus, pathogenic enteric bacteria, Lyme disease, and histoplasmosis. Recently, the U.S. Department of Agriculture, Interior, and Health and Human Services have developed a strategic plan for detecting avian influenza in the United States. The plan calls for sampling live birds (cloacal and tracheal swabs), dead birds (cloacal and tracheal swabs), and collecting fecal samples. Fecal samples collected for this study will be analyzed as part of the 2006 U.S. strategic plan. The results from our surveys will provide baseline information to the Golden Gate National Recreation Area (NPS) and for the Golden Gate National Parks Conservancy (GGNPC). Where appropriate, we suggest management actions for reducing risks of potential disease transmission to humans from wildlife and their habitat.