The relationship between climate variability and wildlife diseases: A retrospective study of avian botulism outbreaks

Diseases are increasingly being recognized by conservation biologists as a major concern and challenge for wildlife conservation. Although outbreaks of wildlife diseases may be caused by a range of ecosystem alterations, climatic changes are increasingly becoming a topic of concern since changes in the climate system worldwide are projected to increase in the future. This retrospective, long-term (29-year) study investigated the relationship between outbreaks of avian botulism type C and climate variability in the United States.; The work presented here involves a substantially new analysis of existing avian botulism data and significantly contributes to a better understanding of whether temperature and precipitation anomalies may influence outbreak occurrence in the contiguous United States. Eight research questions were addressed to explore the major hypothesis, including the following three primary questions: (1) whether avian botulism outbreaks occurred during warmer than normal temperatures, (2) during higher than average precipitation, and (3) during lower than average precipitation. The other five were secondary research questions mostly derived from a combination of the primary questions and developed to test for certain patterns predicted by the epizootiology of avian botulism.; Findings from this study included the following: (1) there seems to be a relationship between outbreaks and warmer than normal temperatures for both minimum and maximum temperature anomalies; (2) there seems to be a much stronger relationship between outbreak occurrence and warmer than normal minimum temperatures than with warmer than normal maximum temperature, suggesting that a minimum temperature anomaly is the limiting factor and plays a much more important role in the initiation of outbreaks; (3) precipitation anomalies only seem to play a role in initiation of outbreaks under very specific conditions which combine a series of climatic events, which include outbreak occurrence during drier than normal conditions combined with warmer than normal temperatures; wetter than normal conditions followed by drier than normal conditions two months prior and one month prior, respectively, to outbreak initiation; and a combination of warmer than normal minimum temperatures one month before outbreak initiation and wetter than normal conditions in the same month an outbreak occurs.; There are a number of other policy measures that should be considered. Currently, there is a paucity of long-term wildlife disease data, which hampers management, control, and eradication efforts as well as the ability to detect changes in disease patterns. Wildlife disease programs and natural resource management agencies should focus their efforts to conduct long-term disease studies to support this endeavor. A good place to start is with regular surveillance and monitoring efforts, as well as encouraging the sharing of wildlife disease data among natural resource management agencies to obtain a national perspective, and which traditionally has not been a standard practice in the animal disease community. Sharing of avian botulism and other wildlife disease data is critical to obtain a national perspective of disease occurrence, but it is also necessary to establish baseline and long-term disease data records. A centralized wildlife disease database would assist in capturing this information, and the current lack of such database is a major deficiency in the wildlife disease community. A centralized, comprehensive database that captures spatiotemporal disease information would be most valuable to conduct analyses and to promote informed decision making for the prevention, control, management, and eradication of avian botulism and other wildlife diseases, as well as to document the prevalence and spread of those diseases. (Abstract shortened by UMI.)...