DISTRIBUTION AND PREVALENCE OF ELAEOPHORA SCHNEIDERI IN MOOSE IN WYOMING

Abstract

Elaeophora schneideri causes disease in aberrant hosts such as moose. Documented E. schneideri infections in moose are relatively rare, yet noteworthy enough that individual cases describing morbidity and mortality have been the norm for reporting. Surveillance efforts for E. schneideri in Wyoming moose in the 1970s found zero cases, but since 2000 several moose in Wyoming discovered dead or showing clinical signs of elaeophorosis have been found infected with E. schneideri. In 2009 we searched for worms in the carotid arteries of 168 hunter-harvested moose from across Wyoming to determine the prevalence and distribution of E. schneideri in moose; 82 (48.8%; 95% CI: 41.4-56.3%) were positive for E. schneideri. Prevalence did not differ between sexes or among age classes but there was difference in prevalence among herd units (range = 5-82.6%). Intensity of infection (range = 1-26 worms) did not differ between sexes, among age classes, or among herd units. Our findings indicate that moose do not succumb to the parasite to the extent previously thought. Prevalence and intensity were constant across age classes, suggesting that infected moose are surviving and an acquired, immunological resistance to further infection develops. In addition, moose might sometimes act as natural hosts to the parasite, as indicated by 1) high prevalence of infection in moose in areas where sympatric mule deer had much lower prevalence of infection, and 2) preliminary necropsy findings that revealed microfilariae in skin samples from 3 moose. However, negative impacts to moose and moose populations cannot be ruled out entirely, as this study was limited to apparently healthy hunter-harvested animals. While moose appear to often survive infection with E. schneideri, prevalence of ~50% is still cause for concern because it is unknown to what extent this parasite causes subclinical effects in moose that might impact recruitment or productivity. Subsequent research on moose herds where E. schneideri occurs should consider the effects of elaeophorosis and attempt to clarify its role.