Aoudad (Ammotragus lervia) as disease reservoirs for bighorn sheep (Ovis canadensis): experimental and epidemiological evidence.

This study evaluates the role of aoudad (Ammotragus lervia) as a maintenance host and reservoir for significant respiratory pathogens hindering bighorn sheep (Ovis canadensis) conservation; Mycoplasma ovipneumoniae and leukotoxigenic Pasteurellaceae. An experimental commingling trial and regional disease surveillance revealed significant interspecies transmission risks and epidemiological patterns. Experimentally, 80% of bighorn sheep exposed to aoudad inoculated with M. ovipneumoniae and leukotoxigenic Pasteurellaceae died of pneumonia under both indirect and direct contact conditions. Conversely, aoudad exhibited prolonged relatively asymptomatic shedding of M. ovipneumoniae without severe clinical outcomes. Surveillance of 351 free-ranging aoudad revealed 9.4% with M. ovipneumoniae DNA in nasal swabs and M. ovipneumoniae-specific antibodies in 55.8%. Aoudad diagnostic profiles were heterogeneous across populations, including variations in strain diversity and distribution. Shedding rates were higher among juveniles than adults. Aoudad can sustain and transmit M. ovipneumoniae under free-ranging and experimental conditions, presenting significant risks to bighorn sheep populations. Research on strategies to mitigate pathogen transmission, such as reducing shared water access and aoudad removal, is critical for predicting complex biological outcomes for multi-species management. This study emphasizes the importance of longitudinal herd-specific disease surveillance and fundamental pathobiology research for understanding M. ovipneumoniae dynamics in aoudad to inform bighorn sheep conservation efforts in Texas.