A team of researchers from the Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS) has discovered that aoudad – an animal in the sheep and goat family – can catch and spread many of the same respiratory pathogens that can affect desert bighorn sheep. , a native species in Texas that often shares its habitat with aoudad.
The new research, recently published in the journal PLOS ONEwill help conservationists better understand the complex relationship between these two species and promote management of both species. The project was made possible through funding from the Wild Sheep Foundation and support from the Texas Parks & Wildlife Department.
Aoudad (pronounced “AH-dad”) originated in North Africa and was introduced to Texas in the late 1950s for hunting opportunities. Some wildlife experts estimate that as many as 40,000 people could live in the state.
“Not much research has been done on disease transmission between Texas Aoudad and native species such as bighorn sheep. This makes it difficult for wildlife experts to monitor disease and maintain animal populations,” said Dr. Logan Thomas, assistant professor at the Kansas State University and former postdoctoral researcher under Dr. Walter Cook, Clinical Associate Professor in the Department of Veterinary Pathobiology at VMBS.
“If we can measure disease exposure in both species, we can begin to understand how they might affect each other,” he said. “By analyzing samples from both types of animals, we were ultimately able to determine that they too can carry and transmit the same respiratory diseases.”
It takes two
Both aoudad and bighorn sheep are important animals for Texas conservation and the state’s economy. In West Texas, both animals are hunted as game, and some landowners make a significant portion of their income by charging hunters a fee to hunt on their land.
“Aoudad in particular is economically valuable for hunting,” Thomas said. “Because it is a non-native species, there are no season or bag limits, which is very attractive to hunters.”
Although bighorn sheep are also a favorite game animal among hunters, they require intensive management in Texas to keep their population numbers sustainable.
The respiratory illnesses, including pneumonia, common to both species have already wreaked havoc among bighorn populations, leading experts to worry about what these diseases could do, in addition to worsening the situation for bighorns.
“When outbreaks of these diseases occur in bighorn sheep, we usually see two waves of population decline,” Thomas said. “There is a decline across all age groups when the outbreak first occurs. Then there is another surge after the lambs are born – many of them do not survive because they have not been exposed to the disease and therefore do not have an immune response like the older bighorns have.”
Complicating the problem is that some adult bighorns carry the disease for several years after the initial outbreak, meaning the population may never have a chance to recover.
“We’ve known about this cycle in bighorn sheep for a while, but no one has investigated whether the same thing might be happening in aoudad or whether the two species could spread these pathogens back and forth,” he said. “We don’t suspect it will be a significant health problem for Aoudad, but we want to learn more as we continue our research.”
Keep a close eye
Now that researchers have confirmed that aoudad can carry the same respiratory pathogens as bighorn sheep, wildlife experts can begin monitoring disease transmission within and between these populations.
“Based on previous reports on this family of diseases, it is also possible that they could spread to mule deer, which would further complicate matters,” Thomas said. “We’re very interested in studying that in the future, as well as how these diseases affect ancient populations, because they haven’t received as much research attention on this as native species.
“Ultimately, we want all of these animal populations to thrive within a well-managed balance in Texas,” Thomas said. “Disease monitoring is one way we can take steps to make that happen.”
