From respiratory disease in bighorn sheep to the threat of flesh-eating screwworm larvae, wildlife managers are monitoring an array of diseases across the Trans-Pecos.
Dr. Sara Wyckoff, one of two wildlife veterinarians with the Texas Parks and Wildlife Department, recently provided an update on several diseases of concern in West Texas, including Mycoplasma ovipneumoniae, chronic wasting disease, rabbit hemorrhagic disease and New World screwworm.
One focus is Mycoplasma ovipneumoniae, commonly called M. ovi, a bacterium associated with respiratory disease in bighorn sheep. Domestic sheep and goats commonly carry the bacterium and can transmit it to wild bighorns.
TPWD continues extensive surveillance, testing bighorn sheep and aoudad when animals are handled and expanding monitoring into additional mountain ranges. Elephant Mountain Wildlife Management Area and the Franklin Mountains continue to have clean herds.
“We really want to see all of the different landscapes out there and the story that they are telling when it comes to Mycoplasma,” Wyckoff said.
Researchers also are examining the genetic strains of M. ovi found in Texas bighorn sheep and aoudad. The information could be particularly important when wildlife managers consider moving bighorn sheep between populations because introducing a different strain could increase disease risks.
Wyckoff said relatively little research has been conducted on diseases in aoudad, making the Texas work particularly valuable.
“We’re really doing some groundbreaking things here by collecting this data from aoudad, sending it in for strain typing and seeing, are they matching the bighorn sheep strains?” she said.
A recent investigation involving sick aoudad illustrated the difficulty of diagnosing disease in wild animals.
Landowners reported aoudad with cloudy, painful-looking eyes, while some animals appeared to be circling. Initial testing identified infectious keratoconjunctivitis, commonly known as infectious pink eye, which can be spread by flies.
But animals with normal-looking eyes also showed neurological symptoms. Further investigation found heavy concentrations of nightshade in the rumens of some affected animals.
Researchers ultimately concluded that two problems were occurring simultaneously: infectious pink eye and plant toxicity.
“It was really great cooperation between biologists and landowners, finding out who was seeing these cases, when, and helping us get to those animals quickly so we could get these important diagnostic tissues,” Wyckoff said.
Chronic wasting disease, or CWD, remains another concern. TPWD and research partners are monitoring interactions among elk, white-tailed deer and mule deer in areas where CWD has been detected, including the Hueco Mountains and the Panhandle. Hundreds of animals have been fitted with tracking collars to study their movements and investigate mortalities.
Wyckoff encouraged hunters to continue submitting samples for voluntary CWD testing.
“Every little bit of information is information that we can gain knowledge from,” she said.
Researchers also are studying rabbit hemorrhagic disease virus, or RHDV2, which has been present in Texas since 2020. TPWD is working with the Caesar Kleberg Wildlife Research Institute on research involving the Davis Mountains cottontail, including whether vaccination could help protect vulnerable rabbit populations.
Researchers also are assessing the cottontail’s population status and studying why susceptibility to the disease varies among rabbit species.
Wyckoff saved one of the most closely watched threats for last: New World screwworm.
The parasitic fly lays eggs in wounds or body openings of warm-blooded animals. After the eggs hatch, larvae feed on living tissue. Even a wound as small as a tick bite can provide an entry point, and severe untreated infestations can kill an animal.
The screwworm life cycle can be completed in as little as 21 days, making rapid detection critical.
“We really rely on you guys and everybody else out there to tell us when you see any of these maggots in any animals,” Wyckoff said. “We need to stop them, pull them out and do what we need to with the animal or the carcass, and stop them from turning into a pupa, which can then turn into mating flies.”
At the time of the conference, Wyckoff reported 45 active cases and said infested zones extended into the Big Bend area, including Elephant Mountain. No detections had been documented in wildlife.
TPWD is coordinating with the Texas Animal Health Commission, U.S. Department of Agriculture, U.S. Fish and Wildlife Service, Texas Division of Emergency Management and other partners. Surveillance efforts include field monitoring, drones, trail cameras, fly traps and reports from the public. The USDA also is responsible for dispersing sterile flies, a primary tool used to suppress screwworm populations.
For landowners, hunters and others spending time in the Trans-Pecos, Wyckoff said the most important contribution may be simply paying attention to animals and quickly reporting anything unusual.
“Early detection is key,” she said. “You can’t ever let us know too soon. We’d much rather respond to a negative maggot than miss out on a positive one.”
