Arizona is preparing itself for a bighorn sheep die-off as a deadly strain of pneumonia that originated in California and Nevada makes its way through the state. Bighorns within both California and Nevada have already been severely impacted and Arizona officials believe that it’s only a matter of time before their bighorns meet a similar fate.

While Arizona Game and Fish Department (AGFD) officials were fortunate to have some hunters report early symptoms within the wild herds, because the animals are scattered across the state, knowing how many of the sheep are infected is difficult to gauge. In fact, without a vaccine or really any way to stop the deadly virus, all wildlife officials can do is track its progress and hope that some of the bighorns will be able to resist it.

“Even if we had a successful vaccine, how do we vaccinate animals in the wild?” Anne Justice-Allen, a wildlife health program manager, told Arizona PBS. “It’s nearly impossible to provide a vaccination protocol.”

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Initial lab results show that Arizona’s herds have previously been exposed to a similar strain, which means that they could, in theory, have a higher resistance to the virus, according to Arizona PBS. Yet, Justice-Allen maintains a realistic view, saying, “We know historically that mortality events due to pneumonia can cause anywhere from a 90 to a 50 percent loss in sheep numbers.”

This is sad news for Arizona bighorns, especially considering the efforts AGFD has taken recently to relocate bighorns to boost the dwindling numbers. Hopefully, the assumption that a die-off will occur will prove false.