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Drought and wildfire increase disease risk to cattle herds

Boehringer Ingelheim press release Published on 27 June 2011

In the midst of one of the worst droughts in Texas history, ranchers across the region are slowly realizing that the devastation left by a continuing drought and wildfires stretches far beyond their dusty soil.

Texas Farm Bureau estimates that as much as 3 million acres have been burned in Texas alone. With that were likely hundreds of miles of fence, which to cattle producers is a precious biosecurity border between herds, according to Dr. Mac Devin, Professional Services Veterinarian for Boehringer Ingelheim Vetmedica, Inc., who is based in College Station, Texas. Dr. Devin says, “When we lose fence line integrity, and this biosecurity barrier is broken, we must question how this changes the picture of the immune status of a herd as well as its disease risk.”

The loss of fences means cattle may be crossing property lines and commingling freely, which could come with a steep cost. “Anytime you break down the herd formation and commingle groups, you put your cattle at risk for transmittable diseases like BVD and leptospirosis, or sexually transmitted diseases like trichomoniasis and vibrio,” Dr. Devin says.

Cattle aren’t the only ones moving around; drought and fires also force wild animals to relocate. “Commingling doesn’t just play a role in cattle herds,” adds Dr. Devin. “We should also think about how natural disasters may change group formations of wild animals like feral hogs, deer, skunks or raccoons. The risk of exposing your livestock to a disease like leptospirosis is much more likely in situations in which they are exposed to wild animals.”

The timing of the fires doesn’t help the situation, either. “If the fires and subsequent commingling occurred when cows were in the first half of gestation, there’s a good chance that pregnant cows could have been exposed to animals that are persistently infected with BVDV. Exposure to BVDV when the cow is 40 to120 days pregnant creates a situation where transfer from dam to fetus is likely,” continues Dr. Devin.

And, while transmittable diseases like BVD or trichomoniasis may be a big issue during drought, the story doesn’t stop there. “Droughts make for stressed cattle, and when we have stressed cattle, diseases like IBR that may be latent inside of cattle may cause them to start shedding virus,” he says.

It is tough times like these that help us realize how important disease prevention is, says Dr. Devin. “These unusual circumstances underline the importance of vaccinating calves at weaning this fall and at other times in an animal’s life,” he adds.

Dr. Devin recommends testing for persistently infected (PI) BVD calves in next year’s calf crop in case of recent fetal exposure. He also suggests testing bulls before the next breeding season for trichomoniasis, and pregnancy-checking cows. “Identifying if an exposure has happened and aggressively going after a diagnosis are vitally important,” Dr. Devin says.

He recommends that producers work closely with their veterinarians to ensure that the cowherd is healthy and the impact on future production is minimized after the environmental challenges of this winter and spring. end_mark