Parasites a Growing Problem for U.S.

Parasites a Growing Problem for U.S.

Sheep Industry News Contributor

Drug-resistant parasites are a growing sheep industry problem.

“This is no longer just a problem in other countries,” said Anna O’Brien, a veterinarian with the Food and Drug Administration’s Center for Veterinary Medicine. “In the southeastern United States, nearly half of parasites were found to have resistance in three major antiparasitic classes of drugs.”

O’Brien, speaking during the Animal Health Committee meeting in Charleston, said resistance has increased because producers relied more heavily on antiparasitic drugs, for example Ivermectin, while other control measures, like pasture management, went by the wayside.

“We need a paradigm shift,” said O’Brien. “We need to get away from the idea that antiparasitics are a silver bullet.” She said producers may want to consider parasite management instead of parasite eradication.

One approach is preserving refugia – or parasites in refuge from the drug. O’Brien explained that if the entire flock is treated for parasites, all susceptible parasites die, leaving resistant parasites to breed and pass on their resistance. But if only half the flock is treated, some susceptible parasites remain to dilute the resistant parasites, slowing the development of a fully resistant parasite population.

“This can save producers money on drugs in the short run and slow total flock resistance to antiparasitic drugs,” O’Brien said.

Cindy Wolf, a veterinarian with the University of Minnesota, offered an overview of testing for major diseases, which she described as those with real or perceived importance to producers and their customers as well as those that can hit producers in the pocketbook.

Wolf said climate change means producers will likely see more vector-borne diseases, and she advised them to beware of “Dr. Google” when diagnosing their animals.

“Get a good relationship with veterinarian,” she said. “Get good advice. Talk to people you trust.”

Wolf listed types of tests, locations for having them done and costs for: parasites, ovine progressive pneumonia, caseous lymphadenitis, Johnes, pneumonia, brucella ovis, scrapie, bluetongue and Q fever.

Diane Sutton and Katherine Marshall, both veterinarians with USDA-APHIS Veterinary Services, reported, respectively, on scrapie and the 2011 National Animal Health Monitoring System (NAHMS) sheep study.

Sutton, sheep and goat health commodity coordinator, said that at the end of fiscal 2013, cull sheep found positive for scrapie at slaughter, adjusted for face color, was 0.0146 percent, a 90 percent decrease of prevalence since the slaughter study was started in fiscal 2003.

On the docket for 2014, she said, are changes that would, among other things, provide more flexibility for dealing with infected flocks, add a genetic-based approach to regulation, make goat identification similar to that for sheep and tighten the definition of slaughter channels.

“To find the last scrapie cases,” said Sutton, “we need producers, especially those who do not market cull animals through traditional channels, to submit heads of mature sheep and goats found dead on the farm for scrapie testing.”

Marshall reported on Part IV of the 2011 NAHMS study, Changes in Health and Production Practices in the U.S. Sheep Industry, 1996-2011, currently in draft.

This is the third NAHMS study, following studies in 1996 and 2001, designed to provide animal health information that can help with disease prevention and control, animal welfare, the environment and economics.

Conducted in 22 states and representing 70% of sheep operations and 85% of the ewe inventory, the study found that 85% of producers in 2011 were familiar with scrapie, up from less than 70 percent 10 years earlier.

As for antibiotics use, Marshall noted that 69 percent of operations administered antibiotics orally, by injection or topically. Of those, 67.7 percent treated for respiratory diseases, 44.2 percent for mastitis and 35.8% for lameness or foot rot. Of operations that used antibiotics, only 51 percent maintained treatment records.

Julia Murphy, Virginia state public health veterinarian, provided an overview of the public health response to Q fever, a disease that can be transmitted to humans from animals like sheep and goats through the inhalation of infectious aerosols.

She said that infected humans may or may not show symptoms of Q fever. But as symptoms are flu-like, she advised people from agriculture to share that information with their physician if they make a visit for what they think is the flu.

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