“Strep zoo” found in wild horses who died in equine influenza outbreak

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Officials at the BLM holding facility in Colorado said the results of culture and microscopic examination support the initial assessment that the respiratory disease is likely a multifactorial respiratory disease complex.
Officials at the BLM holding facility in Colorado said the results of culture and microscopic examination support the initial assessment that the respiratory disease is likely a multifactorial respiratory disease complex. © Jana Wilson/BLM

Culture and microscopic examination of the samples from some of the 129 horses who died in Equine Influenza Virus (EIV) outbreak among wild horses at Cañon City in Colorado indicate that they also had the bacteria streptococcus equi subspecies zooepidemicus and actinobacillus in their lung tissue.

Although in some cases streptococcus equi subspecies zooepidemicus (commonly called strep zoo) is considered a primary pathogen, these bacteria are generally considered to be ubiquitous bacteria (meaning common and widespread in animals and the environment) and commensal organisms that occur in most if not all horse populations. Commensal means these bacteria are usually thought to be opportunistic pathogens rather than the main cause of disease.

Officials at the Bureau of Land Management (BLM) holding facility say that the findings support the initial clinical assessment that the respiratory disease seen at the facility is likely a multifactorial respiratory disease complex.

On-site clinical evaluations and sampling as well as laboratory testing including DNA analysis and work to identify specific types and strains of the virus and bacteria involved are ongoing.

The outbreak began on April 23, and affected the 445 West Douglas horses who were rounded up in July and August of 2021.

The American Wild Horse Campaign (AWHC), a wild horse protection organization, has described it as the deadliest disease outbreak in BLM history. “According to the University of California Davis School of Veterinary Medicine, there is a nearly 100 percent infection rate for a population of unvaccinated horses with no prior exposure to the disease, and states that the virus can mutate quickly.”

“The virus is primarily affecting Colorado’s West Douglas wild horses, who were only partially vaccinated or completely unvaccinated against EIV despite being in BLM care for nine months after their capture,” the AWHC said.

Two members of congress, Dina Titus (D-NV) and Steve Cohen (D-TN) have urged US Secretary of the Interior Deb Haaland to investigate the holding facilities and put a halt to wild horse and burro roundups, following recent disease outbreaks in Colorado and Wyoming, where there was an outbreak of strangles at the BLM’s Wheatland Wyoming facility. The AWHC said that about half the population “is experiencing symptoms and at least 11 have died as a result of infection”.

“We urge the BLM to investigate the relationship between facility conditions and recent outbreaks,” US Representatives Titus and Cohen wrote, “and consider halting further roundups until the safety of wild horses and burros can be guaranteed, both during the roundups and while they are corralled.”

The letter goes on to note that it is “no surprise” that disease spreads so quickly in the cramped holding corrals and states that continuing with the BLM’s current plan to roundup and remove more than 19,000 wild horses and burros this year alone would be “ill-advised and a waste of taxpayer resources to hold additional federally-protected horses without knowing the impact of current conditions on their health”.

Holly Gann Bice, director of government relations for AWHC, was appreciative of the support from Titus and Cohen, “for their steadfast leadership in the protection and preservation of the nation’s wild horses and burros, both in the wild and in holding facilities”.

“The recent disease outbreaks are further evidence that the federal government’s system of perpetually removing horses and burros year-after-year and stockpiling them in holding facilities is collapsing and endangering these cherished animals,” Gann Bice said.

“The BLM must change its management strategies to focus on implementing a robust fertility control vaccine program to keep wild horses and burros wild, and out of crowded holding pens in the first place.”

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