Outbreak Update: May 6, 2022 – Outbreak Update at BLM’s Wild Horse and Burro Facility

Source: Bureau of Land Management

Number Confirmed: 129;

Facility Type: Public Venue;

Breed: Mustang; Clinical Signs: A respiratory condition characterized by mild/moderate fever, coughing or nasal discharge, depression, labored breathing; Horse Status: 119 Deceased;

Notes- Update May 5, 202: Culture and microscopic examination of samples obtained at necropsy have identified the bacteria streptococcus equi subspecies zooepidemicus (commonly called strep zoo) and actinobacillus species of bacteria in lung tissues as well as evidence of these infections consistent with severe suppurative bronchopneumonia. Although in some cases 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 principle causes of disease. While it is possible for these bacteria to be spread from horses to humans, this is a rare occurrence. These findings support the initial clinical assessment that the respiratory disease and mortality seen at the facility is likely a multifactorial respiratory disease complex that includes the equine influenza virus, bacterial pathogens that are common in the environment and among all types of horses as well as environmental and host specific cofactors and comorbidities. 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.

Situation Report Summary: On April 23, 2022 9 horses were found dead in 4 pens containing horses gathered from the West Douglas Herd Area in July/August of 2021. Several horses were gravely ill showing signs initially thought to be neurologic but later attributed to hypoxia from severe pneumonia. Over the next 3 days about two dozen horses died or were euthanized for severe debilitating respiratory distress in the West Douglas group of horses. Post mortem examinations consistently found pneumonia characterized by severe pulmonary edema and hemorrhage. Morbidity characterized by respiratory signs including fever, nasal discharge and coughing were also noted in 40-60% of the West Douglas horses with growing morbidity to about 20% noted in other pens throughout the facility. Over the course of the next 5 days PCR testing of blood, swabs and tissues for EHV-1 and -4 were consistently negative, however several nasal swabs and lung tissue specimens tested positive for equine influenza, confirmed to be H3N8 by PCR testing. Contributing factors include a history of gather and removal of West Douglas horses after a severe wildfire in their herd area, severe winds and dust storms in the area in the days before the outbreak. The West Douglas horses had been in the facility for about 9 months but are still unsettled, flighty as a group and easily disturbed in the pens. Most of the facility population is current (within 6 months) for flu/rhino vaccination, however the West Douglas horses in pens 40-43 are either unvaccinated, have only received one shot, or only recently received their booster shots about 10 days before the outbreak.

 

For more information go to BLM situation report.