Risk factors for owner-reported occurrence of equine protozoal myeloencephalitis in the US equine population.

This study investigates the risk factors associated with the occurrence of equine protozoal myeloencephalitis (EPM) – a serious and often fatal neurologic disease in horses. It uses data from 1,178 operations that represent 83.9% of horses in the US. Results found that factors like age, sex, and breed of the horse, opossum regional ecology, reported small wildlife exposure, climate and terrain, housing, choice of bedding material, and primary use of horses all affected the likelihood of EPM occurrence.

Methodology

• The study assessed the risk of EPM occurrence in the US. Data was collected from 1,178 operational units, representative of 83.9% of the total horse population and 51.6% of operations with three or more horses in 28 states across the country. The sample was chosen through probability-based selection to ensure representation.
• Personal interviews were conducted to get information on the health and management practices with respect to horses at these operations. Furthermore, a nested case-control study was utilized to examine the risk factors from individual horses.

Data Consolidation

• The data collected through interviews for the horses was combined with other critical information. This included climate data, human population density, and opossum regional ecology categories. The purpose of this consolidation was to present a holistic dataset for analysis.
• This comprehensive dataset was then subjected to logistic regression to help identify potential risk factors associated with EPM occurrence.

Results & Conclusions

• The study revealed that 95% of EPM cases were diagnosed by veterinarians, establishing the authenticity of owner-reported cases.
• The chief risk factors for EPM occurrence in premises were associated with opossum regional ecology, small wildlife exposure, climate and terrain, type of horse housing and bedding material used, method of storing feeds, equine stocking density, and the primary use of horses.
• At the individual horse level, age was observed to be most strongly associated with EPM risk. Other identified associations were with respect to the horse’s sex, breed, primary use, and engagement in competitions.
• As EPM risk is closely linked with factors impacting exposure to opossums, their feces, and their environment, controlling these exposures may aid in preventing the occurrence of EPM.