Cross-sectional evaluation of environmental, host, and management factors associated with risk of seropositivity to Ehrlichia risticii in horses of New York state.

This research studied the prevalence of Ehrlichia risticii infection in horses across different counties in New York state, and identified different environmental, host, and management factors associated with the risk of infection. The study also explored the potential role of arthropods and helminths in the transmission of this disease.

Methodology

• The research was a cross-sectional study that used a random sample of 3,000 out of the 39,000 equine operations in New York state. 2,587 horses from these 511 operations were tested.
• Blood samples were collected from these horses and tested for seropositivity, using the indirect fluorescent antibody technique.
• Personal interviews were conducted to gather data on each horse and the management practices of each farm.
• Mixed-effect logistic regression was used to evaluate the impact of each factor on the risk of seropositivity.

Results

• The study found that 7.3% of non-vaccinated horses were seropositive for E risticii.
• The seroprevalence varied across different counties, with a range from 0 to 27%. Counties with higher risk were typically located at lower elevations.
• Similarly, farms at higher risk for having seropositive horses were typically located at low elevations, and usually didn’t have bodies of water nearby.
• Risk of seropositivity was linked with the duration of time a horse spent in a stall or run-in shed, the frequency of applying fly spray, and depending on the duration of residency at the farm, the frequency of deworming with benzimidazole and pyrantel.
• By breed, Standardbred horses were 2 to 3 times more likely to be exposed to the bacteria than Thoroughbreds.
• By age and gender, middle-aged and male horses were at greater risk of being seropositive, depending on the length of residency at the farm.

Conclusion

• The study concluded that arthropods and helminths may possibly play a part in the transmission of E risticii.
• Management factors were identified that can either directly or indirectly influence the risk of a horse getting exposed to E risticii, which suggests potential control measures that go beyond traditional vaccination strategies.