Fistulous withers in horses: 24 cases (1984-1990).

This study, conducted from 1984 to 1990, investigated the prevalence of a condition known as fistulous withers in horses and its possible connection to Brucella abortus, a bacterial infection. Results showed that horses who tested positive for this infection were more likely to have been in contact with infected cattle and showed signs of vertebral osteomyelitis. Various treatments were attempted, with mixed results.

Study Design and Participants

• The researchers monitored a group of 27 horses admitted to a veterinary medical center between January 1, 1984, and August 1, 1990, all of which were suffering from fistulous withers.
• Fistulous withers is a chronic inflammatory disease affecting the upper part of a horse’s back.
• The focus of the research was to determine a possible connection between the condition and Brucella abortus, a bacterial infection.
• A serology test was performed on 24 out of the 27 horses for presence of antibodies against Brucella abortus.

Findings and Analysis

• Out of the 24 horses tested, 37.5% were found to have antibodies indicating past or present infection with Brucella abortus, a potentially zoonotic bacterium.
• Statistical analysis revealed that seropositive horses were significantly more likely (P=0.046) to have had past contact with cattle that were also seropositive for the same bacteria.
• Similarly, those horses that were seropositive were found to have radiographic signs of vertebral osteomyelitis, a type of bone infection, at a significantly higher rate (P=0.01) compared to horses that were seronegative.

Treatments and Outcomes

• Five horses that were seropositive for Brucella abortus were given the strain 19 brucella vaccine, either subcutaneously (sc) or intravenously (iv).
• The single horse treated with a sc injection showed signs of improvement during the time in the hospital, though post treatment follow-up was not available on it.
• Out of four horses treated by iv injection, three (75%) died. The remaining horse recovered within a month of starting the treatment.

Conclusions

• The findings suggest that fistulous withers in horses may be associated with Brucella abortus, especially in animals that have been pastured with infected cattle.
• The outcomes of attempted treatments with brucella vaccine suggest further research is needed to develop effective treatment protocols for the condition.