Outbreak of vesicular dermatitis among horses at a midwestern horse show.

This research paper is about an infectious outbreak of blisters, specifically vesicular dermatitis, in horses at a midwestern horse show which was heavily linked to wood shavings bedding used at the show grounds.

Introduction and Purpose

• The study was prompted by an unexpected outbreak of vesicular dermatitis – a form of illness characterized by blisters on the nose and body, along with cases of jaundice, hematuria (blood in urine) and anorexia – among horses at a Midwestern horse show.
• The intent of the research was to ascertain the cause of the outbreak, which affected a significant proportion of the horses at the event.

Methods and Results

• The outbreak was investigated by gathering information on 239 horses that participated in the show. Out of these, 58 (24%) were found to have been affected by the illness.
• The disease showed a median duration of five days, but all horses recovered eventually.
• The factors examined included age, sex, water and grain sources, and stabling location, but none of these were associated with the outbreak.
• The research found a strong association between the use of wood shavings bedding obtained from the show grounds and the development of vesicular lesions. Horses who fell ill were 43 times as likely to have been bedded on wood shavings from the showgrounds compared to those who did not fall ill.

Bedding Analysis and Further Findings

• This risk increased five-fold if the wood shavings bedding had been wetted.
• While neither organic nor heavy metal toxicants were found in the wood shavings samples, they were found to contain plant tissues from a tree belonging to the family Simaroubaceae.
• The link to the Simaroubaceae family was significant because some species in this family are known to cause vesicular eruptions in people. This suggests a potential for a similar effect in horses, although the study does not definitively prove this.

Conclusion

• The study concludes that the outbreak of vesicular dermatitis among horses was most likely associated with the type of bedding used. Specifically, wood shavings bedding obtained from the show grounds that had been in contact with water posed a higher risk.
• Further research, however, may be required to confirm the role of the Simaroubaceae family in this outbreak.