Abortion in two foals associated with Nocardia infection.

This research paper discusses the cases of abortion in two horse foals linked to Nocardia infection, a type of bacteria predominantly found in soil. It provides a detailed analysis of the symptoms, findings, and the diagnoses following necropsy and histological examinations of the aborted fetuses.

Background of the Case

• The case involved two mares, an Arabian and a Thoroughbred, from separate farms that both aborted during the sixth month of gestation.
• Despite appearing healthy and receiving vaccinations against herpesvirus and Eastern equine encephalitis virus, both mares had a history of unsuccessful pregnancies with undetermined causes.

Fetal Necropsies and Observations

• Fetal necropsies revealed lesions in the lung, liver, and placenta. The lungs were firm and did not lose their shape when opened, while the liver was enlarged and blotchy. The placenta also exhibited an irregular pattern.
• On microscopic examination, there were extensive inflammatory infiltrates present, indicating an infection. The findings also revealed necrosis, indicating tissue death caused by disease or injury.
• Minuscule filamentous bacteria with certain dye-reactive properties, indicative of the Nocardia species, were identified within the fetal organs examined.

Diagnostic Findings and Conclusions

• Nocardia asteroides were grown from the uterus of the Arabian mare in a culture, despite unsuccessful attempts to grow cultures from the placenta, lung, and liver.
• The infections were deemed to be caused by Nocardia, based on the morphologic and dye-reactive features of the bacterial organisms.
• Nocardial infections resulting in abortions are not reported to be contagious; the horses had not been exposed to cows or pigs which can also harbour the Nocardia species.
• The combination of the distinctive massive inflammation in the lungs and the liver, and the presence of Nocardia asteroides in the uterus of one mare, strongly suggested that Nocardia was responsible for the abortions in these mares.

Implications of the Study

• While Nocardia infections are more commonly observed in cattle and swine, they are considered rare in horses.
• The identified instances of abortion caused by Nocardia represented a small percentage of mid-to-late equine miscarriages over a two-year period at the University of Florida.
• The authors suggest that Nocardia should be considered in diagnostic evaluations when aborted horse fetuses present with similar symptoms.