Equine monocytic Ehrlichiosis (Potomac horse fever) in horses in Uruguay and southern Brazil.

This research discovered that a disease known to local communities in Uruguay and southern Brazil as churrío or churrido equino, which has been prevalent for 100 years, is actually equine monocytic ehrlichiosis (Potomac horse fever). Clinical signs from 12 horses, together with epidemiological, pathological, and DNA analysis, confirmed this finding. Plus, the disease showed high connection with the marshy ecosystem doing summers near Merín Lake, where large numbers of Pomacea spp. snails are found. Interestingly, nonnative horses were found to be almost eight times more likely to contract the disease than native horses.

Overview of the Study

• The purpose of this research was to accurately identify a mostly misinterpreted disease known amongst local communities in Uruguay and southern Brazil as equine scours or churrido equino.
• This study involved the examination of 12 affected horses, with the extensive analysis of clinical signs, as well as the postmortem findings of 3 horses.
• In addition, the research also involved an epidemiological investigation conducted on an endemic farm.

Findings and Evidence

• The symptoms exhibited by the 12 horses involved fever, depression, diarrhea, dehydration, and occasionally edema in the hind limbs and colic.
• The acute enterocolitis found in the postmortem of three horses, along with cytoplasmic inclusion of ehrlichial organisms in a horse’s large colon, linked strongly to Potomac horse fever.
• Evidence of Ehrlichia risticii was found in 11 of the horses using the indirect fluorescent antibody assay. More so, a nested polymerase chain reaction in the peripheral blood of an affected horse identified Ehrlichia risticii DNA.
• Furthermore, a healthy horse developed the disease and antibodies to E. risticii upon inoculation with peripheral blood from a sick horse, providing further validation of the finding.

Disease Incidence and Associations

• The research showed a peak incidence of the disease in March, the summer season, and found significant correlation with marshy ecosystems around Merín Lake.
• This region was noted for having large numbers of Pomacea spp. snails, suggesting a possible vector or environmental factor in the disease’s prevalence.
• The study also found that nonnative horses were nearly 8 times as likely to contract the disease as native horses, suggesting possible genetic or environmental adaptations in the latter.

Conclusion

• The research hence concluded that the disease traditionally identified as churrido equino in Uruguay and southern Brazil is actually equine monocytic ehrlichiosis (Potomac horse fever).
• It emphasizes the importance of accurate disease identification and understanding of local epidemiological factors in disease management and control.