Brazilian spotted fever in cart horses in a non-endemic area in Southern Brazil.

The study investigates the potential exposure of cart horses in Southern Brazil to Brazilian Spotted Fever (BSF), a typically fatal disease in humans caused by Rickettsia rickettsii bacteria, and suggests these animals may serve as indicators of the disease’s presence in certain areas.

Background

• Brazilian Spotted Fever (BSF) is a fatal zoonosis, or disease that can be transmitted from animals to humans. It’s caused by the Rickettsia rickettsii bacterium which typically lives inside ticks of the Amblyomma species.
• Horses show evidence of past infection by the bacteria but its effects on these animals isn’t fully understood. Because cart horses are often used in urban or semi-urban areas in Brazil, they could function as indicators or “sentinels” for the presence of BSF in these areas.
• The study specifically looked at cart horses in Sao Jose dos Pinhais, where the first case of BSF in the state of Parana was diagnosed.

Methods

• Researchers collected serum samples from 75 cart horses between April 2005 and June 2006. They used the indirect immunofluorescence assay (IFA) to test for antibodies against the spotted fever group of rickettsia in these samples.

Findings

• Out of the 75 cart horses, approximately 9.33% tested positive for the antibodies. The titer values (a measure of the concentration of antibodies) ranged from 64 to 1,024.

Conclusions

• The researchers concluded that although the rate of exposure in the horses is low, the results do indicate the presence of the zoonotic agent in the surveyed areas.
• This study reinforces the potential role of horses in monitoring the spread and presence of BSF in human populations, particularly in areas where other indicators may not be readily available.