Rickettsial infection in equids, opossums and ticks in the municipality of Monte Mor, state of São Paulo, Brazil.

This research examines the presence of rickettsial infection, a bacterial disease, in equids (horse family animals), opossums, and ticks in Monte Mor, Brazil, where a case of Brazilian spotted fever was previously reported. The study also explored potential factors linked to horses having this infection.

Research Methodology

• The primary objective was to understand and investigate the incidence of rickettsial infection within a specific geographical location – Monte Mor.
• The study carried out an indirect immunofluorescence assay (IFA), a trusted detection technique used to identify and quantify the rickettsial infection in horses, mules, and opossums (scientifically known as Didelphis albiventris).
• The researchers collected ticks from the animals and identified them. Particularly, Amblyomma sculptum ticks from the equids were taken, and further tested using Polymerase Chain Reaction (PCR), a method used to amplify the copies of a segment of DNA, for the presence of Rickettsia spp. bacteria.

Research Findings

• The research noticed the presence of anti-R. rickettsii antibodies in 22.6% of the horses, however, none of the mules showed the infection.
• The presence of these antibodies indicated previous or current infection with R. rickettsii bacteria, which cause Brazilian spotted fever. The infection rate was comparatively lower in opossums, with 21.7% seropositivity.
• Interestingly, all of the 166 Amblyomma sculptum ticks tested using PCR were negative for Rickettsia spp, suggesting that ticks might not be the primary transmitters of this infection in the region.
• Among the variables analyzed, only horses older than 12 years displayed seropositivity, which means that age is a significant factor contributing to the susceptibility of infections among equids.

Implications of the Research

• The study results are an evidence of the circulation of spotted fever group rickettsiae in the community of Monte Mor during the period the samples were taken.
• These findings emphasize the need for active surveillance and possibly preventive measures for Brazilian spotted fever in this region, especially among horses older than 12 years.