Detection of Ehrlichia sp. in Amblyomma sculptum parasitizing horses from Brazilian Pantanal wetland.

The research investigated Ehrlichia bacteria, a type of tick-transmitted pathogen, in horses and ticks in Brazil’s Pantanal wetland. The study highlighted Ehrlichia infection within horses and various tick species, with further exploration urged for improved understanding of equine Ehrlichia infection, given the crucial role of horses as tick hosts in this region.

Study Details

• The study was conducted on a ranch in the southern Pantanal wetland of Brazil, where horses were being parasitized by Amblyomma sculptum, Rhipicephalus microplus, and Dermacentor nitens ticks.
• The research aimed at determining the presence of Ehrlichia spp., a genus of bacteria transmitted by ticks, that can cause infection in wild and domestic mammals including horses. This infection has been previously reported from USA, Nicaragua and Brazil, but this study focuses on the Brazilian Pantanal.

Methodology

• The researchers collected blood from 12 horses; they conducted an indirect immunofluorescence assay (IFA) using Ehrlichia canis crude antigen to investigate for antibodies.
• Along with this, molecular analysis using the polymerase chain reaction (PCR) was conducted to amplify fragments of the 16S rRNA, dsb, groEL, and sodB genes of Ehrlichia spp.
• A total of 164 tick specimens were also collected from the horses, these were preserved in isopropanol and later identified as D. nitens, A. sculptum, and R. microplus.
• Analysis of the tick specimens was carried out similarly, by extracting DNA from ticks and running them through PCR assays.

Results

• Anti-Ehrlichia spp. antibodies were found in 5 of the 12 horses (41.7%), suggestive of exposure to an ehrlichial agent. However, the horses’ DNA samples were negative for the Ehrlichia spp genes.
• Only one female A. sculptum tick showed positive results for all target genes of Ehrlichia.
• The tick was found on a horse that tested seropositive for Ehrlichia with an antibody titer of 80.

Conclusion and Further Study

• The study found that the detection of anti-Ehrlichia sp. antibodies implies the exposure of horses to Ehrlichia in the Pantanal region.
• The nucleotide sequences from the positive A. sculptum tick showed close relationship with different strains of Ehrlichia detected in wild mammals, Amblyomma ticks and horses from Brazil and Argentina.
• The results encourage further research into Ehrlichia infection to gain a better understanding of equine ehrlichiosis, especially because horses are important hosts for ticks within the Brazilian Pantanal wetlands.