Molecular identification of vector-borne organisms in Ehrlichia seropositive Nicaraguan horses and first report of Rickettsia felis infection in the horse.

This research focuses on identifying the frequency and types of vector-borne infections in Ehrlichia-seropositive horses found in Mérida, revealing diseases such as Babesia caballi, Theileria equi, a novel Ehrlichia species, and for the first time in horses, Rickettsia felis.

Objective and Methodology

• After identifying a new species of Ehrlichia in Nicaraguan horses from Mérida, the researchers intended to determine how frequently these horses are infected with various vector-borne organisms.
• They conducted Polymerase Chain Reaction (PCR) tests on 93 Ehrlichia-seropositive horses that had been exposed to ticks.
• These tests screened for infections linked to several genera, notably Anaplasma, Babesia, Bartonella, Ehrlichia, Leishmania, Mycoplasma, Neorickettsia, Rickettsia, and Theileria.

Findings

• Results revealed that 90 of the 93 tested horses, or 96.8%, were infected by at least one of the vector-borne organisms.
• The most common infection among them was Theileria equi, found in the same 90 horses.
• Babesia caballi was discovered in 21 of the horse samples, equivalent to 26.8% of the total.
• Nine of the tested horses were found to be infected with the newly identified Ehrlichia species, earlier labeled H7, which had been previously spotted in horses in Nicaragua and Brazil.
• The researchers also found Rickettsia felis in two of the horses, marking the first time this infection had been detected in horses.
• No traces of Anaplasma, Bartonella, Leishmania, Mycoplasma, or Neorickettsia species were uncovered in any of the horses.
• The researchers identified the ticks as Amblyomma cajennense sensu lato and Dermacentor nitens, both known vectors of various diseases.

Significance of the Study

• This study sheds light on the wide range of vector-borne organisms that infect horses in Mérida.
• Diseases, such as Babesia caballi, Theileria equi, and the novel Ehrlichia species, were identified in the horses.
• The study also reports the first ever identification of Rickettsia felis in horses, which broadens our understanding of vector-borne diseases in equine populations.