Authors: Neves Lucianne Cardoso, Paula Warley Vieira de Freitas, de Paula Luiza Gabriella Ferreira, da Silva Bianca Barbara Fonseca, Dias Sarah Alves, Pereira Brenda Gomes, Silva Bruno Sérgio Alves, Sevá Anaiá da Paixão, Dantas-Torres Filipe, Labruna Marcelo B, Krawczak Felipe da Silva
Journal: Animals : an open access journal from MDPI
Summary
# Brazilian Spotted Fever in Goiás: Identifying the Rickettsial Agent Behind Human Cases Recent human cases of Brazilian spotted fever in Goiás state have been serologically confirmed but remain epidemiologically puzzling, as cross-reactivity among spotted fever group (SFG) rickettsiae complicates definitive identification of the causative agent. Between March 2020 and April 2022, researchers collected ticks from domestic animals (horses and dogs), wildlife (capybaras), and vegetation across affected and surveillance areas, conducting molecular and serological screening to characterise circulating rickettsial species. Whilst dogs, horses and capybaras all demonstrated seroreactivity to SFG antigens (25.4%, 22.7% and 41.2% respectively), the most significant finding was detection of *Rickettsia bellii*—a non-SFG species—in *Amblyomma dubitatum* ticks, with notably higher antibody titres against *R. bellii* in dogs and capybaras, suggesting this may be the primary circulating rickettsia in the region rather than classical SFG agents. For equine professionals, this work underscores the importance of tick management and awareness that *Dermacentor nitens* and *Amblyomma sculptum* infesting horses in endemic areas may carry rickettsial agents; further investigation is essential to establish whether *R. bellii* represents a genuine human pathogen or an incidental finding requiring clarification of its epidemiological role.
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Practical Takeaways
- •Horses in Goiás state Brazil are at risk of spotted fever group rickettsial infection; veterinarians should maintain clinical vigilance for rickettsiosis signs in endemic areas
- •Multiple tick species infest horses in this region (A. sculptum, D. nitens, R. microplus); comprehensive tick control protocols are essential for disease prevention
- •Serological cross-reactivity among rickettsial species complicates diagnosis; molecular identification methods are needed to confirm the specific causative agent in suspected cases
Key Findings
- •Seroreactivity to spotted fever group Rickettsia was detected in 22.7% (10/44) of horses in the endemic area of Goiás state, Brazil
- •Rickettsia bellii was identified in Amblyomma dubitatum ticks collected from the region, with higher antibody titers in dogs and capybaras than horses
- •Multiple Amblyomma species tick infestations were documented on horses including A. sculptum, Dermacentor nitens, and Rhipicephalus microplus
- •The specific rickettsial agent responsible for BSF cases in Goiás remains unconfirmed despite serological evidence of SFG rickettsiae circulation