Molecular identification of Bartonella henselae in dogs with clinical suspicion of visceral leishmaniasis.

The genus Bartonella includes species responsible for severe infections. Bartonella henselae, commonly linked to human disease, also infects dogs with or without symptoms. In Brazil, visceral leishmaniasis (VL) caused by Leishmania infantum is prevalent in Mato Grosso State, Brazil, particularly in Rondonopolis city, affecting both humans and dogs. Although reports of co-infection with Bartonella spp. and L. infantum exist in other countries, Brazilian studies are scarce. This study investigates the presence of B. henselae using culture and molecular methods in dogs suspected of having VL in Rondonopolis, while also assessing potential co-infections and evaluating diagnostic limitations of VL. Results showed B. henselae DNA in 53.75% (43/80) of these dogs, with Leishmania spp. DNA found in 65.11% (28/43) of them. Of the 80 dogs, 43.75% (35) lacked VL serological confirmation, yet 48.57% (17/35) were positive for B. henselae. This is the first report of B. henselae bacteremia in dogs from Rondonopolis. The high occurrence of dogs with clinical VL suggests a need for further research to understand the bacterium's role in VL-suspected cases, regardless of diagnostic confirmation. The study highlights a significant finding: approximately half of the dogs suspected of zoonotic parasitosis, with or without serological confirmation, were infected with B. henselae. Additionally, the detection of Leishmania sp. DNA in dogs not confirmed by Brazil's Health Department serological criteria suggests that these diagnostic standards may need reevaluation by health authorities, though caution is warranted due to the limitations of blood-based PCR for Leishmania sp. detection.