Molecular epidemiology and phylogenetics of canine haemoprotozoan and rickettsial infections in southern India.

Haemoprotozoan infections pose significant health risks to dogs, especially in tropical regions. This study investigated the epidemiology and molecular characteristics of Babesia gibsoni, Babesia vogeli, Hepatozoon canis, Ehrlichia canis, Anaplasma platys, and Rickettsia spp. in 120 clinically affected dogs from southern India (November 2023-September 2024). Dogs exhibiting pyrexia, anorexia, and thrombocytopenia were screened via blood smear microscopy and PCR. Babesia spp. were most prevalent (66.7 %, 80/120), with co-infections of B. gibsoni and B. vogeli (76.3 % of Babesia-positive cases) being common. In contrast, E. canis (6/120, 5.0 %), A. platys (2/120, 1.7 %), and H. canis (2/120, 1.7 %) were detected at much lower rates; no Rickettsia spp. were found. Infected dogs were more often male and typically 1-3 years old, with a peak in cases during the pre-monsoon season (March-May). Tick infestation was frequently observed among cases. Clinically, affected dogs showed fever, pallor, splenomegaly, lymphadenopathy, and dehydration. Haematological and biochemical analyses revealed anaemia, thrombocytopenia, leukocytosis, elevated ALT, ALP, and bilirubin, and reduced total protein in infected dogs. Phylogenetic analysis of the amplified 18S and 16S rRNA gene sequences showed close relationships with strains from other Asian regions. Our findings highlight the high prevalence of multi-pathogen co-infections and underscore the need for improved diagnostic, treatment, and vector-control strategies. A One Health perspective is recommended to address the zoonotic risk of these tick-borne pathogens.