Detection of vector-borne organisms in domestic cats in the United States and Canada (2019 – 2025) with analysis of Hepatozoon variants

Published large-scale vector-borne organism (VBO) PCR prevalence studies in domestic cats in the United States are limited. We determined the prevalence of VBOs in feline blood samples tested by PCR at a veterinary diagnostic laboratory between January 2, 2019, and December 23, 2025 (n = 7,581). Feline blood samples were tested by PCR for Anaplasma, Apicomplexa, Babesia, Bartonella, Cytauxzoon, Ehrlichia, hemotropic Mycoplasma, and Rickettsia. We detected VBOs in 1,373/7,581 (18.1%) blood samples, with Mycoplasma haemominutum (8.87%) and Bartonella henselae (5.99%) being the most prevalent. Hepatozoon spp. were identified in 40 (0.58%) cats, prompting further genetic and epidemiologic characterization. Sequence analysis of a 182-bp fragment of the Hepatozoon 18S rRNA gene from 40 PCR-positive cats identified seven haplotypes with the highest sequence similarities to Hepatozoon silvestris, Hepatozoon felis, and bobcat-associated Hepatozoon spp. Phylogenetic analysis resolved the variants into major groups clustering with H. silvestris, H. felis, and nondomestic felid-associated Hepatozoon spp. Most Hepatozoon-positive cats originated from the Northeast and Mid-Atlantic regions of the United States (34/40; 85.0%), of which seven infections (7/40; 17.5%) involved cats undergoing blood donor screening. Overall, PCR testing confirmed infection with a VBO in approximately one in five cats tested in the U.S and Canada. Hepatozoon infections were more common than previously recognized, underscoring the value of Hepatozoon-specific PCR in feline VBO diagnostic testing.