Detection and prevalence of Cercopithifilaria bainae infection in shelter dogs in Oklahoma, USA

Background Cercopithifilaria bainae is a filarioid nematode of dogs. Infection with the parasite was not reported in the USA until 2017, when a dog with skin lesions in Florida was diagnosed. Brown dog ticks, Rhipicephalus sanguineus sensu lato, are the purported tick vectors, and are widespread in the USA. Therefore, C. bainae is likely present in additional states. Here, we tested dogs and ticks in Oklahoma for evidence of C. bainae infection.Methods Dermal punch biopsies were opportunistically collected from municipal shelter and client-owned dogs. Multiple skin samples collected from interscapular and head regions were tested by saline sedimentation to recover live microfilariae for morphometric identification and by PCR to amplify a 330 bp region of 12S filarioid rDNA. Also, ticks observed on surveyed dogs were collected, identified to species level, and tested for filarioid DNA.Results A total of 1,521 biopsy samples were collected from 230 shelter and 20 client-owned dogs. Cercopithifilaria bainae infections were identified in 2.6% (6/230) of shelter dogs by morphometry of microfilariae in sedimentations and/or amplification of DNA from skin. DNA sequences amplified from PCR positive skin samples were 99–100% identical to C. bainae reported in Italy. All skin samples from client-owned dogs were negative for filarioid infection by saline sedimentation and PCR. A total of 112 ticks, comprised of four species, were collected. Two of 72 R. sanguineus s.l., both replete females found attached to a C. bainae infected dog, harbored C. bainae DNA (99–100% identity). One attached R. sanguineus s.l. male on the same dog harbored filarioid DNA sequence which was difficult to interpret at numerous base-pair locations, but was closest in identity (~80%) to C. bainae.Conclusions The distribution of C. bainae is more widespread than previously known. Here, we document C. bainae infections in dogs and DNA in brown dog ticks in Oklahoma for the first time. As brown dog ticks are commonly found throughout the USA, veterinarians in this region should consider C. bainae infection as a differential diagnosis in canine patients with dermatitis or polyarthritis.