Emergence of Babesia conradae infection in coyote-hunting Greyhounds in Oklahoma, USA

Abstract

Background Babesia species are intraerythrocytic Apicomplexan parasites that infect a wide range of vertebrate hosts. These pathogens are typically transmitted either by tick vectors or by direct blood-to-blood contact, and may cause life-threatening clinical disease, such as thrombocytopenia, hemolytic anemia and acute renal failure, in canine hosts. While Babesia vogeli and Babesia gibsoni infections have both been reported in Oklahoma, reports of Babesia conradae infections have been limited to California. Methods Four separate kennels of coyote-hunting dogs were identified in Oklahoma after the kennels had consulted with Oklahoma State University Boren Veterinary Medical Teaching Hospital (antemortem cases) or the Oklahoma Animal Disease Diagnostic Lab (postmortem cases). Upon owner consent, every accessible dog from each of the four kennels was briefly examined for ectoparasites, particularly ticks, and whole blood samples were collected in EDTA tubes. Clinically ill dogs were examined by a practicing veterinarian, and clinical signs included anorexia, vomiting, lethargy, fever and anemia. DNA was extracted from each blood sample, and a nested PCR was performed using general apicomplexan primers for the partial 18S rRNA gene. PCR products were electrophoresed in agarose matrix, and appropriately sized amplicons were sequenced. Sequences were compared to reference 18S rRNA gene sequences available in GenBank, and samples with > 98% homology to B. conradae (GenBank: AF158702) were considered positive. Babesia conradae-positive dogs were then treated with atovaquone (13.5 mg/kg three times per day) and azithromycin (10 mg/kg once daily) for 10 days and retested at 30 and 60 days post-treatment by PCR. Results Of 40 dogs tested, 15 (37.5%) were positive for B. conradae with 98–99% sequence homology to B. conradae from California. All positive cases were coyote-hunting Greyhounds. Ectoparasites were not identified on any of the dogs at the time of blood collection. Treatment of clinically ill dogs with atovaquone and azithromycin resulted in complete clinical recovery in all treated dogs with negative follow-up PCR at 30 and 60 days post-treatment. Conclusions Collectively, this study (i) documents the occurrence of B. conradae in Oklahoma, (ii) highlights this pathogen as a differential to be considered when clinical signs are present, (iii) supports the use of atovaquone and azithromycin as effective treatment in these cases and (iv) demonstrates chronic subclinical carrier dogs serving as potential reservoirs of B. conradae infection to naïve dogs. Graphical abstract

Vector‐borne disease and its relationship to hematologic abnormalities and microalbuminuria in retired racing and show‐bred greyhounds

“…and infection with hemotropic Mycoplasma recently have been documented in kennels of coyote hunting greyhounds. 25 , 60 In addition to transmission by arthropod vectors, the authors hypothesized that some agents may be transmitted vertically or through biting. 24 , 68 , 69 The species and diversity of organisms and high prevalence of coinfection in retired racing greyhounds may reflect cotransmission of multiple pathogens by R. sanguineus or simultaneous exposure to multiple vectors or other means of transmission.…”

“…Ehrlichia canis seroprevalence has ranged between 0.4% and 12% in greyhounds 37,59 . Infection with B. conradae recently was documented in coyote hunting greyhounds and greyhound mixes in California and Oklahoma 25,60 . The prevalence of A. platys , Bartonella spp., E. ewingii , E. chaffeensis and hemotropic Mycoplasma in racing greyhounds has not been reported.…”

Babesiosis and Theileriosis in North America

“…Although R. sanguineus may transmit B. gibsoni in other parts of the world, most of the cases due to this protozoon in the US occur by direct blood contact during dog bites in fighting dogs [15]. B. conradae was historically found in California [16,28] but has recently been reported in Greyhounds used to hunt coyotes (Canis latrans) in Oklahoma [60]. B. vulpes has been reported in gray (Urocyon cinereoargenteus) and red foxes (Vulpes vulpes) from the US and Canada [17] and hunting dogs in the US [36].…”

“…These infected dogs had no history of tick infestation but had aggressive interactions with coyotes. Analysis of blood samples from 40 dogs originating from four separate kennels in Oklahoma showed that 15 (37.5%) were infected by B. conradae [60]. The tick vector and the role of wild carnivores as reservoirs in the epizootiology of B. conradae have not been fully determined [60].…”

“…Analysis of blood samples from 40 dogs originating from four separate kennels in Oklahoma showed that 15 (37.5%) were infected by B. conradae [60]. The tick vector and the role of wild carnivores as reservoirs in the epizootiology of B. conradae have not been fully determined [60]. Barash et al [17] investigated the presence of Babesia species in 9376 dog samples and found 157 (1.7%) infected with B. gibsoni, 19 (0.20%) with B. vulpis, and 29 (0.31%) coinfected with B. gibsoni and B. vulpis.…”