Babesiosis is an important cause of fever, splenomegaly, and hemolytic anemia in dogs. Babesia microti-like infection has been reported in domesticated European dogs and wild North American foxes; however, infection in domestic dogs from North America has only been rarely reported. Due to the genetic differences from other Babesia organisms that cause canine babesiosis, detection of B. microti-like DNA requires use of species-specific PCRs or broader Piroplasma PCR primers. The North Carolina State University-College of Veterinary Medicine- Vector-borne Disease Diagnostic Laboratory (NCSU-CVM-VBDDL) recently validated and implemented a novel PCR assay designed to amplify a wide range of Babesia spp. Using the new PCR assay, dog blood samples (n = 5214) submitted to the NCSU-CVM-VBDDL for PCR testing between June 2015 and December 2017 were analyzed for Babesia DNA prevalence.
Babesia spp. were detected in 195/5214 (3.74%) dogs, including B. gibsoni (2.26%), B. vogeli (0.44%), B. microti-like (0.42%), B. canis (0.33%) and B. coco (0.29%). B. microti-like specimens were further evaluated by amplification and sequencing of multiple mitochondrial and nuclear genes. Geographical location and available clinical data were collated. All B. microti-like infected dogs (n = 22) resided in North America, primarily in the eastern and southern US (predominant source of NCSU-CVM-VBDDL accessions), with no known travel to Europe.
Clinicopathologic abnormalities in 7 B. microti-like infected dogs included regenerative anemia (n = 6), thrombocytopenia (n = 3), proteinuria (n = 2), splenomegaly (n = 2), and hyperglobulinemia (n = 2). 81.8% (18/22) of B. microti-like infected dogs were American Pitt Bull Terrier-type breeds. Of 9 B. microti-like PCR positive dogs tested by B. vogeli and B. gibsoni IFA, only 6 (66.7%) were seroreactive, further suggesting that antibody detection is inadequate to fully screen for babesiosis in dogs. B. microti-like coinfections included B. gibsoni (n = 12) and Mycoplasma spp. (n = 2); one dog was E. canis IFA seroreactive. We conclude that: 1) B. microti-like infection occurs in dogs in North America. 2) Infection with these organisms induce clinicopathological abnormalities consistent with babesiosis. 3) Clearance of the infection (based upon seroreversion and negative PCRs) correlates with clinical improvement. 4) Dogs suspected of vector-borne infections in North America should be screened using PCR assays that detect B. microti-like parasites.
North Carolina State University College of Veterinary Medicine
Nanelle Barash is a graduate of UC Davis School of Veterinary Medicine, where she also received her PhD in Microbiology. She is currently a Resident in Small Animal Internal Medicine at North Carolina State University.
Thursday, June 14
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