Babesia microti-like organisms have recently been identified in Spanish dogs as a cause of hemolytic anemia and azotemia. Currently there are no reports of B. microti-like infections in domestic dogs that have not traveled to or resided in the northwestern region of Spain. However, a B. microti-like parasite has been described in a single fox from the Northeastern United States and foxes are suspected to be the reservoir host for the parasites in Spain. Based on epidemiological studies Ixodes hexagonus is presumed to be the tick vector for dogs.
In order to assess the prevalence of this parasite in North American wild canids, blood samples from 149 legally trapped or injured/ill foxes from North Carolina or Canada and 3 coyotes from Canada were tested for the presence B. microti-like DNA by polymerase chain reaction.
Babesia microti-like DNA was detected by PCR in 37% (48/129) of the fox samples tested. Babesia microti-like DNA was not detected in any of the coyotes. DNA sequencing of the amplicons from 19 randomly selected cases revealed >99.9% sequence identity with the B. microti-like parasite from Spain.
These results indicate that the prevalence of B. microti-like infections in North American foxes is similar to that described in European foxes. However, the ability of the B. microti-like parasite of North American foxes to infect domestic dogs and induce disease remains unknown. An underlying cause is not identified in many North American dogs with hemolytic anemia and/or renal failure despite intensive diagnostic investigations. Babesia microti-like parasites may represent a potential health threat to North American domestic dogs and may be an under recognized cause of hemolytic anemia and azotemia. Further studies investigating the pathogenic potential of this parasite in domestic dogs, prevalence of B. microti-like infections in North American domestic dogs, as well as the vector competence and capacity of North American tick species are indicated.