Use of a polymerase chain reaction assay to detect and differentiate two strains of Haemobartonella felis in naturally infected cats

Abstract

Objective—To develop a polymerase chain reaction (PCR) assay that detects and differentiates the Ohio strain of Haemobartonella felis (H felis-OH) and the California strain of H felis (H felis-CA) and to apply the assay to blood samples from cats with and without suspected haemobartonellosis (suspect and control cats, respectively). Sample Population—220 blood samples were examined; 82 were from suspect cats, and 138 were from control cats. Procedure—A PCR assay was designed to detect and differentiate H felis-OH and H felis-CA. Results—On the basis of PCR assay results, the overall prevalence of H felis infection was 19.5% (43/220). Suspect cats (28.0%; 23/82) were significantly more likely than control cats (14.5%; 20/138) to be H felis infected. Significantly greater numbers of suspect cats were H felis-OH infected (12.2%, 9/82) or H felis-OH and H felis-CA infected (4.9%, 4/82) than control cats (0% [0/138] and 0.7% [1/138], respectively). Significantly more anemic cats were H felis-OH infected (14.3%; 4/28) or H felis-OH and H felis-CA infected (7.1%; 2/28) than nonanemic cats (2.3% [3/128] and 0.8% [1/128], respectively). The PCR assay was more accurate than cytologic examination for detection of H felis. Conclusion and Clinical Relevance— Haemobartonella felis infections are more common in cats than previously recognized. Haemobartonella felis-OH is apparently more pathogenic than H felis-CA. The PCR assay is more accurate than cytologic examination for detection of H felis infection and is an effective clinical tool for the detection and differentiation of both H felis strains known to infect cats. (Am J Vet Res 2001;62:604–608)