Update on Canine and Feline Blood Donor Screening for Blood-Borne Pathogens

Wardrop, K.J.; Birkenheuer, A.; Blais, M.C.; Callan, M.B.; Kohn, B.; Lappin, M.R.; Sykes, J.

Hemoplasmas. Hemoplasmosis or "feline infectious anemia" is caused by Mycoplasma haemofelis. Other species of hemoplasmas that infect cats in North America are "Candidatus M. haemominutum" (Mhm) and "Candidatus M. turicensis" (Mtc), but these organisms are substantially less pathogenic and frequently detected (10-25% prevalence) using PCR in the blood of nonanemic client-owned pet cats that are either apparently healthy or brought to veterinary clinics for reasons other than anemia. 83, [93] [94] [95] By contrast, in North America, M. haemofelis is rarely (<1%) detected in non-anemic cats using PCR. 94, 95 When cats that were chronically infected with "Candidatus M. haemominutum" were splenectomized and concurrently treated with high doses of glucocorticoids, persistent subclinical infection occurred in the absence of anemia. 96 Although fleas have been suggested to be involved in transmission, the evidence for flea-borne transmission is weak. Epidemiologic evidence suggests that aggressive interactions between cats may lead to transmission. 95 Intravenous inoculation of infected blood has been used to produce experimental infections. 97 No serologic assay for infection is commercially available. Blood smear evaluation is insensitive (especially for chronic carrier cats) and also lacks specificity (organisms can be easily confused with stain precipitate or drying artifacts), and thus the diagnostic test of choice for screening blood donors is PCR. Because of the pathogenicity of M. haemofelis, the panel agreed that all cats should be tested for M. haemofelis and those that test positive should be excluded from the blood donor pool. Optimally, cats should be tested for "Candidatus M. haemominutum" and "Candidatus M. turicensis" and excluded from the donor pool, but given the high prevalence of these organisms in the cat population and the lack of strong evidence that they are associated with disease even in immunosuppressed cats, the panel agreed that screening for these pathogens could be considered optional and positive cats could be used as donors in the absence of a source of negative blood ( Table 2) . Because antimicrobial therapy does not reliably eliminate hemoplasmas (and appears particularly ineffective for treatment of "Candidatus M. haemominu-tum" infections), the panel does not recommend treating potential donors with antimicrobials in an attempt to eliminate infection.