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.

Trypanosoma cruzi. American trypanosomiasis (Chagas disease) is caused by Trypanosoma cruzi, a hemoflagellate protozoan. Transmission most commonly occurs through a feces-contaminated bite from, or ingestion of, triatomine bug vectors. 51 A small number of transfusion-acquired T. cruzi infections have been reported in people in North America. All patients were immunocompromised at the time of infection, and 6 of the donors were from countries where T. cruzi is endemic (South and Central America). 52 In 2010, the Food and Drug Administration recommended that all presenting human blood donors be asked about a history of Chagas disease in addition to being tested at least once using a licensed screening test. 53,54 Infection in dogs can result in acute or chronic myocarditis, but in 1 study, 55 dogs that were experimentally inoculated with T. cruzi were parasitemic but only developed transient lymphadenopathy. Survivors of acute disease can remain subclinically infected for several months until chronic myocarditis develops. Infection is characterized by detectable concentrations of specific antibodies and low concentrations of circulating parasites. 56 Most dogs that develop trypanosomiasis in the United States reside in Texas or in the southwestern states. The seroprevalence in a 2014 study of 205 dogs from 7 shelters in diverse ecoregions in Texas was 8.8%. 57 Transmission to dogs by blood transfusion has not been reported. Dogs with a history of travel to and from endemic areas (Texas, New Mexico, Arizona, southern California, Mexico, Central America and South America) should be considered for serological screening by IFA, indirect hemagglutination assays (IHA), ELISA, or immunochromatographic dipstick tests, and seropositive donors should be excluded from the donor pool. Serologic cross-reactions between T. cruzi and Leishmania spp. have been documented. 58 A PCR assay to detect T. cruzi in whole blood also could be considered. 59 Non Vector-borne Pathogens-Testing Recommended Brucella canis. Brucella canis, a zoonotic pathogen, is a gram-negative bacterium that causes brucellosis in dogs. Venereal transmission can occur during breeding, or transmission can follow oronasal contact with vaginal discharges, aborted material, and urine from infected dogs. In humans, only a few transfusion-transmitted Brucella infections have been documented worldwide. 60-62 Transmission of B. canis by blood transfusion has not been documented in dogs. However, infection is associated with prolonged bacteremia that may be subclinical, and thus the potential for transmission by transfusion exists. 63 Because it is commercially available and results can be obtained in minutes, serological screening of potential donors for antibodies using the rapid slide agglutination test (RSAT) initially is recommended. e Positive dogs should be excluded as blood donors and additional confirmatory diagnostic assays performed using blood culture, PCR on whole blood, tube agglutination tests, agarose gel immunodiffusion tests, or ELISA tests. A single negative RSAT is sufficient for neutered donors to meet optimal standards, but RSAT screening should be repeated in sexually active intact dogs. This approach is supported by numerous studies that have concluded that RSAT is highly sensitive, but lacks specificity. 64 In recent studies, PCR assays performed on whole blood or genitourinary secretions were found to be more sensitive than serologic tests, notably in the early phas