Introduction

Canine and feline blood component transfusion therapy is currently widely practiced as a life-saving measure in veterinary medicine and has also become a routine in human medicine. There are several risks to blood transfusion including adverse effects with allergic hypersensitivity reactions to the introduced blood product, contamination, and the risk of introducing infectious diseases. Blood products range from whole blood, to packed red blood cells (pRBC), leukoreduced RBC, plasma, and platelet concentrates such as fresh frozen plasma (FFP). Each of these components may harbor and transmit infectious agents from donors to recipients.

Screening of Blood Donors

In human medicine, every blood unit is tested for certain infectious diseases such as HIV, and blood donors are screened for risk factors for additional infectious diseases. In veterinary medicine, it is often cost-prohibitive to evaluate every blood unit or derived blood product, and therefore, often donors are interviewed and screened for infectious agents in their blood periodically. The American College of Veterinary Internal Medicine (ACVIM) published a consensus statement on infectious disease testing for canine and feline blood donors in 2005. Since then, advances have been made in diagnostic techniques, in particular the use of the polymerase chain reaction (PCR) for the detection of infectious agents has become more available. Infections with some pathogens, such as feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV), are evaluated by serologic methods. In addition to infectious agent screening, canine and feline blood donors or their blood units need to be tested for several other parameters including blood type, which is crucial in cats as transfusion of the wrong blood type may be rapidly fatal, cross-matching of the donor's blood with the recipient's blood, and a complete blood count.

Screening Recommendations for Pathogens

Based on the recommendations of the ACVIM consensus statement and subsequent research, lists of pathogens for which screening is recommended in blood donors have been formed for cats and dogs (see Tables 1 and 2). Some of these pathogens are "core" pathogens for which every donor should be screened, for instance, FIV and FeLV in cats, and Babesia spp. in dogs. Other pathogens are limited geographically, like Trypanosoma cruzi and Leishmania infantum, and therefore, it is necessary to test for them in dogs that live in endemic regions, originated from such areas, or have travelled to such areas.

Selection of Screening Test

The testing technique employed to evaluate infection in blood donors should typically be sensitive and specific. None of the tests have 100% sensitivity and specificity and every assay has its limitations. A test should indicate that the donor is currently infected with the pathogen, or has been exposed, as manifested by a positive antibody titer, and might harbor the infectious agent and transmit it in its blood. In that respect, PCR detects the presence of pathogen DNA indicating infection. The FeLV antigen test detects the presence of a circulating viral antigen, also indicating active infection. However, the main test for FIV is based on the detection of specific antibodies against the virus, and although this indicates exposure, sufficient levels of such antibodies are in agreement with FIV infection.

Prevention of Donor Infection

Blood donors must be prevented as much as possible from being infected with pathogens that can be transmitted in transfusions. This can be achieved by isolation from possible sources of infection, vaccination when available with a vaccine that does not create a diagnostic conflict (e.g., does not impede the possibility to detect real infection), and use of topical insecticides to prevent transmission of pathogens such as Babesia and Ehrlichia spp. by ectoparasites.

References

1.  Davidow B. Transfusion medicine in small animals. Vet Clin North Am Small Anim Pract. 2013;43:735–756.

2.  Kisielewicz C, Self IA. Canine and feline blood transfusions: controversies and recent advances in administration practices. Vet Anaesth Analg. 2014;41:233–242.

3.  Reine NJ. Infection and blood transfusion: a guide to donor screening. Clin Tech Small Anim Pract. 2004;19:68–74.

4.  Wardrop KJ, Reine N, Birkenheuer A, Hale A, Hohenhaus A, Crawford C, Lappin MR. Canine and feline blood donor screening for infectious disease. J Vet Intern Med. 2005;19:135–142.