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Preventing infectious disease transmission in blood transfusions

Wardrop KJ, Birkenheuer A, et al.  Update on canine and feline blood donor screening for blood-borne pathogens.  J Vet Intern Med 2016;30:15-35.

This article is one of the Consensus Statements of the American College of Veterinary Internal Medicine, drafted by specialists in various fields to provide the veterinary community with current information regarding the pathophysiology, diagnosis, and treatment of clinically important diseases of animals.  Recommendations are made in this paper regarding appropriate blood-borne pathogen testing for canine and feline blood donors in North America so that this life-saving therapy can be provided as safely as possible to dogs and cats in need of whole blood and blood component transfusions.

All potential animal blood donors should be appropriately screened for infectious agents prior to being accepted to provide blood donations.  The consensus panel that produced this update categorized blood-borne pathogens into the following groups:  (1) vector-borne pathogens; testing for these is definitely recommended; (2) non-vector-borne pathogens; testing for these is also definitely recommended; and (3) other pathogens, for which testing is not recommended.

Screening recommendations for pathogens of concern were further subdivided into optimal and minimal standards.  The minimal standards were developed with the understanding that all recommended diagnostic tests may not be relevant for all geographic locations and donor backgrounds. Also, in some emergency situations, screening of potential donors may not be optimally comprehensive due to time constraints in the face of a pressing need for a blood transfusion by a recipient whose life is at imminent risk without the transfusion.  However, best practices in safe blood banking always include pre-emptive identification and screening of healthy blood donors prior to development of an emergent situation.

While individual blood units are generally tested for infectious agents in the human field, financial constraints in veterinary medicine make testing of the blood donors themselves the best option.  The panel recommends minimal yearly testing of all blood donors for blood-borne pathogens, with more frequent re-testing of donors for some pathogens in endemic areas and in those donors, usually dogs, with repeated exposure to risk factors such as tick exposure.  The paper includes a discussion of the selection criteria used by the panel to identify the pathogens for which donors should be screened.

Prior to investing in screening tests, all potential blood donors should have a thorough history evaluation and physical examination. This will eliminate many animals that are likely to be poor donor candidates.  The screening test(s) for individual blood-borne pathogens should be selected on the basis of which test(s) have the greatest analytical sensitivity.  In situations where the prevalence of infection with a relevant blood-borne pathogen is low, confirmatory testing with a second test through a reference laboratory is recommended in the case of animals with a positive screening test. The authors discuss the basic utility and limitations of common tests such as microscopic cytology of blood smears for infectious agents, blood cultures, serum antigen tests, molecular assays such as polymerase chain reaction (PCR), and serum antibody tests.  A list of laboratories offering point-of-care and laboratory-based tests that may be used in screening blood donors is provided.

A comprehensive list of significant blood-borne pathogens likely to be found in dogs and cats in North America is included, along with recommended tests for these agents.  All donor cats, regardless of geographic location, should be tested for the following vector-borne pathogens:  Bartonella spp. (the cat should be PCR negative at a minimum; optimally, the cat should be seronegative and PCR or culture negative for Bartonella henselae as well); Mycoplasma haemofelis (the cat should be PCR negative, and ideally PCR negative for Candidatus Mycoplasma haemominutum and Candidatus Mycoplasma turicensis as well).  Testing for other vector-borne pathogens and infections, such as Cytauxzoon felis, anaplasmosis, ehrlichiosis, and neorickettsiosis by PCR is recommended based on geographic location.

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are the two non-vector-borne pathogens for which potential feline blood donors should be tested.  Ideally donors should be FeLV antigen negative and proviral DNA PCR negative; minimally they should be FeLV antigen negative.  Donor cats should also be FIV antibody negative by ELISA.  All FIV-positive cats should be excluded as blood donors, as it is currently impossible to accurately differentiate between a cat infected with FIV and a cat that has been vaccinated against FIV.  The panel recommends that all free-roaming cats be excluded as potential blood donors as they have constant potential exposure to FeLV and FIV.

Testing of potential feline donors for feline coronavirus, Rickettsia felis, and toxoplasmosis is not recommended by the panel.  Previous recommendations in other references may include the advisability of testing for these pathogens, but positive test results for these pathogens may unnecessarily eliminate otherwise qualified and clinically healthy animals as donors.  Transmission of feline coronavirus or Toxoplasma gondii via blood transfusion has never been documented.  In the case of Rickettsia felis, the dog is actually the reservoir for this pathogen, and studies have failed to amplify R. felis DNA from feline blood.

General recomendations regarding management of blood transfusion activities and programs designed to reduce the risk of transfusion-associated disease transmission are also outlined by the panel, including donor selection and care, blood collection procedures, and record keeping.  The use of antimicrobial drugs to prevent or treat possible infection is not acceptable as a substitute for laboratory testing of potential blood donors.  Moreover, all blood for transfusion should be collected in an aseptic manner; this is especially true in the case of feline donations, as closed blood collection systems are not available for cats.

Included in this consensus statement are examples of comprehensive species-specific history forms for canine and feline blood donors.  One feline template is provided for animals being screened for suitability as blood donors, and includes history and lifestyle questions for the potential donor’s owner, as well as information to be entered by the attending clinician or transfusion technician.  The second feline template included in the paper is a pre-donation form which includes recent history questions for the donor’s owner as well as information for the attending clinician or transfusion technician to record prior to blood collection.  The resources and information provided in this paper are invaluable in creating a blood transfusion program based on current standards of care in primary care, referral, and emergency practices. [PJS]

See also:

Pennisi MG, Hartmann K, et al.  Blood transfusion in cats:  ABCD guideline for minimizing risks of infectious iatrogenic complications.  J Feline Med Surg 2015;17:588-93.