Canadian Blood Services will commence testing for a tropical disease rarely found north of the 49th parallel when the blood donation production process is overhauled in mid-to-late 2008.
Dana Devine, Canadian Blood Services vice-president of medical, scientific and research affairs, says 2 tests for Chagas disease (also called American trypanosomiasis) are in line for Health Canada approval. But testing donated blood for Chagas will be delayed until the agency switches to the “Buffy Coat”method of blood platelet production. (Used in Europe for 2 decades, the method produces a more consistent product and yields more platelets. Buffy Coat refers to the layer of white blood cells left atop the mass of red cells when whole blood is centrifuged). “This is a production method that allows us to prepare a pool platelet product for transmission that we can test for bacteria,” says Devine.
Between 8 and 11 million people in Mexico, Central America, and South America are believed to have Chagas, with upwards of 45 000 deaths a year. Caused by Trypanosoma cruzi parasites, it is transmitted by insects found mainly in rural, poverty-stricken areas. While some victims are symptom free, others suffer fever, swelling, an enlarged spleen, liver and lymph nodes, and heart inflammation immediately after infection or sometimes decades later (CMAJ 2006;174:1096).
Insects bite sleeping victims, usually on the face (earning them the moniker “kissing bugs”). The parasites, carried in feces, infect through mucous membranes or breaks in skin. Infection also occurs through consumption of contaminated uncooked food, congenital transmission, organ transplants and accidental laboratory exposure.
Two cases are known to have been transmitted via blood transfusions in Canada, both in Manitoba (1986 and 2000). The patients died of underlying conditions. Studies of high-risk populations in Washington and California showed 1/500 may have been infected, with 20% of those able to transmit the infection. Devine says potential Chagas sufferers in Canada have been screened out for years via an agency questionnaire that asks if potential donors have visited or lived in affected areas.
Is waiting until 2008 to test too long?
No, says Dr. Jay Keystone, Toronto General Hospital's Tropical Disease Unit staff physician. “There has always been a low but definite risk to the blood supply from people from the Chagas areas of the world.” But while it's prudent to test, suggesting Chagas is a medical emergency “takes it all out of perspective,” he adds. — Pauline Comeau, Ottawa