Routine Testing Covers a Limited Number of Agents:
Parasites and Other Known Pathogens

Although as many as 25 known pathogens may be present in blood [35], only HIV, HCV, HBV, and a few others are required to be screened after collection. Detection tests are not yet developed or implemented for all recognized pathogens, including parasites.

Risks from parasites With the increase in global travel and migration over the last 20 years, blood-borne parasitic diseases such as malaria and Chagas' diseases have become more common in blood transfusions throughout Europe. Parasite screening tests are not routinely used, and donor interviews remain the primary defense against such infections.

Malaria Globally, malaria is estimated to infect 300 - 500 million people every year in tropical regions [36]. Though primarily spread by mosquito bite, the disease can be transmitted through blood transfusion, which accounted for 91 cases in the US between 1963 and 1999 [37]. Currently, donors who have visited areas in which malaria is endemic may be deferred from donating blood for six months.

Chagas' DiseaseTrypanosoma cruzi, the causative agent of Chagas' disease, is endemic in much of South America. Although the disease can be transmitted through blood transfusion and has been documented in the US and Canada, routine screening of blood for T. cruzi is not performed. Studies in the US (Los Angeles, California) have indicated that in some regions as many as 1 in 7500 blood donors show evidence of infection [38].

Reduviid bug vector

T. cruzi trypomastigote in Giemsa-stained thin smear

Global distribution of Chagas' disease

Photo courtesy of World Health Organization / TDR / Stammers.

Leishmaniasis Leishmaniasis, caused by the Leishmania sp., is a serious illness endemic to subtropical regions. Recent studies of Leishmania/HIV co-infection have revealed that the true prevalence of Leishmania in Spain and Southern Europe may be under-reported and the parasite can pose a serious health risk to immunocompromised patients [39].

Sandfly vector (Phlebotomous dubosci)

Leishmania promastigote in fixed Giemsa-stained thin smear

Global distribution of Leishmaniasis

Photos are courtesy of World Health Organization / TDR / Stammers, and map data is from WHO/CDC, 1987.

Additional viral risk Although most of the routine screening tests in common use are directed against viral pathogens, the blood supply remains vulnerable to many known viral diseases.

• Cytomegalovirus (CMV) is such a common infection that it is not routinely screened due to its high prevalence (from 40 - 100% in Western adult populations [40]). However, CMV can pose a serious threat to immunocompromised individuals, who receive CMV-seronegative units from a limited supply. Although leukoreduction has been proposed as an alternative to the use of CMV-seronegative units, some studies have indicated that leuko-filtration is not completely effective at preventing transmission of CMV [41].
• Parvovirus B19 is another virus which is widespread (up to 70 - 90% estimated seroprevalence in adults [42]), and is not included in the panel of blood bank screening tests. Though many transfusion recipients may already be immune to this agent, B19 infection can be hazardous for certain populations such as those who are immunocompromised, sickle cell/thalassemia patients, and pregnant women.

Benefits of the INTERCEPT Blood System The broad-spectrum pathogen inactivation of the INTERCEPT Blood System allows a single new safety measure to simultaneously address multiple infectious risks of transfusion.

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