The constant increase of population movements related to emigration, business or tourism, leads to the spread of infections until now restricted to endemic areas.
In the case of Central and South Americas, Chagas disease has become a matter of concern during the last decade in countries which receive Latino American immigrants. This disease is caused by a protozoan parasite, Trypanosoma cruzi, transmitted in endemic areas predominantly by a Triatomine vector. The probable routes of infection in non-endemic countries, where the vector is non-existent, are therefore blood transfusion, organ transplantation and vertical transmission. In Europe, Spain is the country that receives most part of immigrants proceeding from Central and South Americas. In Spanish blood banks, anti-T. cruzi screening is mandatory since September 2005 in donors at-risk for Chagas disease. From this date, this new selective screening allowed to identify 110 infected blood donors in the Catalonian Blood Bank. A large part of positive donors was from Bolivia, country with the highest seroprevalence of infection. Other positive donors were from Argentina, Paraguay, Ecuador etc., but also from Spain (mother born in endemic area, or donor born in endemic area or who had resided in endemic area). At the same time, look-back procedures were initiated in those donors who had donated before and whose blood products had been transfused. Screening for T. cruzi infection is generally selective, only done in at-risk donors, although the USA blood banks perform a universal screening since 2007. The selective screening strategy is finally discussed.
Besides Chagas disease, malaria is also a parasitic infection caused by Plasmodium and transmitted by the bite of Anopheles mosquito in endemic areas. Two of the five Plasmodium species, P. falciparum and P. vivax, are most often found in Central and South Americas. Cases of transfusion-transmitted malaria are mostly associated to P. falciparum, although cases of transmission of P. malariae, vivax or ovale have also been described. The growing number of donors who travel to malaria endemic areas, or who were born in an endemic region increases the probability to fail to identify an at-risk donor and to transfuse a contaminated blood component. In non-endemic countries, the measures taken to prevent malaria transmission by transfusion generally consist in deferral of at-risk donors, based on questionnaire reporting travels to or residence in malaria areas. Some blood bank use a screening test to detect anti-Plasmodium antibodies, but have then to face the problem of confirmation of an initially reactive result and of donor’s counselling. To opt for a screening or for a deferral strategy could depend once again on the epidemiological profile of blood donors.