Abstract
BackgroundThe incidence of transfusion-transmitted malaria is very low in non-endemic countries due to strict donor selection. The optimal strategy to mitigate the risk of transfusion-transmitted malaria in non-endemic countries without unnecessary exclusion of blood donations is, however, still debated and asymptomatic carriers of Plasmodium species may still be qualified to donate blood for transfusion purposes.Case descriptionIn April 2011, a 59-year-old Dutch woman with spiking fevers for four days was diagnosed with a Plasmodium malariae infection. The patient had never been abroad, but nine weeks before, she had received red blood cell transfusion for anaemia. The presumptive diagnosis of transfusion-transmitted quartan malaria was made and subsequently confirmed by retrospective PCR analysis of donor blood samples. The donor was a 36-year-old Dutch male who started donating blood in May 2006. His travel history outside Europe included a trip to Kenya, Tanzania and Zanzibar in 2005, to Thailand in 2006 and to Costa Rica in 2007. He only used malaria prophylaxis during his travel to Africa. The donor did not show any abnormalities upon physical examination in 2011, while laboratory examination demonstrated a thrombocytopenia of 126 × 109/L as the sole abnormal finding since 2007. Thick blood smear analysis and the Plasmodium PCR confirmed an ongoing subclinical P. malariae infection. Chloroquine therapy was started, after which the infection cleared and thrombocyte count normalized. Fourteen other recipients who received red blood cells from the involved donor were traced. None of them developed malaria symptoms.DiscussionThis case demonstrates that P. malariae infections in non-immune travellers may occur without symptoms and persist subclinically for years. In addition, this case shows that these infections pose a threat to transfusion safety when subclinically infected persons donate blood after their return in a non-endemic malaria region.Since thrombocytopenia was the only abnormality associated with the subclinical malaria infection in the donor, this case illustrates that an unexplained low platelet count after a visit to malaria-endemic countries may be an indicator for asymptomatic malaria even when caused by non-falciparum Plasmodium species.
Highlights
The incidence of transfusion-transmitted malaria is very low in non-endemic countries due to strict donor selection
Since thrombocytopenia was the only abnormality associated with the subclinical malaria infection in the donor, this case illustrates that an unexplained low platelet count after a visit to malaria-endemic countries may be an indicator for asymptomatic malaria even when caused by non-falciparum Plasmodium species
All results together with the longstanding thrombocytopenia and travel history demonstrated that the donor must have had a subclinical P. malariae infection for at least four years and that the infection was most probably acquired during his travel through Kenya, Tanzania and Zanzibar in 2005 or during his visit to Thailand in 2006
Summary
This case of TTM is remarkable, for being the first TTM case in the Netherlands in 43 years [16], and because the donor was a non-immune traveller from a non-endemic country who never suffered from malaria and was without any symptoms for at least four years after acquisition of the P. malariae infection. It is noteworthy that the most commonly used serological test for screening donors for IgG antibodies to Plasmodium spp., the Malaria Total Antibody EIA kit (Lab, Healthcare Ltd., Kentford, UK), used by the Dutch blood bank as well as by several other blood transfusion services in nonendemic countries to shorten deferral periods for exresidents of malaria endemic areas and for individuals with a history of malaria, did not detect this asymptomatic malaria infection in the donor. This test was performed retrospectively (Table 2). As long as effective methods for pathogen inactivation of red cell units or whole blood are not available, cases of TTM can continue to occur in areas that are not endemic for malaria, irrespective of the safety measures currently adopted by the blood bank community
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