title: A case report of transfusion-transmitted Plasmodium malariae from an asymptomatic non-immune traveller.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  In 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.
  
  
  CONCLUSIONS
  This 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.
authors.forename: Emmaline E
authors.initials: EE
authors.lastname: Brouwer
authors.forename: Jaap J
authors.initials: JJ
authors.lastname: van Hellemond
authors.forename: Perry Jj
authors.initials: PJ
authors.lastname: van Genderen
authors.forename: Ed
authors.initials: E
authors.lastname: Slot
authors.forename: Lisette
authors.initials: L
authors.lastname: van Lieshout
authors.forename: Leo G
authors.initials: LG
authors.lastname: Visser
authors.affiliation: Department of Internal Medicine, Harbour Hospital and Institute for Tropical Diseases, Haringvliet 2 3011 TD, Rotterdam, The Netherlands. p.wismans@havenziekenhuis.nl.
authors.forename: Pieter J
authors.initials: PJ
authors.lastname: Wismans
mesh_terms: D058345:Asymptomatic Infections; D001782:Blood Donors; D005260:Female; D006801:Humans; D008288:Malaria / Q000097:blood / Q000209:etiology* / Q000469:parasitology / Q000635:transmission*; D008875:Middle Aged; D010965:Plasmodium malariae / Q000302:isolation & purification*; D065227:Transfusion Reaction