Plasmodium falciparum infection in semi-immune nonparasitemic patients_B

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Record number: 
Adverse Occurrence type: 
MPHO Type: 
Estimated frequency: 
Rare in non-endemic countries; likely very common in endemic and hyper endemic geographical areas.
Time to detection: 
3 months
Alerting signals, symptoms, evidence of occurrence: 
A 76-year-old white male with significant vascular disease and associated clinical co-mobidities reported 1 day history of fever; on presentation he was febrile, tachycardic and hypotensive. He had mild anemia, borderline leukopenia and a urinalysis with 10,041 WBCs and many bacteria seen. He was initiated on broad-spectrum antibiotics for sepsis of urinary origin and required vasopressors. A routine peripheral smear for a manual differential incidentally revealed intraerythrocytic forms consistent with malarial parasites. Treatment with atovaquone-proguanil was initiated, in addition to levofloxacin for a culture proven Morganella morganii urinary tract infection. Plasmodium malariae was confirmed by polymerase chain reaction (PCR) testing; parasitamia was detected over the next 7 days. The patient was a retired army soldier who had been living in Augusta, Georgia, for over 40 years. He had been deployed to Vietnam and had a brief layover in Brazil and Germany but no other overseas travel. Over the prior 6 years, the patient received 22 units of blood products, including 15 unitys of RBC. Archive index samples from 10 donors were retrospectively tested, including all 8 units transfused in the year preceding the diagnosis of malaria. All were negative by realtime PCR but one tested positive for P. malariae antibodies by immunofluorescence assay (dilution of 1:640). The implicated unit was transfused 3 months before he was diagnosed with malaria. The donor was identified as a 20-year-old male born in Liberia who immigrated to the United States at the age of 5 and had no subsequent foreign travel. Malarial antibody tests were repeatedly negative but P. malariae was detected by PCR and DNA sequencing. The donor was treated with chloroquine and never developed symptoms of malaria.
Demonstration of imputability or root cause: 
The donor is presumed to have carried the malarial parasites for 16 years since leaving Liberia. Recipient serology could not be performed to exclude a pre-existing quiescet malarial infection before the implicated transfusion, but the authors mention that 23 peripheral blood smears had been performed in the 4 months before the diagnosis of malaria, with no parasites seen.
Imputability grade: 
2 Probable
Suggest new keywords: 
malaria, Plasmodium malariae, transfusion-transmitted, partial immunity, semi-immune, fever, night sweats,
Suggest references: 
1) Characterization of posttransfusion Plasmodium falciparum infection in semi-immune nonparasitemic patients. Allain JP, Assennato SM, Osei EN et al. Transfusion. 2016 Sep;56(9):2374-83. 2) Plasmodium genome in blood donors at risk for malaria after several years of residence in Italy. Assennato SM et al. Transfusion. 2014 Oct;54(10):2419-24. 3) Investigating the prevalence of transfusion transmission of Plasmodium within a hyperendemic blood donation system. Freimanis G et al. Transfusion. 2013 Jul;53(7):1429-41 4) Detection of malarial DNA in blood donors--evidence of persistent infection. Kitchen AD et al. Vox Sang. 2014 Aug;107(2):123-31. 5) Transfusion-transmitted Malaria in Sub-Saharan Africa. A. Owusu-Ofori et al. ISBT Science Series (2015) 10 (Suppl. 1), 206–210. 6) Transfusion-transmitted malaria not preventable by current blood donor screening guidelines: a case report. Arthur Holtzclaw et al. TRANSFUSION 2016;56;2221–2224.
The paper dicussed is Holtzclaw's one; the other ones are references to remain attached to the record for information.
Expert comments for publication: 
Cases of transfusion transmitted malaria that are not preventable by strict adherence to various screening criteria tend to be associated to donors with partial immunity to malaria. This partial immunity is due to repeated exposures to malaria in endemic countries, which lead to a lowgrade, asymptomatic parasitemia that can persist for years. As such, residents of endemic countries are much more likely to become semi-immune carriers of malaria than short-term travelers. Because the period of parasitaemia may be very prolonged, current deferral criteria alone cannot mitigate this risk. The paper dicussed in this record is Holtzclaw et al, TRANSFUSION 2016;56;2221–2224. Several references that discuss semi-immunity to malaria and blood safety in endemic and non-endemic countries are listed in this record.