Plasmodium knowlesi

A 23-year old splenectomized female patient with beta thalassaemia major presented with fever, headache and dizziness 11 days after receiving a blood transfusion. She lived in a malaria endemic area in Sabah, Malaysia; she developed metabolic acidosis and multi-organ failure. A blood film taken on arrival was positive for malaria parasites resembling P. knowlesi, with a parasite count of 84,000 parasites/µL. She responded well to intravenous artesunate and recovered. High parasite counts and severe disease with P. knowlesi usually occur in elderly patients, but the severity of presentation was likely linked to the asplenia in this young adult; mode of acquisition of infection might have played a role too. A species specific PCR was performed and confirmed the diagnosis. The blood donor was a 51-year old male farmer who lived in a malaria-endemic area and was asymptomatic on the day of donation but presented to medical care 12 days later with a 5 day history of fever, nausea, headache and malaise. P. falciparum were reported from a blood film but a PCR performed retrospectively confirmed P. knowlesi infection. Blood film microscopy of blood donor sample is used in Malaysia at the time of donation but this is not sufficienlty sensitive to detect low level asymptomatic parasitemia, as in this case.