Plasmodium knowlesi infection in East Kalimantan, Indonesia

Plasmodium knowlesi is the fifth species of plasmodium infecting humans and the infection was first discovered in Southeast Asia in 2004. The incidence has been increasingly reported from almost all Southeast Asian countries, including Indonesia. Although the global incidence of malaria has decreased around 50% in the last decade, the increase of knowlesi malaria infection which can cause severe malaria is of concern. During the period of 2018 to 2021, there were seven newfound cases of knowlesi malaria infection in patients treated at hospital in Samarinda, East Kalimantan, Indonesia. The clinical manifestations and laboratory examinations of these patients are described here. All patients were male and worked in mining and palm oil plantations in the forest in several districts in East, North, and South Kalimantan. The diagnosis was based on microscopic examination of Giemsa-stained thin blood smear and confirmed by polymerase chain reaction (PCR) test. Antimalarial treatment was artemisinin-based combination therapy (ACT) / dihydroartemisinin-piperaquine (DHP) fixed-dose combination via oral administration for three days with the doses were based on body weight. All knowlesi malaria patients in this report were presented as uncomplicated cases with great response to ACT after 2-3 days of administration without any adverse effects. Besides fever, gastrointestinal symptoms were major symptoms. Anemia was rare, leukocyte count was normal, however thrombocytopenia was found in all patients. P. knowlesi infection has been discovered in East Kalimantan Province and recently the incidence might be higher than the reported cases, making it resemble an iceberg phenomenon. Therefore, we should build awareness of the rapid increasing of knowlesi malaria cases and its prevention.