First case of Plasmodium knowlesi infection in a Japanese traveller returning from Malaysia

Abstract

This is the first case of Plasmodium knowlesi infection in a Japanese traveller returning from Malaysia. In September 2012, a previously healthy 35-year-old Japanese man presented to National Center for Global Health and Medicine in Tokyo with a two-day history of daily fever, mild headaches and mild arthralgia. Malaria parasites were found in the Giemsa-stained thin blood smear, which showed band forms similar to Plasmodium malariae. Although a nested PCR showed the amplification of the primer of Plasmodium vivax and Plasmodium knowlesi, he was finally diagnosed with P. knowlesi mono-infection by DNA sequencing. He was treated with mefloquine, and recovered without any complications. DNA sequencing of the PCR products is indispensable to confirm P. knowlesi infection, however there is limited access to DNA sequencing procedures in endemic areas. The extent of P. knowlesi transmission in Asia has not been clearly defined. There is limited availability of diagnostic tests and routine surveillance system for reporting an accurate diagnosis in the Asian endemic regions. Thus, reporting accurately diagnosed cases of P. knowlesi infection in travellers would be important for assessing the true nature of this emerging human infection.

Case Report: Case Series of Human Plasmodium knowlesi Infection on the Southern Border of Thailand

“…[10][11][12][13][14][15][16][17] A number of infections were also found in international travelers. [18][19][20][21][22][23][24] In Thailand, a retrospective study of blood samples obtained from malaria patients in northwestern Tak Province during 1996 uncovered a case of mixed species infection of Plasmodium vivax and P. knowlesi. 25 In 2000, a case of human P. knowlesi malaria infection was stated in Prachuap Khiri Khan Province.…”

Combining Parasite Lactate Dehydrogenase-Based and Histidine-Rich Protein 2-Based Rapid Tests To Improve Specificity for Diagnosis of Malaria Due to Plasmodium knowlesi and Other Plasmodium Species in Sabah, Malaysia

“…Several case reports of returned travelers with PCR-confirmed P. knowlesi monoinfection have demonstrated this cross-reactivity, with Plasmodium genus pLDH-, P. falciparum pLDH-, and P. vivax pLDH-based RDTs all yielding positive results but with poor sensitivity at low parasite counts (21)(22)(23)(24). In a previous prospective evaluation of RDTs for P. knowlesi malaria, a pan-pLDHbased RDT demonstrated a moderate overall sensitivity for P. knowlesi of 74% (95/129; 95% confidence interval [CI], 65 to 80%), which improved for pretreatment samples (88%; 30/34; CI, 73 to 95%) and for severe disease (95%; 36/38; CI, 83 to 99%) (25).…”

Plasmodium knowlesi: Clinical Presentation and Laboratory Diagnosis of the First Human Case in a Scottish Traveler

“…Plasmodium knowlesi has a periodicity of 24 h, and tends to manifest itself between 3 and 14 days although longer incubation times have been noted in other imported cases. [9][10][11] Relapse of the disease is not a noted feature of a P. knowlesi infection. Although there are no distinctive features or clinical symptoms that assist in a specific diagnosis of P. knowlesi from any other malaria species, infection most typically presents with a nonspecific febrile illness; thrombocytopenia is common whereas anemia is rarely observed in adult cases on hospital admissions.…”