Outbreaks and Updates Travel Health Tropical Medicine

Plasmodium Knowlesi Malaria

When people think of malaria, they think of 4 major types: Plasmodium Malariae, Plasmodium Vivax, Plasmodium Ovale and Plasmodium Falciparum. A recent publication in Clinical Infectious Diseases says there should be another name added to that list. Plasmodium Knowlesi is a species found in Malaysia and has been often misdiagnosed as P. Malariae.

For a quick re-cap on malaria, vist the Adventure Doc Malaria Page

P. Knowlesi has been previously thought to be a disease of primates and of little importance in humans. This changed in 2004-2005 when Malaysia suffered 4 deaths due to what was believed to be P. Malariae. P. Malariae is not a parasite that is normally associated with mortality. It seems the new fatalities were due to P. Knowlesi infection.

 Reccs from the article are to confirm the diagnosis of the more benign P. Malariae in travelers from Malaysia and SE Asia to ensure P. Knowlesi is not missed.  Treatment of P. Knowlesi should be as aggressive as P. Falciparum, as well.

The article provides some interesting information and a look at investigations into malaria disease and transmission.

Many thanks to the authors and editors who produced this! Here’s the official citation, too:

Plasmodium knowlesi Malaria in Humans Is Widely
Distributed and Potentially Life Threatening

Janet Cox-Singh, Timothy M. E. Davis, Kim-Sung Lee, Sunita S. G. Shamsul, Asmad Matusop, Shanmuga Ratnam, Hasan A. Rahman, David J. Conway, and Balbir Singh

Clinical Infectious Diseases 2008;46:165–171

Adventure Doc

1 comment

  1. The view that human knowlesi malaria rarely infects humans first changed when we described a large focus of human infections in the Kapit division of Malaysian Borneo (Singh et al 2004, A large focus of naturally acquired Plasmodium knowlesi infections in human beings. Lancet 2004; 363: 1017-24). Subsequently we reported in our paper in Clin. Infec. Dis. (Cox-Singh et al) that human knowlesi malaria cases are distributed throughout Malaysian Borneo and Peninsular Malaysia. Human infections are not restricted to Malaysia and have been reported to have been acquired in southern Thailand, Myanmar, the Philippines and even in Singapore (refs below). The infections are as widely distributed as their simian hosts, the longtailed and pigtailed macaques. Human infections respond to treatment with chloroquine and primaquine (Singh et al 2004) but when parasite counts are high, more aggressive intravenous antimalarial treatment and management as for falciparum malaria is recommended

    1. Jongwutiwes S, Putaporntip C, Iwasaki T, Sata T, Kanbara H. Naturally acquired Plasmodium knowlesi malaria in human, Thailand. Emerg Infect Dis 2008; 10: 2211-213.
    2. Zhu HM, Li J, Zheng H. Human natural infection of Plasmodium knowlesi. Chinese J Parasitol Parasit Dis 2006; 24: 70-1
    3. Luchavez J, Espino F, Curameng P, et al. Human infections with Plasmodium knowlesi, the Philippines. Emerg Infect Dis 2008; 14: 811-13.
    4. Ng OT, Ooi EE, Lee CC, et al. Naturally acquired human Plasmodium knowlesi infection, Singapore. Emerg Infect Dis 2008; 14: 814-16.

Leave a Reply