P. knowlesi versus P. falciparum: Treatment and Prevention

QUESTION

I would like to know about the P. knowlesi – treatment compared to P. falciparum? preventive medicine?

ANSWER

At this point in time, P. knowlesi is completely susceptible to chloroquine, and so can be treated successfully using this drug. P. falciparum, on the other hand, is known to have widespread resistance to chloroquine, and so the World Health Organization recommends that chloroquine should not be used to treat P. falciparum malaria. Instead, for non-complicated malaria, the WHO recommends treatment with artemisinin-based combination therapies (ACTs). These drugs can also be used against other forms of malaria, including P. knowlesi, particularly if the hospital also treats cases of P. falciparum regularly and so has supplies of ACTs on hand. One study even showed that treatment with ACTs (specifically artemether-lumefantrine) was more effective than chloroquine in treating P. knowlesi. Severe cases of either infection should be treated with intravenous artesunate or quinine.

Prevention for both is roughly similar – chemoprophylaxis should be taken by people travelling to an area where transmission of these types of malaria occurs. However, given P. knowlesi‘s susceptibility to chloroquine, this drug is effective as a prophylactic for this malaria species, whereas it is not appropriate for P. falciparum, given high levels of resistance. In terms of prevention of mosquito bites, this differs due to the types of mosquito vectors each of these species of malaria uses. P. knowlesi is only found in south-east Asia, where the mosquitoes that transmit it tend to be forest dwelling. As such, people who spend time in the forest in the evening and at night are most at risk of contracting P. knowlesi. Wearing long-sleeved clothing and insecticide while in the forest may help prevention in this case. P. falciparum is found throughout the world, and uses many different species of mosquito vector. In Africa, the mosquitoes which transmit P. falciparum tend to rest indoors and thus bite people at night while they are sleeping. Therefore, in these settings, it is especially beneficial to sleep under a long-lasting insecticide treated bednet. Indoor residual spraying, which coats the inside walls of a house with insecticide to kill indoor-resting mosquitoes, can also be beneficial.