Tropical Health Matters

Two news items require greater world-wide attention if current malaria control tools are to remain effective.

News-Medical.net asks the question, is “Monkey malaria the next bird flu?” The article reports that Dr. McCutchen, “An expert at the NIH, has highlighted the threat of an emergent highly virulent form of malaria, questioning whether the disease has made the jump from animal to man.”

The news story further states that, “Although at least ten species of Plasmodium can infect humans, only four forms of specifically human malaria are believed to exist. In the case of these four established human malaria types, the parasite is transmissible from one human to another, and a stable transmission cycle is established in the absence of any other vertebrate host. Now Dr McCutchan has raised the question – has a monkey malaria made that switch and become the fifth human malaria?” The full article appears in Future Microbiology and focuses on Borneo.

Dr McCutchan explained that interest was generated because of the severity of the infections and that, “The study of P. knowlesi is extremely significant regardless of whether it has entered humans permanently or represents a zoonosis. In either case, we face a health problem of potentially widespread significance and one that will present new problems for malaria control.”

Two other recent studies have documented the transmission of Plasmodium knowlesi to humans in the Philippines and Singapore. Research by Luchavez et al. (2008) extends the geographic range of known human P. knowlesi infections from Thailand, Myanmar, peninsular Malaysia, and Malaysian Borneo to Palawan Island in the Philippines. Their “report documents autochthonous human cases in the country. Major progress in malaria control has been achieved in many malarious areas in the Philippines. However, P. knowlesi forms a previously unrecognized pool of infections that may be maintained in forested areas through its presence in a simian reservoir, despite control efforts in the human population.”

Ng et al. (2008) in the Singapore example note that the case was originally misdiagnosed as Dengue, which is endemic in the region. They were fortunate that the infection responded to chloroquine.

Finally, another malaria control challenge was reported by Wongsrichanalai and Meshnick (2008) in the form of growing resistance to artesunate-mefloquine on the Cambodia-Thailand border. They suggest that, “These ACT failures might be caused by high-level mefl oquine resistance because mefloquine was used for monotherapy long before the introduction of ACT. This observation raises 2 questions. First, how can existing P. falciparum–resistant strains be controlled? Second, how can the evolution of new ACT- resistant strains be avoided elsewhere, e.g., in Africa?”

Not only does malaria not respect political borders, but now it seems, not even the ‘borders’ between species.

Coming into the immigration office in Bukavu, Democratic Republic of Congo, one is welcomed by a 2008 calendar that features chloroquine products made by Pharmakina, a company that has set up production in DRC. Another copy of the calendar is seen in the provincial office of the national AIDS coordinating agency. According to the company “PHARMAKINA combats malaria supplying drugs of natural origin. PHARMAKINA cultivates 1,200 hectares of quinquina that guarantees the stocks of barks for a LONG-TERM production.”

While it is admirable that local botanical production is being promoted, the sale of chloroquine when drug resistance is rendering this anti-malaria drug useless in most of Africa is questionable. [see comment for correction] The East African Network for Monitoring Antimalarial Treatment observed that “Between 1998 and 2001, Kenya, Uganda, Tanzania, Zanzibar, Rwanda and Burundi changed antimalarial drug policy, in the face of widespread chloroquine resistance.” Specifically in DRC researchers reported that CQ is no longer efficacious in the treatment of malaria.

Furthermore DRC’s malaria grant from the Global Fund remarks on the change of national malaria drug policy to use artesunate-amodiaquine as first line treatment. The August 2007 progress report on that grant observed that there was, “Concern with the impact of the switch from chloroquine to ACTs on the program’s Phase 2 targets on the Principal Recipient’s ability to purchase sufficient drugs to enable it to reach targets and the CCM’s proposal in the Phase 2 request to reduce the program’s timeline from 5 to 4 years.” Maybe this is why CQ is still popular?

Local production of malaria drugs does have the potential to reduce costs and increase access. Just as Pharmakina is promoting local cultivation of quinine, other companies and countries are promoting growing of artemisinin. The principle is the same, but the drugs are not. The challenge is producing the most efficacious drugs that come in combination form. Following WHO malaria treatment guidelines is a good place to start.