Epidemiology &Resistance Bill Brieger | 05 May 2008 12:27 pm
Malaria warnings from the east
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.