Artemisinin-Resistant Malaria Detected in Western Cambodia
By Linda on Nov 16, 2009 in Infections
NEW YORK (Reuters Health) Jul 29 – New research indicates that artemisinin resistance among Plasmodium falciparum isolates is common in western Cambodia and that in vitro testing may give false results.
Findings from another study indicate that inoculation of intact sporozoites can induce protection against malaria challenge. Both studies are reported in The New England Journal of Medicine for July 30.
Recent research suggests that artemisinin-based therapies are losing their efficacy against falciparum malaria on the Thai-Cambodian border, a site where antimalarial-drug resistance has been described in the past.
In the first study, Dr. Arjen M. Dondorp, from Mahidol University, Bangkok, and colleagues assessed the response to artesunate with or without mefloquine in 40 patients living in western Cambodia and 40 in northwestern Thailand.
The time to parasitic clearance was significantly longer in the Cambodian patients: 84 vs. 48 hours in Thai patients (p < 0.001). In vitro testing, however, did not show reduced sensitivity to artesunate.
“Measures for containment are now urgently needed to limit the spread of these parasites from western Cambodia and to prevent a major threat to current plans for eliminating malaria,” the authors conclude.
In the second study, Dr. Robert Sauerwein, from Radboud University, Nijmegen, the Netherlands, and colleagues examined sporozoite inoculation, via mosquito bite, as a means of inducing immunity against malaria.
Ten healthy subjects received bites from infected mosquitos (vaccine group) and 5 received bites from uninfected mosquitos (control group), once a month for 3 months. Chloroquine prophylaxis was given to both groups during this immunization phase. One month after stopping chloroquine, all of the subjects underwent malaria challenge with mosquitos infected with P. falciparum.
The subjects in the vaccine group were fully protected against malaria challenge, whereas all subjects in the control group developed parasitemia. No serious adverse events were seen in either group.
Although the described study protocol does not represent a vaccine strategy that can be widely implemented, “the induction of sterile protection against a homologous malaria challenge suggests that the concept of a whole-parasite malaria vaccine warrants further consideration,” the authors conclude.
N Engl J Med 2009;361:455-477.
