Chloroquine Resistant Plasmodium falciparum in Saudi Arabia
ABSTRACT & COMMENTARY
Kinsara and colleagues report two cases of Plasmodium falciparum infection, autochthonously acquired in Saudi Arabia, that were resistant to treatment with chloroquine. Neither patient had been out of the country or had other potential identified exposures, such as injection drug use or receipt of blood transfusions. One patient, with approximately 2% of his red cells infected at presentation, had no reduction in parasitemia after treatment with a standard course of chloroquine phosphate. Sequential treatment with quinine and Fansidar resulted in complete resolution of parasitemia without recrudescence.
The second patient had no reduction of his 1% parasitemia after chloroquine treatment but had complete resolution after sequential treatment with quinine and tetracycline.
n COMMENT BY STAN DERESINSKI, MD, FACP
Of the more than 18,000 cases of malaria reported in Saudi Arabia in 1993, 26% were imported. Of the remainder, 85% were due to P. falciparum and 14% to P. vivax (Scrimgour EM. Trop Dis Bull 1995;92:R80-R95).
Areas of Saudi Arabia endemic for malaria include the western provinces, with the exception of high altitude areas of Asir Province near the border with Yemen, and the urban areas of Jeddah, Mecca, Medina, and Taif. The distribution within these areas is primarily in cultivated areas and in settled oasis populations, with the highest incidence in the southwestern region. The second of the two patients described by the authors had visited Al Lith, 200 km southwest of Jeddah, 10 days prior to becoming ill.
The Middle East is one of the few remaining malaria endemic areas where chloroquine remains the malaria prophylaxis of choice in most instances. While mefloquine prophylaxis is recommended for visitors likely to experience malaria exposure in Iran and Oman, chloroquine is still recommended for similar travelers to Saudi Arabia, Iraq, Syria, Turkey, and the United Arab Emirates.
In the absence of in vitro susceptibility testing, drug resistance of malaria parasites is defined by the response (or lack thereof) to treatment.
Clearance of parasitemia by day 7 with recrudescence by day 28 is type RI resistance. Marked reduction of parasitemia without complete clearance by day 7 is type RII. RIII, the type of resistance present in the two subjects reported by the authors, is demonstrated by the absence of reduction in the level of parasitemia by day 7.
While chloroquine remains the prophylactic agent of choice for prevention of malaria in Saudi Arabia, these two cases indicate the need for careful attention to the changing antimalarial susceptibility of P. falciparum in the Middle East.