Resistance of Plasmodium falciparum to chemotherapy with 4-aminoquinolines in the Ok Tedi area of Papua New Guinea

Abstract

In the North Fly region of the Western Province of Papua New Guinea 491 cases of Plasmodium falciparum infection were monitored in vivo for sensitivity to chloroquine and amodiaquine over a 2-year period; 41% resistance was detected. The RI type accounted for 74% of the resistant strains detected; 43% of these recrudesced on day 28 or shortly thereafter. 22% of resistant strains were RII type and 4% R III. The infections were categorized as imported or locally acquired. Imported infections accounted for 58% of the cases monitored and showed a resistance rate of 49%. Resistance was detected in 24% of the cases indigenous to the North Fly region (13% in the Kiunga-Ningerum area and 38% in the Ok Tedi-Star Mountains area). Linguistic groups immediate to the Ok Tedi mining operation, the Wopkaimin and Kamfaiwolmin, showed an increase in resistance from 28% in 1986 to 55% the following year. This increase was associated with renewed construction activity within the mine's development area. Two falciparum malaria outbreaks were experienced during this study, the second being attributed to introduced strains. The study showed the impact of age and variation of malaria endemicity in suppressing resistance. The study also demonstrated a possible cross-resistance problem between imported cases of P. falciparum treated with amodiaquine and chloroquine, with resistance rates of 58% and 60%, respectively, demonstrated in children under 10 years of age. The 61% amodiaquine resistance rate in locally acquired infection in children was attributed to drug pressure, since chloroquine resistance in the same group was reported at 19%. RIII-type resistance in children was only detected in those treated with amodiaquine. The efficacy of amodiaquine in clearing only 41% of the P. falciparum infections in children was a major concern. All 201 resistant P. falciparum infections detected over the 24-month monitoring period responded to treatment with quinine and Fansidar.