Abstract
BackgroundIn Cambodia, elimination of artemisinin resistance through direct elimination of the Plasmodium falciparum parasite may be the only strategy. Prevalence and incidence at district and village levels were assessed in Chey Saen district, Preah Vihear province, North of Cambodia. Molecular and clinical indicators for artemisinin resistance were documented.MethodsA cross sectional prevalence survey was conducted at village level in the district of Chey Saen from September to October 2014. Plasmodium spp. was assessed with high volume quantitative real-time polymerase chain reaction (qPCR). Plasmodium falciparum-positive samples were screened for mutations in the k13-propeller domain gene. Treatment effectiveness was established after 28 days (D28) using the same qPCR technique. Data from the provincial surveillance system targeting symptomatic cases, supported by Médecins Sans Frontières (MSF), were used to assess incidence.ResultsDistrict P. falciparum prevalence was of 0.74 % [0.41; 1.21]; village prevalence ranged from 0 to 4.6 % [1.4; 10.5]. The annual incidence of P. falciparum was 16.8 cases per 1000 inhabitants in the district; village incidence ranged from 1.3 to 54.9 for 1000 inhabitants. Two geographical clusters with high number of cases were identified by both approaches. The marker for artemisinin resistance was found in six samples out of the 11 tested (55 %). 34.9 % of qPCR blood analysis of symptomatic patients were still positive at D28.ConclusionsThe overall low prevalence of P. falciparum was confirmed in Chey Saen district in Cambodia, while there were important variations between villages. Symptomatic cases had a different pattern and were likely acquired outside the villages. It illustrates the importance of prevalence surveys in targeting interventions for elimination. Mutations in the k13-propeller domain gene (C580Y), conferring artemisinin resistance, were highly prevalent in both symptomatic and asymptomatic cases (realizing the absolute figures remain low). Asymptomatic individuals could be an additional reservoir for artemisinin resistance. The low effectiveness of dihydroartemisinin–piperaquine (DHA–PPQ) for symptomatic cases indicates that PPQ is no longer able to complement the reduced potency of DHA to treat falciparum malaria and highlights the need for an alternative first-line treatment.
Highlights
In Cambodia, elimination of artemisinin resistance through direct elimination of the Plasmodium falciparum parasite may be the only strategy
June to August incidence was around 0.7/1000 per month, September to December incidence ranged from 2.2 to 3.6/1000 per month, and February to May incidence ranged from 0.2 to 0.6/1000 per month (Fig. 5). 149 villagers had blood taken 28 days after case notification, Discussion The primary objectives of this study were to estimate the prevalence of Plasmodium spp. and P. falciparum at district and village level in Chey Saen district and to compare this with the incidence reported through the passive case detection system
The findings of this study indicate that DHA–PPQ may no longer be effective for symptomatic cases with high parasitaemia
Summary
In Cambodia, elimination of artemisinin resistance through direct elimination of the Plasmodium falciparum parasite may be the only strategy. Since 2000, huge efforts in malaria control have resulted in a 47 % decrease in malaria-associated mortality worldwide and in a 30 % decrease in incidence of malaria [1]. These achievements are threatened by the emergence and spread of Plasmodium falciparum resistance to artemisinin and partner drugs. Elimination of artemisinin resistance through direct elimination of the P. falciparum parasite may be the only present strategy [3]. Successful attempts to identify and quantify the asymptomatic reservoir have only rarely been documented
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