The efficacy of ACTELLIC 50 EC, pirimiphos methyl, for indoor residual spraying in Ahafo, Ghana: area of high vector resistance to pyrethroids and organochlorines.

Insecticide resistance in the main malaria vectors in Africa is a major concern for malaria vector control program managers. The most common insecticides used for indoor residual spraying (IRS) and treating bed nets are becoming increasingly ineffective. The quest for safer and more effective insecticides for malaria vector control is urgent. This study sought to evaluate the efficacy of ACTELLIC 50 EC (pirimiphos methyl), an organophosphate, for IRS in Ghana, where there is high vector resistance to pyrethroids and organochlorines. Before the commencement of the study, standard World Health Organization (WHO) vector susceptibility tests against a common malaria vector, Anopheles gambiae s.l, were conducted using preparations of pyrethroids, organochlorines, carbamates, and organophosphates. The vector was found to be resistant to the pyrethroids, the organochlorines, and the carbamates, but susceptible to the organophosphates. The emulsifiable organophosphate concentrate formulation, ACTELLIC 50 EC, was then evaluated to determine the efficacy and the length of its residual effect. The wall bioassay test, using recommended cones from WHO, was conducted on sprayed surfaces with ACTELLIC 50 EC from 27 July 2009 to 16 October 2009. After 15 wk of trials on painted cement surface, it was found out that the main malaria vector, An. gambiae s.l, was susceptible to the insecticide even though the WHO Pesticide Evaluation recommends 2- to 3-mo duration of effective action. Therefore, it is recommended for use in IRS programs in this part of Ghana, where there is high vector resistance to most of the insecticides.

Malaria morbidity in Papua Indonesia, an area with multidrug resistant Plasmodium vivax and Plasmodium falciparum.

BACKGROUND: Multidrug resistance has emerged to both Plasmodium vivax and Plasmodium falciparum and yet the comparative epidemiology of these infections is poorly defined. METHODS: All laboratory-confirmed episodes of malaria in Timika, Papua, Indonesia, presenting to community primary care clinics and an inpatient facility were reviewed over a two-year period. In addition information was gathered from a house-to-house survey to quantify the prevalence of malaria and treatment-seeking behaviour of people with fever. RESULTS: Between January 2004 and December 2005, 99,158 laboratory-confirmed episodes of malaria were reported, of which 58% (57,938) were attributable to P. falciparum and 37% (36,471) to P. vivax. Malaria was most likely to be attributable to pure P. vivax in children under one year of age (55% 2,684/4,889). In the household survey, the prevalence of asexual parasitaemia was 7.5% (290/3,890) for P. falciparum and 6.4% (248/3,890) for P. vivax. The prevalence of P. falciparum infection peaked in young adults aged 15-25 years (9.8% 69/707), compared to P. vivax infection which peaked in children aged 1 to 4 years (9.5% 61/642). Overall 35% (1,813/5,255) of people questioned reported a febrile episode in the preceding month. Of the 60% of people who were estimated to have had malaria, only 39% would have been detected by the surveillance network. The overall incidence of malaria was therefore estimated as 876 per 1,000 per year (Range: 711-906). CONCLUSION: In this region of multidrug-resistant P. vivax and P. falciparum, both species are associated with substantial morbidity, but with significant differences in the age-related risk of infection.