First Observations of Plasmodium Malariae and Its Evolution During the Parasitological Evaluation of the Long-term Village Scale Malaria Vector Control Program in the Balombo Area of Angola

Abstract Background: A long-term village scale vector control program was implemented in eight villages around the Balombo town (Benguela Province, Angola) to compare the efficacy of four methods of vector control inside houses including long-lasting deltamethrin insecticide treated nets (PermaNet© 2.0 model or P.2.0); association of P.2.0 and deltamethrin Insecticide Treated Plastic Sheeting (ITPS)-Zero Fly© model; deltamethrin ITPS-Wall Lining model alone; and 2 rounds of lambdacyhalothrin Inside Residual Spraying followed by installation of ITPS.Methods: Cross sectional parasitological surveys (CSS) were done every two months. Thick blood films (TBF) were microscopically examined at the Medical Department of the Angolese Sonamet company in Lobito and a sample of them were double-checked in Yaoundé. Plasmodium species determination, parasitaemia and gametocytes presence, and evolution in time were analyzed.Results: A total of 190 CSS was done between 2007 and 2011, Plasmodium spp. were observed in 5,431 of the 21,804 TBF done. Plasmodium malariae alone was observed in 22 TBF (0.4%) and mixed infections P. falciparum and P. malariae in 44 TBF (0.8%).Conclusion: The very low frequency of P. malariae could explain the fact it is usually not reported in classical point prevalence surveys. Our study confirms the presence of this species in Angola, which must be known due to its special clinical impact, quartan fever, kidney failure, chronicity, symptomless carriers, persistence for several years with long term recrudescence and reported cases of resistance to classical ACTs. The prevalence of P. malariae decreased after implementation of vector control methods.