The Balombo Project (Angola). A long-term village-scale malaria vector control program, comparing four methods: long-lasting insecticide-treated nets alone, insecticide-treated plastic sheeting alone or combined with long-lasting insecticide-treated

Study Design A long-term, village-scale malaria vector control project, beginning in 2007, and scheduled for eleven years, was implemented in eight villages around Balombo town (Benguela Province, Angola) to compare the epidemiological efficacy of four methods, each one implemented in two villages: Long-lasting insecticide-treated nets, PermaNet® 2.0, alone; durable lining model ZeroFly® in association with PermaNet®; durable lining model ZeroVector® alone and durable lining following two rounds of lambdacyhalothrin indoor residual spraying (one model of treated plastic sheeting per village.) Methodology The project was done in complete natural conditions, planned and implemented in three successive phases: a) First five years: simultaneous regular field surveys with entomological, parasitological, and immunological evaluation in the eight villages (two years before vector control, done in December 2008, and three years after); b) Five years more: long-term regular parasitological evaluation in four villages (each with one vector control method) with regular cross-sectional surveys on symptomless children ≤15 years old; c) One final overall parasitological survey in the eight villages in February 2018, compared to the plasmodial infections in February 2008. During the first five years, three entomological indicators and three parasitological indicators were analyzed, before and after vector control: the number of main vectors (Anopheles gambiae and An. funestus) caught by CDC Light traps; their infectivities and the inoculation rate, and, simultaneously, Plasmodium prevalence, parasitaemia, and gametocyte index in symptomless children ≤15 years old. Results A total of 202 CDC “catching sessions” were done, representing 1,880 “trap-nights.” 1,153 Anopheles were captured, belonging to 11 species. The main vectors (“MV”) were An. funestus and An. gambiae. After implementation of vector control, the densities of MV per trap dropped by 70%, similarly with all four methods. Infectivity of vectors dropped from 4.53%, (n= 375), to 2.73% (n=183), a noteworthy, if not significant, 43% reduction. Inoculation rates decreased similarly by some 80% after the implementation of each one the four vector control methods. A total of 190 surveys were performed; Plasmodium were noticed in 5,330 of the 20,188 thick blood films examined, i.e. an overall Plasmodium prevalence of 26.4%, and gametocytes in 553, i.e. a gametocyte index of 2.74%. P. falciparum was largely preponderant with few P. malariae. After vector control, Plasmodium prevalence, parasitaemia, and gametocytes index were significantly reduced, similarly by each method. An important impact was noticed the first two years after vector control and less the third year, but still noticeable with the combination of long-lasting insecticide-treated nets and ZeroFly® durable lining. Entomological and parasitological data were remarkably consistent underlining the interest of such combined protocol. Conclusion Durable lining alone was as efficient as house spraying while having a longer-lasting effect. Combinations of methods were not much better than methods implemented alone. The initial great acceptability of durable lining by communities was confirmed.