Risk factors for malaria infection prevalence and household vector density between mass distribution campaigns of long-lasting insecticidal nets in Northern Tanzania [post]

Jacklin Franklin Mosha, Eliud Lukole, J Derek Charlwood, Alexandra Wright, Olivia Bullock, Alphaxard Manjurano, William Kisinza, Franklin W Mosha, Immo Kleinschmidt, Mark Rowland, Natacha Protopopoff
2020 unpublished
Background Long Lasting Insecticidal nets (LLINs) are the most widely deployed vector control intervention in Sub-Saharan Africa to prevent malaria. Recent reports indicate selection of pyrethroid insecticide resistance is widespread in mosquito vectors. This paper explores net coverage indicators and other risk factors associated with malaria infection prevalence and vector density three years after a mass distribution campaigns of LLINs in Northwest Tanzania. Methods A cross sectional malaria
more » ... s sectional malaria survey of 3,456 children was undertaken in 2014 in Muleba district in the Lake Zone. Vector density was assessed using indoor light traps and outdoor tent traps. Anophelines were identified to species using PCR and tested for falciparum circumsporozoite protein. Logistic regression was used to identify household and environmental factors associated with malaria infection and vector density. Results LLINs use was 27.7%. Only 16.9% of households had sufficient nets to cover all sleeping places. Malaria infection was independently associated with access to LLINs (OR: 0.57; 95%CI 0.34 – 0.98). LLINs less than 2 years old were more protective than older LLINs (53% vs 65% prevalence of infection); however, there was no evidence that LLINs in good condition (hole index <65) were more protective than LLINs which were more holed. Other risk factors for malaria infection were age group, altitude and house construction quality. Independent risk factors for vector density were consistent with malaria outcomes and included altitude, wind, livestock, house quality, open eaves and LLINs usage. Indoor collections comprised 4.6% Anopheles funestus and 95.4% An. gambiae of which 4.5% were An. arabiensis and 93.5% were An. gambiae s.s.Conclusion Three years after the mass distribution campaign and despite top-ups, LLINs usage had declined considerably. While children living in households with access to LLINs were at lower risk of malaria, infection prevalence remained high even among users of LLINs in good condition. While effort should be made to maintain high coverage between campaigns, distribution of standard pyrethroid-only LLINs appears insufficient to prevent malaria transmission in this area of intense pyrethroid resistance.
doi:10.21203/rs.3.rs-20694/v2 fatcat:jeik2gvy6fghtlhr4phgx5w5p4