Risk Factors for Household Vector Abundance Using Indoor CDC Light Traps in a High Malaria Transmission Area of Northern Zambia

Abstract

Malaria transmission is dependent on the density and distribution of mosquito vectors, but drivers of vector abundance have not been adequately studied across a range of transmission settings. To inform intervention strategies for high-burden areas, further investigation is needed to identify predictors of vector abundance. Active household (HH) surveillance was conducted in Nchelenge district, Luapula Province, northern Zambia, a high-transmission setting with limited impact of malaria control. Between April 2012 and July 2017, mosquitoes were collected indoors during HH visits using CDC light traps. Demographic, environmental, and climatological correlates of vector abundance were identified using log-binomial regression models with robust standard errors. The primary malaria vectors in this setting were Anopheles funestus sensu stricto (s.s.) and Anopheles gambiae s.s. Anopheles funestus predominated in both seasons, with a peak in the dry season. Anopheles gambiae peaked at lower numbers in the rainy season. Environmental, climatic, and demographic factors were correlated with HH vector abundance. Higher vector counts were found in rural areas with low population density and among HHs close to roads and small streams. Vector counts were lower with increasing elevation and slope. Anopheles funestus was negatively associated with rainfall at lags of 2-6 weeks, and An. gambiae was positively associated with rainfall at lags of 3-10 weeks. Both vectors had varying relationships with temperature. These results suggest that malaria vector control in Nchelenge district should occur throughout the year, with an increased focus on dry-season transmission and rural areas.

The Impact of Three Years of Targeted Indoor Residual Spraying with Pirimiphos-Methyl on Household Vector Abundance in a High Malaria Transmission Area of Northern Zambia

“…gambiae, and 44 anophelines of other species. 39 Anopheles funestus had the highest vector counts throughout the year, with a peak in abundance in the dry season ( Figure 2). Anopheles gambiae counts peaked in the rainy season and were rare or absent in the dry season ( Figure 3).…”

“…gambiae abundance peaks in smaller relative numbers primarily in lakeside areas shortly after the start of the rainy season. 12,13,39 Data collection. The Southern and Central Africa ICEMR has conducted active surveillance in Nchelenge district since April 2012.…”

Combination of Serological, Antigen Detection, and DNA Data for Plasmodium falciparum Provides Robust Geospatial Estimates for Malaria Transmission in Haiti

“…All schools in this western cluster were outside of urban areas, and many were located in a low-elevation valley (see Fig. 2) -both factors which are known to support the lifecycle of the Anopheline vector [40][41][42] . Even with that stated, other rural and low-elevation schools in the same commune did not show these same higher levels for malaria prevalence and exposure, emphasizing that favorable vector conditions are not a guarantee of increased malaria transmission.…”

Genetic diversity ofAnopheles coustaniin high malaria transmission foci in southern and central Africa

“…Despite successful reductions in morbidity and mortality, malaria remains endemic with over 6 million reported cases in 2018 (MIS 2019, WHO 2019a). While the scaling-up of malaria interventions such as widespread coverage by LLINS and IRS reduced transmission and parasitemia throughout many parts of Zambia, the disease continues to be a significant public health concern, especially in the northern region where Nchelenge District, Luapula Province, is recognized as a high transmission focus (Chanda et al 2013, Mukonka et al 2014, Nambozi et al 2014, Hast et al 2019). This region of Zambia reports over 350 confirmed cases per 1000 population (Moss et al 2012, PMI 2019a, WHO 2019a).…”

“…In Nchelenge, the primary vectors of malaria in both the dry and wet seasons have been found to be An. funestus s.s. and Anopheles gambiae s.s. (Das et al 2016, Jones et al 2018, Hast et al 2019). Malaria is also holoendemic in the DRC which borders Zambia to the north, but much less is known about malaria vectors and their phenology, other than that An.…”