Spatial abundance and human biting rate of Anopheles arabiensis and Anopheles funestus in savannah and rice agro-ecosystems of Central Tanzania

Abstract

This study was carried out to determine the spatial variations in malaria mosquito abundance and human biting rate in five villages representing rice-irrigation and savannah ecosystems in Kilosa District, central Tanzania. The study involved five villages namely Tindiga and Malui (wetland/rice irrigation), Twatwatwa and Mbwade (dry savannah) and Kimamba (wet savannah). Indoor mosquitoes were sampled using Centers for Disease Control and Prevention light traps in three houses in each village. <em>Anopheles gambiae</em> s.l. molecular identification was carried out using polymerase chain reaction (PCR). A total of 936 female mosquitoes were collected. About half (46.9%) were malaria mosquitoes (<em>Anopheles gambiae</em> s.l.=28.6%; <em>An. funestus</em>= 18.3%). A total of 161 (60.1%) of the morphologically identified <em>An. gambiae</em> s.l. (268) and subjected to PCR analysis for speciation were genotyped as <em>An. arabiensis</em>. The <em>An. funestus</em> complex mosquitoes were composed of <em>An. funestus</em> funestus and <em>An. rivulorum</em> at the 5:1 ratio. On average, 17.9 Anopheles mosquitoes were collected per village per day. Two-thirds (62.8%) of the malaria mosquitoes were collected in Malui (rice agro-ecosystem) and the lowest number (2.3%) in Twatwatwa (dry savannah ecosystem). The biting rate per person per night for <em>An. arabiensis</em>+<em>An. funestus</em> s.s. was highest in Malui (46.0) and lowest in Twatwatwa (1.67). The parity rate of the <em>An. funestus</em> mosquitoes was lower compared to that of <em>An. arabiensis</em> and none of the mosquitoes was infected with malaria sporozoites. In conclusion, <em>An. arabiensis</em> is the most abundant malaria vector in Kilosa district and its variation is related to the ecological system. The heterogeneity in malaria mosquito abundance and human biting rate could be used to guide selection of locally appropriated control interventions.