Influence of livestock keeping on feeding behavior, host choice, and spatial distribution of malaria vectors in rural northwestern Tanzania

Malaria transmission remains high in rural Tanzania despite widespread use of insecticide-treated nets and indoor residual spraying. Outdoor biting and flexible host-feeding behavior of Anopheles mosquitoes reduce the effectiveness of these interventions. Livestock near households may influence vector behavior, but evidence from high-transmission rural settings is limited. A cross-sectional study was conducted from November 2022 to February 2023 in 5 villages of Misungwi District, involving 44 households (22 livestock-keeping and 22 non-livestock-keeping). Adult Anopheles mosquitoes were collected indoors and outdoors using Center for Disease Control light traps, identified morphologically and by PCR, and blood-meal sources were determined by ELISA. Host-feeding patterns were assessed using the human blood index, bovine blood index, and foraging ratios. A total of 611 female mosquitoes were collected, dominated by An. gambiae s.l. (96.1%) and An. funestus s.l. (3.9%). Livestock households had more mosquitoes (61.5%) and higher outdoor activity (67.3%), while non-livestock households had higher indoor collections (73.6%). Among 231 blood-fed mosquitoes, 150 (64.9%) were from livestock households and 81 (35.1%) from non-livestock households. In livestock households, 108 (72.0%) had animal blood only, 27 (18.0%) mixed blood, and 15 (10.0%) human blood only. In non-livestock households, 44 (54.3%) had human blood only, 24 (29.6%) mixed blood, and 13 (16.0%) animal blood only. An. arabiensis was opportunistic, while An. gambiae s.s. and An. funestus s.s. remained strongly anthropophilic. Livestock shifts feeding toward animals and increases outdoor activity but does not eliminate human feeding, highlighting the need for integrated malaria control strategies.