Human and vector behaviors determine exposure to Anopheles in Namibia

Area of Science:

• Medical Entomology
• Public Health
• Vector-borne Disease Control

Background:

• Namibia faces persistent malaria transmission despite reduced rates.
• Progress towards malaria elimination is hindered by regular outbreaks.
• Understanding human and Anopheles mosquito behavior is crucial for evaluating long-lasting insecticidal net (LLIN) efficacy and protection gaps.

Purpose of the Study:

• To determine where and when humans are exposed to Anopheles mosquito bites in malaria-endemic regions of Namibia.
• To evaluate the protective efficacy and identify gaps associated with LLIN use.
• To analyze the interplay between human and vector behaviors in malaria transmission dynamics.

Main Methods:

• Entomological surveillance and human behavior observations were conducted over eight nights during the malaria transmission season in March 2018.
• Human landing catches were performed in sentinel structures representative of local constructions.
• Data collection involved two-person teams from 1800 to 0600 hours, with a focus on consented participation.

Main Results:

• Primary vectors (Anopheles arabiensis, Anopheles gambiae s.s., Anopheles funestus s.s.) and secondary vectors were identified.
• Both indoor and outdoor biting behaviors were observed, varying by region.
• Human behaviors significantly influenced exposure, with primary exposure occurring indoors in Kavango East and outdoors in Ohangwena and Zambezi.

Conclusions:

• Increased LLIN use enhances protection but does not fully bridge indoor and outdoor exposure gaps.
• Alternative interventions are necessary to address remaining malaria transmission risks.
• Operational entomological surveillance combined with human behavioral observations improves understanding of transmission and intervention effectiveness.