Indoor transmission dominance and vector efficiency of Anopheles gambiae s.s. among sibling species of the Anopheles gambiae complex in southeastern Nigeria
NJE Vol. 42(1) : 117-134, 2026
DOI.10.36108/NJE/6202/24.0190
Ezihe Kingsley Chukwuebuka 1&2, Ubachukwu Patience Obiageli 2, Ezihe Grace Chinonyelum3, Ukonze Blessing Chikaodili4&5, Obi Juliet Onyinye4, Nwangwu Udoka Chukwubuofu6, Agashi Nneka6, Dogunro Festus6, Nwankwo Edith Nonye4, Olayemi Kayode Isreal7
1Malaria Consortium, Abuja, Nigeria,
2Department of Zoology and Environmental Biology, University of Nigeria Nsukka, Nsukka, Nigeria
3Department of Data Science, Nasarrawa State University, Keffi, Nigeria
4Department of Parasitology and Entomology, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria
5School of Biological Science, Universit Sains Malaysia, 11800 Penang, Malaysia
6 Department of Animal Biology, Federal University of Technology Minna, Minna, Niger State, Nigeria
7 National Arbovirus and Vector Research Centre (NAVRC), Federal Ministry of Health, Enugu, Nigeria
Abstract
This study investigates the ecological and epidemiological roles of sibling species within the Anopheles gambiae complex, focusing on their behaviors and transmission indices impacting malaria dynamics. Utilizing human-baited CDC light traps and Pyrethrum Spray Catch, anophelines were collected from selected structures. Species-specific analysis revealed that 66/551(12%) of Anopheles gambiae s.l. were An. gambiae s.s., 258/551(47%) An. coluzzii, and 227/551(41%) An. arabiensis. The highest proportions of An. gambiae s.s.(6/10), An. coluzzii (15/46), and An. arabiensis (21/59) fed on human blood indoors in Awba-ofemili [42/115(36.5%). Plasmodium falciparum sporozoite rates in An. gambiae s.s. collected indoors ranged from 12.5% in Achalla to 18.2% in Awba-ofemili. Infective bites/person/annnum (ib/p/a) which is used to measure the entomology inoculation rate (EIR) were more frequent indoors, with An. gambiae s.s. recording 3 infective bites/person/annum in Achalla and 6.01 ib/p/a in Awba-ofemili. An. coluzzii showed 3 ib/p/a in Ebenebe and Awba-ofemili, while An. arabiensis recorded 3 ib/p/a indoors in Awba ofemili. No infective bites were recorded outdoors. The finding highlights the significant roles of An. gambiae s.s., An. coluzzii, and An. arabiensis in malaria transmission in the study communities. The finding of An. gambiae s.s., An. coluzzii and An. arabiensis transmitting malaria in the study communities calls for urgent malaria intervention that will target all the primary malaria species as the density and diversity of Anopheles species is highly influenced by availability of humans sleeping without bed nets. This study provides details into malaria transmission pattern in southeastern Nigeria as it suggests that malaria control programs should prioritize high-risk locations like Awba-Ofemili, where all three sibling species were active indoors with high EIRs. Although no infective bites were recorded outdoors across any site or species, the outdoor biting pressure of An. arabiensis in Ebenebe warrants attention: this species recorded the highest outdoor human biting rate across all the study communities (2 bites/person/night) and its predominantly exophilic and zoophilic behaviour means that standard indoor-targeted interventions would offer limited protection against its biting activity. Therefore, tailored vector control strategies addressing species-specific and spatial transmission patterns, including measures capable of protecting against outdoor-biting species, are essential to reducing malaria incidence and achieving elimination goals.
Keywords: malaria, molecular, ecology, mosquito control, Anopheles, sporozoite, Plasmodium