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Patterns of human exposure to early evening and outdoor biting mosquitoes and residual malaria transmission in Ethiopia.
Acta Trop. 2021 Apr; 216:105837.AT

Abstract

Ethiopia has shown a notable progress in reducing malaria burden over the past decade, mainly due to the scaleup of vector control interventions such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Based on the progress, the country has set goals to eliminate malaria by 2030. However, residual malaria transmission due to early evening and outdoor biting vectors could pose a challenge to malaria elimination efforts. This study assessed vector behavior, patterns of human exposure to vector bites and residual malaria transmission in southwestern Ethiopia. Anopheles mosquitoes were collected monthly from January to December 2018 using human landing catches (HLCs), human-baited double net traps, CDC light traps and pyrethrum spray catches. Human behavior data were collected using questionnaire to estimate the magnitude of human exposure to mosquito bites occurring indoors and outdoors at various times of the night. Enzyme-linked immunosorbent assay (ELISA) was used to determine mosquito blood meal sources and sporozoite infections. A total of 2,038 female Anopheles mosquitoes comprising Anopheles arabiensis (30.8%), An. pharoensis (40.5%), An. coustani (28.1%), An. squamosus (0.3%) and An. funestus group (0.2%) were collected. Anopheles arabiensis and An. pharoensis were 2.4 and 2.5 times more likely to seek hosts outdoors than indoors, respectively. However, 66% of human exposure to An. arabiensis and 39% of exposure to An. pharoensis bites occurred indoors for LLIN non-users. For LLIN users, 75% of residual exposure to An. arabiensis bites occurred outdoors while 23% occurred indoors before bed time. Likewise, 84% of residual exposure to An. pharoensis bites occurred outdoors while 15% occurred indoors before people retired to bed. Anopheles arabiensis and An. pharoensis were 4.1 and 4.8 times more likely to feed on bovine than humans, respectively. Based on the HLC, an estimated indoor and outdoor EIR of An. arabiensis was 6.2 and 1.4 infective bites/person/year, respectively, whereas An. pharoensis had an estimated outdoor EIR of 3.0 infective bites/person/year. In conclusion, An. arabiensis and An. pharoensis showed exophagic and zoophagic behavior. Human exposure to An. arabiensis bites occurred mostly indoors for LLIN non-users, while most of the exposure to both An. arabiensis and An. pharoensis bites occurred outdoors for LLIN users. Malaria transmission by An. arabiensis occurred both indoors and outdoors, whereas An. pharoensis contributed exclusively to outdoor transmission. Additional control tools targeting early-evening and outdoor biting malaria vectors are required to complement the current control interventions to control residual transmission and ultimately achieve malaria elimination.

Authors+Show Affiliations

School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia. Electronic address: teshedege@gmail.com.Center for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA 92697, USA.Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA 92697, USA.School of Medical Laboratory Sciences, Faculty of Health Sciences, Jimma University, Jimma, Ethiopia; Tropical and Infectious Diseases Research Center (TIDRC), Jimma University, Jimma, Ethiopia.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

33485868

Citation

Degefa, Teshome, et al. "Patterns of Human Exposure to Early Evening and Outdoor Biting Mosquitoes and Residual Malaria Transmission in Ethiopia." Acta Tropica, vol. 216, 2021, p. 105837.
Degefa T, Githeko AK, Lee MC, et al. Patterns of human exposure to early evening and outdoor biting mosquitoes and residual malaria transmission in Ethiopia. Acta Trop. 2021;216:105837.
Degefa, T., Githeko, A. K., Lee, M. C., Yan, G., & Yewhalaw, D. (2021). Patterns of human exposure to early evening and outdoor biting mosquitoes and residual malaria transmission in Ethiopia. Acta Tropica, 216, 105837. https://doi.org/10.1016/j.actatropica.2021.105837
Degefa T, et al. Patterns of Human Exposure to Early Evening and Outdoor Biting Mosquitoes and Residual Malaria Transmission in Ethiopia. Acta Trop. 2021;216:105837. PubMed PMID: 33485868.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Patterns of human exposure to early evening and outdoor biting mosquitoes and residual malaria transmission in Ethiopia. AU - Degefa,Teshome, AU - Githeko,Andrew K, AU - Lee,Ming-Chieh, AU - Yan,Guiyun, AU - Yewhalaw,Delenasaw, Y1 - 2021/01/22/ PY - 2020/09/24/received PY - 2021/01/10/revised PY - 2021/01/12/accepted PY - 2021/1/25/pubmed PY - 2021/5/20/medline PY - 2021/1/24/entrez KW - Ethiopia KW - Exposure KW - Human behavior KW - Malaria KW - Residual transmission KW - Vector behavior SP - 105837 EP - 105837 JF - Acta tropica JO - Acta Trop VL - 216 N2 - Ethiopia has shown a notable progress in reducing malaria burden over the past decade, mainly due to the scaleup of vector control interventions such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Based on the progress, the country has set goals to eliminate malaria by 2030. However, residual malaria transmission due to early evening and outdoor biting vectors could pose a challenge to malaria elimination efforts. This study assessed vector behavior, patterns of human exposure to vector bites and residual malaria transmission in southwestern Ethiopia. Anopheles mosquitoes were collected monthly from January to December 2018 using human landing catches (HLCs), human-baited double net traps, CDC light traps and pyrethrum spray catches. Human behavior data were collected using questionnaire to estimate the magnitude of human exposure to mosquito bites occurring indoors and outdoors at various times of the night. Enzyme-linked immunosorbent assay (ELISA) was used to determine mosquito blood meal sources and sporozoite infections. A total of 2,038 female Anopheles mosquitoes comprising Anopheles arabiensis (30.8%), An. pharoensis (40.5%), An. coustani (28.1%), An. squamosus (0.3%) and An. funestus group (0.2%) were collected. Anopheles arabiensis and An. pharoensis were 2.4 and 2.5 times more likely to seek hosts outdoors than indoors, respectively. However, 66% of human exposure to An. arabiensis and 39% of exposure to An. pharoensis bites occurred indoors for LLIN non-users. For LLIN users, 75% of residual exposure to An. arabiensis bites occurred outdoors while 23% occurred indoors before bed time. Likewise, 84% of residual exposure to An. pharoensis bites occurred outdoors while 15% occurred indoors before people retired to bed. Anopheles arabiensis and An. pharoensis were 4.1 and 4.8 times more likely to feed on bovine than humans, respectively. Based on the HLC, an estimated indoor and outdoor EIR of An. arabiensis was 6.2 and 1.4 infective bites/person/year, respectively, whereas An. pharoensis had an estimated outdoor EIR of 3.0 infective bites/person/year. In conclusion, An. arabiensis and An. pharoensis showed exophagic and zoophagic behavior. Human exposure to An. arabiensis bites occurred mostly indoors for LLIN non-users, while most of the exposure to both An. arabiensis and An. pharoensis bites occurred outdoors for LLIN users. Malaria transmission by An. arabiensis occurred both indoors and outdoors, whereas An. pharoensis contributed exclusively to outdoor transmission. Additional control tools targeting early-evening and outdoor biting malaria vectors are required to complement the current control interventions to control residual transmission and ultimately achieve malaria elimination. SN - 1873-6254 UR - https://www.unboundmedicine.com/medline/citation/33485868/Patterns_of_human_exposure_to_early_evening_and_outdoor_biting_mosquitoes_and_residual_malaria_transmission_in_Ethiopia_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0001-706X(21)00016-4 DB - PRIME DP - Unbound Medicine ER -