Cargando…

Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study

BACKGROUND: This study was part of the work to prepare for a cluster-randomized controlled trial to evaluate the effect of combining indoor residual spraying and long-lasting insecticidal nets on malaria incidence. A pilot study was done to estimate the variations of malaria incidence among villages...

Descripción completa

Detalles Bibliográficos
Autores principales: Gari, Taye, Kenea, Oljira, Loha, Eskindir, Deressa, Wakgari, Hailu, Alemayehu, Balkew, Meshesha, Gebre-Michael, Teshome, Robberstad, Bjarne, Overgaard, Hans J., Lindtjørn, Bernt
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4784280/
https://www.ncbi.nlm.nih.gov/pubmed/26957044
http://dx.doi.org/10.1186/s12936-016-1199-4
_version_ 1782420234907418624
author Gari, Taye
Kenea, Oljira
Loha, Eskindir
Deressa, Wakgari
Hailu, Alemayehu
Balkew, Meshesha
Gebre-Michael, Teshome
Robberstad, Bjarne
Overgaard, Hans J.
Lindtjørn, Bernt
author_facet Gari, Taye
Kenea, Oljira
Loha, Eskindir
Deressa, Wakgari
Hailu, Alemayehu
Balkew, Meshesha
Gebre-Michael, Teshome
Robberstad, Bjarne
Overgaard, Hans J.
Lindtjørn, Bernt
author_sort Gari, Taye
collection PubMed
description BACKGROUND: This study was part of the work to prepare for a cluster-randomized controlled trial to evaluate the effect of combining indoor residual spraying and long-lasting insecticidal nets on malaria incidence. A pilot study was done to estimate the variations of malaria incidence among villages, combined with entomological collections and an assessment of susceptibility to insecticides in malaria vectors. METHODS: A cohort of 5309 residents from four kebeles (the lowest government administrative unit) in 996 households was followed from August to December 2013 in south-central Ethiopia. Blood samples were collected by a finger prick for a microscopic examination of malaria infections. A multilevel mixed effect model was applied to measure the predictors of malaria episode. Adult mosquitoes were collected using light traps set indoors close to a sleeping person, pyrethrum spray sheet catches and artificial outdoor pit shelters. Enzyme-linked immunosorbent assays were used to detect the sources of mosquito blood meals, while mosquito longevity was estimated based on parity. The World Health Organization’s tube bioassay test was used to assess the insecticide susceptibility status of malaria vectors to pyrethroids and carbamates. RESULTS: The average incidence of malaria episode was 4.6 per 10,000 person weeks of observation. The age group from 5 to 14 years (IRR = 2.7; 95 % CI 1.1–6.6) and kebeles near a lake or river (IRR = 14.2, 95 % CI 3.1–64) were significantly associated with malaria episode. Only 271 (27.3 %) of the households owned insecticide-treated nets. Of 232 adult Anopheles mosquitoes collected, Anopheles arabiensis (71.1 %) was the predominant species. The average longevity of An. arabiensis was 14 days (range: 7–25 human blood index days). The overall human blood index (0.69) for An. arabiensis was higher than the bovine blood index (0.38). Statistically significant differences in Anopheline mosquitoes abundance were observed between the kebeles (P = 0.001). Anopheles arabiensis was susceptible to propoxur, but resistant to pyrethroids. However, An. pharoensis was susceptible to all pyrethroids and carbamates tested. CONCLUSIONS: This study showed a high variation in malaria incidence and Anopheles between kebeles. The observed susceptibility of the malaria vectors to propoxur warrants using this insecticide for indoor residual spraying, and the results from this study will be used as a baseline for the trial.
format Online
Article
Text
id pubmed-4784280
institution National Center for Biotechnology Information
language English
publishDate 2016
publisher BioMed Central
record_format MEDLINE/PubMed
spelling pubmed-47842802016-03-10 Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study Gari, Taye Kenea, Oljira Loha, Eskindir Deressa, Wakgari Hailu, Alemayehu Balkew, Meshesha Gebre-Michael, Teshome Robberstad, Bjarne Overgaard, Hans J. Lindtjørn, Bernt Malar J Research BACKGROUND: This study was part of the work to prepare for a cluster-randomized controlled trial to evaluate the effect of combining indoor residual spraying and long-lasting insecticidal nets on malaria incidence. A pilot study was done to estimate the variations of malaria incidence among villages, combined with entomological collections and an assessment of susceptibility to insecticides in malaria vectors. METHODS: A cohort of 5309 residents from four kebeles (the lowest government administrative unit) in 996 households was followed from August to December 2013 in south-central Ethiopia. Blood samples were collected by a finger prick for a microscopic examination of malaria infections. A multilevel mixed effect model was applied to measure the predictors of malaria episode. Adult mosquitoes were collected using light traps set indoors close to a sleeping person, pyrethrum spray sheet catches and artificial outdoor pit shelters. Enzyme-linked immunosorbent assays were used to detect the sources of mosquito blood meals, while mosquito longevity was estimated based on parity. The World Health Organization’s tube bioassay test was used to assess the insecticide susceptibility status of malaria vectors to pyrethroids and carbamates. RESULTS: The average incidence of malaria episode was 4.6 per 10,000 person weeks of observation. The age group from 5 to 14 years (IRR = 2.7; 95 % CI 1.1–6.6) and kebeles near a lake or river (IRR = 14.2, 95 % CI 3.1–64) were significantly associated with malaria episode. Only 271 (27.3 %) of the households owned insecticide-treated nets. Of 232 adult Anopheles mosquitoes collected, Anopheles arabiensis (71.1 %) was the predominant species. The average longevity of An. arabiensis was 14 days (range: 7–25 human blood index days). The overall human blood index (0.69) for An. arabiensis was higher than the bovine blood index (0.38). Statistically significant differences in Anopheline mosquitoes abundance were observed between the kebeles (P = 0.001). Anopheles arabiensis was susceptible to propoxur, but resistant to pyrethroids. However, An. pharoensis was susceptible to all pyrethroids and carbamates tested. CONCLUSIONS: This study showed a high variation in malaria incidence and Anopheles between kebeles. The observed susceptibility of the malaria vectors to propoxur warrants using this insecticide for indoor residual spraying, and the results from this study will be used as a baseline for the trial. BioMed Central 2016-03-08 /pmc/articles/PMC4784280/ /pubmed/26957044 http://dx.doi.org/10.1186/s12936-016-1199-4 Text en © Gari et al. 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Gari, Taye
Kenea, Oljira
Loha, Eskindir
Deressa, Wakgari
Hailu, Alemayehu
Balkew, Meshesha
Gebre-Michael, Teshome
Robberstad, Bjarne
Overgaard, Hans J.
Lindtjørn, Bernt
Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study
title Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study
title_full Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study
title_fullStr Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study
title_full_unstemmed Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study
title_short Malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in Ethiopia: results from a pilot study
title_sort malaria incidence and entomological findings in an area targeted for a cluster-randomized controlled trial to prevent malaria in ethiopia: results from a pilot study
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4784280/
https://www.ncbi.nlm.nih.gov/pubmed/26957044
http://dx.doi.org/10.1186/s12936-016-1199-4
work_keys_str_mv AT garitaye malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT keneaoljira malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT lohaeskindir malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT deressawakgari malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT hailualemayehu malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT balkewmeshesha malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT gebremichaelteshome malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT robberstadbjarne malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT overgaardhansj malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy
AT lindtjørnbernt malariaincidenceandentomologicalfindingsinanareatargetedforaclusterrandomizedcontrolledtrialtopreventmalariainethiopiaresultsfromapilotstudy