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Volume 11 Supplement 1

Challenges in malaria research

Insecticide resistance: a challenge to malaria vector control in Ethiopia

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Background

In Ethiopia, indoor residual spraying (IRS) and insecticide-treated bed nets form the main malaria vector control. As the two tools rely on synthetic insecticides, it was found necessary to document the up-to-date distribution and levels of insecticide susceptibility of Anopheles arabiensis.

Materials and methods

Between 2008 and 2011, insecticide susceptibility tests were carried out in 39 localities out of which 12 were repeatedly visited from 2 to 4 years. Tests were conducted using WHO test kits and procedures [1] on non-blood fed, 48-72 hours old female An. arabiensis which were reared from field collected larvae and pupae. The insecticides were discriminating doses of DDT, malathion, fenitrothion, primiphos-methyl, propoxur, bendiocarb, deltamethrin and lambdacyhalothrin. Controls were exposed to insecticide free oil impregnated papers. The WHO recommendations were applied to classify the population as susceptible, acquiring possible resistance and resistance [1]. The presence and frequency of the target site insensitive resistance mechanisms, kdr (L1014F mutation) and ace-1 (G119S mutation) were investigated from vector populations of nine localities following the procedures described in [2, 3].

Results

All results depicted very low mortalities of An. arabiensis due to DDT, implicating wide distribution of resistance to this insecticide (Table 1). Resistance is also significantly high to deltamethrin, lambdacyhalothrin and malathion. Bendiocarb resistant populations were also detected from a few localities. The vector populations are susceptible to primiphos-methyl and propoxur, susceptibility was also very high to fenithrotion. Of 229 An. arabiensis, more than 95% were found to carry the kdr gene (both homozygous and heterozygous genotypes) while 47 tested specimens were without the ace-1 allele mutation.

Table 1 Mortality results of Anopheles arabiensis and number of localities with susceptible and resistant populations (2008-2011)

Conclusions

Similar studies in the past by other workers [47] together with this one showed increased resistance of An. arabiensis to insecticides belonging to the four major classes. This would pose a serious challenge to vector control in the coming years. Given the small number of insecticides for IRS and LLINs, the Federal Ministry of Health of Ethiopia should take timely measure by formulating a policy as well as implementing insecticide resistance management within the frame work of integrated vector management.

References

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    WHO: Test procedures for insecticide resistance monitoring in malaria vectors, bio-efficacy and persistence of insecticides on treated surfaces. WHO, Geneva, Switzerland, WHO/CDS/CPC/MAL/98.12

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    Huynh LY, Sandve SR, Hannan LM, Van Ert M, Gimnig JE: Fitness costs of pyrethroidinsecticide resistance in Anopheles gambiae. Annual Meeting of the Society for the Study of Evolution, Christchurch, New Zealand. 2007

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    Weill M: The unique mutation in ace-1 giving high insecticide resistance is easily detectable in mosquito vectors. Insect Mol Biol. 2004, 13: 1-7. 10.1111/j.1365-2583.2004.00452.x.

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    Balkew M, Ibrahim M, Koekemoer LL, Brooke BD, Engers H, Aseffa A, Gebre-Michael T, Elhassen I: Insecticide resistance in Anopheles arabiensis (Diptera: Culicidae) from villages in central, northern and south west Ethiopia and detection of kdr mutation. Parasites & Vectors. 2010, 3: 40-10.1186/1756-3305-3-40.

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    Yewhalaw D, Bortel VW, Denis L, Coosemans M, Duchateau L, Speybroeck N: First evidence of high knockdown resistance frequency in Anopheles arabiensis (Diptera: Culicidae) from Ethiopia. Am J Trop Med Hyg. 2010, 3: 122-125.

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    Yewhalaw D, Wassie F, Steurbaut W, Spanoghe P, Van Bortel W: Multiple insecticide Resistance: An impediment to insecticide-based malaria vector control program. PLoS ONE. 2011, 6 (1): e16066-10.1371/journal.pone.0016066.

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    Abate A, Haddis M: Susceptibility of Anopheles gambiae s.l. to DDT, malathion, permethrin and deltamethrin in Ethiopia. Tropl Med Int Health. 2011, 16: 486-91. 10.1111/j.1365-3156.2011.02728.x.

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Acknowledgements

The assistance of regional MOH staff including those retired is greatly acknowledged. The study obtained financial support from the President’s Malaria Initiative and World Health Organization.

Author information

Correspondence to Meshesha Balkew.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Balkew, M., Getachew, A., Chibsa, S. et al. Insecticide resistance: a challenge to malaria vector control in Ethiopia. Malar J 11, P139 (2012) doi:10.1186/1475-2875-11-S1-P139

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Keywords

  • Malathion
  • Indoor Residual Spray
  • Insecticide Resistance
  • Vector Population
  • Fenitrothion

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