| Autor: |
Adeogun AO; Department of Biological Sciences, LEAD City University, Ibadan, Nigeria.; Molecular Entomology and Vector Control Unit, Public Health and Epidemiology Department, Nigerian Institute of Medical Research, P.M.B, 2013, Yaba, Lagos, Nigeria., Brooke BD; Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Disease, Johannesburg, South Africa and the WITS Malaria Research Institute, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand., Olayanju DR; Department of Biological Sciences, LEAD City University, Ibadan, Nigeria., Adegbehingbe K; Department of Biological Sciences, LEAD City University, Ibadan, Nigeria., Oyeniyi TA; Molecular Entomology and Vector Control Unit, Public Health and Epidemiology Department, Nigerian Institute of Medical Research, P.M.B, 2013, Yaba, Lagos, Nigeria., Olakiigbe AK; Molecular Entomology and Vector Control Unit, Public Health and Epidemiology Department, Nigerian Institute of Medical Research, P.M.B, 2013, Yaba, Lagos, Nigeria., Awolola TS; Molecular Entomology and Vector Control Unit, Public Health and Epidemiology Department, Nigerian Institute of Medical Research, P.M.B, 2013, Yaba, Lagos, Nigeria. |
| Abstrakt: |
The assortment of paracentric chromosomal inversion 2La is associated with the maintenance of dieldrin resistance in laboratory colonies of the malaria vector Anopheles gambiae. This association has not been tested in field populations. The aim of this study was to test the association between inversion 2La and dieldrin resistance in a field population of An. coluzzii in Nigeria. Field collected immature stages of Anopheles were raised to adults and exposed to 4% dieldrin according to WHO criteria. Knockdown was recorded at 10 min intervals for 1 hour and final mortality was recorded 24 hours post exposure. Species and inversion 2La diagnostic PCR assays were conducted on the resistant and susceptible mosquitoes. The mosquitoes were highly resistant to 4% dieldrin (17.1% knock down and 25.7% final mortality; KDT 50 and KDT 95 calculated as 170 and 1, 514 minutes respectively). Frequencies of 2La in both the resistant and susceptible cohorts assorted within HardyWeinberg estimates (χ 2 =1.32, p=0.8 for dead/susceptible mosquitoes and χ 2 =2.54, p=0.5 for survivors or resistant mosquitoes). However, a higher number of heterozygous mosquitoes were observed in the resistant cohort compared to the susceptible, with significant variation in karyotype frequencies (χ 2 =11.08, DF=2, p<0.05) and a significantly higher frequency of the 2La inversion arrangement in the resistant cohort (Pearson's χ 2 = 4.58, p = 0.03.). These data are the first to associate paracentric chromosome inversion 2La and dieldrin resistance in field population of An. coluzzii. Dieldrin resistance shows a weak but significant association with 2La whose assortment is affected by positive heterosis. Variation in the assortment of 2La inversion arrangements between resistant and susceptible cohorts of this An. coluzzii population suggests that dieldrin resistance is at least partially linked to inversion 2La which may explain the persistence of dieldrin resistance in this population despite a significant absence of selection for resistance to this insecticide. |
