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. 2021 Dec 20;20(1):480.
doi: 10.1186/s12936-021-04005-5.

Putative pleiotropic effects of the knockdown resistance (L1014F) allele on the life-history traits of Anopheles gambiae

Adandé A Medjigbodo  1   2   3 , Luc S Djogbénou  4   5   6 , Oswald Y Djihinto  1   3 , Romaric B Akoton  1 , Emmanuella Abbey  1   3 , Rosaria M Kakossou  1   3 , Eric G Sonounameto  1   3 , Esther B J Salavi  1   3 , Laurette Djossou  3 , Athanase Badolo  2
Affiliations

Putative pleiotropic effects of the knockdown resistance (L1014F) allele on the life-history traits of Anopheles gambiae

Adandé A Medjigbodo et al. Malar J. .

Abstract

Background: Existing mechanisms of insecticide resistance are known to help the survival of mosquitoes following contact with chemical compounds, even though they could negatively affect the life-history traits of resistant malaria vectors. In West Africa, the knockdown resistance mechanism kdrR (L1014F) is the most common. However, little knowledge is available on its effects on mosquito life-history traits. The fitness effects associated with this knockdown resistance allele in Anopheles gambiae sensu stricto (s.s.) were investigated in an insecticide-free laboratory environment.

Methods: The life-history traits of Kisumu (susceptible) and KisKdr (kdr resistant) strains of An. gambiae s.s. were compared. Larval survivorship and pupation rate were assessed as well as fecundity and fertility of adult females. Female mosquitoes of both strains were directly blood fed through artificial membrane assays and then the blood-feeding success, blood volume and adult survivorship post-blood meal were assessed.

Results: The An. gambiae mosquitoes carrying the kdrR allele (KisKdr) laid a reduced number of eggs. The mean number of larvae in the susceptible strain Kisumu was three-fold overall higher than that seen in the KisKdr strain with a significant difference in hatching rates (81.89% in Kisumu vs 72.89% in KisKdr). The KisKdr larvae had a significant higher survivorship than that of Kisumu. The blood-feeding success was significantly higher in the resistant mosquitoes (84%) compared to the susceptible ones (34.75%). However, the mean blood volume was 1.36 µL/mg, 1.45 µL/mg and 1.68 µL/mg in Kisumu, homozygote and heterozygote KisKdr mosquitoes, respectively. After blood-feeding, the heterozygote KisKdr mosquitoes displayed highest survivorship when compared to that of Kisumu.

Conclusions: The presence of the knockdown resistance allele appears to impact the life-history traits, such as fecundity, fertility, larval survivorship, and blood-feeding behaviour in An. gambiae. These data could help to guide the implementation of more reliable strategies for the control of malaria vectors.

Keywords: Anopheles gambiae; Fitness effects; Kdr R allele; Life-history traits; Malaria.

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Conflict of interest statement

The authors declare that they have no competing interests for this study.

Figures

Fig. 1
Fig. 1
Fecundity in KisKdr and Kisumu strains. Each dot denotes the number of eggs laid by each female in each strain. Only females that laid at least one egg were included. A diamond point represents the mean number of eggs in each strain and the box plots represent the median and its 25 and 75% interquartile. Pie charts represent percentages of mosquito females that laid eggs in each strain. (n) indicates the total number of mosquito females subjected to the oviposition. Significant difference was observed in fecundity between both Kisumu and KisKdr mosquito females (p= 1.07x10−10)
Fig. 2
Fig. 2
Kisumu and KisKdr larval-hatching percentages. Each dot denotes the percentage of larvae hatched from individual female eggs batch within each strain. A diamond point represents the mean percentage of larvae hatched from each strain and the box plot represents the median and 25% and 75% interquartile ranges. Significant difference was observed in hatching rates between both Kisumu and KisKdr females (p = 0.02 × 10–1)
Fig. 3
Fig. 3
KisKdr and Kisumu larvae longevity A and pupation percentages B. A Dotted lines are 95% confidence intervals (CIs) around the respective survival curve. Arrow indicates the median survival time. B Error bars are 95% confidence intervals (CIs) around each percentage. ***indicate p = 0.01 × 10–2
Fig. 4
Fig. 4
Percentages of blood-fed females A and blood meal size B in kdrR (1014F)-resistant Anopheles gambiae. KisKdr and Kisumu are, respectively, the homozygous kdr-resistant and -susceptible parents. F1-1 (♀ Kis X ♂ KisKdr) and F1-2 (♂ Kis X ♀ KisKdr) represent the first-generation heterozygous offspring. In panel A, *** and n.s. indicate, respectively, p = 2.2 × 10–16 and not significant. In panel B, *** indicate p = 8.10–4. The sample sizes were showed in brackets on the top of scatter dots
Fig. 5
Fig. 5
Parents and first generation female longevity after blood-feeding. Dotted lines are 95% confidence intervals (CIs) around the respective survival curve. Arrows indicate the median survival time
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