Malaria Vector Anopheles Coluzzii Research Articles

Investigation of the Role of ABC Transporters in Pyrethroids Resistance in the Major Malaria Vector Anopheles coluzzii from Northern Nigeria

Resistance to currently available insecticides in the major malaria vectors like Anopheles coluzzii is seriously reducing the effectiveness of core vector control tools. Overexpression of ATP binding cassette transporters (ABC transporters) has been implicated in insecticides resistance in the major malaria vector Anopheles funestus and An. gambiae. To identify the potential role of ABC transporters in pyrethroids resistance in this work, we use verapamil-a p-glycoprotein inhibitor in a synergist bioassay with pyrethroids on one An. coluzzii populations from northern Nigeria. Genomic DNA extraction and SINE 200 PCR established that the Anopheles s. l. from Auyo, Jigawa State was An. coluzzii. Pre-exposure to verapamil followed by Permethrin results in 0.12% knockdown after 1 hour exposure and 10.7% mortality after 24 hours, which was higher than that for permethrin alone, but not statistically significant. This bioassay result reveals that ABC transporters possibly do not contribute to the resistance.

Effects of insecticide resistance on the reproductive potential of two sub-strains of the malaria vector Anopheles coluzzii.

The emergence and spread of insecticide resistance in African malaria vectors raise concerns over the control of malaria disease. Therefore, the implementation of better control strategies need a thorough understanding of the effects and mechanisms of resistance on vector adaptation capacities. We studied the effects of insecticide resistance on the reproductive potential of two laboratory sub-strains of the malaria vector Anopheles coluzzii characterised by phenotypic resistance/susceptibility to DDT. The two sub-strains were selected from a laboratory strain of An. coluzzii using WHO test tubes. For each sub-strain, the number of produced and hatched eggs, developmental time, mosquito stages mortality, sex ratio and insemination rates after dissection of spermathecae were compared as measures of reproductive potential. Overall, the susceptible sub-strain produced higher but not significant mean numbers of eggs. However, the mean numbers of hatched eggs, larvae, pupae and adults were significantly lower than those of the resistant substrain. The mean time from egg-hatching to adult-emergence, egg-flooding to hatching, I instar to pupae and pupae to adult were similar between the two sub-strains. The mortality rates at the pupal stage were significantly different between the two sub-strains. Of the dissected spermathecae, 85.1% of the females from the resistant sub-strain were fertilized compared to 66.1% of the females from the susceptible sub-strain (p <0.0001). The resistant sub-strain produced more females in comparison to the susceptible sub-strain (respective mean sex ratio 1.37 vs 1.03, p = 0.01). The results show differential life history traits between the two sub-strains of the malaria vector An. coluzzii, particularly fertility, insemination rate and sex ratio. They may have varied implications for insecticide resistance spread, monitoring and management; and hence underscore the need of further investigations before any generalization.

Native entomopathogenic Metarhizium spp. from Burkina Faso and their virulence against the malaria vector Anopheles coluzzii and non-target insects

BackgroundGenetically enhanced Metarhizium pingshaense are being developed for malaria vector control in Burkina Faso. However, not much is known about the local prevalence and pathogenicity of this fungus, so we prospected mosquitoes and plant roots (a common habitat for Metarhizium spp.) for entomopathogenic fungi.ResultsOur investigations showed that Metarhizium spp. represented between 29–74% of fungi isolated from plant root rhizospheres in diverse collection sites. At low spore dosages (1 × 106 conidia/ml), two mosquito-derived M. pingshaense isolates (Met_S26 and Met_S10) showed greater virulence against Anopheles coluzzii (LT80 of ~7 days) than isolates tested in previous studies (LT80 of ~10 days). In addition, the local isolates did not cause disease in non-target insects (honeybees and cockroaches).ConclusionsOur work provides promising findings for isolating local Metarhizium strains for application in mosquito biological control and for future transgenic biocontrol strategies in Burkina Faso.

First detection of N1575Y mutation in pyrethroid resistant Anopheles gambiae in Southern Côte d’Ivoire

Background. The intensification of insecticide use for both public health and agriculture in Africa has contributed to growing insecticide resistance. Today, resistance to World Health Organization (WHO)-approved insecticide classes is widespread. In an agricultural area of Southern Côte d’Ivoire, the main malaria vector Anopheles coluzzii shows multiple resistance across insecticides mediated by both target site mutation and metabolic mechanisms. To plan new vector control strategies and avert future resistance liabilities caused by cross-resistance mechanisms extant within populations, it is crucial to monitor the development and spread of both resistance and mechanisms. Methods. Larvae of Anopheles gambiae were collected from natural breeding sites in Tiassalé and Elibou, between April and November 2016 and raised to adults . Adult female non-blood fed mosquitoes, three to five days old, were exposed to deltamethrin in WHO bioassays. Extracted DNA samples from exposed mosquitoes were used for species characterisation and genotyping. Results. Most adult An. gambiae tested were resistant to deltamethrin, with mortality rates of only 25% in Tiassalé and 4.4% in Elibou. Molecular analysis of DNA from samples tested showed the presence of both An. coluzzii and An. gambiae s.s in Elibou and only An. coluzzii for Tiassalé. As previously, the L1014F kdr mutation was present at high frequency (79%) in Tiassalé and the L1014S mutation was absent. The N1575Y mutation, which amplifies resistance conferred by L1014F was detected in a single unique individual from a Tiassalé An. coluzzii female whereas in Elibou 1575Y was present in 10 An. gambiae s.s, but not in An. coluzzii. Conclusion. This is the first report of the N1575Y mutation in Côte d’Ivoire, and as in other populations, it is found in both dominant West African malaria vector species. Continued monitoring of N1575Y is underway, as are studies to elucidate its contribution to the resistance of local vector populations.

First detection of N1575Y mutation in pyrethroid resistant Anopheles gambiae in Southern Côte d'Ivoire.

Background. The intensification of insecticide use for both public health and agriculture in Africa has contributed to growing insecticide resistance. Today, resistance to World Health Organization (WHO)-approved insecticide classes is widespread. In an agricultural area of Southern Côte d'Ivoire, the main malaria vector Anopheles coluzzii shows multiple resistance across insecticides mediated by both target site mutation and metabolic mechanisms. To plan new vector control strategies and avert future resistance liabilities caused by cross-resistance mechanisms extant within populations, it is crucial to monitor the development and spread of both resistance and mechanisms. Methods. Larvae of Anopheles gambiae were collected from natural breeding sites in Tiassalé and Elibou, between April and November 2016 and raised to adults . Adult female non-blood fed mosquitoes, three to five days old, were exposed to deltamethrin in WHO bioassays. Extracted DNA samples from exposed mosquitoes were used for species characterisation and genotyping. Results. Most adult An. gambiae tested were resistant to deltamethrin, with mortality rates of only 25% in Tiassalé and 4.4% in Elibou. Molecular analysis of DNA from samples tested showed the presence of both An. coluzzii and An. gambiae s.s in Elibou and only An. coluzzii for Tiassalé. As previously, the L1014F kdr mutation was present at high frequency (79%) in Tiassalé and the L1014S mutation was absent. The N1575Y mutation, which amplifies resistance conferred by L1014F was detected in a single unique individual from a Tiassalé An. coluzzii female whereas in Elibou 1575Y was present in 10 An. gambiae s.s, but not in An. coluzzii. Conclusion. This is the first report of the N1575Y mutation in Côte d'Ivoire, and as in other populations, it is found in both dominant West African malaria vector species. Continued monitoring of N1575Y is underway, as are studies to elucidate its contribution to the resistance of local vector populations.

Microbiota-induced peritrophic matrix regulates midgut homeostasis and prevents systemic infection of malaria vector mosquitoes.

Manipulation of the mosquito gut microbiota can lay the foundations for novel methods for disease transmission control. Mosquito blood feeding triggers a significant, transient increase of the gut microbiota, but little is known about the mechanisms by which the mosquito controls this bacterial growth whilst limiting inflammation of the gut epithelium. Here, we investigate the gut epithelial response to the changing microbiota load upon blood feeding in the malaria vector Anopheles coluzzii. We show that the synthesis and integrity of the peritrophic matrix, which physically separates the gut epithelium from its luminal contents, is microbiota dependent. We reveal that the peritrophic matrix limits the growth and persistence of Enterobacteriaceae within the gut, whilst preventing seeding of a systemic infection. Our results demonstrate that the peritrophic matrix is a key regulator of mosquito gut homeostasis and establish functional analogies between this and the mucus layers of the mammalian gastrointestinal tract.

The contribution of dietary restriction to extended longevity in the malaria vector Anopheles coluzzii

BackgroundVariation in longevity has long been of interest in vector biology because of its implication in disease transmission through vectorial capacity. Recent studies suggest that Anopheles coluzzii adults persist during the ~7 month dry season via aestivation. Recently there has been a growing body of evidence linking dietary restriction and low ratio of dietary protein to carbohydrate with extended longevity of animals. Here, we evaluated the effects of dietary restriction and the protein : carbohydrate ratio on longevity of An. coluzzii.ResultsIn our experiment, we combined dietary regimes with temperature and relative humidity to assess their effects on An. coluzzii longevity, in an attempt to simulate aestivation under laboratory conditions. Our results showed significant effects of both the physical and the dietary variables on longevity, but that diet regimen had a considerably greater effect than those of the physical conditions. Higher temperature and lower humidity reduced longevity. At 22 °C dietary protein (blood) shortened longevity when sugar was not restricted (RH = 85%), but extended longevity when sugar was restricted (RH = 50%).ConclusionsDietary restriction extended longevity in accord with predictions, but protein : carbohydrate ratio had a negligible effect. We identified conditions that significantly extend longevity in malaria vectors, however, the extent of increase in longevity was insufficient to simulate aestivation.