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Larval Productivity and Detoxification Enzymes Profile in Response to Physico-chemical Environmental Factors of Anopheles gambiae Breeding Ecologies in Nigeria
... Raised activities of detoxification enzymes have been reported in resistance populations of An. gambiae from Nigeria and An. sinensis from China (12,(29)(30)(31)(32). ...
... Therefore, esterases has the highest activity, which clearly explains the mechanism of resistance to bendiocarb. This finding agrees with previous studies conducted in Kano and Jigawa in northern Nigeria, where increased activity was seen with GSTs, esterase and monooxygenase in resistant populations of An. gambiae exposed to DDT, bendiocarb and deltamethrin (12,31,32). Similarly, some studies conducted in Cote d'lvoire and Dakar reported increased levels of monooxygenase, GSTs and esterase (30,48). ...
Background: Malaria is a parasitic vector-borne disease endemic in the tropical and subtropical countries of the world. The aim of this study was to investigate the current activities of the detoxification enzymes in resistant and susceptible Anopheles gambiae s.l. in northern Nigeria.
Methods: Anopheles larvae were collected from northeast and northwestern Nigeria between Aug and Nov 2018. Biochemical analyses was carried out on the mosquitoes exposed to various insecticides (deltamethrin, DDT, bendiocarb, malathion) to measure and compare the enzymatic activities of the major detoxification enzymes (P450, GSTs, Esterase).
Results: High levels of resistance was observed; DDT 37%-53% (95%, CI: 29-61), bendiocarb 44%-55% (CI: 39-60) and deltamethrin 74%-82% (CI: 70-86). However, these mosquitoes were found to be susceptible to malathion 99%-100% (CI: 98-100). The P450 and GSTs enzymes were found to be elevated in the resistant mosquitoes exposed to deltamethrin (1.0240±0.1902); (1.3088±1.2478), DDT (1.7703±1.4528); (1.7462±0.9418) and bendiocarb (1.1814±0.0918); (1.4479±1.0083) compared to the Kisumu strain (0.764±0.4226); (0.6508±0.6542), (0.3875±0.3482); (0.4072±0.4916) and (0.6672±0.3949); (0.7126±0.7259) at P
... Breeding sites of mosquitoes have been found to be contaminated with several pollutants including organic pollutants (sewage, rotting plants, domestic and animal wastes and other industrial organic chemicals); also inorganic pollutants such as heavy metals (Zn, Au, Mn, Hg, Pb, Cu, Fe, Cd and Co) [79,80] and others (industrial and agrochemicals). Pollutants affect the physical-chemical parameters of breeding sites, consequently may affect mosquitoes' genetic makeup [81][82][83][84]. These physical-chemical parameters include pH, conductivity, turbidity, total dissolved solids (TDS) and total suspended solids (TSS), Na + , Ca 2+ , K + , NH 4 78,81]. ...
... Some pollutants and levels of physical-chemical parameters in An. gambiae s.l. breeding sites have shown to be positively associated with their insecticide resistance [81,83,84,88]. These pollutants and physicalchemical parameters include greases, oils, TDS, NH 3 , NH 4 + , SO 4 2− , PO4 2− , NO 3 − , NO 2 − and F − . ...
Background
Malaria still claims substantial lives of individuals in Tanzania. Insecticide-treated nets (ITNs) and indoor residual spray (IRS) are used as major malaria vector control tools. These tools are facing great challenges from the rapid escalating insecticide resistance in malaria vector populations. This review presents the information on the dynamics and monitoring of insecticide resistance in malaria vectors in mainland Tanzania since 1997. The information is important to policy-makers and other vector control stakeholders to reflect and formulate new resistance management plans in the country.
Methods
Reviewed articles on susceptibility and mechanisms of resistance in malaria vectors to insecticides across mainland Tanzania were systematically searched from the following databases: PubMed, Google scholar, HINARI and AGORA. The inclusion criteria were articles published between 2000 and 2017, reporting susceptibility of malaria vectors to insecticides, mechanisms of resistance in the mainland Tanzania, involving field collected adult mosquitoes, and mosquitoes raised from the field collected larvae. Exclusion criteria were articles reporting insecticide resistance in larval bio-assays, laboratory strains, and unpublished data. Reviewed information include year of study, malaria vectors, insecticides, and study sites. This information was entered in the excel sheet and analysed.
Results
A total of 30 articles met the selection criteria. The rapid increase of insecticide resistance in the malaria vectors across the country was reported since year 2006 onwards. Insecticide resistance in Anopheles gambiae sensu lato (s.l.) was detected in at least one compound in each class of all recommended insecticide classes. However, the Anopheles funestus s.l. is highly resistant to pyrethroids and DDT. Knockdown resistance (kdr) mechanism in An. gambiae s.l. is widely studied in the country. Biochemical resistance by detoxification enzymes (P450s, NSE and GSTs) in An. gambiae s.l. was also recorded. Numerous P450s genes associated with metabolic resistance were over transcribed in An. gambiae s.l. collected from agricultural areas. However, no study has reported mechanisms of insecticide resistance in the An. funestus s.l. in the country.
Conclusion
This review has shown the dynamics and monitoring of insecticide resistance in malaria vector populations across mainland Tanzanian. This highlights the need for devising improved control approaches of the malaria vectors in the country.
... This is because higher levels of organic compounds lead to increase in microbial population which depletes dissolved oxygen [22] . However, the levels of Na + , K + and Clwere significantly different between the sites, in the context of this study; high concentrations of these parameters can be suitable to Culex spp [23,24] . Nevertheless, the occurrence of high levels of Na + , K + , Cland conductivity in Culex mosquitoes breeding sites are suspected to originate from the human related activities [25][26][27] . ...
... A similar study reported that high water conductivity due to high salinity and other dissolved ions have a negative impact on the primary production of mosquito larvae (Closs et al. 2003). This findings are inconsistent with a study conducted from Nigeria that conductivity and TDS appeared to have no influence on Anopheles larval density (Imam and Deeni 2015). Also, this finding disagrees with Anopheles larvae abundance in water with high salinity and conductivity (Emidi et al. 2017). ...
Malaria is a widespread vector-borne disease in the tropics and subtropics causing nearly half a million deaths every year. Malaria vector control intervention mainly rely on the control of adults using Indoor residual sprayings (IRS) and long lasting insecticidal nets (LLINs). The purpose of this study was to assess the species composition of Anopheles mosquitoes and determine the environmental and physicochemical parameters of their breeding habitats in Bambasi district, Benshangul Gumuz regional state, northwestern Ethiopia. Three major Anopheles breeding habitats were identified in three Kebeles namely; drainage ditch (Keshmando), swamp (Amba 46), and stagnant water (Amba 47). Anopheles mosquito larvae were sampled twice a month from September 2020 to November 2020. A total of 2185 Anopheles mosquito larvae were collected. Of those collected larvae three Anopheles species (Anopheles gambiae s.l. An. funestus and An. coustani complex) were identified. Anopheles gambiae s.l was the most abundant whereas An. funestus and An. coustani were the least in all the study kebeles. Of the three kebeles, Amba 47 was found the most productive for Anopheles followed by Amba 46 and Keshmando. The highest mean density of larvae per dip was sampled in September in all the study sites. The three sampling sites varied in physicochemical characteristics. The findings of this study showed that dissolved oxygen (DO) was highest (7.07 ± 0.55 mg/L) in the swamps and lowest (0.32 ± 0.04 mg/L) in the drainage ditches. Conductivity across different habitats showed wide variations. There were slight variations in temperature between different habitats. Higher total dissolved solids (TDS) 12.19 ± 0.26 mg/L was recorded from the drainage ditches; whereas TDS 9.49 ± 1.62 mg/L was recorded from the swamp. Salinity in the drainage ditches and stagnant water was 5.54 ± 1.00PSU and 3.30 ± 0.97 PSU respectively. There were negative strong correlation between the larval density with temperature and EC but positive correlation between larval density with salinity. However, there was no significant correlation between Anopheles larval density with TDS and DO. In conclusion this study suggested that environmental and physicochemical factors could play an important role in the development of mosquito larvae. Therefore, characterizing mosquito larval habitats is important for targeted control of malaria vectors in Ethiopia.
... The physicochemical and environmental factors in mosquito breeding sites exert an effect on the density of mosquito larvae as well as on their detoxification enzyme activities. They can present an impact on insecticide resistance occurrence (23). It has been reported that the management of the pH of favored breeding sites could serve as a tool to control mosquito, and it can also assist the choice of biopesticides to use (24). ...
Background
The knowledge of key elements of the ecosystem affecting mosquito distribution and their population dynamics is essential for designing mosquito-borne disease interventions. The present study characterized the physicochemical properties of Aedes mosquito breeding habitats in Democratic Republic of the Congo.
Methods
A cross-sectional survey was carried out in Kinshasa, from February to April 2021. The physicochemical characteristics of the natural and artificial aquatic habitats of Aedes were measured using a multiparametric device.
Results
Out of 438 breeding habitats inspected, 273 (62.3%) contained mosquito larvae. The Aedes mosquitoes identified in 76.19% of positive breeding sites were Aedes albopictus (67.30%) and Aedes aegypti (37.98%). The median values of dissolved oxygen (DO) (1.0), turbidity (19.15), and salinity (0.115) in water breeding sites of Aedes were respectively 0.8, 55.0, and 0.29 in Culex breeding sites ( p < 0.05). The physicochemical characteristics of the breeding habitat for Ae. aegypti and Ae. albopictus were almost identical. In urban areas, the median temperature was 29.82 while it was 29.60 in suburban areas ( p < 0.05). Significantly, the salinity was higher in bamboo and metal containers while DO was higher in tins. After analysis using simple linear regression, total dissolved solids (r = 0.23; p = 0.000), conductivity (r = 0.23), salinity (r = 0.23), and temperature (r = 0.13) were associated with larval density ( p < 0.05). In the final model (r = 0.30, p = 0.01), salinity (r = 0.23) and DO (r = 0.138) adjusted to temperature, pH, and turbidity were associated positively to larvae density.
Conclusion
The Aedes breeding sites and mosquito density were significantly influenced by water salinity, DO, temperature, pH, and turbidity.
... The development of resistance has also been linked to an increase in the activities of detoxification enzymes in mosquito populations in oil polluted breeding habitat (Imam and Yusuf, 2015). Therefore the impact of the environment in the present study findings cannot be ruled out. ...
The capacity of malaria vectors to transmit Plasmodium parasites and their
vulnerability to vector control measures vary by mosquito species and are
influenced by local environmental factors. This study evaluated the susceptibility
of Anopheles mosquito populations from four study sites in Eastern Obolo
L.G.A, Akwa Ibom State, Nigeria to Permethrin(0.75%), Lambdacyhalothrin (0.5%),
alphacypermethrin (0.75%) and Deltamethrin (0.5%) insecticides. The
mosquitoes were obtained as aquatic forms from the study sites and reared under
laboratory conditions to adults. The adults were subjected to WHO susceptibility
bioassays following standard procedure. Across the study sites, the ranges of
mean mortality in groups treated with deltamethrin (23.75 ± 0.50 – 24.25 ± 0.50),
lambdacyhalothrin (23.25 ± 0.50 - 24.00 ± 0.00) and alphacypermethrin (22.75 ±
0.05 -23.00 ± 0.82), were significantly (p < 0.05) higher than that observed in the
permethrin (3.75 ± 0.50 - 17.75 ± 0.50) treated groups. This implies that malaria
vectors were resistant to permethrin. Vector Populations in all the study sites
showed marginal susceptibility to deltamethrin, lambdacyhalothrin and
alphacypermethrin (mortality rate: 90 % - 97 %). KDT50 and KDT95 estimated for
each insecticide using a log-time probit model revealed that knockdown was
more rapid for deltamethrin (KDT50 = 33.93 - 47.48 min; KDT95 = 76.07 - 144.39
min), lambdacyhalothrin (KDT50 = 33.01 - 44.01 min; KDT95 = 74.63 - 148.31
min) and alphacypermethrin (KDT50 = 38.92 - 47.53 min; KDT95 = 95.32 -
166.93 min) than for permethrin (KDT50 = 37.28 - 587.83 min; KDT95 = 174.14 -
2391.91 min). Morphological identification of all the mosquitoes used for the
tests revealed populations of only Anopheles gambiae s.l. Emergence of focal
points with insecticide resistance and marginal susceptibility in this study gives
serious concern especially with the scale-up in the distribution of pyrethriod
treated nets to these areas. This may increase selection pressures due to overexposure
and compromise vector control interventions employing these insecticides.
In malaria-endemic countries, monitoring of insecticide resistance in malaria vectors in areas contaminated with different sources of pollutants is still lacking. This study investigated insecticide resistance and its mechanisms in Anopheles arabiensis across four villages in Southeast Tanzania. Mosquitoes were collected from breeding habitats and tested against permethrin, deltamethrin, lambda-cyhalothrin, pirimiphos-methyl, and bendiocarb. Mechanisms of resistance [P450s enzymes and knockdown resistance (kdr)] were investigated. Comparison of mosquito mortality between sites was performed through one-way analysis of variance (ANOVA) and Tukey–Kramer tests. Anopheles arabiensis was highly resistant to pyrethroid and fully susceptible to bendiocarb and pirimiphos-methyl with mortality ranges of 29%−57%; 37%−65%; 34%−53%; 98%−100%; and 100% in permethrin, deltamethrin, lambda-cyhalothrin, pirimiphos-methyl, and bendiocarb respectively. Anopheles arabiensis mortality, particularly, in permethrin and deltamethrin was significantly higher in less polluted areas (Mofu and Namwawala) p < 0.001 as compared to areas with agrochemicals (Minepa) and domestic pollutants (Ifakara town) (p < 0.01). Moreover, significant involvement of P450s enzymes in pyrethroid resistance was observed while kdr mutations were not detected. The present study shows that pollution of mosquito breeding habitats might accelerate insecticide resistance which could impede the control of malaria vectors.
There is limited evidence on the effects of physicochemical factors of breeding sites on the density of Culex pipiens (L.) (Diptera: Culicidae) larvae in Qalyubia Governorate. Therefore, the aim of this study was to investigate C. pipiens larval density and the response of their detoxification enzymes to levels of various physicochemical environmental factors present in their breeding sites. Larvae were collected from three different zones (domestic, agriculture and petrochemical) from March-June 2020. Water samples were collected during larval collection and levels of 10 physicochemical parameters (temperature, pH, conductivity, turbidity, total dissolved solids, phosphates, sulphates, nitrates, oil and grease) were measured. Activities of the three major detoxification enzymes, P450, GST and α & β-esterases were determined on the sampled larvae. Data were assessed by One-way ANOVA followed by Tukey's post-hoc test and Pearson Correlation analysis. Results showed significant difference in the mean larval density of C. pipiens within the three study zones with the residential zone having the highest mean larval density. The activities of the detoxification enzymes were higher in the agricultural and petrochemical zones, which recorded higher levels of the physicochemical factors. There was a significant negative correlation between the density of C. pipiens larvae and temperature, pH, turbidity, phosphates, sulphates, nitrates, oil and grease levels, whereas conductivity and total dissolved solids had no significant correlation with larval density. The concentrations of oil and grease which were significantly higher in petrochemical zone were strongly positively correlated with P450 activities. While, phosphate, sulphate and nitrate which were significantly higher in agricultural zone were associated with GST and α & β-esterase activities. The correlations observed between the physicochemical factors and larval density as well as the inductive impact on detoxification enzymes can confirm the effect of these factors on mosquito breeding activity and these observations could have a significant effect on the environmental management and approach to mosquito control in Qalyubia Governorate.
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