Anopheles gambiae, An. coluzzii and An. arabiensis are the three major vectors of malaria in Nigeria. These mosquitoes have developed resistance to different insecticides. Insecticides resistance intensity assay was recently introduced to provide insight into the potential operational significance of insecticide resistance. Here, we present data on pyrethroids resistance intensity and resistance mechanisms from six vector surveillance sites (Lagos, Ogun, Edo, Anambra, Kwara and Niger) in Nigeria. Adult Anopheles reared from larval collections were tested using WHO insecticides susceptibility protocol with 1x concentration of permethrin and deltamethrin followed with intensity assays with 5x and 10x concentrations of both insecticides. Synergistic and biochemical assays were carried out and underlying resistance mechanisms determined following standard protocols. Anopheles gambiae constituted >50% samples tested in five sites. Permethrin and deltamethrin resistance was observed at all the sites. The Kdt50 varied from 15 minutes (CI = 13.6–17.2) in deltamethrin to 42.1 minutes (CI = 39.4–44.1) in permethrin. For both insecticides, Kdt95 was >30 minutes with 25% to 87% post exposure mortality at the different sites. The West Africa knock down resistance (kdr-w) mechanism was found at each site. Resistant An. gambiae from Lagos, Ogun and Niger synergized prior to permethrin or deltamethrin exposure showed significant mortality (89–100%) compared to unsynergized mosquitoes (Lagos, p = 0.031; Ogun, p = 0.025; Niger, p = 0.018). Biochemical analyses revealed significant increased levels of P450 enzymes in resistant Anopheles gambiae from Lagos (p = 0.038); Ogun (p = 0.042) and Niger (p = 0.028) in addition to GST in Lagos (p = 0.028) and Ogun (p = 0.033). Overall, the results revealed high pyrethroid resistance associated with increased activities of metabolic enzymes (P450 + GST) in An. gambiae and An. coluzzii from Lagos and Ogun. The presence of kdr + P450 conferred moderate resistance whereas low resistance was the case where kdr was the sole resistance mechanism. Findings thus suggests that elevated levels of cytochrome P450 enzymes together with GST were responsible for high or severe pyrethroid resistance.
Background Aedes aegypti transmits several arboviral diseases of global public health threat such as dengue, zika, and yellow fever. Recently, a series of yellow fever outbreaks have been reported in different parts of the country. Globally, the control of mosquito-borne diseases has relied heavily on insecticides based vector control efforts. Therefore, we assessed the susceptibility status to three different classes of WHO approved insecticides and evaluated the importance of detoxifying enzymes on insecticides resistance in Aedes aegypti collected from Lagos State, Nigeria. Aedes aegypti immature stages were collected from suitable habitats in peri-domestic areas of Alimosho, Kosofe, Badagry, and Ibeju-Lekki Local Government Areas (LGAs) of Lagos State, 2–5 days old glucose-fed adult female mosquitoes were exposed to discriminating doses of DDT, permethrin, bendiocarb, and PBO synergist using WHO standard procedure and kits. Identification was through morphological means only. Results Resistance to DDT and permethrin was recorded in all the LGAs, suspected resistance to bendiocarb was recorded in Aedes aegypti from Alimosho while full susceptibility was recorded in other LGAs. PBO synergist significantly increases the 24 h mortality of DDT and permethrin-resistant Aedes aegypti in all the LGAs. The activities of both GSTs and cytochrome P450s increase with decreasing mortality for Aedes aegypti, regression value (R2) ranges from 0.8889 to 0.6224 for GSTs and 0.4379 to 0.616 for cytochrome P450s. Conclusions Aedes aegypti population from Lagos State, Nigeria, have developed resistance to DDT and permethrin, the activities of P450s and GST were implicated in DDT and permethrin resistance in this study. Therefore, a need for regular insecticides monitoring and PBO should be incorporated into Aedes aegypti insecticides control strategies to forestall development of resistance to DDT and pyrethriods.
Background Incidence of malaria and anaemia are of public health importance especially in pregnant women in endemic regions, due to the negative health consequences to the mother and fetus. This study aimed to assess the pattern of falciparum malaria infection and anaemia, based on malaria prevention methods practiced by participants. Methods A semi-structured tool was used to capture information on demographic, socio-economic and malaria prevention practices from 113 pregnant women attending antenatal clinics in 2 peri-urban health facilities in Lagos, southwest Nigeria. Malaria microscopy was conducted and haematocrit was measured. Logistic regression analysis was performed on the data collated from the survey. Results The prevalence of anaemia among pregnant women was 87.2%. The mean (± sd) packed cell volume (PCV) (%) of the 22 (19.5%) infected subjects (26.8 ± 6.6), was significantly lower (t = −2.60, P value = 0.007) than that of the 91 (80.5%) uninfected subjects (30.8 ± 6.0). The prevalence of infection was highest in the 3rd trimester (n = 40, 35.4%) at 27.5% (11/40) and among those in their first pregnancy (n = 32, 28.3%) at 25.0% (8/32). There was a significant difference (t = −2.23, P-value = 0.01) in the mean PCV % of pregnant women who consumed herbal teas in pregnancy (28.2 ± 5.2) compared to those who did not (30.8 ± 6.6). Regression analysis showed that first pregnancy, anti-malarial use and insecticide-treated nets use the night before study had increased odds of malaria infection in participants (OR = 1.35, P = 0.006, 95% CI 0.52−2.49; OR = 2.3, P = 0.005, 95% CI 0.14−0.41; OR = 1.92, P = 0.001, 95% CI 0.62−5.98) while intermittent preventive treatment (IPT) participation and formal education were strongly and significantly associated with lower risk of parasitaemia (OR = 0.95, P = 0.025, 95% CI 0.41−2.26; OR = 0.44, P = 0.005, 95% CI 0.34−10.50). Conclusion Interventions that will reduce malaria and moderate to severe anaemia, especially in a first pregnancy, should include education on the correct use of long-lasting insecticide-treated bed nets (LLIN), IPT and the dangers of herbal teas in pregnancy.
Selection of vector populations capable of withstanding doses of insecticides is a major threat facing insecticide based vector control interventions. In view of the rapidly evolving insecticide resistance in the primary vector, Anopheles, there is need to provide information on the status of insecticide resistance in Oyo State where Long Lasting Insecticide Treated Nets (LLIN) is the only intervention that has been deployed over the years. Morphologically identified Anopheles mosquito larva were collected from six localities (Ojoo, Iwo road, Bodija, Oluyole, Oyo town and Eruwa) in Oyo State. The larval samples were reared to adults and exposed to DDT (4%) and Deltamethrin (0.05%), according to WHO criteria. Knockdown was recorded every ten minutes and mortality scored at 24 hrs post exposure. The KDT 50 and KDT 95 were determined using probit regression analysis and species identification was by adult morphology and Polymerase Chain Reaction techniques. A total of 1,800 female anopheline mosquitoes were exposed to DDT and Deltamethrin insecticides. All the Anopheles mosquito populations from the six localities were resistant to DDT with 13-84% mortality. The anopheline mosquito populations from Iwo road and Oyo town were susceptible to Deltamethrin, while those from Ojoo and Eruwa showed reduced susceptibility to the insecticide. However,mosquito populations from Oluyole and Bodija were resistant to Deltamethrin. The knock down values for DDT and Deltamethrin across all sites was comparatively high indicative of some degree of selection within the populations. Of the 1,764 positively identified anophelines, 639 (36.2%), 1,034 (58.6%) and 91 (5.2%) were Anopheles coluzzi, Anopheles arabiensis and Anopheles gambiae s.s. respectively. This data indicates the widespread resistance of Anopheles coluzzi, Anopheles arabiensis and Anopheles gambiae s.s. to Dichlotrichloroethane (DDT) in Oyo State. It also showed an ongoing selection against pyrethroid which poses a major threat to the ongoing LLIN intervention in the State.
Malaria is a leading public health challenge causing mortality and morbidity in sub-Saharan Africa. Prominent malaria vector control methods employed in sub-Saharan Africa include Long Lasting Insecticide Nets (LLINs) and Indoor Residual spraying (IRS). This study investigated knowledge, attitude and practices (KAP) of malaria vector control methods in Lagos, South-West Nigeria. Structured questionnaires were employed for the cross-sectional survey which was carried out between May and August 2018. Multi-stage sampling technique was used to select Lagos Mainland, Kosofe, and Ojo local government areas (LGAs). Five hundred and twenty questionnaires were used for the study. Data were analyzed for descriptive statistics, whereas χ 2 was used to determine influence of respondents’ LGA, level of education and type of dwelling on respondents’ attitude and practice. Respondents’ LGAs have no significant impact on attitude and practice to malaria vector control methods. However, ‘level of education’ as well as ‘type of dwelling structure’ impacted significantly on some practices and attitude. Basically, IRS is the major tool employed in malaria vector control, but sometimes it is used in combination with other methods. A good number of residents also use LLINs. ‘Choice of method’ employed is mainly based on the effectiveness of method. General perception about LLINs and IRS is that they are effective, cheap and safer. Considering the widespread use of IRS and LLINs for malaria vector control in Lagos, implementation of malaria control programs should consider KAP to these two strategies.
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