Pyrethroids and DDT are key insecticides in the control of malaria, yellow fever, and lymphatic filariasis vectors. Knockdown and metabolic resistance mechanisms have been proven to be important in determining the efficacy of insecticides. Here we investigated cytochrome P450 as a resistance mechanism in Anopheles gambiae Giles and Culex quinquefasciatus Say exposed to deltamethrin and DDT. Two- to three-days-old adult female mosquitoes were used for insecticide exposures and PBO synergistic assays using WHO standard guidelines, kits and test papers (DDT 4%, deltamethrin 0.05%, and PBO 4%). Polymerase chain reaction (PCR) assays were used for the identification of the species and for characterization of the kdr allele. Mortality at 24 h post-exposure was 18 and 17% in An. gambiae s.s. exposed to DDT and deltamethrin, respectively; 1 and 5% in Cx. quinquefasciatus exposed to DDT and deltamethrin respectively. Significant ( P < 0.01) levels of susceptibility was recorded in mosquitoes pre-exposed to PBO, as KDT 50 and 24 h of exposure ranged from 37.6 min to 663.4 min and 27 to 80%, respectively. Presence of a knockdown resistance allele was recorded in An. gambiae s.s., 22.5% for homozygote resistance and 7.5% for heterozygotes, while Cx. quinquefasciatus populations showed no kdr allele despite the high level of resistance to DDT and deltamethrin. Findings from this study indicated that cytochrome P450 mono-oxygenase expression is highly implicated in the resistance phenotype to DDT and pyrethroids in An. gambiae and Cx. quinquefasciatus in the study area.
Objective Nigeria bears 25% of global malaria burden despite concerted efforts towards its control and elimination. The emergence of drug resistance to first line drugs, artemisinin combination therapies (ACTs), indicates an urgent need for continuous molecular surveillance of drug resistance especially in high burden countries where drug interventions are heavily relied on. This study describes mutations in Plasmodium falciparum genes associated with drug resistance in malaria; Pfk1 3, Pfmdr1 , PfATPase6 and Pfcrt in isolates obtained from 83 symptomatic malaria patients between 1-61 years old from Lagos, a Mega city in South-west Nigeria. Results Two Pfmdr 1, N86 and Y184 variants were present at a prevalence of 56% and 13.25% of isolates respectively. There was one synonymous (S679S) and two non-synonymous (M699V, S769M) mutations in the Pfatp6 gene, while Pfcrt genotype (CVIET), had a prevalence of 45%. The Pfk13 C580Y mutant allele was detected by allelic discrimination in two samples with mixed genotypes. Pfk13 C580Y in west Africa is rare and this result calls for robust and larger scale surveillance of artemisinin resistance associated polymorphisms and delayed clearance phenotype in Nigeria.
Schistosomiasis, a major public health challenge is caused by trematodes of the genus Schistosoma whose intermediate host is snails. Sub-Saharan African (SSA) carried 85% of the global burden of this infection principally amongst school age children. Similarly, Nigeria bears the highest weight of this highly preventable infection in SSA. Preventive chemotherapy (PC) with 40-60 mg\kg praziquantel (PZQ) annually is the focal control strategy in endemic areas. Despite more than two decades of PZQ usage in Nigeria, the disease is still prevalent in affected communities. Thus, the study sought to assess the current post-treatment efficacy of PZQ use for urinary schistosomiasis among primary school age children of Ipogun village. Urine reagent strip (Haemastix) ® was initially used to screen pupils for haematuria, while Kato-Katz and urine filtration were employed to confirm the presence of schistosome ova in the faeces and urine of the study population pre-and post-treatment. A total of 202 children were screened, out of which 117 (57.9%) were positive for microhaematuria and 91 (45.0%) had ova of Schistosoma haematobium in their urine. The 14 and 21 day post-treatment assessment revealed 73.6% and 23.1% of the initially infected children to still be with infection respectively. Additionally, there was a statistical significant (P=0.02) in the reduction of egg count twenty-one days post-treatment. Though the efficacy of the drug as observed in the egg reduction rate in the study area can be classified as satisfactory, continuous monitoring of schistosome response should not cease if the global target of eliminating morbidity due to schistosomiasis by year 2020 is to be achieved.
Background: Culex mosquitoes are important vectors of several human pathogens causing infections such as lymphatic filariasis and several viruses. Poor and blocked drainage system can lead to impediment in water flow, leading to the artificial creation of larval habitats for Culex mosquitoes. Culex mosquitoes has the ability to breed in organically polluted water bodies and exhibit high resistance to insecticides. Therefore, this study assessed the species and insecticides susceptibility status of Culex breeding in blocked drainages in Lagos State. Methods: Culex mosquito larvae were collected from blocked drainages in three Local Government Areas (LGAs) of Lagos State, Nigeria, using standard WHO technique. The physicochemical parameters of the larval habitats were also recorded. Collected mosquito larvae were raised to adult, 2-3 days old. Glucose fed adults female mosquitoes were exposed to permethrin (0.75%) and DDT (4.0%) WHO insecticide test papers. Morphological identification was carried out using standard keys and molecular identification of Culex pipiens sub-species and kdr genotyping was carried out using PCR Results: High level of resistance was recorded with mortality r ate after 24 hour s for DDT ranging from 20% to 32% while permethrin ranges from 14% to 36%. The pH of the all the Culex mosquito larva habitats ranges from 7.38±0.11 to 7.62±0.29, while TDS ranges from 592.6±79.1 to 655±68.1. A total of 1113 Culex pipiens mosquitoes that were identify morphologically, some were selected for molecular identification using PCR assays, out of which 96.2% were identified as Culex p. quinquefasciatus while 3.7% were unidentified. Knockdown mutation (L1014F) was not detected in DDT and pyrethroids resistant Cx. quinquefasciatus in this study. Conclusion: Unplanned ur banization, inadequate w ater su pply and inefficient solid w aste and sewage management practices can result in the creation artificial larval habitats for Culex mosquitoes leading to potential outbreak of Culex mosquito borne diseases. The resistance to DDT and permethrin insecticides in Cx. quinquefasciatus in Lagos State may represent a threat towards the efficacy of ITNs and other forms of vector control such as indoor residual spraying in the future.
Background: Decline in malaria prevalence is usually attributed to the efficient vector control strategies implemented in such endemic areas. The spread of insecticide resistance in Anopheles mosquitoes is a major drawback to the gains in malaria vector control. Here we assessed the susceptibility status of Anopheles gambiae s.l. to some selected WHO-approved insecticides and frequency of knockdown resistance gene in two Local Government Areas of Lagos State, Nigeria. Methods: Three to five days old adult female mosquitoes were exposed to deltamethrin, permethrin and bendocarb. Knockdown time was recorded every ten minutes and % mortality taken at 24hr post exposure. KDT50 and KDT95 were determined using probit regression analysis. The resistant mosquitoes were used for species identification by Polymerase Chain Reaction (PCR) assays and characterized for the knockdown resistance (kdr) mutation by allele-specific PCR (AS-PCR). Results: The results of twenty-four hour post exposure mortality rate showed that mosquitoes sampled at differ-ent locations were resistant to permethrin (39% mortality for Lagos Mainland L.G.A.; 45% for Kosofe L.G.A.), del-tamethrin (51% for Lagos Mainland L.G.A; 68% for Kosofe L.G.A), but susceptible to bendiocarb (100% for Lagos Mainland L.G.A.; 99% for Kosofe L.G.A.). The KDT50 varied from 34 minutes in bendiocarb for both LGAs to 190 minutes in deltamethrin for Kosofe and 119 minutes in permethrin for Lagos Mainland. In all insecticides tested for both LGAs, KDT95 was greater than 60 minutes. Only the 1014F kdr mutation was detected. The overall kdr frequen-cy was low (1.79%). There was no significant association between the presence of the 1014F kdr allele and ability of Anopheles mosquitoes to survive exposure to the tested insecticides (P > 0.05). Conclusion: This level of resistance to WHO approved insecticides is a threat to control programs and can have significant operational impact, if action is not taken.
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