Dataset Information

Additional selection for insecticide resistance in urban malaria vectors: DDT resistance in Anopheles arabiensis from Bobo-Dioulasso, Burkina Faso.

ABSTRACT: In the city of Bobo-Dioulasso in Burkina Faso, Anopheles arabiensis has superseded Anopheles gambiae s.s. as the major malaria vector and the larvae are found in highly polluted habitats normally considered unsuitable for Anopheles mosquitoes. Here we show that An. gambiae s.l. adults emerging from a highly polluted site in the city centre (Dioulassoba) have a high prevalence of DDT resistance (percentage mortality after exposure to diagnostic dose=65.8% in the dry season and 70.4% in the rainy season, respectively). An investigation into the mechanisms responsible found an unexpectedly high frequency of the 1014S kdr mutation (allele frequency=0.4), which is found at very low frequencies in An. arabiensis in the surrounding rural areas, and an increase in transcript levels of several detoxification genes, notably from the glutathione transferase and cytochrome P450 gene families. A number of ABC transporter genes were also expressed at elevated levels in the DDT resistant An. arabiensis. Unplanned urbanisation provides numerous breeding grounds for mosquitoes. The finding that Anopheles mosquitoes adapted to these urban breeding sites have a high prevalence of insecticide resistance has important implications for our understanding of the selective forces responsible for the rapid spread of insecticide resistant populations of malaria vectors in Africa.

SUBMITTER: Jones CM

PROVIDER: S-EPMC3457957 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Additional selection for insecticide resistance in urban malaria vectors: DDT resistance in Anopheles arabiensis from Bobo-Dioulasso, Burkina Faso.

Jones Christopher M CM Toé Hyacinthe K HK Sanou Antoine A Namountougou Moussa M Hughes Angela A Diabaté Abdoulaye A Dabiré Roch R Simard Frederic F Ranson Hilary H

PloS one 20120925 9

In the city of Bobo-Dioulasso in Burkina Faso, Anopheles arabiensis has superseded Anopheles gambiae s.s. as the major malaria vector and the larvae are found in highly polluted habitats normally considered unsuitable for Anopheles mosquitoes. Here we show that An. gambiae s.l. adults emerging from a highly polluted site in the city centre (Dioulassoba) have a high prevalence of DDT resistance (percentage mortality after exposure to diagnostic dose=65.8% in the dry season and 70.4% in the rainy ...[more]

PMID: 23049917

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Project description:Swarming is a key part of the natural system of reproduction of anopheline mosquito populations, and a better understanding of swarming and mating systems in a targeted species in its natural habitat would contribute to better design control strategies with a greater chance of success. Our study investigated the monthly occurrence of swarming and the mating frequency (within swarms) of Anopheles arabiensis in Dioulassoba, Burkina Faso and their relationship with local environmental factors. Mosquitoes collected from swarms were described in terms of body size, recent sugar meal intake, and female repletion, insemination, and Plasmodium falciparum infection status. Swarms of An. arabiensis were found in each month of the year. Both start and end times of swarming varied significantly between months, correlating with the time of sunset. Swarming mostly started after or coincided with sunset from late July to early October but occurred before sunset from late October to early July. Swarming duration, the number of mosquitoes and mating pairs per swarm, and time to first mating were significantly different between months in an inverse relationship with the monthly rainfall. The number of mating pairs was strongly and positively correlated with swarm size. Almost all the females caught in copula were inseminated but a very few were blood fed; no P. falciparum infection was observed. Males caught in copula and in solo were similar in body size and in the proportion which had taken a recent sugar meal. Our investigations showed that An. arabiensis reproductive activities are most frequent during the dry season, suggesting either the species' preference for dry climatic conditions or a lack of available breeding sites during the rainy season due to the seasonal flooding in this area. Targeting interventions to kill mosquitoes in swarms or to achieve an over-flooding ratio of sterile males during the rainy season would increase their efficiency in reducing the population density of this vector.

Project description:Background and methodsA longitudinal Anopheles gambiae s.l. insecticide-resistance monitoring programme was established in four sentinel sites in Burkina Faso. For three years, between 2008 and 2010, WHO diagnostic dose assays were used to measure the prevalence of resistance to all the major classes of insecticides at the beginning and end of the malaria transmission season. Species identification and genotyping for target site mutations was also performed and the sporozoite rate in adults determined.ResultsAt the onset of the study, resistance to DDT and pyrethroids was already prevalent in An. gambiae s.l. from the south-west of the country but mosquitoes from the two sites in central Burkina Faso were largely susceptible. Within three years, DDT and permethrin resistance was established in all four sites. Carbamate and organophosphate resistance remains relatively rare and largely confined to the south-western areas although a small number of bendiocarb survivors were found in all sites by the final round of monitoring. The ace-1R target site resistance allele was present in all localities and its frequency exceeded 20% in 2010 in two of the sites. The frequency of the 1014F kdr mutation increased throughout the three years and by 2010, the frequency of 1014F in all sites combined was 0.02 in Anopheles arabiensis, 0.56 in An. gambiae M form and 0.96 in An. gambiae S form. This frequency did not differ significantly between the sites. The 1014S kdr allele was only found in An. arabiensis but its frequency increased significantly throughout the study (P = 0.0003) and in 2010 the 1014S allele frequency was 0.08 in An. arabiensis. Maximum sporozoite rates (12%) were observed in Soumousso in 2009 and the difference between sites is significant for each year.ConclusionPyrethroid and DDT resistance is now established in An. gambiae s.l. throughout Burkina Faso. Results from diagnostic dose assays are highly variable within and between rounds of testing, and hence it is important that resistance monitoring is carried out on more than one occasion before decisions on insecticide procurement for vector control are made. The presence of 1014S in An. gambiae s.l., in addition to 1014F, is not unexpected given the recent report of 1014S in Benin but highlights the importance of monitoring for both mutations throughout the continent. Future research must now focus on the impact that this resistance is having on malaria control in Burkina Faso.

Project description:BackgroundPyrethroid resistance is one of the major threats for effectiveness of insecticide-treated bed nets (ITNs) in malaria vector control. Genotyping of mutations in the voltage gated sodium channel (VGSC) gene is widely used to easily assess the evolution and spread of pyrethroid target-site resistance among malaria vectors. L1014F and L1014S substitutions are the most common and best characterized VGSC mutations in major African malaria vector species of the Anopheles gambiae complex. Recently, an additional substitution involved in pyrethroid resistance, i.e. V402L, has been detected in Anopheles coluzzii from West Africa lacking any other resistance alleles at locus 1014. The evolution of target-site resistance mutations L1014F/S and V402L was monitored in An. coluzzii and Anopheles arabiensis specimens from a Burkina Faso village over a 10-year range after the massive ITN scale-up started in 2010.MethodsAnopheles coluzzii (N = 300) and An. arabiensis (N = 362) specimens collected both indoors and outdoors by different methods (pyrethrum spray catch, sticky resting box and human landing collections) in 2011, 2015 and 2020 at Goden village were genotyped by TaqMan assays and sequencing for the three target site resistance mutations; allele frequencies were statistically investigated over the years.ResultsA divergent trend in resistant allele frequencies was observed in the two species: 1014F decreased in An. coluzzii (from 0.76 to 0.52) but increased in An. arabiensis (from 0.18 to 0.70); 1014S occurred only in An. arabiensis and slightly decreased over time (from 0.33 to 0.23); 402L increased in An. coluzzii (from 0.15 to 0.48) and was found for the first time in one An. arabiensis specimen. In 2020 the co-occurrence of different resistance alleles reached 43% in An. coluzzii (alleles 410L and 1014F) and 32% in An. arabiensis (alleles 1014F and 1014S).ConclusionsOverall, an increasing level of target-site resistance was observed among the populations with only 1% of the two malaria vector species being wild type at both loci, 1014 and 402, in 2020. This, together with the co-occurrence of different mutations in the same specimens, calls for future investigations on the possible synergism between resistance alleles and their phenotype to implement local tailored intervention strategies.

Project description:BackgroundTwenty-seven villages were selected in southwest Burkina Faso to implement new vector control strategies in addition to long lasting insecticidal nets (LLINs) through a Randomized Controlled Trial (RCT). We conducted entomological surveys in the villages during the dry cold season (January 2017), dry hot season (March 2017) and rainy season (June 2017) to describe malaria vectors bionomics, insecticide resistance and transmission prior to this trial.MethodsWe carried out hourly catches (from 17:00 to 09:00) inside and outside 4 houses in each village using the Human Landing Catch technique. Mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Anopheles funestus group were identified using molecular techniques as well as detection of Plasmodium falciparum infection and insecticide resistance target-site mutations.ResultsEight Anopheles species were detected in the area. Anopheles funestus s.s was the main vector during the dry cold season. It was replaced by Anopheles coluzzii during the dry hot season whereas An. coluzzii and An. gambiae s.s. were the dominant species during the rainy season. Species composition of the Anopheles population varied significantly among seasons. All insecticide resistance mechanisms (kdr-w, kdr-e and ace-1 target site mutations) investigated were found in each members of the An. gambiae complex but at different frequencies. We observed early and late biting phenotypes in the main malaria vector species. Entomological inoculation rates were 2.61, 2.67 and 11.25 infected bites per human per month during dry cold season, dry hot season and rainy season, respectively.ConclusionThe entomological indicators of malaria transmission were high despite the universal coverage with LLINs. We detected early and late biting phenotypes in the main malaria vector species as well as physiological insecticide resistance mechanisms. These data will be used to evaluate the impact of complementary tools to LLINs in an upcoming RCT.

Project description:BACKGROUND: Malaria during pregnancy remains a serious public health problem. The aim of this study was to determine the prevalence and possible risk factors for malaria in pregnant women attending antenatal clinic at two primary health facilities in Bobo-Dioulasso. METHODS: We conducted a cross sectional study from September to December 2010 in two primary health facilities located in the periurban area of Bobo-Dioulasso. Pregnant women attending antenatal clinic (ANC) were included in the study after signing informed consent. For each participant, the social-demographic profile, malaria and obstetric histories were investigated through a questionnaire. Peripheral blood was collected and thick and thin blood smears were prepared to check Plasmodium falciparum parasitaemia. Hemoglobin concentration was measured. The associations between age, parity, gestational age, schooling, number of ANC visits, use of IPTp-SP, use of insecticide-treated nets (ITN) and anemia with the occurrence of P. falciparum malaria infection during pregnancy were analyzed through logistic regression. RESULTS: During the period of study, 105 (18.1%) out of 579 pregnant women were infected by P. falciparum. The hemoglobin concentration mean was 10.5?±?1.7/dL and was significantly lower in pregnant women with malaria infection (9.8 g/dL ±1.6) than in those who had no malaria infection (10.6 g/dL ±1.7) (P?<?0.001). Multivariate analysis indicated that, education (AOR 1.9, 95% CI?=?[1.2-3.2]), parity [primigravidae (AOR 5.0, 95% CI?=?[2.5-9.8]) and secundigravidae (AOR 2.1, 95% CI?=?[1.2-3.8])], and anaemia (AOR 2.1, 95% CI?=?[1.3-3.5]) were significantly associated with P. falciparum malaria infection. The use of IPTp-SP was not associated with P. falciparum malaria infection. CONCLUSIONS: P. falciparum malaria infection is common in pregnant women attending antenatal clinic and anaemia is an important complication. The results show that the use of IPTp-SP does not reduce the risk of malaria incidence during pregnancy.

Dataset Information

Additional selection for insecticide resistance in urban malaria vectors: DDT resistance in Anopheles arabiensis from Bobo-Dioulasso, Burkina Faso.

Publications

Additional selection for insecticide resistance in urban malaria vectors: DDT resistance in Anopheles arabiensis from Bobo-Dioulasso, Burkina Faso.

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