Anopheles Funestus Sensu Stricto Research Articles

Temperature, mosquito feeding status and mosquito density influence the measured bio-efficacy of insecticide-treated nets in cone assays

BackgroundThe WHO cone bioassay is routinely used to evaluate the bioefficacy of insecticide-treated nets (ITNs) for product pre-qualification and confirmation of continued ITN performance during operational monitoring. Despite its standardized nature, variability is often observed between tests. We investigated the influence of temperature in the testing environment, mosquito feeding status and mosquito density on cone bioassay results.MethodsCone bioassays were conducted on MAGNet (alphacypermethrin) and Veeralin (alphacypermethrin and piperonyl butoxide (PBO)) ITNs, using laboratory-reared pyrethroid-resistant Anopheles funestus sensu stricto (FUMOZ strain) mosquitoes. Three experiments were conducted using standard cone bioassays following WHO-recommended test parameters, with one variable changed in each bioassay: (i) environmental temperature during exposure: 22–23 °C, 26–27 °C, 29–30 °C and 32–33 °C; (ii) feeding regimen before exposure: sugar starved for 6 h, blood-fed or sugar-fed; and (iii) mosquito density per cone: 5, 10, 15 and 20 mosquitoes. For each test, 15 net samples per treatment arm were tested with four cones per sample (N = 60). Mortality after 24, 48 and 72 h post-exposure to ITNs was recorded.ResultsThere was a notable influence of temperature, feeding status and mosquito density on An. funestus mortality for both types of ITNs. Mortality at 24 h post-exposure was significantly higher at 32–33 °C than at 26–27 °C for both the MAGNet [19.33% vs 7%; odds ratio (OR): 3.96, 95% confidence interval (CI): 1.99–7.87, P < 0.001] and Veeralin (91% vs 47.33%; OR: 22.20, 95% CI: 11.45–43.05, P < 0.001) ITNs. Mosquito feeding status influenced the observed mortality. Relative to sugar-fed mosquitoes, The MAGNet ITNs induced higher mortality among blood-fed mosquitoes (7% vs 3%; OR: 2.23, 95% CI: 0.94–5.27, P = 0.068) and significantly higher mortality among starved mosquitoes (8% vs 3%, OR: 2.88, 95% CI: 1.25–6.63, P = 0.013); in comparison, the Veeralin ITNs showed significantly lower mortality among blood-fed mosquitoes (43% vs 57%; OR: 0.56, 95% CI: 0.38–0.81, P = 0.002) and no difference for starved mosquitoes (58% vs 57%; OR: 1.05, 95% CI: 0.72–1.51, P = 0.816). Mortality significantly increased with increasing mosquito density for both the MAGNet (e.g. 5 vs 10 mosquitoes: 7% vs 12%; OR: 1.81, 95% CI: 1.03–3.20, P = 0.040) and Veeralin (e.g. 5 vs 10 mosquitoes: 58% vs 71%; OR 2.06, 95% CI: 1.24–3.42, P = 0.005) ITNs.ConclusionsThe results of this study highlight that the testing parameters temperature, feeding status and mosquito density significantly influence the mortality measured in cone bioassays. Careful adherence to testing parameters outlined in WHO ITN testing guidelines will likely improve the repeatability of studies within and between product testing facilities.Graphical

Life expectancy of Anopheles funestus is double that of Anopheles arabiensis in southeast Tanzania based on mark-release-recapture method

Anopheles arabiensis and Anopheles funestus sensu stricto mosquitoes are major East African malaria vectors. Understanding their dispersal and population structure is critical for developing effective malaria control tools. Three mark-release-recapture (MRR) experiments were conducted for 51 nights to assess daily survival and flight range of An. arabiensis and An. funestus mosquitoes in south-eastern, Tanzania. Mosquitoes were marked with a fluorescent dye as they emerged from breeding sites via a self-marking device. Mosquitoes were collected indoors and outdoors using human landing catches (HLC) and Centers for Disease Control and Prevention light traps (CDC-LT). In total, 4210 An. arabiensis and An. funestus were collected with 316 (7.5%) marked and recaptured (MR). Daily mean MR was 6.8, standard deviation (SD ± 7.6) for An. arabiensis and 8.9 (SD ± 8.3) for An. funestus. Probability of daily survival was 0.76 for An. arabiensis and 0.86 for An. funestus translating into average life expectancy of 3.6 days for An. arabiensis and 6.5 days for An. funestus. Dispersal distance was 654 m for An. arabiensis and 510 m for An. funestus. An. funestus life expectancy was substantially longer than that of An. arabiensis. The MRR method described here could be routinely utilized when evaluating the impact of new vector control tools on mosquito survival.

Baseline characterization of entomological drivers of malaria transmission in Namibia: a targeted operational entomological surveillance strategy

BackgroundNamibia’s focus on the elimination of malaria requires an evidence-based strategy directed at understanding and targeting the entomological drivers of malaria transmission. In 2018 and 2019, the Namibia National Vector-borne Diseases Control Program (NVDCP) implemented baseline entomological surveillance based on a question-based approach outlined in the Entomological Surveillance Planning Tool (ESPT). In the present study, we report on the findings of the ESPT-based NVDCP on baseline vector species composition and bionomic traits in malaria endemic regions in northern Namibia, which has the aim of generating an evidence base for programmatic decision-making.MethodsNine representative sentinel sites were included in the 2018 entomological surveillance program (Kunene, Omusati, Oshana, Ohangwena, Oshikoto, Otjozondjupa, Kavango West, Kavango East and Zambezi); the number was reduced to four sites in 2019 due to limited funding (Ohangwena, Kavango West, Kavango East, and Zambezi). In the 2018 baseline collections, multiple sampling methods (human landing catches, pyrethroid spray catches, U.S. Centers for Disease Control and Prevention light traps [CDC-LTs], resting boxes [RBs] and larval sampling) were utilized to evaluate indoor/outdoor human biting rates, resting behaviors and insecticide resistance (IR). CDC-LTs and RBs were not used in 2019 due to low and non-representative sampling efficacies.ResultsOverall, molecular evidence demonstrated the presence of three primary mosquito vectors, namely Anopheles arabiensis, rediscovered Anopheles gambiae sensu stricto and Anopheles funestus sensu stricto, alongside Anopheles squamosus and members of the Anopheles coustani complex. Vectors were found to bite throughout the night (1800 hours 0600 hours) both indoors and outdoors, with An. arabiensis having the highest biting rates outdoors. Low numbers of indoor resting Anopheles point to possible low indoor residual spraying (IRS) efficacy—with An. arabiensis found to be the major vector species resting indoors. The IR tests demonstrated varying country-wide resistance levels to the insecticide deltamethrin, with the resistance levels confirmed to have increased in 2019, evidence that impacts national programmatic decision-making. Vectors demonstrated susceptibility to the insecticides dichlorodiphenyltrichloroethane, bendiocarb and Actellic 300CS in 2018, with mosquitoes from only one site (Kavango West) demonstrating possible resistance to DDT. Targeted and question-based entomological surveillance enabled a rapid and focused evidence base to be built, showing where and when humans were being bitten and providing entomological data on long-lasting insecticidal nets, IRS efficacy and insecticide resistance, which the Ministry of Health and Social Services-Namibia can use to further build a monitoring and evaluation framework for understanding the drivers of transmission.ConclusionIdentification and characterization of species-specific bionomic traits allows for an understanding of where and when vector human contact may occur as well as the potential impact of interventions. Low indoor resting rates as well as the presence of insecticide resistance (and the increase in its frequency) point to the need for mosquito-behavior-directed and appropriate interventions as well as the requirement for a resistance mitigation strategy. The ESPT-based question- and minimal essential indicator-based operational research strategy provides programs with directed and focused data for facilitating decision-making while requiring limited funding and capacity.Graphical

Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania

BackgroundVector control through long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) is a major component of the Tanzania national malaria control strategy. In mainland Tanzania, IRS has been conducted annually around Lake Victoria basin since 2007. Due to pyrethroid resistance in malaria vectors, use of pyrethroids for IRS was phased out and from 2014 to 2017 pirimiphos-methyl (Actellic® 300CS) was sprayed in regions of Kagera, Geita, Mwanza, and Mara. Entomological surveillance was conducted in 10 sprayed and 4 unsprayed sites to determine the impact of IRS on entomological indices related to malaria transmission risk.MethodsWHO cone bioassays were conducted monthly on interior house walls to determine residual efficacy of pirimiphos-methyl CS. Indoor CDC light traps with or without bottle rotator were hung next to protected sleepers indoors and also set outdoors (unbaited) as a proxy measure for indoor and outdoor biting rate and time of biting. Prokopack aspirators were used indoors to capture resting malaria vectors. A sub-sample of Anopheles was tested by PCR to determine species identity and ELISA for sporozoite rate.ResultsAnnual IRS with Actellic® 300CS from 2015 to 2017 was effective on sprayed walls for a mean of 7 months in cone bioassay. PCR of 2016 and 2017 samples showed vector populations were predominantly Anopheles arabiensis (58.1%, n = 4,403 IRS sites, 58%, n = 2,441 unsprayed sites). There was a greater proportion of Anopheles funestus sensu stricto in unsprayed sites (20.4%, n = 858) than in sprayed sites (7.9%, n = 595) and fewer Anopheles parensis (2%, n = 85 unsprayed, 7.8%, n = 591 sprayed). Biting peaks of Anopheles gambiae sensu lato (s.l.) followed periods of rainfall occurring between October and April, but were generally lower in sprayed sites than unsprayed. In most sprayed sites, An. gambiae s.l. indoor densities increased between January and February, i.e., 10–12 months after IRS. The predominant species An. arabiensis had a sporozoite rate in 2017 of 2.0% (95% CI 1.4–2.9) in unsprayed sites compared to 0.8% (95% CI 0.5–1.3) in sprayed sites (p = 0.003). Sporozoite rates were also lower for An. funestus collected in sprayed sites.ConclusionThis study contributes to the understanding of malaria vector species composition, behaviour and transmission risk following IRS around Lake Victoria and can be used to guide malaria vector control strategies in Tanzania.

Anopheles arabiensis and Anopheles funestus biting patterns in Dielmo, an area of low level exposure to malaria vectors

BackgroundIn Dielmo, Senegal, the widespread use of long-lasting insecticidal nets has decreased both the incidence of malaria and the density of the Anopheles population. However, persistent low-level malaria transmission may hamper efforts to eliminate the disease. Therefore, continuous monitoring of the vector population is needed in order to improve knowledge of Anopheles biting behaviour and to readjust control interventions.MethodsIn 2015, Anopheles were collected every month for a whole year and each specimen was identified using morphological and molecular techniques. The biting pattern of each species was analysed according to night (7 pm–7am) and morning (7am–11am) periods, the place of biting and the season. The ELISA CSP technique was used to assess the Plasmodium falciparum sporozoite rate to evaluate the entomological inoculation rate (EIR).ResultsAnopheles arabiensis and Anopheles funestus sensu stricto were found to be the main vectors biting humans. Overall, the biting rate was low, at 3.84bites per night (bpn) and 1.27 bites per morning (bpm), respectively (IRR = 3.04, CI [1.84–5.00], p < 0.001). The EIR was 2.51 and 5.03 infectious bites per year during the night and morning, respectively. During the night, the An. arabiensis and An. funestus biting rate was 1.81 bpn and 1.71 bpn, respectively (IRR = 0.95, CI [0.46–1.92], p = 0.88). During the morning, their density decreased to 0.51 bpm and 0.73 bpm for An. arabiensis and An. funestus, respectively (IRR = 1.47, CI [0.58–3.71], p = 0.41). During the night and the morning, no specific trend of indoor or outdoor biting was observed in the dry and rainy season for both vectors.ConclusionThis study highlighted low level Anopheles nocturnal and diurnal biting and the associated risk of malaria transmission. It showed also the influence of the season on the indoor and outdoor biting pattern, indicating that the human population could be exposed all year round to a low level of Anopheles bites. Control programmes should increase awareness of the use of bed nets throughout the year and promote the development and implementation of complimentary tools to target Anopheles biting shortly after dawn when people are still indoors and outside the bed nets.

Exploring the Mechanisms of Multiple Insecticide Resistance in a Highly Plasmodium-Infected Malaria Vector Anopheles funestus Sensu Stricto from Sahel of Northern Nigeria.

The Nigerian Government is scaling up the distribution of insecticide-treated bed nets for malaria control, but the lack of surveillance data, especially in the Sudan/Sahel region of the country, may hinder targeting priority populations. Here, the vectorial role and insecticide resistance profile of a population of a major malaria vector Anopheles funestus sensu stricto from Sahel of Nigeria was characterised. An. funestus s.s. was the only vector found, with a high human blood index (100%) and a biting rate of 5.3/person/night. High Plasmodium falciparum infection was discovered (sporozoite rate = 54.55%). The population is resistant to permethrin (mortality = 48.30%, LT50 = 65.76 min), deltamethrin, DDT (dichlorodiphenyltrichloroethane) and bendiocarb, with mortalities of 29.44%, 56.34% and 54.05%, respectively. Cone-bioassays established loss of efficacy of the pyrethroid-only long-lasting insecticidal nets (LLINs); but 100% recovery of susceptibility was obtained for piperonylbutoxide (PBO)-containing PermaNet®3.0. Synergist bioassays with PBO and diethyl maleate recovered susceptibility, implicating CYP450s (permethrin mortality = 78.73%, χ2 = 22.33, P < 0.0001) and GSTs (DDT mortality = 81.44%, χ2 = 19.12, P < 0.0001). A high frequency of 119F GSTe2 mutation (0.84) was observed (OR = 16, χ2 = 3.40, P = 0.05), suggesting the preeminent role of metabolic resistance. These findings highlight challenges associated with deployment of LLINs and indoor residual spraying (IRS) in Nigeria.

Risk Factors for Household Vector Abundance Using Indoor CDC Light Traps in a High Malaria Transmission Area of Northern Zambia.

Malaria transmission is dependent on the density and distribution of mosquito vectors, but drivers of vector abundance have not been adequately studied across a range of transmission settings. To inform intervention strategies for high-burden areas, further investigation is needed to identify predictors of vector abundance. Active household (HH) surveillance was conducted in Nchelenge district, Luapula Province, northern Zambia, a high-transmission setting with limited impact of malaria control. Between April 2012 and July 2017, mosquitoes were collected indoors during HH visits using CDC light traps. Demographic, environmental, and climatological correlates of vector abundance were identified using log-binomial regression models with robust standard errors. The primary malaria vectors in this setting were Anopheles funestus sensu stricto (s.s.) and Anopheles gambiae s.s. Anopheles funestus predominated in both seasons, with a peak in the dry season. Anopheles gambiae peaked at lower numbers in the rainy season. Environmental, climatic, and demographic factors were correlated with HH vector abundance. Higher vector counts were found in rural areas with low population density and among HHs close to roads and small streams. Vector counts were lower with increasing elevation and slope. Anopheles funestus was negatively associated with rainfall at lags of 2-6 weeks, and An. gambiae was positively associated with rainfall at lags of 3-10 weeks. Both vectors had varying relationships with temperature. These results suggest that malaria vector control in Nchelenge district should occur throughout the year, with an increased focus on dry-season transmission and rural areas.

Application of hydrolysis probe analysis to identify clade types of the malaria vector mosquito Anopheles funestus sensu stricto from Muheza, northeastern Tanzania.

A hydrolysis probe analysis (TaqMan assay) was used to study clade types in Anopheles funestus sensu stricto Giles, a major malaria vector in sub-Saharan Africa, with specimens collected from Muheza in Tanga, northeastern Tanzania. A total of 186 An. funestus specimens were analysed, revealing that 176 (94.6%) were of clade I and 10 (5.4%) of clade II. These findings extend the distribution of clade type II from southern Mozambique and northern Zambia to northeastern Tanzania. The technique used can also be of great value in assessing the role and contribution of these clade types in malaria transmission and insecticide resistance frequencies for An. funestus s.s.

Evidence of a multiple insecticide resistance in the malaria vector Anopheles funestus in South West Nigeria.

BackgroundKnowing the extent and spread of insecticide resistance in malaria vectors is vital to successfully manage insecticide resistance in Africa. This information in the main malaria vector, Anopheles funestus sensu stricto, is completely lacking in the most populous country in Africa, Nigeria. This study reports the insecticide susceptibility status and the molecular basis of resistance of An. funestus as well as its involvement in malaria transmission in Akaka-Remo, a farm settlement village in southwest Nigeria.Results Plasmodium infection analysis using TaqMan protocol coupled with a nested PCR revealed an infection rate of 8% in An. funestus s.s. from Akaka-Remo. WHO susceptibility tests showed this species has developed multiple resistance to insecticides in the study area. Anopheles funestus s.s. population in Akaka-Remo is highly resistant to organochlorines: dieldrin (8%) and DDT (10%). Resistance was also observed against pyrethroids: permethrin (68%) and deltamethrin (87%), and the carbamate bendiocarb (84%). Mortality rate with DDT slightly increased (from 10 to 30%, n = 45) after PBO pre-exposure indicating that cytochrome P450s play little role in DDT resistance while high mortalities were recorded after PBO pre-exposure with permethrin (from 68 to 100%, n = 70) and dieldrin (from 8 to 100%, n = 48) suggesting the implication of P450s in the observed permethrin and dieldrin resistance. High frequencies of resistant allele, 119F in F0 (77%) and F1 (80% in resistant and 72% in susceptible) populations with an odd ratio of 1.56 (P = 0.1859) show that L119F-GSTe2 mutation is almost fixed in the population. Genotyping of the A296S-RDL mutation in both F0 and F1 samples shows an association with dieldrin resistance with an odd ratio of 81 (P < 0.0001) (allelic frequency (R) = 76% for F0; for F1, 90 and 10% were observed in resistant and susceptible populations, respectively) as this mutation is not yet fixed in the population.ConclusionThe study reports multiple insecticide resistance in An. funestus from Akaka Remo. It is, therefore, necessary to pay more attention to this major malaria vector for effective malaria control in Nigeria.

Habitat Partitioning of Malaria Vectors in Nchelenge District, Zambia.

Nchelenge District in Luapula Province, northern Zambia, experiences holoendemic malaria despite implementation of vector control programs. The major Anopheles vectors that contribute to Plasmodium falciparum transmission in this area had not previously been well defined. Three collections performed during the 2012 wet and dry seasons and the 2013 wet season revealed Anopheles funestus sensu stricto and Anopheles gambiae sensu stricto as the main vectors, where 80-85% of each collection was composed of An. funestus Both vectors were found to be highly anthropophilic, and An. funestus has higher sporozoite infection rates (SIRs) and entomological inoculation rates (EIRs) year-round compared with An. gambiae: SIRs of 1.8-3.0% and 0-2.5%, respectively, and EIRs of 3.7-41.5 infectious bites per 6-month period (ib/p/6mo) and 0-5.9 ib/p/6mo, respectively. Spatial and temporal changes in each vector's dynamics and bionomics were also observed. Anopheles funestus was the predominant vector in the villages near Kenani Stream in both wet and dry seasons, whereas An. gambiae was found to be the main vector in areas near Lake Mweru during the wet season. The vector data illustrate the need for broader temporal and spatial sampling in Nchelenge and present unique opportunities to further our understanding of malarial transmission and implications for malarial control in high-risk areas.

Insecticide resistance, Host preference and Plasmodium falciparum parasite rates in Anopheles mosquitoes in Mwea and Ahero rice schemes

The ability of Anopheles mosquito to transmit malaria in nature is partly enhanced by; resistance of mosquito to insecticides, feeding preference for human host and infection by Plasmodium falciparum . An assessment was conducted to determine the status of these parameters in Anopheles populations in Mwea and Ahero rice irrigation schemes in Kenya. This was important in order to understand their potential influence on local malaria transmission. A total of 1,200 female Anopheles mosquitoes (gravid and blood fed) were sampled from both sites by indoor and outdoor methods. Anopheles samples identification to their respective species in the field was done using morphological features and taxonomic keys. In Mwea scheme, all the 600 Anopheles mosquitoes collected were An. gambiae s.l out of which 195 were gravid. In Ahero, 250 An. gambiae s.l (out of which 81 were gravid) and 350 An. funestus (out of which 181 were gravid) were collected. Gravid Anopheles mosquitoes were allowed to oviposit to give F 1 generations in the insectary. These F 1 , (four replicates of 25 mosquitoes per species per insecticide) were assessed for susceptibility to permethrin, deltamethrin, dichlorodiphenyltrichloroethane (DDT), bendiocarb or fenitrothion using standard WHO protocol. Susceptible An. gambiae s.s Kisumu strain (25 mosquitoes per the 100 test mosquitoes) was used as positive control. The 1,200 field samples were further identified to their respective species using rDNA-PCR using their legs and wings. Source (s) of blood meal in 405 An. gambiae s.l from Mwea, 169 An. gambiae s.l and 269 An. funestus from Ahero were determined using blood meal Elisa. The presence of Plasmodium falciparum Welch, 1897 in the salivary glands was assessed by sporozoite Elisa in all the field collected samples. All Anopheles mosquito samples from Mwea were Anopheles arabiensis Patton, 1905, while those from Ahero were a mixed species of Anopheles arabiensis (41.7%), Anopheles funestus sensu stricto Giles , 1900 (57%), Anopheles rivulorum Leesoni, 1935 (0.66%), Anopheles leesoni Evans, 1931 (0.3%) and Anopheles parensis Gillies, 1935 (0.3%). Mosquito samples from both study sites showed reduced susceptibility to the test insecticides. An. arabiensis mosquitoes from Mwea had a human blood meal index at 0.22 (n=405). P. falciparum circumsporozoite infection in An. arabiensis from Mwea were reported in Murinduko village at 1.5% (n=200). In Ahero, human blood meal indices were at 0.00 (n=169) and 0.17 (n=269) for An. arabiensis and An. funestus respectively. P. falciparum circumsporozoite infections in An. funestus sampled from Kamagaga and Wagai villages in Ahero were at 5% (n=147) and 2.2% (n=183) respectively.

Diversity of clades I and II within Anopheles funestus sensu stricto in southern Africa

Anopheles funestus sensu stricto is a major malaria vector in Africa. Recently, two clades were identified in this species based on mitochondrial DNA sequence data. We investigated differences between the two An. funestus clades based on nuclear genes and internal transcribed spacer 2 (ITS2) in the ribosomal DNA. Samples were collected from Malawi and Mozambique and were then used to sequence five nuclear genes (BU21, 9K1, 6Z3,BU021 and BU92) and the ITS2 region. The DNA sequence data was used to assess the diversity of the two An. funestus clades. We identified 12, 10, 24, 10, and 21 polymorphisms in the two An. funestus clades in the BU21, 9K1, 6Z3, BU021, and BU92 genes, respectively. No differences or polymorphisms were found in the ITS2 region between the two clades. This report assesses the diversity of the two An. funestus clades based on nuclear genes and the ITS2 region. Single nucleotide polymorphisms were found between the two clades of An. funestus. This could be explained by the existence of remaining introgression regions in the genomes of the two An. funestus clades and limited divergent regions. Further investigation is needed to determine the specific status of the two clades within An. funestus.

Efficacy of ACTELLIC 300 CS, pirimiphos methyl, for indoor residual spraying in areas of high vector resistance to pyrethroids and carbamates in Zambia.

The selection of insecticide resistance in malaria vectors has the potential to compromise any insecticide-based malaria vector control program. To ensure that transmission-interrupting tools remain effective, and their choice is evidence based, insecticide surveillance and monitoring is essential. This study assessed and compared the residual efficacy of an organophosphate insecticide pirimiphos methyl (ACTELLIC 300 CS, 0-2-diethylamino-6-methylpyrimidin-4-yl 0, 0-dimethylphosphorothioate) at 1 g/m2 and the pyrethroid deltamethrin (K-Othrine WG 250, (S)-alpha-cyano-3-phenoxybenzyl (1R, 3R)-3- (2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylate) at 20 mg/m2 for indoor residual spraying on cement and mud-rendered walls inside houses. Insecticide susceptibility profiles of local malaria vectors were also assessed using World Health Organization standard protocols. The residual efficacy of ACTELLIC 300 CS on cement and mud walls lasted for 5 mo on both surfaces, with complete mortality of Anopheles gambiae sensu stricto Giles (Kisumu strain) (Diptera: Culicidae) in cone assays. By 8 mo, the average residual effect of ACTELLIC 300 CS remained much better on cement walls than on mud walls but not significantly different from deltamethrin-treated cement walls. Anopheles funestus sensu stricto Giles was resistant to 0.05% deltamethrin and 0.01% bendiocarb but remained completely susceptible to 5% malathion and 4% dichlorodiphenyltrichloroethane. The duplicated P450 genes, CYP6P9a and CYP6P9b, were found to be highly overexpressed in deltamethrin-resistant An. funestus s.s as compared with bendiocarb-resistant individuals. Pirimiphos methyl CS is recommended for intra-domiciliary spraying for malaria control and could replace dichlorodiphenyltrichloroethane within the context of an insecticide resistance management strategy.

Detection of clade types (clades I and II) within Anopheles funestus sensu stricto by the hydrolysis probe analysis (Taqman assay)

BackgroundRecent studies presented two clades (clades I and II) within the major malaria vector, Anopheles funestus s.s. on the mitochondrial DNA. We describe a hydrolysis probe analysis (Taqman assay) method for the rapid identification of these two clades.FindingsA total of 53 An. funestus s.s. from Malawi and Mozambique were tested for detection of clade types using the hydrolysis probe analysis. Results were compared to DNA sequence analysis to verify the accuracy of the probes Taqman assay for this vector species. Analysis using the hydrolysis probe revealed that there were 21 individuals from Malawi and 13 individuals from Mozambique for clade I, and 19 individuals from Mozambique for clade II. The results were consistent with the results of DNA sequences. A field sample from northern Zambia revealed the presence of both clade types.ConclusionA diagnostic method using the hydrolysis probe analysis was developed to identify clade types within An. funestus s.s. This assay will be useful for screening clade types of field-collected An. funestus specimens accurately and efficiently in malaria vector research and control studies.

CHROMOSOMAL DIFFERENTIATION OF ANOPHELES FUNESTUS FROM LUANDA AND HUAMBO PROVINCES, WESTERN AND CENTRAL ANGOLA

The chromosomal polymorphism of Anopheles funestus sensu stricto from Angola was analyzed from indoor-resting samples collected in 11 peri-urban and rural sites of the Luanda and Huambo Provinces, which are > 450 km apart and have distinct eco-climatic conditions. Five polymorphic paracentric inversions were observed (scored chromatids range = 202 to 248): 2Ra, 2Rh, 3Ra, 3Rb, and 3La. Inversions 3Rb and 3La were highly polymorphic; the 2Ra and 3Ra arrangements were absent in Luanda. No significant departures from Hardy-Weinberg and linkage equilibria were found at the locality, commune, or province level (sites <or= 50 km from each other), indicating panmixia in each locale. Pooling the Luanda and Huambo samples produced a Wahlund effect, with significant levels of genetic differentiation suggestive of restrictions to gene flow due to geographic distance. The observation that differentiation was limited to inversions 2Ra and 3Ra can also be interpreted as divergent selection acting on these chromosomal regions between populations from the two provinces.