The Experts below are selected from a list of 4680 Experts worldwide ranked by ideXlab platform

Maureen Coetzee - One of the best experts on this subject based on the ideXlab platform.

  • molecular and physiological analysis of Anopheles Funestus swarms in nchelenge zambia
    Malaria Journal, 2018
    Co-Authors: Jacek W Zawada, Maureen Coetzee, R H Hunt, Yael Dahanmoss, Mbanga Muleba, Roch K Dabire, Hamid Maiga, Nelius Venter, Craig Davies, Lizette L Koekemoer
    Abstract:

    Anopheles Funestus has been recognized as a major malaria vector in Africa for over 100 years, but knowledge on many aspects of the biology of this species is still lacking. Anopheles Funestus, as with most other anophelines, mate through swarming. A key event that is crucial for the An. Funestus male to mate is genitalia rotation. This involves the 135° to 180° rotation of claspers, which are tipped with claws. This physical change then enables the male to grasp the female during copulation. The aim of this investigation was to molecularly characterize wild An. Funestus swarms from Zambia and examine the degree of genitalia rotation within the swarm. Anopheles Funestus swarms were collected from Nchelenge, northern Zambia, during dusk periods in May 2016. All the adults from the swarm were analysed morphologically and identified to species level using a multiplex PCR assay. Anopheles Funestus s.s. specimens were molecularly characterized by restriction fragment length polymorphism type and Clade type assays. The different stages of genitalia rotation were examined in the adult males. A total of six swarms were observed during the study period and between 6 and 26 mosquitoes were caught from each swarm. Species analysis revealed that 90% of the males from the swarms were An. Funestus s.s. MW-type, with 84% belonging to clade I compared to 14% clade II and 2% failed to amplify. Very few specimens (3.4%) were identified as Anopheles gambiae s.s. Eighty percent of the males from the swarm had complete genitalia rotation. This is the first time that An. Funestus swarms have been molecularly identified to species level. Anopheles Funestus swarms appear to be species-specific with no evidence of clade-type differentiation within these swarms. The An. Funestus swarms consist mainly of males with fully rotated genitalia, which strongly suggests that swarming behaviour is triggered primarily when males have matured.

  • Application of hydrolysis probe analysis to identify clade types of the malaria vector mosquito Anopheles Funestus sensu stricto from Muheza, northeastern Tanzania
    Medical and Veterinary Entomology, 2017
    Co-Authors: Eliningaya J Kweka, Nelius Venter, Emmanuel A. Mausa, Y. A. Derua, E. E. Kimaro, Maureen Coetzee
    Abstract:

    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.

  • characterization of the Anopheles Funestus group including Anopheles Funestus like from northern malawi
    Transactions of The Royal Society of Tropical Medicine and Hygiene, 2013
    Co-Authors: Lizette L Koekemoer, Maureen Coetzee, Samuel B Vezenegho, John Chiphwanya, R H Hunt, Chris Bass
    Abstract:

    Background Limited information is available on malaria vector composition, feeding habits and malaria transmission in northern Malawi. Evidence of mosquito species diversity in this area was established in 2009, when Anopheles Funestus-like, a new member of the An. Funestus group was described. Additional biological information is needed to identify this species and to understand its role in malaria transmission. Methods Anopheline mosquitoes were collected in northern Malawi and analyzed for Plasmodium species infection, blood meal source and susceptibility to insecticides. A new hydrolysis probe assay was designed to identify An. Funestus-like. Results Anopheles Funestus and An. rivulorum predominated in the indoor collections. Most An. Funestus-like were collected indoors, mainly fed on animals and were uninfected with P. falciparum. Anopheles Funestus showed insecticide resistance to deltamethrin and bendiocarb. A high-precision hydrolysis probe assay was successfully developed to identify An. Funestus-like. Discussion Four species in the An. Funestus group were collected in Karonga. Resistance to deltamethrin and bendiocarb was observed in An. Funestus and further investigation is needed on the insecticide resistance mechanisms. Anopheles Funestus-like, while collected indoors, is mainly zoophilic and most likely not a malaria vector. Accession numbers An. Funestus (GenBank accession no. KC771136), An. Funestus-like (GenBank accession no. KC771137), An. parensis GenBank accession no. KC771138) and An. vaneedeni GenBank accession no. KC771139).

  • Larval salinity tolerance of two members of the Anopheles Funestus group.
    Medical and Veterinary Entomology, 2013
    Co-Authors: Lizette L Koekemoer, Basil D Brooke, K. Waniwa, G. Nkosi, Aaron Mabuza, Maureen Coetzee
    Abstract:

    : The Anopheles Funestus group (Diptera: Culicidae) is one of the main species groups involved in malaria transmission in the Afrotropical regions. Basic research into this group has been limited because its members are eurygamic (they tend not to mate in confined spaces), which makes laboratory colonization difficult. Currently, only a few An. Funestus Giles colonies are available and no colonies of other members of the group have been established. As information on the larval biology of members of the An. Funestus group is limited, the present study aims to determine the effects of different salt concentrations on survival rates of the aquatic stages of two members of the An. Funestus group, Anopheles Funestus and Anopheles rivulorum Leeson. There were statistically significant negative trends in hatch rate and larval survival rate in An. Funestus with increasing salt concentrations, with no larvae surviving to pupae at concentrations that included >15% seawater. Anopheles rivulorum, by contrast, showed no significant trends in hatch rate or larval survival with increasing salt concentrations. This is the first report on salinity tolerance in An. rivulorum. A basic understanding of these variations in salinity tolerance provides vital information on the biology, ecology and colony rearing of members of the An. Funestus group.

  • detection of clade types clades i and ii within Anopheles Funestus sensu stricto by the hydrolysis probe analysis taqman assay
    Parasites & Vectors, 2013
    Co-Authors: Kwang Shik Choi, Maureen Coetzee, Lizette L Koekemoer
    Abstract:

    Background Recent 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.

Lizette L Koekemoer - One of the best experts on this subject based on the ideXlab platform.

  • molecular and physiological analysis of Anopheles Funestus swarms in nchelenge zambia
    Malaria Journal, 2018
    Co-Authors: Jacek W Zawada, Maureen Coetzee, R H Hunt, Yael Dahanmoss, Mbanga Muleba, Roch K Dabire, Hamid Maiga, Nelius Venter, Craig Davies, Lizette L Koekemoer
    Abstract:

    Anopheles Funestus has been recognized as a major malaria vector in Africa for over 100 years, but knowledge on many aspects of the biology of this species is still lacking. Anopheles Funestus, as with most other anophelines, mate through swarming. A key event that is crucial for the An. Funestus male to mate is genitalia rotation. This involves the 135° to 180° rotation of claspers, which are tipped with claws. This physical change then enables the male to grasp the female during copulation. The aim of this investigation was to molecularly characterize wild An. Funestus swarms from Zambia and examine the degree of genitalia rotation within the swarm. Anopheles Funestus swarms were collected from Nchelenge, northern Zambia, during dusk periods in May 2016. All the adults from the swarm were analysed morphologically and identified to species level using a multiplex PCR assay. Anopheles Funestus s.s. specimens were molecularly characterized by restriction fragment length polymorphism type and Clade type assays. The different stages of genitalia rotation were examined in the adult males. A total of six swarms were observed during the study period and between 6 and 26 mosquitoes were caught from each swarm. Species analysis revealed that 90% of the males from the swarms were An. Funestus s.s. MW-type, with 84% belonging to clade I compared to 14% clade II and 2% failed to amplify. Very few specimens (3.4%) were identified as Anopheles gambiae s.s. Eighty percent of the males from the swarm had complete genitalia rotation. This is the first time that An. Funestus swarms have been molecularly identified to species level. Anopheles Funestus swarms appear to be species-specific with no evidence of clade-type differentiation within these swarms. The An. Funestus swarms consist mainly of males with fully rotated genitalia, which strongly suggests that swarming behaviour is triggered primarily when males have matured.

  • Identification and characterization of microRNAs expressed in the African malaria vector Anopheles Funestus life stages using high throughput sequencing.
    Malaria Journal, 2016
    Co-Authors: Mushal Allam, Lizette L Koekemoer, Belinda L. Spillings, Hiba Abdalla, Darlington Mapiye, Alan Christoffels
    Abstract:

    Background Over the past several years, thousands of microRNAs (miRNAs) have been identified in the genomes of various insects through cloning and sequencing or even by computational prediction. However, the number of miRNAs identified in anopheline species is low and little is known about their role. The mosquito Anopheles Funestus is one of the dominant malaria vectors in Africa, which infects and kills millions of people every year. Therefore, small RNA molecules isolated from the four life stages (eggs, larvae, pupae and unfed adult females) of An. Funestus were sequenced using next generation sequencing technology.

  • Analysis of esterase enzyme activity in adults of the major malaria vector Anopheles Funestus.
    Parasites & Vectors, 2016
    Co-Authors: Yael Dahan-moss, Lizette L Koekemoer
    Abstract:

    Anopheles Funestus is a major vector of malaria in sub-Saharan Africa. In order to apply effective control measures against this vector, it is necessary to understand the underlying physiological factors that play a critical role in its development, reproduction, fertility and susceptibility to insecticides. One enzyme family involved in the above mentioned biological pathways is the esterases. The aim of this study was to analyse esterase activity levels at different ages during the life-span of adult Anopheles Funestus Giles in order to better understand the complex biological processes in this species. Isoenzyme electrophoresis (IEE) was used to examine the esterase activity in laboratory colonised An. Funestus adults aged between 2 h (h) and 30 days post eclosion as well as in wild An. Funestus adults aged between 2 h and 15 days post eclosion. Esterase activity was quantified by densitometry analysis of the IEE gels. Esterases were classified according to their activity inhibition by organic phosphates, eserine sulphate and sulphydryl reagents. Nine esterases IEE profiles were common to both the laboratory colonised and wild An. Funestus adults. These esterases were further divided into acetylesterases, arylesterases, carboxylesterases and acetylcholinesterase. The activity level of certain specific esterases was primarily influenced by age and/or gender. The information from this study contributes towards the general understanding of esterase enzyme activity variation in adults of a major malaria vector An. Funestus. This variation likely carries physiological and adaptive significance and may influence specific characteristics, such as reproductive fitness and insecticide resistance that are epidemiologically important.

  • Analysis of the genitalia rotation in the male Anopheles Funestus (Diptera: Culicidae).
    Acta Tropica, 2014
    Co-Authors: Yael Leah Dahan, Lizette L Koekemoer
    Abstract:

    Abstract Anopheles Funestus is a major malaria vector in Africa. Insecticide resistance has developed in populations of this species in several African countries, prompting the need to develop additional vector control methods such as the sterile insect technique (SIT). This technique requires an understanding of those underlying physiological events that lead to sexual maturity of An. Funestus males, the rotation of their genitalia in particular. The aim of this study was to qualitatively and quantitatively describe genital rotation in An. Funestus males as it is an essential function of sexual maturation. Genital rotation of all the males reached its final rotation stage (135–180° rotation) 36 h post emergence at 23 ± 1 °C in laboratory colonised An. Funestus males. These males had a comparable rotation rate to wild caught An. Funestus at the same temperature setting. A temperature change (either 18 ± 1 °C or 29 ± 1 °C versus 23 ± 1 °C) significantly influenced the genital rotation rate such that this rate increased with increasing temperature. This information enhances our knowledge of the An. Funestus male biology. This is important in terms of applying the sterile insect technique as the understanding and manipulation of the rate of sexual maturation in males has implications for the timing of sterile male release.

  • characterization of the Anopheles Funestus group including Anopheles Funestus like from northern malawi
    Transactions of The Royal Society of Tropical Medicine and Hygiene, 2013
    Co-Authors: Lizette L Koekemoer, Maureen Coetzee, Samuel B Vezenegho, John Chiphwanya, R H Hunt, Chris Bass
    Abstract:

    Background Limited information is available on malaria vector composition, feeding habits and malaria transmission in northern Malawi. Evidence of mosquito species diversity in this area was established in 2009, when Anopheles Funestus-like, a new member of the An. Funestus group was described. Additional biological information is needed to identify this species and to understand its role in malaria transmission. Methods Anopheline mosquitoes were collected in northern Malawi and analyzed for Plasmodium species infection, blood meal source and susceptibility to insecticides. A new hydrolysis probe assay was designed to identify An. Funestus-like. Results Anopheles Funestus and An. rivulorum predominated in the indoor collections. Most An. Funestus-like were collected indoors, mainly fed on animals and were uninfected with P. falciparum. Anopheles Funestus showed insecticide resistance to deltamethrin and bendiocarb. A high-precision hydrolysis probe assay was successfully developed to identify An. Funestus-like. Discussion Four species in the An. Funestus group were collected in Karonga. Resistance to deltamethrin and bendiocarb was observed in An. Funestus and further investigation is needed on the insecticide resistance mechanisms. Anopheles Funestus-like, while collected indoors, is mainly zoophilic and most likely not a malaria vector. Accession numbers An. Funestus (GenBank accession no. KC771136), An. Funestus-like (GenBank accession no. KC771137), An. parensis GenBank accession no. KC771138) and An. vaneedeni GenBank accession no. KC771139).

Charles S. Wondji - One of the best experts on this subject based on the ideXlab platform.

  • Implication of Anopheles Funestus in malaria transmission in the city of Yaoundé, Cameroon.
    Parasite, 2020
    Co-Authors: Landre Djamouko-djonkam, Diane Leslie Nkahe, Edmond Kopya, Abdou Talipouo, Carmene Sandra Ngadjeu, Patricia Doumbe-belisse, Roland Bamou, Parfait Awono-ambene, Timoléon Tchuinkam, Charles S. Wondji
    Abstract:

    The contribution of Anopheles Funestus to malaria transmission in the urban environment is still not well documented. The present study assesses the implication of An. Funestus in malaria transmission in two districts, Nsam and Mendong, in the city of Yaounde. Adult mosquitoes were collected using Centers for Disease Control and Prevention miniature light traps (CDC-LT) and human landing catches from April 2017 to March 2018 and were identified morphologically to the species level. Those belonging to the Anopheles gambiae complex and to the Anopheles Funestus group were further processed by PCR to identify members of each complex/group. Anopheline mosquitoes were analysed to determine their infection status using an enzyme-linked immunosorbent assay. Bioassays were conducted with 2–5-day-old female Anopheles Funestus and An. gambiae s.l. to determine their susceptibility to permethrin, deltamethrin and dichlorodiphenyltrichloroethane (DDT). Six anopheline species were collected in the peri-urban district of Mendong: Anopheles gambiae , An. coluzzii , An. Funestus , An. leesoni , An. ziemanni and An. marshallii ; only four out of the six were recorded in Nsam. Of the two members of the Anopheles gambiae complex collected, An. coluzzii was the most prevalent. Anopheles coluzzii was the most abundant species in Nsam, while An. Funestus was the most abundant in Mendong. Both Anopheles Funestus and An. gambiae s.l. were found to be infected with human Plasmodium at both sites, and both were found to be resistant to DDT, permethrin, and deltamethrin. This study confirms the participation of An. Funestus in malaria transmission in Yaounde and highlights the need to also target this species for sustainable control of malaria transmission.

  • Exploring the impact of glutathione S-transferase (GST)-based metabolic resistance to insecticide on vector competence of Anopheles Funestus for Plasmodium falciparum
    Wellcome open research, 2019
    Co-Authors: Edmond Kopya, Helen Irving, Charles S. Wondji
    Abstract:

    Background: Malaria control heavily relies on insecticide-based interventions against mosquito vectors. However, the increasing spread of insecticide resistance is a major threat. The extent to which such resistance, notably metabolic resistance, influences the development of the Plasmodium parasite and its impact on overall malaria transmission remains poorly characterized. Here, we investigated whether glutathione S-transferase-based resistance could influence Plasmodium falciparum development in Anopheles Funestus . Methods: Anopheles Funestus females were infected with P. falciparum gametocytes and midguts were dissected at day 7 post infection for detection/quantification of oocysts. Infection parameters were compared between individuals with different L119F-GSTe2 genotypes, and the polymorphism of the GSTe2 gene was analyzed in infected and uninfected mosquito groups. Results: Overall, 403 An. Funestus  mosquitoes were dissected and genotyped. The frequency of the L119F-GSTe2 resistance allele was significantly higher in non-infected (55.88%) compared to infected (40.99%) mosquitoes (Fisher's exact test, P

  • Molecular basis of permethrin and DDT resistance in an Anopheles Funestus population from Benin.
    Parasites & Vectors, 2018
    Co-Authors: Genevieve M Tchigossou, Rousseau Djouaka, Jacob M Riveron, Akadiri Yessoufou, Romaric Akoton, Helen Irving, Kabirou Moutairou, Seun Michael Atoyebi, Charles S. Wondji
    Abstract:

    Insecticide resistance in Anopheles mosquitoes is threatening the success of malaria control programmes. In order to implement suitable insecticide resistance management strategies, it is necessary to understand the underlying mechanisms involved. To achieve this, the molecular basis of permethrin and DDT resistance in the principal malaria vector, Anopheles Funestus from inland Benin (Kpome), was investigated. Here, using a microarray-based genome-wide transcription and qRT-PCR analysis, we showed that metabolic resistance mechanisms through over-expression of cytochrome P450 and glutathione S-transferase genes (GSTs) are a major contributor to DDT and permethrin resistance in Anopheles Funestus from Kpome. The GSTe2 gene was the most upregulated detoxification gene in both DDT- [fold-change (FC: 16.0)] and permethrin-resistant (FC: 18.1) mosquitoes suggesting that upregulation of this gene could contribute to DDT resistance and cross-resistance to permethrin. CYP6P9a and CYP6P9b genes that have been previously associated with pyrethroid resistance were also significantly overexpressed with FC 5.4 and 4.8, respectively, in a permethrin resistant population. Noticeably, the GSTs, GSTd1-5 and GSTd3, were more upregulated in DDT-resistant than in permethrin-resistant Anopheles Funestus suggesting these genes are more implicated in DDT resistance. The absence of the L1014F or L1014S kdr mutations in the voltage-gated sodium channel gene coupled with the lack of directional selection at the gene further supported that knockdown resistance plays little role in this resistance. The major role played by metabolic resistance to pyrethroids in this An. Funestus population in Benin suggests that using novel control tools combining the P450 synergist piperonyl butoxide (PBO), such as PBO-based bednets, could help manage the growing pyrethroid resistance in this malaria vector in Benin.

  • investigating knockdown resistance kdr mechanism against pyrethroids ddt in the malaria vector Anopheles Funestus across africa
    BMC Genetics, 2017
    Co-Authors: Helen Irving, Charles S. Wondji
    Abstract:

    Understanding the molecular basis of insecticide resistance is key to improve the surveillance and monitoring of malaria vector populations under control. In the major malaria vector Anopheles Funestus, little is currently known about the role of the knockdown resistance (kdr) mechanism. Here, we investigated the presence and contribution of knockdown resistance (kdr) to pyrethroids/DDT resistance observed in Anopheles Funestus across Africa. Pyrosequencing genotyping and sequencing of the voltage gated sodium channel (VGSC) gene did not detect the common L1014F mutation in field collected An. Funestus across Africa. Amplification and cloning of the full-length of the sodium channel gene in pyrethroid resistant mosquitoes revealed evidences of alternative splicing events with three transcripts of 2092, 2061 and 2117 amino acids (93% average similarity to An. gambiae). Several amino acid changes were detected close to the domain II of the protein such as L928R, F938 W, I939S, L802S and T1008 M. However, all these mutations are found at low frequency and their role in pyrethroid resistance could not be established. The presence of the exclusive alternative splicing at exon 19 was not associated with resistance phenotype. Analysis of patterns of genetic diversity of the VGSC gene revealed a high polymorphism level of this gene across Africa with no evidence of directional selection suggesting a limited role for knockdown resistance in pyrethroid resistance in An. Funestus. Patterns of genetic differentiation correlate with previous observations of the existence of barriers to gene flow Africa-wide with southern population significantly differentiated from other regions. Despite an apparent limited role of knockdown resistance in An. Funestus, it is necessary to continue to monitor the contribution of the mutations detected here as increasing selection from insecticide-based interventions may change the dynamic in field populations as previously observed in other vectors.

  • Investigating knockdown resistance (kdr) mechanism against pyrethroids/DDT in the malaria vector Anopheles Funestus across Africa.
    BMC Genetics, 2017
    Co-Authors: Helen Irving, Charles S. Wondji
    Abstract:

    Understanding the molecular basis of insecticide resistance is key to improve the surveillance and monitoring of malaria vector populations under control. In the major malaria vector Anopheles Funestus, little is currently known about the role of the knockdown resistance (kdr) mechanism. Here, we investigated the presence and contribution of knockdown resistance (kdr) to pyrethroids/DDT resistance observed in Anopheles Funestus across Africa. Pyrosequencing genotyping and sequencing of the voltage gated sodium channel (VGSC) gene did not detect the common L1014F mutation in field collected An. Funestus across Africa. Amplification and cloning of the full-length of the sodium channel gene in pyrethroid resistant mosquitoes revealed evidences of alternative splicing events with three transcripts of 2092, 2061 and 2117 amino acids (93% average similarity to An. gambiae). Several amino acid changes were detected close to the domain II of the protein such as L928R, F938 W, I939S, L802S and T1008 M. However, all these mutations are found at low frequency and their role in pyrethroid resistance could not be established. The presence of the exclusive alternative splicing at exon 19 was not associated with resistance phenotype. Analysis of patterns of genetic diversity of the VGSC gene revealed a high polymorphism level of this gene across Africa with no evidence of directional selection suggesting a limited role for knockdown resistance in pyrethroid resistance in An. Funestus. Patterns of genetic differentiation correlate with previous observations of the existence of barriers to gene flow Africa-wide with southern population significantly differentiated from other regions. Despite an apparent limited role of knockdown resistance in An. Funestus, it is necessary to continue to monitor the contribution of the mutations detected here as increasing selection from insecticide-based interventions may change the dynamic in field populations as previously observed in other vectors.

R H Hunt - One of the best experts on this subject based on the ideXlab platform.

  • molecular and physiological analysis of Anopheles Funestus swarms in nchelenge zambia
    Malaria Journal, 2018
    Co-Authors: Jacek W Zawada, Maureen Coetzee, R H Hunt, Yael Dahanmoss, Mbanga Muleba, Roch K Dabire, Hamid Maiga, Nelius Venter, Craig Davies, Lizette L Koekemoer
    Abstract:

    Anopheles Funestus has been recognized as a major malaria vector in Africa for over 100 years, but knowledge on many aspects of the biology of this species is still lacking. Anopheles Funestus, as with most other anophelines, mate through swarming. A key event that is crucial for the An. Funestus male to mate is genitalia rotation. This involves the 135° to 180° rotation of claspers, which are tipped with claws. This physical change then enables the male to grasp the female during copulation. The aim of this investigation was to molecularly characterize wild An. Funestus swarms from Zambia and examine the degree of genitalia rotation within the swarm. Anopheles Funestus swarms were collected from Nchelenge, northern Zambia, during dusk periods in May 2016. All the adults from the swarm were analysed morphologically and identified to species level using a multiplex PCR assay. Anopheles Funestus s.s. specimens were molecularly characterized by restriction fragment length polymorphism type and Clade type assays. The different stages of genitalia rotation were examined in the adult males. A total of six swarms were observed during the study period and between 6 and 26 mosquitoes were caught from each swarm. Species analysis revealed that 90% of the males from the swarms were An. Funestus s.s. MW-type, with 84% belonging to clade I compared to 14% clade II and 2% failed to amplify. Very few specimens (3.4%) were identified as Anopheles gambiae s.s. Eighty percent of the males from the swarm had complete genitalia rotation. This is the first time that An. Funestus swarms have been molecularly identified to species level. Anopheles Funestus swarms appear to be species-specific with no evidence of clade-type differentiation within these swarms. The An. Funestus swarms consist mainly of males with fully rotated genitalia, which strongly suggests that swarming behaviour is triggered primarily when males have matured.

  • characterization of the Anopheles Funestus group including Anopheles Funestus like from northern malawi
    Transactions of The Royal Society of Tropical Medicine and Hygiene, 2013
    Co-Authors: Lizette L Koekemoer, Maureen Coetzee, Samuel B Vezenegho, John Chiphwanya, R H Hunt, Chris Bass
    Abstract:

    Background Limited information is available on malaria vector composition, feeding habits and malaria transmission in northern Malawi. Evidence of mosquito species diversity in this area was established in 2009, when Anopheles Funestus-like, a new member of the An. Funestus group was described. Additional biological information is needed to identify this species and to understand its role in malaria transmission. Methods Anopheline mosquitoes were collected in northern Malawi and analyzed for Plasmodium species infection, blood meal source and susceptibility to insecticides. A new hydrolysis probe assay was designed to identify An. Funestus-like. Results Anopheles Funestus and An. rivulorum predominated in the indoor collections. Most An. Funestus-like were collected indoors, mainly fed on animals and were uninfected with P. falciparum. Anopheles Funestus showed insecticide resistance to deltamethrin and bendiocarb. A high-precision hydrolysis probe assay was successfully developed to identify An. Funestus-like. Discussion Four species in the An. Funestus group were collected in Karonga. Resistance to deltamethrin and bendiocarb was observed in An. Funestus and further investigation is needed on the insecticide resistance mechanisms. Anopheles Funestus-like, while collected indoors, is mainly zoophilic and most likely not a malaria vector. Accession numbers An. Funestus (GenBank accession no. KC771136), An. Funestus-like (GenBank accession no. KC771137), An. parensis GenBank accession no. KC771138) and An. vaneedeni GenBank accession no. KC771139).

  • vectorial status and insecticide resistance of Anopheles Funestus from a sugar estate in southern mozambique
    Parasites & Vectors, 2011
    Co-Authors: Maureen Coetzee, R H Hunt, Graham R Kloke, Eduardo Nhamahanga
    Abstract:

    Background The dual problems of rising insecticide resistance in the malaria vectors and increasing human malaria cases since 2001 in southern Mozambique are cause for serious concern. The selection of insecticides for use in indoor residual spraying (IRS) programmes is highly dependent on the extent to which local mosquitoes are susceptible to the approved classes of insecticides. The insecticide resistance status and role in malaria transmission of Anopheles Funestus was evaluated at the Maragra Sugar Estate in southern Mozambique where an IRS vector control programme has been in operation for seven years using the carbamate insecticide bendiocarb.

  • a new species concealed by Anopheles Funestus giles a major malaria vector in africa
    American Journal of Tropical Medicine and Hygiene, 2009
    Co-Authors: Belinda L. Spillings, Lizette L Koekemoer, Basil D Brooke, Maureen Coetzee, John Chiphwanya, R H Hunt
    Abstract:

    The major malaria vector Anopheles Funestus belongs to a group of morphologically similar species that are commonly distinguished from one another through the use of chromosomal and molecular techniques. Indoor resting collections of mosquitoes from Malawi were initially identified as An. Funestus by morphology, but failed to have this confirmed by the species-specific polymerase chain reaction assay. Sequence analysis of the internal transcribed spacer region 2 identified variations within the An. Funestus-specific primer binding site and showed a sequence variation of 4.5% compared with An. Funestus. Domain 3 analysis showed sequence variation of 1.5% from An. Funestus. Cytogenetic analysis of the polytene chromosome banding arrangements showed that the specimens were homosequential with An. Funestus, with fixed inverted arrangements of the 3a, 3b, and 5a inversions commonly polymorphic in An. Funestus. The chromosomes of hybrid females showed levels of asynapsis typical of inter-species crosses. These molecular and cytogenetic observations support the conclusion that this Malawi population is a new species and it has provisionally been named An. Funestus-like.

  • characterisation of ddt pyrethroid and carbamate resistance in Anopheles Funestus from obuasi ghana
    Transactions of The Royal Society of Tropical Medicine and Hygiene, 2008
    Co-Authors: Lizette L Koekemoer, Basil D Brooke, R H Hunt, Patricia N Okoye, Maureen Coetzee
    Abstract:

    Summary Indoor-resting anopheline mosquitoes were collected from Obuasi, Ghana, and were identified morphologically and by PCR as Anopheles Funestus Giles. Wild-caught females were induced to lay eggs. Samples of F1 progeny from each family were divided into cohorts and were either exposed to DDT and permethrin or were stored for biochemical analysis. Bioassay data by family show evidence of DDT and pyrethroid resistance in the parent A. Funestus population. The sodium channel gene of DDT survivors and DDT-susceptible individuals was PCR amplified and sequenced to determine whether any kdr-type mutations were present. Molecular analysis of the IIS5–IIS6 segment of the sodium channel gene gave no indication of any kdr-type mutations associated with resistance phenotypes. Biochemical analysis suggests that DDT and pyrethroid resistance may be metabolically mediated, although there were no clear correlations between enzyme levels/activities and insecticide resistance across families. Furthermore, an altered acetylcholinesterase conferring carbamate resistance was evident. These results can be used to plan an effective malaria control strategy in the Obuasi region.

Basil D Brooke - One of the best experts on this subject based on the ideXlab platform.

  • Larval salinity tolerance of two members of the Anopheles Funestus group.
    Medical and Veterinary Entomology, 2013
    Co-Authors: Lizette L Koekemoer, Basil D Brooke, K. Waniwa, G. Nkosi, Aaron Mabuza, Maureen Coetzee
    Abstract:

    : The Anopheles Funestus group (Diptera: Culicidae) is one of the main species groups involved in malaria transmission in the Afrotropical regions. Basic research into this group has been limited because its members are eurygamic (they tend not to mate in confined spaces), which makes laboratory colonization difficult. Currently, only a few An. Funestus Giles colonies are available and no colonies of other members of the group have been established. As information on the larval biology of members of the An. Funestus group is limited, the present study aims to determine the effects of different salt concentrations on survival rates of the aquatic stages of two members of the An. Funestus group, Anopheles Funestus and Anopheles rivulorum Leeson. There were statistically significant negative trends in hatch rate and larval survival rate in An. Funestus with increasing salt concentrations, with no larvae surviving to pupae at concentrations that included >15% seawater. Anopheles rivulorum, by contrast, showed no significant trends in hatch rate or larval survival with increasing salt concentrations. This is the first report on salinity tolerance in An. rivulorum. A basic understanding of these variations in salinity tolerance provides vital information on the biology, ecology and colony rearing of members of the An. Funestus group.

  • age related pyrethroid resistance is not a function of p450 gene expression in the major african malaria vector Anopheles Funestus diptera culicidae
    Genetics and Molecular Research, 2011
    Co-Authors: Riann N Christian, Basil D Brooke, Maureen Coetzee, Tonderayi Matambo, B L Spillings, Lizette L Koekemoer
    Abstract:

    Anopheles Funestus is a major vector of malaria in most of the African region. Resistance to pyrethroid and carbamate insecticides has been recorded in populations of this species in South Africa and Mozambique. The P450 gene, CYP6P9, has been shown to be highly transcribed in a permethrin (pyrethroid)-resistant laboratory strain, FUMOZ-R, originating from southern Mozambique. We examined the relationship between pyrethroid resistance and gene transcription levels of two closely related genes, CYP6P9 and CYP6P13, in FUMOZ-R. Levels of resistance to 0.75% permethrin were determined based on standard WHO insecticide susceptibility assays using females and males of different ages, ranging from 3 to 30 days old. The transcription

  • The Effect of Entomopathogenic Fungus Infection on Female Fecundity of the Major Malaria Vector, Anopheles Funestus
    African Entomology, 2011
    Co-Authors: Joel C Mouatcho, Lizette L Koekemoer, Maureen Coetzee, Basil D Brooke
    Abstract:

    Anopheles Funestus is a major vector of malaria in sub-Saharan Africa. It is amenable to control by indoor residual insecticide spraying and insecticide-treated bed nets owing to strong endophagic and endophilic tendencies (Gillies & De Meillon 1968; Sinka et al. 2010). However, the emergence of resistance to insecticides in several populations (Hargreaves et al. 2000; Casimiro et al. 2006; Coetzee et al. 2006; Morgan et al. 2010) necessitates the development of tailored resistance management strategies that could include the use of insecticides in conjunction with biological components.

  • Cuticle thickening associated with pyrethroid resistance in the major malaria vector Anopheles Funestus
    Parasites & Vectors, 2010
    Co-Authors: O. R. Wood, Sarah Hanrahan, Lizette L Koekemoer, Maureen Coetzee, Basil D Brooke
    Abstract:

    Background Malaria in South Africa is primarily transmitted by Anopheles Funestus Giles. Resistance to pyrethroid insecticides in An. Funestus in northern Kwazulu/Natal, South Africa, and in neighbouring areas of southern Mozambique enabled populations of this species to increase their ranges into areas where pyrethroids were being exclusively used for malaria control. Pyrethroid resistance in southern African An. Funestus is primarily conferred by monooxygenase enzyme metabolism. However, selection for this resistance mechanism is likely to have occurred in conjunction with other factors that improve production of the resistance phenotype. A strong candidate is cuticle thickening. This is because thicker cuticles lead to slower rates of insecticide absorption, which is likely to increase the efficiency of metabolic detoxification.

  • evaluation of the pyrrole insecticide chlorfenapyr against pyrethroid resistant and susceptible Anopheles Funestus diptera culicidae
    Tropical Medicine & International Health, 2009
    Co-Authors: Shune V Oliver, O. R. Wood, Maureen Coetzee, Maria L Kaiser, Mark Rowland, Basil D Brooke
    Abstract:

    Summary Objective  To evaluate the pyrrole insecticide chlorfenapyr, which has a novel non-neurotoxic mode of action and is a promising alternative to conventional adulticides, against Anopheles Funestus. Method  The toxicity of a range of concentrations of chlorfenapyr against pyrethroid resistant and susceptible laboratory reared southern African An. Funestus was assessed using standard WHO protocols and analysed using probit analysis. Results  The pyrethroid resistant strain showed consistently higher LD50 and LD95 values compared to the susceptible strain, but these differences were not statistically significant and the magnitude was twofold at most. The LD50 values recorded for An. Funestus are approximately three-fold higher than those reported elsewhere for other species of anopheline. Conclusions  Monooxygenase based pyrethroid resistance in An. Funestus does not influence the toxic effect of chlorfenapyr. It is unlikely that such a small decrease in susceptibility of An. Funestus to chlorfenapyr relative to other anophelines would have any operational implications. Chlorfenapyr is an important addition to insecticides available for malaria vector control, and could be used as a resistance management tool to either circumvent or slow the development of resistance. Objectif:  Evaluer le chlorofenapyr, insecticide pyrrole, qui possede un nouveau mecanisme d’action neurotoxique et est une alternative prometteuse aux adulticides classiques, contre Anopheles Funestus. Methode:  La toxicite d’une plage de concentrations de chlorofenapyr contre des souches d’An. Funestus d’Afrique australe elevees au laboratoire, resistantes et sensibles pyrethroides, a eteevaluee en utilisant des protocoles standards de l’OMS et analysees en utilisant l’analyse probit. Resultats:  La souche resistante aux pyrethroides a montre des valeurs de DL50 et LD95 toujours plus elevee comparea la souche sensible, mais ces differences n’etaient pas statistiquement significatives et la magnitude etait de deux fois au maximum. Les valeurs de DL50 enregistrees pour A. Funestus sont environ trois fois plus elevees que celles rapportees ailleurs pour d’autres especes d’Anopheles. Conclusions:  La resistance de An. Funestus aux pyrethroides basee sur la monooxygenase n’influence pas l’effet toxique du chlorofenapyr. Il est peu probable que cette legere diminution de la sensibilite d’An. Funestus au chlorofenapyr comparea d’autres Anopheles ait des implications operationnelles. Le chlorfenapyr est un important insecticide additionnel pour la lutte contre le vecteur de la malaria et pourrait etre utilise comme un outil dans la gestion de la resistance pour contourner ou ralentir le developpement de la resistance. Objetivo:  Evaluar el insecticida pirrol clorfenapyr, el cual tiene un modelo de accion novedoso, no-neurotoxico, y es una alternativa prometedora a los adulticidas frente a Anopheles Funestus. Metodo:  La toxicidad de una rango de concentraciones de clorfenapyr frente a cepas de laboratorio, del sur de Africa, de An. Funestus susceptibles y resistentes a piretroides se evaluo utilizando protocolos estandar de la OMS y se analizo utilizando la metodologia probit. Resultados:  Las cepas resistentes a piretroides mostraron de forma consistente valores LD50 y LD95 mas altos que la cepa susceptible, pero estas diferencias no eran estadisticamente significativas y la magnitud era como mucho del doble. Los valores LD50 para An. Funestus eran aproximadamente tres veces mas que aquellos reportados en otros lugares para otras especies anofelinas. Conclusiones:  La resistencia a piretroides basada en monooxigenasa en An. Funestus no tiene influencia en el efecto toxico del clorfenapyr. Es poco probable que una disminucion tan pequena en la susceptibilidad de An. Funestus al clorfenapyr con relacion a otros anofelinos tenga implicaciones operativas. El clorfenapyr es una adicion importante a los insecticidas ya disponibles para el control de los vectores de malaria, y podria utilizarse como una herramienta para el manejo de resistencias, bien para sortear o para retrasar el desarrollo de resistencias.