Anopheline Mosquito Species Composition, Kdr Mutation Frequency, and Parasite Infectivity Status in Northern Tanzania

2020 ◽  
Vol 57 (3) ◽  
pp. 933-938 ◽  
Author(s):  
Eliningaya J Kweka ◽  
Humphrey D Mazigo ◽  
Lucile J Lyaruu ◽  
Emmanuel A Mausa ◽  
Nelius Venter ◽  
...  
Keyword(s):  
Species Composition ◽  
Malaria Transmission ◽  
Malaria Vector ◽  
Mosquito Species ◽  
Malaria Prevalence ◽  
Vector Species ◽  
Anopheline Mosquito ◽  
Larval Stages ◽  
Northern Tanzania ◽  
Homozygous Resistant

Abstract The scaling-up of malaria control interventions in northern Tanzania has resulted in a decline in malaria prevalence and vector species composition. Despite this achievement, residual malaria transmission remains a concern in the area. The main aim of this study was to investigate malaria vector species composition, parasite infectivity rates, and the presence of insecticide knockdown resistance (kdr) mutations in three sites that have experienced a significant decline in malaria in northern Tanzania. Adult mosquitoes were sampled using light traps in houses and hand-aspirators in cowsheds, whereas the standard dipping method was used for sampling mosquito larvae. Adult mosquitoes identified as Anopheles gambiae s.l. and An. funestus s.l. and larval stages III and IV of An. gambiae s.l. were stored in absolute ethanol for further laboratory molecular identification. The identified species in the An. gambiae complex were An. gambiae s.s., An. merus, An. quadriannulatus, and An. arabiensis, whereas the An. funestus group comprised An. funestus s.s., An. rivulorum, and An. leesoni. For An. gambiae s.s. analyzed from Zeneth, 47.6% were kdr-East homozygous susceptible, 35.7% kdr-East heterozygous resistant, 9.6% kdr-East homozygous resistant, and 7.1% undefined, whereas specimens from Kwakibuyu were 45.5% kdr-East homozygous susceptible, 32.7% kdr-East heterozygous resistant, 16.3% kdr-East homozygous resistant, and 5.5% undefined. There were no kdr-West alleles identified from any specimen. The overall malaria parasite infectivity rate was 0.75%. No infections were found in Moshi. The findings indicate that populations of the major malaria vector mosquitoes are still present in the study area, with An. funestus taking a lead in malaria transmission.

scholarly journals Impact of sugarcane irrigation on malaria vector Anopheles mosquito fauna, abundance and seasonality in Arjo-Didessa, Ethiopia

2020 ◽  
Author(s):  
Assalif Demissew Shifera ◽  
Dawit Hawaria ◽  
Solomon Kibret ◽  
Abebe Animut ◽  
Arega Tsegaye ◽  
...  
Keyword(s):  
Species Composition ◽  
Malaria Vector ◽  
Mosquito Species ◽  
Malaria Vectors ◽  
Anopheline Mosquito ◽  
Chi Square ◽  
Anopheles Species ◽  
Mosquito Abundance ◽  
Anopheles Mosquitoes ◽  
The Impact

Abstract Background: Although irrigation activities are increasing in Ethiopia, limited studies evaluated their impact on malaria vector mosquito composition, abundance and seasonality. This study aimed at evaluating the impact of sugarcane irrigation on species composition, abundance and seasonality of malaria vectors. Methods : Adult Anopheles mosquitoes were collected using CDC light traps from three irrigated and three non-irrigated clusters in and around Arjo-Didessa sugarcane irrigation scheme in southwestern Ethiopia. Mosquito collections were conducted in four seasons: two wet and two dry, in 2018 and 2019. Mosquito species composition, abundance and seasonality were compared between irrigated and non-irrigated clusters. Anopheles mosquitoes were identified to species using morphological keys and An. gambiae s.l to sibling species using PCR. Chi-square was used to analyze the association between Anopheles species occurrence and environmental and seasonal parameters. Results: Overall, 2,108 female Anopheles mosquitoes comprising of six species were collected. Of these, 92.7% (n=1954) were from irrigated clusters and 7.3% (n=154) from the non-irrigated. An. gambiae s.l was the most abundant (67.3%) followed by An. coustani complex (25.3 %) and An. pharoensis (5.7%). PCR based identification revealed that 74.7% (n=168) of the An. gambiae s.l were An. arabiensis and 22.7% (n=51) An. amharicus . Density of An. gambiae s.l. (both indoor and outdoor) was higher in irrigated than non-irrigated clusters. The overall anopheline mosquito abundance during the wet seasons (87.2%; n=1837) was higher than the dry seasons (12.8%; n=271). Conclusion : The ongoing sugarcane irrigation activities in Arjo-Didessa created conditions suitable for increased malaria transmitting Anopheles species diversity and abundance. This in turn could drive malaria transmission in Arjo-Didessa and its environs in both dry and wet seasons. Thus, currently practiced malaria vector interventions need to be strengthened and consider larval source management to reduce vector abundance in the irrigated areas. Key Words: Malaria, Irrigation, Anopheles mosquitoes, vector density, An. amharicus , Ethiopia

scholarly journals Impact of sugarcane irrigation on malaria vector Anopheles mosquito fauna, abundance and seasonality in Arjo-Didessa, Ethiopia

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Assalif Demissew ◽  
Dawit Hawaria ◽  
Solomon Kibret ◽  
Abebe Animut ◽  
Arega Tsegaye ◽  
...  
Keyword(s):  
Species Composition ◽  
Malaria Vector ◽  
Mosquito Species ◽  
Molecular Techniques ◽  
Malaria Vectors ◽  
Anopheline Mosquito ◽  
Chi Square ◽  
Mosquito Abundance ◽  
Southwestern Ethiopia ◽  
The Impact

Abstract Background Despite extensive irrigation development in Ethiopia, limited studies assessed the impact of irrigation on malaria vector mosquito composition, abundance and seasonality. This study aimed to evaluate the impact of sugarcane irrigation on species composition, abundance and seasonality of malaria vectors. Methods Adult Anopheles mosquitoes were collected using CDC light traps from three irrigated and three non-irrigated clusters in and around Arjo-Didessa sugarcane irrigation scheme in southwestern Ethiopia. Mosquitoes were surveyed in four seasons: two wet and two dry, in 2018 and 2019. Mosquito species composition, abundance and seasonality were compared between irrigated and non-irrigated clusters. Anopheles mosquitoes were sorted out to species using morphological keys and molecular techniques. Chi square was used to test the relationships between Anopheles species occurrence, and environmental and seasonal parameters. Results Overall, 2108 female Anopheles mosquitoes comprising of six species were collected. Of these, 92.7% (n = 1954) were from irrigated clusters and 7.3% (n = 154) from the non-irrigated. The Anopheles gambiae complex was the most abundant (67.3%) followed by Anopheles coustani complex (25.3%) and Anopheles pharoensis (5.7%). PCR-based identification revealed that 74.7% (n = 168) of the An. gambiae complex were Anopheles arabiensis and 22.7% (n = 51) Anopheles amharicus. The density of An. gambiae complex (both indoor and outdoor) was higher in irrigated than non-irrigated clusters. The overall anopheline mosquito abundance during the wet seasons (87.2%; n = 1837) was higher than the dry seasons (12.8%; n = 271). Conclusion The ongoing sugarcane irrigation activities in Arjo-Didessa created conditions suitable for malaria transmitting Anopheles species diversity and abundance. This could drive malaria transmission in Arjo-Didessa and its environs in both dry and wet seasons. Currently practiced malaria vector interventions need to be strengthened by including larval source management to reduce vector abundance in the irrigated areas.

scholarly journals Malaria vector species composition and relative abundance in Mutare and Mutasa districts, Zimbabwe

2015 ◽  
Vol 47 (3) ◽  
pp. 79 ◽  
Author(s):  
S. Sande ◽  
M. Zimba ◽  
P. Chinwada ◽  
H.T. Masendu ◽  
A. Makuwaza
Keyword(s):  
Species Composition ◽  
Relative Abundance ◽  
Malaria Vector ◽  
Sibling Species ◽  
Mosquito Species ◽  
Sensu Stricto ◽  
Malaria Vectors ◽  
Morphological Identification ◽  
Vector Species ◽  
Vector Behaviour

Regular entomological monitoring is important to determine changes in mosquito species composition and relative densities of malaria vectors in relation to vector control interventions. A study to gain insights into malaria vector species composition and relative abundance was undertaken in Mutare and Mutasa districts, Zimbabwe. Two methods; indoor resting catches and larval sampling were used to collect indoor resting adults and larvae from May 2013 to April 2014. Mosquitoes collected as adults and reared from larvae that were identified morphologically as potential malaria vectors were further processed to sibling species by polymerase chain reaction (PCR). Morphological identification of anopheline mosquitoes showed presence of two complexes: <em>An. funestus</em> and <em>An. gambiae</em>. The total number of female members of the <em>An. funestus</em> group and <em>An. gambiae</em> complex collected by both methods from the two sites was 840 and 31 respectively. Malaria vector species of both complexes were more abundant in Mutare than in Mutasa. The PCR-based assays showed the presence of four sibling species: <em>An. funestus</em> <em>sensu</em> <em>stricto</em> (90.8%, 267/294) and <em>An. leesoni</em> (5.1%, 15/294), of <em>An. funestus</em> group; <em>An. arabiensis</em> (41.9%, 13/31) and <em>An. quadriannulatus</em> (48.4%, 15/31) of the <em>An. gambiae</em> complex. About 4% and 5% of specimens of <em>An. gambiae</em> complex and A<em>n. funestus</em> group respectively did not amplify. Of the two identified malaria vector sibling species, An. funestus sensu stricto was more abundant (95.4%, 267/280) than <em>An. arabiensis</em> (4.6%, 13/280), suggesting the replacement to secondary vector of <em>An. arabiensis</em>, which was previously the predominant vector species. <em>An. funestus</em> <em>sensu</em> <em>stricto</em> and <em>An</em>. <em>arabiensis</em>, the most important vectors of human malaria were identified in this study, but their resting and biting habits as well as insecticide susceptibility are unclear. Further studies on vector behaviour are therefore recommended.

scholarly journals Impact of sugarcane irrigation on malaria vector Anopheles mosquito fauna, abundance and seasonality in Arjo-Didessa, Ethiopia

2020 ◽  
Author(s):  
Assalif Demissew Shifera ◽  
Dawit Hawaria ◽  
Solomon Kibret ◽  
Abebe Animut ◽  
Arega Tsegaye ◽  
...  
Keyword(s):  
Species Composition ◽  
Malaria Vector ◽  
Mosquito Species ◽  
Molecular Techniques ◽  
Anopheline Mosquito ◽  
Anopheles Species ◽  
Gambiae Complex ◽  
Mosquito Abundance ◽  
Anopheles Mosquitoes ◽  
The Impact

Abstract BackgroundDespite extensive irrigation development in Ethiopia, limited studies assessed the impact of irrigation on malaria vector mosquito composition, abundance and seasonality. This study aimed to evaluate the impact of sugarcane irrigation on species composition, abundance and seasonality of malaria vectors.MethodsAdult Anopheles mosquitoes were collected using CDC light traps from three irrigated and three non-irrigated clusters in and around Arjo-Didessa sugarcane irrigation scheme in southwestern Ethiopia. Mosquitoes were surveyed in four seasons: two wet and two dry, in 2018 and 2019. Mosquito species composition, abundance and seasonality were compared between irrigated and non-irrigated clusters. Anopheles mosquitoes were sorted out to species using morphological keys and molecular techniques. Chi-square was used to test the relationships between Anopheles species occurrence, and environmental and seasonal parameters.ResultsOverall, 2,108 female Anopheles mosquitoes comprising of six species were collected. Of these, 92.7% (n=1,954) were from irrigated clusters and 7.3% (n=154) from the non-irrigated. The Anopheles gambiae complex was the most abundant (67.3%) followed by Anopheles coustani complex (25.3 %) and Anopheles pharoensis (5.7%). PCR-based identification revealed that 74.7% (n=168) of the An. gambiae comlex were Anopheles arabiensis and 22.7% (n=51) Anopheles amharicus. The density of An. gambiae complex (both indoor and outdoor) was higher in irrigated than non-irrigated clusters. The overall anopheline mosquito abundance during the wet seasons (87.2%; n=1,837) was higher than the dry seasons (12.8%; n=271).ConclusionThe ongoing sugarcane irrigation activities in Arjo-Didessa created conditions suitable for malaria transmitting Anopheles species diversity and abundance. This could drive malaria transmission in Arjo-Didessa and its environs in both dry and wet seasons. Currently practiced malaria vector interventions need to be strengthened by including larval source management to reduce vector abundance in the irrigated areas.

scholarly journals Impact of Sugarcane Irrigation on Malaria Vector Anopheles Mosquito Fauna, Abundance and Seasonality in Arjo-Didessa, Ethiopia

2020 ◽  
Author(s):  
Assalif Demissew Shifera ◽  
Dawit Hawaria ◽  
Solomon Kibret ◽  
Abebe Animut ◽  
Arega Tsegaye ◽  
...  
Keyword(s):  
Species Composition ◽  
Malaria Vector ◽  
Mosquito Species ◽  
Malaria Vectors ◽  
Anopheline Mosquito ◽  
Chi Square ◽  
Anopheles Species ◽  
Mosquito Abundance ◽  
Anopheles Mosquitoes ◽  
The Impact

Abstract Background: Although irrigation activities are increasing in Ethiopia, limited studies evaluated their impact on malaria vector mosquito composition, abundance and seasonality. This study aimed at evaluating the impact of sugarcane irrigation on species composition, abundance and seasonality of malaria vectors. Methods: Adult Anopheles mosquitoes were collected using CDC light traps from three irrigated and three non-irrigated clusters in and around Arjo-Didessa sugarcane irrigation scheme in southwestern Ethiopia. Mosquito collections were conducted in four seasons: two wet and two dry, in 2018 and 2019. Mosquito species composition, abundance and seasonality were compared between irrigated and non-irrigated clusters. Anopheles mosquitoes were identified to species using morphological keys and An. gambiae s.l to sibling species using PCR. Chi-square was used to analyze the association between Anopheles species occurrence and environmental and seasonal parameters. Results: Overall, 2,108 female Anopheles mosquitoes comprising of six species were collected. Of these, 92.7% (n=1954) were from irrigated clusters and 7.3% (n=154) from the non-irrigated. An. gambiae s.l was the most abundant (67.3%) followed by An. coustani complex (25.3 %) and An. pharoensis (5.7%). PCR based identification revealed that 74.7% (n=168) of the An. gambiae s.l were An. arabiensis and 22.7% (n=51) An. amharicus. Density of An. gambiae s.l. (both indoor and outdoor) was higher in irrigated than non-irrigated clusters. The overall anopheline mosquito abundance during the wet seasons (87.2%; n=1837) was higher than the dry seasons (12.8%; n=271). Conclusion: The ongoing sugarcane irrigation activities in Arjo-Didessa created conditions suitable for increased malaria transmitting Anopheles species diversity and abundance. This in turn could drive malaria transmission in Arjo-Didessa and its environs in both dry and wet seasons. Thus, currently practiced malaria vector interventions need to be strengthened and consider larval source management to reduce vector abundance in the irrigated areas.

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

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Charles Kakilla ◽  
Alphaxard Manjurano ◽  
Karen Nelwin ◽  
Jackline Martin ◽  
Fabian Mashauri ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Vector ◽  
Lake Victoria ◽  
Indoor Residual Spraying ◽  
Transmission Risk ◽  
Malaria Vectors ◽  
Vector Species ◽  
Sporozoite Rate ◽  
Pirimiphos Methyl

Abstract Background Vector 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. Methods WHO 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. Results Annual 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. Conclusion This 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.

High Annual and Seasonal Variations in Malaria Transmission by Anophelines and Vector Species Composition in Dielmo, a Holoendemic Area in Senegal

1997 ◽  
Vol 56 (3) ◽  
pp. 247-253 ◽  
Author(s):  
Didier Fontenille ◽  
Lassana Konate ◽  
Nafissatou Diagne ◽  
Jean-Jacques Lemasson ◽  
Mathurin Diatta ◽  
...  
Keyword(s):  
Species Composition ◽  
Malaria Transmission ◽  
Seasonal Variations ◽  
Vector Species

scholarly journals Multiple Novel Clades of Anopheline Mosquitoes Caught Outdoors in Northern Zambia

2021 ◽  
Vol 2 ◽  
Author(s):  
Christine M. Jones ◽  
Ilinca I. Ciubotariu ◽  
Mbanga Muleba ◽  
James Lupiya ◽  
David Mbewe ◽  
...  
Keyword(s):  
Malaria Vector ◽  
Sequence Data ◽  
Mosquito Species ◽  
Gene Segment ◽  
Morphological Data ◽  
Vector Species ◽  
Phylogenetic Groups ◽  
Continue Development ◽  
Anopheline Species ◽  
Anopheline Mosquitoes

Residual vector populations that do not come in contact with the most frequently utilized indoor-directed interventions present major challenges to global malaria eradication. Many of these residual populations are mosquito species about which little is known. As part of a study to assess the threat of outdoor exposure to malaria mosquitoes within the Southern and Central Africa International Centers of Excellence for Malaria Research, foraging female anophelines were collected outside households in Nchelenge District, northern Zambia. These anophelines proved to be more diverse than had previously been reported in the area. In order to further characterize the anopheline species, sequencing and phylogenetic approaches were utilized. Anopheline mosquitoes were collected from outdoor light traps, morphologically identified, and sent to Johns Hopkins Bloomberg School of Public Health for sequencing. Sanger sequencing from 115 field-derived samples yielded mitochondrial COI sequences, which were aligned with a homologous 488 bp gene segment from known anophelines (n = 140) retrieved from NCBI. Nuclear ITS2 sequences (n = 57) for at least one individual from each unique COI clade were generated and compared against NCBI’s nucleotide BLAST database to provide additional evidence for taxonomical identity and structure. Molecular and morphological data were combined for assignment of species or higher taxonomy. Twelve phylogenetic groups were characterized from the COI and ITS2 sequence data, including the primary vector species Anopheles funestus s.s. and An. gambiae s.s. An unexpectedly large proportion of the field collections were identified as An. coustani and An. sp. 6. Six phylogenetic groups remain unidentified to species-level. Outdoor collections of anopheline mosquitoes in areas frequented by people in Nchelenge, northern Zambia, proved to be extremely diverse. Morphological misidentification and underrepresentation of some anopheline species in sequence databases confound efforts to confirm identity of potential malaria vector species. The large number of unidentified anophelines could compromise the malaria vector surveillance and malaria control efforts not only in northern Zambia but other places where surveillance and control are focused on indoor-foraging and resting anophelines. Therefore, it is critical to continue development of methodologies that allow better identification of these populations and revisiting and cleaning current genomic databases.

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

2020 ◽  
Author(s):  
Charles Elias Kakilla ◽  
Alphaxard Manjurano ◽  
Karen Nelwin ◽  
Jackline Martin ◽  
Fabian Mashauri ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Vector ◽  
Lake Victoria ◽  
Indoor Residual Spraying ◽  
Transmission Risk ◽  
Malaria Vectors ◽  
Vector Species ◽  
Sporozoite Rate ◽  
Pirimiphos Methyl

Abstract 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 potentially 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 (s.l) 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.

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