scholarly journals Community Knowledge, Perceptions, And Practices Regarding Malaria and Its Control In Jabi Tehnan District, Amhara Region, Northwest Ethiopia

2021 ◽  
Author(s):  
Abebe Asale ◽  
Zewdu Abro ◽  
Bayu Enchalew ◽  
Alayu Tesager ◽  
Aklilu Belay ◽  
...  
Keyword(s):  
Vector Control ◽  
Malaria Control ◽  
Community Education ◽  
Indoor Residual Spraying ◽  
Community Empowerment ◽  
Malaria Episode ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Health Seeking ◽  
Malaria Parasites

Abstract Background: Key program components of malaria control in Ethiopia include community empowerment and mobilization, vector control using long-lasting insecticidal nets (LLINs), indoor residual spraying (IRS), prompt diagnosis and treatment, and disease surveillance. However, the effectiveness of these interventions is often undermined by various challenges, including insecticide and drug resistance, the plasticity of malaria vectors feeding and biting behavior, and certain household factors that lead to misuse and poor utilization of LLINs. The primary objective of this study was to document households’ perceptions towards malaria and assess the prevalence of the disease and the constraints related to the ongoing interventions in Ethiopia (LLINs, IRS, community mobilization house screening). Method: The study was conducted in Jabi Tehnan district, Northwestern Ethiopi,a from November 2019 to March 2020. A total of 3,010 households distributed over 38 kebeles (villages) were randomly selected for socio-economic and demographic survey. Focus group discussions (FGDs) were conducted in 11 different health clusters taking into account agro-ecological differences. A total of 1,256 children under 10 years of age were screened for malaria parasites using microscopy in order to determine malaria prevalence. Furthermore, five-year malaria trend analysis was undertaken based on data obtained from the district health office to understand the disease dynamics.Result: Malaria knowledge in the area was high as all FGD participants correctly identified mosquito bites during the night as sources of malaria transmission. Delayed health seeking behavior remains a key behavioral challenge in malaria control as it took patients on average 4 days before reporting the case at the nearby health facility. On average households lost 2.53 working days per person-per malaria episode and theey spent US$ 18 per person perepisode. Out of the 1,256 randomly selected under 10 children tested for malaria parasites, 11 (0.89%) were found to be positive. Malaria disproportionately affected the adult segment of the population more, 50% of the total cases reported from households whose age was 15 and beyond. The second most affected group was the age group between 5 and 14 years followed by children under 10, with 31% and 14% burden,respectively.Conclusion: Despite the achievement of universal coverage in terms of LLINs access, utilization of vector control interventions in the area remained low.Using bed nets for unintended purposes remained a major challenge. Therefore, continued community education and communication work should be prioritised in the study area to bring about the desired behavioral changes.

scholarly journals Community knowledge, perceptions, and practices regarding malaria and its control in Jabi Tehnan district, Amhara Region, Northwest Ethiopia

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Abebe Asale ◽  
Zewdu Abro ◽  
Bayu Enchalew ◽  
Alayu Teshager ◽  
Aklilu Belay ◽  
...  
Keyword(s):  
Community Education ◽  
Indoor Residual Spraying ◽  
Northwest Ethiopia ◽  
Primary Objective ◽  
Malaria Episode ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Health Seeking ◽  
District Health ◽  
Malaria Parasites

Abstract Background Use of long-lasting insecticidal nets (LLINs), indoor residual spraying (IRS), community-based malaria education, prompt diagnosis and treatment are key programme components of malaria prevention and control in Ethiopia. However, the effectiveness of these interventions is often undermined by various challenges, including insecticide and drug resistance, the plasticity of malaria vectors feeding and biting behaviour, and certain household factors that lead to misuse and poor utilization of LLINs. The primary objective of this study was to document households’ perceptions towards malaria and assess the prevalence of the disease and the constraints related to the ongoing interventions in Ethiopia (LLINs, IRS, community mobilization house screening). Methods The study was conducted in Jabi Tehnan district, Northwestern Ethiopia, from November 2019 to March 2020. A total of 3010 households from 38 villages were randomly selected for socio-economic and demographic survey. Focus group discussions (FGDs) were conducted in 11 different health clusters considering agro-ecological differences. A total of 1256 children under 10 years of age were screened for malaria parasites using microscopy to determine malaria prevalence. Furthermore, 5-year malaria trend analysis was undertaken based on data obtained from the district health office to understand the disease dynamics. Results Malaria knowledge in the area was high as all FGD participants correctly identified mosquito bites during the night as sources of malaria transmission. Delayed health-seeking behaviour remains a key behavioural challenge in malaria control as it took patients on average 4 days before reporting the case at the nearby health facility. On average, households lost 2.53 working days per person-per malaria episode and they spent US$ 18 per person per episode. Out of the 1256 randomly selected under 10 children tested for malaria parasites, 11 (0.89%) were found to be positive. Malaria disproportionately affected the adult segment of the population more, with 50% of the total cases reported from households being from among individuals who were 15 years or older. The second most affected group was the age group between 5 and 14 years followed by children aged under 5, with 31% and 14% burden, respectively. Conclusion Despite the achievement of universal coverage in terms of LLINs access, utilization of vector control interventions in the area remained low. Using bed nets for unintended purposes remained a major challenge. Therefore, continued community education and communication work should be prioritized in the study area to bring about the desired behavioural changes.

Mosquitoes and Malaria Control – A Complex Problem for Entomologists to Unravel

2019 ◽  
Vol 30 (5) ◽  
pp. 213-216
Author(s):  
Basil Brooke
Keyword(s):  
Vector Control ◽  
Malaria Vector ◽  
Malaria Control ◽  
Life Stage ◽  
Indoor Residual Spraying ◽  
Transmission Intensity ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Vector Species

The control of malaria transmitting mosquitoes hinges on accurate species identification. This enables assessments of insecticide susceptibilities and important behavioural characteristics (such as feeding and resting behaviours) by species, leading to the design of coherent insecticide-based control strategies that can be enhanced by additional methodologies for malaria elimination. Malaria is a mosquito-borne parasitic disease that affects many vertebrates including humans. Prior to the 20th century the human malarias (Plasmodium falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi) occurred in tropical and temperate regions but their distribution has since reduced to the tropical belt with by far the highest incidence in sub-Saharan Africa. Global incidence for 2017 was estimated by the WHO at 219 million cases corresponding to 435 000 deaths. It is also estimated that investment in malaria control and elimination amounted to $3.1 billion in 2017. The control (and elimination) of malaria largely hinges on the suppression of mosquito vectors, accurate diagnosis and case detection, and case management using appropriate antimalarial drug regimens. Controlling malaria vector mosquitoes (and of course other mosquito-borne diseases) means being able to identify that which needs to be controlled. This is not unlike the maxim of knowing one's enemy, and disease vector control is often phrased in militaristic terms. The arsenal of tools in the war against malaria vectors includes insecticides, bed nets, repellents, larvicides, endectocides, toxic baits and even modified genes. This call to arms against the transmitters of a deadly disease presupposes that the enemy can be identified, which, unfortunately, is not as easy as it sounds. Identifying malaria vectors to species has posed a significant challenge ever since Ronald Ross and Giovanni Grassi implicated dappled-winged Anopheles mosquitoes in malaria transmission. They could not have known the Pandora's Box they had opened, because several Anopheles species are cryptic. Many hide in cryptic species complexes and groups that confound straightforward morphological methods of identifying them. A species complex is a group of morphologically identical species that are very closely related, but nevertheless vary significantly in their feeding and resting behaviours, and mate assortatively (i.e. they recognise and tend only to mate with conspecific partners) enough that hybridisations between them are rare. Many member species of these complexes are sufficiently diverged that cross-mating between them yields infertile or non-viable offspring, but not in all cases. A species group is a looser assortment of related species whose morphological features match to a point where they are very nearly identical, often requiring specimens from more than one life stage to identify them. They also mate assortatively, and hybrids are rarer or simply never occur. The problem for malaria control is that several vector species, including many primary vectors, are members of cryptic complexes or groups. These invariably contain vector and non-vector species, requiring a complex and laborious system to unravel them and ascribe unambiguous genetic methods for their identification. Added to this complexity is the possibility that any Anopheles. species that takes human blood is a potential vector of the human malarias, with the added caveat that not all populations within a species are vectors. Some member species, and even populations within a species, feed either exclusively on humans (anthropophagy) and are potentially high transmission intensity vectors, or exclusively on livestock animals (zoophagy) making them non-vectors, or take blood from a range of sources including humans, becoming potential vectors of low to medium transmission intensity. An added layer of complexity is genetic heterogeneity between populations within a species. It can be argued that this complexity is not necessarily a problem for malaria control. After all, the aim of suppressing or even eliminating vector populations is the interruption of transmission, regardless of what species they are. But mosquito adaptability dictates otherwise. This is because the primary method of malaria vector control is deployment of specially formulated insecticides against adult mosquitoes, either by indoor residual spraying (IRS) or the treatment of bed nets. Mosquito adaptability has enabled a powerful response to these interventions, with resistance to insecticides becoming so widespread that fully insecticide susceptible malaria vector populations are now quite rare.

scholarly journals Status of insecticide susceptibility in Anopheles arabiensis and detection of the knockdown resistance mutation (kdr) concerning agricultural practices from Northern Sudan state, Sudan

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
M. Y. Korti ◽  
T. B. Ageep ◽  
A. I. Adam ◽  
K. B. Shitta ◽  
A. A. Hassan ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Anopheles Arabiensis ◽  
Resistance Mutation ◽  
Indoor Residual Spraying ◽  
Mortality Rates ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Knockdown Resistance ◽  
Insecticide Susceptibility

Abstract Background Chemical control has been the most efficient method in mosquito control, the development of insecticide resistance in target populations has a significant impact on vector control. The use of agricultural pesticides may have a profound impact on the development of resistance in the field populations of malaria vectors. Our study focused on insecticide resistance and knockdown resistance (kdr) of Anopheles arabiensis populations from Northern Sudan, related to agricultural pesticide usage. Results Anopheles arabiensis from urban and rural localities (Merowe and Al-hamadab) were fully susceptible to bendiocarb 0.1% and permethrin 0.75% insecticides while resistant to DDT 4% and malathion 5%. The population of laboratory reference colony F189 from Dongola showed a mortality of 91% to DDT (4%) and fully susceptible to others. GLM analysis indicated that insecticides, sites, site type, and their interaction were determinant factors on mortality rates (P < 0.01). Except for malathion, mortality rates of all insecticides were not significant (P > 0.05) according to sites. Mortality rates of malathion and DDT were varied significantly (P < 0.0001 and P < 0.05 respectively) by site types, while mortality rates of bendiocarb and permethrin were not significant (P >0.05). The West African kdr mutation (L1014F) was found in urban and rural sites. Even though, the low-moderate frequency of kdr (L1014F) mutation was observed. The findings presented here for An. arabiensis showed no correlation between the resistant phenotype as ascertained by bioassay and the presence of the kdr mutation, with all individuals tested except the Merowe site which showed a moderate association with DDT (OR= 6 in allelic test), suggesting that kdr genotype would be a poor indicator of phenotypic resistance. Conclusion The results provide critical pieces of information regarding the insecticide susceptibility status of An. arabiensis in northern Sudan. The usage of the same pesticides in agricultural areas seemed to affect the Anopheles susceptibility when they are exposed to those insecticides in the field. The kdr mutation might have a less role than normally expected in pyrethroids resistance; however, other resistance genes should be in focus. These pieces of information will help to improve the surveillance system and The implication of different vector control programs employing any of these insecticides either in the treatment of bed nets or for indoor residual spraying would achieve satisfactory success rates.

scholarly journals Pengendalian Vektor Malaria di Daerah Endemis Kabupaten Purworejo, Indonesia

2018 ◽  
pp. 1-12
Author(s):  
Riyani Setiyaningsih ◽  
Wiwik Trapsilowati ◽  
Mujiyono Mujiyono ◽  
Lasmiati Lasmiati
Keyword(s):  
Vector Control ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Control Methods ◽  
Mosquito Nets ◽  
Bioassay Test ◽  
Insecticide Treated Bed Nets ◽  
And Control ◽  
Breeding Place

Purworejo is the endemic area of ​​malaria with the highest case increase occurring in 2015 amounted to 1411 cases. Appropriate control can be performed effectively based on vector bionomics. The aims of study were to determine species, behavior, resistance, and control methods of malaria vectors. Methods were larva andmosquitoes collection, breeding place of mosquitoes surveys, resistance of mosquito and evaluation of the effectiveness of vector control. The research was conducted in Sendangsari Village, Bener District, Purworejo Regency The result of the research showed that An. barbirostris sucked blood indoor, outdoor, and cage. An. balabacensis sucked blood indoor and cage. An. maculatus, An. aconitus, An. kochi, An. Indifinitus, and An. fagus were found to suck blood in the cage. An. maculatus showed resistance to insecticide permetrin 0,75% Indoor Residual spraying (IRS) and the use of insecticide treated bed nets were the vector control perfomed in the area of study. The breeding place of mosquito were in hole around unused fields and pond. Based on bioassay test, the effectiveness of IRS application for one months were not effectively kill An. maculatus while the use of mosquito nets for three months were still effectively kill An. maculatus.

scholarly journals Mosquito feeding behavior and how it influences residual malaria transmission across Africa

2019 ◽  
Vol 116 (30) ◽  
pp. 15086-15095 ◽  
Author(s):  
Ellie Sherrard-Smith ◽  
Janetta E. Skarp ◽  
Andrew D. Beale ◽  
Christen Fornadel ◽  
Laura C. Norris ◽  
...  
Keyword(s):  
Vector Control ◽  
Indoor Residual Spraying ◽  
Malaria Prevention ◽  
Health Impact ◽  
Time Of Day ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Outdoor Biting ◽  
Residual Malaria Transmission ◽  
Year 2000

The antimalarial efficacy of the most important vector control interventions—long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS)—primarily protect against mosquitoes’ biting people when they are in bed and indoors. Mosquito bites taken outside of these times contribute to residual transmission which determines the maximum effectiveness of current malaria prevention. The likelihood mosquitoes feed outside the time of day when LLINs and IRS can protect people is poorly understood, and the proportion of bites received outdoors may be higher after prolonged vector control. A systematic review of mosquito and human behavior is used to quantify and estimate the public health impact of outdoor biting across Africa. On average 79% of bites by the major malaria vectors occur during the time when people are in bed. This estimate is substantially lower than previous predictions, with results suggesting a nearly 10% lower proportion of bites taken at the time when people are beneath LLINs since the year 2000. Across Africa, this higher outdoor transmission is predicted to result in an estimated 10.6 million additional malaria cases annually if universal LLIN and IRS coverage was achieved. Higher outdoor biting diminishes the cases of malaria averted by vector control. This reduction in LLIN effectiveness appears to be exacerbated in areas where mosquito populations are resistant to insecticides used in bed nets, but no association was found between physiological resistance and outdoor biting. Substantial spatial heterogeneity in mosquito biting behavior between communities could contribute to differences in effectiveness of malaria control across Africa.

scholarly journals Ivermectin as an endectocide may boost control of malaria vectors in India and contribute to elimination

2022 ◽  
Vol 15 (1) ◽  
Author(s):  
Sundus Shafat Ahmad ◽  
Manju Rahi ◽  
Poonam Saroha ◽  
Amit Sharma
Keyword(s):  
Vector Control ◽  
Malaria Elimination ◽  
Control Strategies ◽  
Mosquito Species ◽  
Indoor Residual Spraying ◽  
World Health ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Malaria Vector Control ◽  
Indian Government

AbstractMalaria constitutes one of the largest public health burdens faced by humanity. Malaria control has to be an efficient balance between diagnosis, treatment and vector control strategies. The World Health Organization currently recommends indoor residual spraying and impregnated bed nets as two malaria vector control methods that have shown robust and persistent results against endophilic and anthropophilic mosquito species. The Indian government launched the National Framework for Malaria Elimination in 2016 with the aim to achieve the elimination of malaria in a phased and strategic manner and to sustain a nation-wide malaria-free status by 2030. India is currently in a crucial phase of malaria elimination and novel vector control strategies maybe helpful in dealing with various challenges, such as vector behavioural adaptations and increasing insecticide resistance among the Anopheles populations of India. Ivermectin can be one such new tool as it is the first endectocide to be approved in both animals and humans. Trials of ivermectin have been conducted in endemic areas of Africa with promising results. In this review, we assess available data on ivermectin as an endectocide and propose that this endectocide should be explored as a vector control tool for malaria in India. Graphical Abstract

scholarly journals Impact of seasonality and malaria control interventions on Anopheles density and species composition from three areas of Uganda with differing malaria endemicity

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Henry Ddumba Mawejje ◽  
Maxwell Kilama ◽  
Simon P. Kigozi ◽  
Alex K. Musiime ◽  
Moses Kamya ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Control ◽  
Mosquito Species ◽  
Density Ratio ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Vector Density ◽  
Llin Distribution

Abstract Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the malaria control interventions primarily responsible for reductions in transmission intensity across sub-Saharan Africa. These interventions, however, may have differential impact on Anopheles species composition and density. This study examined the changing pattern of Anopheles species in three areas of Uganda with markedly different transmission intensities and different levels of vector control. Methods From October 2011 to June 2016 mosquitoes were collected monthly using CDC light traps from 100 randomly selected households in three areas: Walukuba (low transmission), Kihihi (moderate transmission) and Nagongera (high transmission). LLINs were distributed in November 2013 in Walukuba and Nagongera and in June 2014 in Kihihi. IRS was implemented only in Nagongera, with three rounds of bendiocarb delivered between December 2014 and June 2015. Mosquito species were identified morphologically and by PCR (Polymerase Chain Reaction). Results In Walukuba, LLIN distribution was associated with a decline in Anopheles funestus vector density (0.07 vs 0.02 mosquitoes per house per night, density ratio [DR] 0.34, 95% CI: 0.18–0.65, p = 0.001), but not Anopheles gambiae sensu stricto (s.s.) nor Anopheles arabiensis. In Kihihi, over 98% of mosquitoes were An. gambiae s.s. and LLIN distribution was associated with a decline in An. gambiae s.s. vector density (4.00 vs 2.46, DR 0.68, 95% CI: 0.49–0.94, p = 0.02). In Nagongera, the combination of LLINs and multiple rounds of IRS was associated with almost complete elimination of An. gambiae s.s. (28.0 vs 0.17, DR 0.004, 95% CI: 0.002–0.009, p < 0.001), and An. funestus sensu lato (s.l.) (3.90 vs 0.006, DR 0.001, 95% CI: 0.0005–0.004, p < 0.001), with a less pronounced decline in An. arabiensis (9.18 vs 2.00, DR 0.15 95% CI: 0.07–0.33, p < 0.001). Conclusions LLIN distribution was associated with reductions in An. funestus s.l. in the lowest transmission site and An. gambiae s.s. in the moderate transmission site. In the highest transmission site, a combination of LLINs and multiple rounds of IRS was associated with the near collapse of An. gambiae s.s. and An. funestus s.l. Following IRS, An. arabiensis, a behaviourally resilient vector, became the predominant species, which may have implications for malaria vector control activities. Development of interventions targeted at outdoor biting remains a priority.

scholarly journals Addressing key gaps in implementation of mosquito larviciding to accelerate malaria vector control in southern Tanzania: results of a stakeholder engagement process in local district councils

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Salum A. Mapua ◽  
Marceline F. Finda ◽  
Ismail H. Nambunga ◽  
Betwel J. Msugupakulya ◽  
Kusirye Ukio ◽  
...  
Keyword(s):  
Malaria Control ◽  
Public Engagement ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Malaria Vector Control ◽  
Production Plant ◽  
Community Members ◽  
Key Informants ◽  
Larval Source Management ◽  
Source Management

Abstract Background Larval source management was historically one of the most effective malaria control methods but is now widely deprioritized in Africa, where insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are preferred. However, in Tanzania, following initial successes in urban Dar-es-Salaam starting early-2000s, the government now encourages larviciding in both rural and urban councils nationwide to complement other efforts; and a biolarvicide production-plant has been established outside the commercial capital. This study investigated key obstacles and opportunities relevant to effective rollout of larviciding for malaria control, with a focus on the meso-endemic region of Morogoro, southern Tanzania. Methods Key-informants were interviewed to assess awareness and perceptions regarding larviciding among designated health officials (malaria focal persons, vector surveillance officers and ward health officers) in nine administrative councils (n = 27). Interviewer-administered questionnaires were used to assess awareness and perceptions of community members in selected areas regarding larviciding (n = 490). Thematic content analysis was done and descriptive statistics used to summarize the findings. Results A majority of malaria control officials had participated in larviciding at least once over the previous three years. A majority of community members had neutral perceptions towards positive aspects of larviciding, but overall support for larviciding was high, although several challenges were expressed, notably: (i) insufficient knowledge for identifying relevant aquatic habitats of malaria vectors and applying larvicides, (ii) inadequate monitoring of programme effectiveness, (iii) limited financing, and (iv) lack of personal protective equipment. Although the key-informants reported sensitizing local communities, most community members were still unaware of larviciding and its potential. Conclusions The larviciding programme was widely supported by both communities and malaria control officials, but there were gaps in technical knowledge, implementation and public engagement. To improve overall impact, it is important to: (i) intensify training efforts, particularly for identifying habitats of important vectors, (ii) adopt standard technical principles for applying larvicides or larval source management, (iii) improve financing for local implementation and (iv) improve public engagement to boost community awareness and participation. These lessons could also be valuable for other malaria endemic areas wishing to deploy larviciding for malaria control or elimination.

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.

scholarly journals Insecticide resistance status of Anopheles arabiensis in irrigated and non-irrigated areas in western Kenya

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Pauline Winnie Orondo ◽  
Steven G. Nyanjom ◽  
Harrysone Atieli ◽  
John Githure ◽  
Benyl M. Ondeto ◽  
...  
Keyword(s):  
Insecticide Resistance ◽  
Vector Control ◽  
Anopheles Arabiensis ◽  
Crop Protection ◽  
Indoor Residual Spraying ◽  
Malaria Vectors ◽  
Western Kenya ◽  
Animal Protection ◽  
Selection Of ◽  
Selection Of Resistance

Abstract Background Malaria control in Kenya is based on case management and vector control using long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). However, the development of insecticide resistance compromises the effectiveness of insecticide-based vector control programs. The use of pesticides for agricultural purposes has been implicated as one of the sources driving the selection of resistance. The current study was undertaken to assess the status and mechanism of insecticide resistance in malaria vectors in irrigated and non-irrigated areas with varying agrochemical use in western Kenya. Methods The study was carried out in 2018–2019 in Homa Bay County, western Kenya. The bioassay was performed on adults reared from larvae collected from irrigated and non-irrigated fields in order to assess the susceptibility of malaria vectors to different classes of insecticides following the standard WHO guidelines. Characterization of knockdown resistance (kdr) and acetylcholinesterase-inhibiting enzyme/angiotensin-converting enzyme (Ace-1) mutations within Anopheles gambiae s.l. species was performed using the polymerase chain reaction (PCR) method. To determine the agricultural and public health insecticide usage pattern, a questionnaire was administered to farmers, households, and veterinary officers in the study area. Results Anopheles arabiensis was the predominant species in the irrigated (100%, n = 154) area and the dominant species in the non-irrigated areas (97.5%, n = 162), the rest being An. gambiae sensu stricto. In 2018, Anopheles arabiensis in the irrigated region were susceptible to all insecticides tested, while in the non-irrigated region reduced mortality was observed (84%) against deltamethrin. In 2019, phenotypic mortality was decreased (97.8–84% to 83.3–78.2%). In contrast, high mortality from malathion (100%), DDT (98.98%), and piperonyl butoxide (PBO)-deltamethrin (100%) was observed. Molecular analysis of the vectors from the irrigated and non-irrigated areas revealed low levels of leucine-serine/phenylalanine substitution at position 1014 (L1014S/L1014F), with mutation frequencies of 1–16%, and low-frequency mutation in the Ace-1R gene (0.7%). In addition to very high coverage of LLINs impregnated with pyrethroids and IRS with organophosphate insecticides, pyrethroids were the predominant chemical class of pesticides used for crop and animal protection. Conclusion Anopheles arabiensis from irrigated areas showed increased phenotypic resistance, and the intensive use of pesticides for crop protection in this region may have contributed to the selection of resistance genes observed. The susceptibility of these malaria vectors to organophosphates and PBO synergists in pyrethroids offers a promising future for IRS and insecticide-treated net-based vector control interventions. These findings emphasize the need for integrated vector control strategies, with particular attention to agricultural practices to mitigate mosquito resistance to insecticides. Graphic abstract

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