Sterilized Anopheles funestus can autodisseminate sufficient pyriproxyfen to the breeding habitat under semi-field settings
Hamisi J. Kunambi,
Halfan Ngowo,
Ali Ali
et al.
Abstract:Background
Anopheles funestus, the main malaria vector, prefer to oviposit in permanent and/or semi-permanent breeding habitats located far from human dwellings. Difficulties in identifying and accessing these habitats jeopardize the feasibility of conventional larviciding. In this way, a semi-field study was conducted to assess the potential of autodissemination of pyriproxyfen (PPF) by An. funestus for its control.
Methods
The study was conducted… Show more
“…Since there are many and diverse breeding habitats in rural areas, locating and treating them can present significant challenges. The efficacy of novel approaches like autodissemination of pyriproxyfen has been shown to be promising in addressing these situations [ 30 , 38 ]. Fig.…”
Background
The efficacy of the autodissemination of pyriproxyfen to control malaria vectors has been demonstrated under semi field environment in Tanzania. However, the information on how best communities should be engaged for its routine and large-scale adoption are lacking. This study assessed the community’s level of knowledge, perceptions, acceptability of the autodissemination of pyriproxyfen, and the perceived risks on the safety of pyriproxyfen on the environment.
Methods
This was a concurrent mixed methods study, comprised of a community-based survey of 400 household representatives and eight focus group discussions (FGDs). The study was conducted in two villages in Mlimba district in south-eastern Tanzania between June and August 2022. For the quantitative data analysis, descriptive statistics were applied using R software, while inductive approach was used for qualitative data analysis, using NVivo software.
Results
Knowledge on autodissemination of pyriproxyfen approach was found to be relatively low among both the FGD respondents and surveyed community members (36%, n = 144). Nevertheless, when it was explained to them, the envisioned community support for the autodissemination approach was relatively high (97%, n = 388). One of the major perceived benefits of the autodissemination of pyriproxyfen was the reduction of malaria-transmitting mosquitoes and associated malaria transmission. Environmental impact of pyriproxyfen on non-target organisms and health risk to children were among the major concerns. When provided with information on the safety and its utilization particularly through autodissemination approach, 93.5% (n = 374) of the survey respondents said that they would allow the PPF-contaminated pots to be placed around their homes. Similarly, FGD respondents were receptive towards the autodissemination of pyriproxyfen, but emphasized on the need for raising awareness among community members before related field trials.
Conclusion
This study indicates a low knowledge but high support for scaling up of the autodissemination of pyriproxyfen as a complementary tool for malaria control in rural Tanzania. The Findings of this study suggest that community sensitization activities are required to improve the community’s acceptability and trust of the approach before respective field trials.
“…Since there are many and diverse breeding habitats in rural areas, locating and treating them can present significant challenges. The efficacy of novel approaches like autodissemination of pyriproxyfen has been shown to be promising in addressing these situations [ 30 , 38 ]. Fig.…”
Background
The efficacy of the autodissemination of pyriproxyfen to control malaria vectors has been demonstrated under semi field environment in Tanzania. However, the information on how best communities should be engaged for its routine and large-scale adoption are lacking. This study assessed the community’s level of knowledge, perceptions, acceptability of the autodissemination of pyriproxyfen, and the perceived risks on the safety of pyriproxyfen on the environment.
Methods
This was a concurrent mixed methods study, comprised of a community-based survey of 400 household representatives and eight focus group discussions (FGDs). The study was conducted in two villages in Mlimba district in south-eastern Tanzania between June and August 2022. For the quantitative data analysis, descriptive statistics were applied using R software, while inductive approach was used for qualitative data analysis, using NVivo software.
Results
Knowledge on autodissemination of pyriproxyfen approach was found to be relatively low among both the FGD respondents and surveyed community members (36%, n = 144). Nevertheless, when it was explained to them, the envisioned community support for the autodissemination approach was relatively high (97%, n = 388). One of the major perceived benefits of the autodissemination of pyriproxyfen was the reduction of malaria-transmitting mosquitoes and associated malaria transmission. Environmental impact of pyriproxyfen on non-target organisms and health risk to children were among the major concerns. When provided with information on the safety and its utilization particularly through autodissemination approach, 93.5% (n = 374) of the survey respondents said that they would allow the PPF-contaminated pots to be placed around their homes. Similarly, FGD respondents were receptive towards the autodissemination of pyriproxyfen, but emphasized on the need for raising awareness among community members before related field trials.
Conclusion
This study indicates a low knowledge but high support for scaling up of the autodissemination of pyriproxyfen as a complementary tool for malaria control in rural Tanzania. The Findings of this study suggest that community sensitization activities are required to improve the community’s acceptability and trust of the approach before respective field trials.
“…Of importance, it has been demonstrated that sterilized mosquitoes can still transfer PPF sufficient to prevent adult emergence at the contaminated habitats 94 . This development, highlights the unique complementarity of autodissemination with bednets co-treated with pyriproxyfen.…”
Section: Potential Integration To Current Malaria Interventionsmentioning
Despite the progress made in reducing malaria burden, new ways to address the increasing challenges of insecticide resistance and the invasion and spread of exotic malaria vectors such as Anopheles stephensi in Africa are urgently needed. While African countries are adopting larviciding as a complementary intervention for malaria vector control, the autodissemination technology has the potential to overcome barriers associated with the identification and treatment of prolific habitats that impede conventional larviciding approaches in rural settings. The autodissemination technology as a “lure and release” strategy works by exploiting the resting behavior of gravid mosquitoes to transfer lethal concentration of biological or chemical insecticide such as pyriproxyfen (PPF), an insect growth regulator (IGRs) to their oviposition sites and result in adult emergence inhibition. Despite the evidence of the autodissemination approach to control other mosquito-borne diseases, there is growing and promising evidence for its use in controlling malaria vectors in Africa, which highlights the momentous research that needs to be sustained. This article reviews the evidence for efficacy of the autodissemination approach using PPF and discusses its potential as efficient and affordable complementary malaria vector control intervention in Africa. In the previous studies that were done in controlled semi-field environments, autodissemination with PPF demonstrated its potential in reducing densities of captive population of malaria vectors such as Anopheles gambiae and Anopheles arabiensis. Of importance, empirical evidence and biology-informed mathematical models to demonstrate the utility of the autodissemination approach to control wild populations of malaria vectors under field environment either alone or in combination with other tools are underway. Among others, the key determining factors for future introduction of this approach at scale is having scalable autodissemination devices, optimized PPF formulations, assess its integration/complementarity to existing conventional larviciding, and community perception and acceptance of the autodissemination approach.
“…The topical application of methoprene, another JHA, downregulated the expression of the ecdysone-regulated genes USP , HR3 , and Vg , which are involved in 20E action and oogenesis ( 20 ). Furthermore, exposure to PPF has been demonstrated to result in sterilization and fertility effects in adult male and female Anopheles arabiensis , Anopheles gambiae , Aedes aegypti , and Culex quinquefasciatus ( 12 , 21 – 24 ). In addition, exposure to non-lethal doses of PPF as larvae has been previously demonstrated to increase the susceptibility of Ae.…”
IntroductionControl of the mosquito Aedes albopictus is confounded by its behavior due to females preferring to oviposition in small natural and artificial containers that are often difficult to remove or treat with insecticides. Autodissemination strategies utilizing highly potent insect growth regulators (IGRs) have emerged as promising tools for the control of this container-inhabiting species. The intended goal of autodissemination approaches is to use mosquitoes to self-deliver an IGR to these cryptic oviposition locations. Previous studies have focused on the efficacy of these approaches to impact natural populations, but little focus has been placed on the impacts on mosquitoes when exposed to non-lethal doses of IGRs similar to the levels they would be exposed to with autodissemination approaches.MethodsIn this study, the impact of non-lethal doses of pyriproxyfen (PPF) on the reproductive fitness of Ae. albopictus was investigated. Female and male Ae. albopictus mosquitoes were exposed to non-lethal doses of PPF and their fecundity and fertility were measured. To examine the impact of non-lethal doses of PPF, the expression of the ecdysone-regulated genes USP, HR3, and Vg, which are involved in vitellogenesis, was determined.ResultsOur results demonstrated a significant reduction in female fecundity and in the blood feeding and egg hatching rates upon exposure to non-lethal doses of PPF. Oocyte development was also delayed in PPF-treated females. Furthermore, exposure to non-lethal doses of PPF altered the expression of the genes involved in vitellogenesis, indicating disruption of hormonal regulation. Interestingly, PPF exposure also reduced the sperm production in males, suggesting a potential semi-sterilization effect.DiscussionThese findings suggest that non-lethal doses of PPF could enhance the efficacy of autodissemination approaches by impacting the reproductive fitness of both males and females. However, further research is needed to validate these laboratory findings in field settings and to assess their practical implications for vector control strategies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
