Perceptions and recommendations by scientists for a potential release of genetically modified mosquitoes in Nigeria

Willingness to accept and participate in a Microsporidia MB-based mosquito release strategy: a community-based rapid assessment in western Kenya

BACKGROUND

Microsporidia MB, an endosymbiont naturally found in Anopheles mosquitoes inhibits transmission of Plasmodium and is a promising candidate for a transmission-blocking strategy that may involve mosquito release. A rapid assessment was carried out to develop insight into sociodemographic factors, public health concerns, and malaria awareness, management, and prevention practices with the willingness to accept and participate in Microsporidia MB-based transmission-blocking strategy to develop an informed stakeholder engagement process.

METHODS

The assessment consisted of a survey conducted in two communities in western Kenya that involved administering a questionnaire consisting of structured, semi-structured, and open questions to 8108 household heads.

RESULTS

There was an overall high level of willingness to accept (81%) and participate in the implementation of the strategy (96%). Although the willingness to accept was similar in both communities, Ombeyi community was more willing to participate (OR 22, 95% CI 13-36). Women were less willing to accept (OR 0.8, 95% CI 0.7-0.9) compared to men due to fear of increased mosquito bites near homes. Household heads with incomplete primary education were more willing to accept (OR 1.6, 95% CI 01.2-2.2) compared to those educated to primary level or higher. Perceiving malaria as a moderate or low public health issue was also associated with a lower willingness to accept and participate. Experience of > 3 malaria cases in the family over the last six months and knowledge that malaria is transmitted by only mosquito bites, increased the willingness to accept but reduced the willingness to participate. Awareness of malaria control methods based on mosquitoes that cannot transmit malaria increases the willingness to participate.

CONCLUSION

The study showed a high level of willingness to accept and participate in a Microsporidia MB-based strategy in the community, which is influenced by several factors such as community, disease risk perception, gender, education level, knowledge, and experience of malaria. Further research will need to focus on understanding the concerns of women, educated, and employed community members, and factors that contribute to the lower disease risk perception. This improved understanding will lead to the development of an effective communication strategy.

Perspectives of African stakeholders on gene drives for malaria control and elimination: a multi-country survey

BACKGROUND

Gene drive modified mosquitoes (GDMMs) have the potential to address Africa's persistent malaria problem, but are still in early stages of development and testing. Continuous engagement of African stakeholders is crucial for successful evaluation and implementation of these technologies. The aim of this multi-country study was, therefore, to explore the insights and recommendations of key stakeholders across Africa on the potential of GDMMs for malaria control and elimination in the continent.

METHODS

A concurrent mixed-methods study design was used, involving a structured survey administered to 180 stakeholders in 25 countries in sub-Saharan Africa, followed by 18 in-depth discussions with selected groups and individuals. Stakeholders were drawn from academia, research and regulatory institutions, government ministries of health and environment, media and advocacy groups. Thematic content analysis was used to identify key topics from the in-depth discussions, and descriptive analysis was done to summarize information from the survey data.

RESULTS

Despite high levels of awareness of GDMMs among the stakeholders (76.7%), there was a relatively low-level of understanding of their key attributes and potential for malaria control (28.3%). When more information about GDMMs was provided to the stakeholders, they readily discussed their insights and concerns, and offered several recommendations to ensure successful research and implementation of the technology. These included: (i) increasing relevant technical expertise within Africa, (ii) generating local evidence on safety, applicability, and effectiveness of GDMMs, and (iii) developing country-specific regulations for safe and effective governance of GDMMs. A majority of the respondents (92.9%) stated that they would support field trials or implementation of GDMMs in their respective countries. This study also identified significant misconceptions regarding the phase of GDMM testing in Africa, as several participants incorrectly asserted that GDMMs were already present in Africa, either within laboratories or released into the field.

CONCLUSION

Incorporating views and recommendations of African stakeholders in the ongoing research and development of GDMMs is crucial for instilling stakeholder confidence on their potential application. These findings will enable improved planning for GDMMs in Africa as well as improved target product profiles for the technologies to maximize their potential for solving Africa's enduring malaria challenge.

Conceptual risk assessment of mosquito population modification gene-drive systems to control malaria transmission: preliminary hazards list workshops

The field-testing and eventual adoption of genetically-engineered mosquitoes (GEMs) to control vector-borne pathogen transmission will require them meeting safety criteria specified by regulatory authorities in regions where the technology is being considered for use and other locales that might be impacted. Preliminary risk considerations by researchers and developers may be useful for planning the baseline data collection and field research used to address the anticipated safety concerns. Part of this process is to identify potential hazards (defined as the inherent ability of an entity to cause harm) and their harms, and then chart the pathways to harm and evaluate their probability as part of a risk assessment. The University of California Malaria Initiative (UCMI) participated in a series of workshops held to identify potential hazards specific to mosquito population modification strains carrying gene-drive systems coupled to anti-parasite effector genes and their use in a hypothetical island field trial. The hazards identified were placed within the broader context of previous efforts discussed in the scientific literature. Five risk areas were considered i) pathogens, infections and diseases, and the impacts of GEMs on human and animal health, ii) invasiveness and persistence of GEMs, and interactions of GEMs with target organisms, iii) interactions of GEMs with non-target organisms including horizontal gene transfer, iv) impacts of techniques used for the management of GEMs and v) evolutionary and stability considerations. A preliminary hazards list (PHL) was developed and is made available here. This PHL is useful for internal project risk evaluation and is available to regulators at prospective field sites. UCMI project scientists affirm that the subsequent processes associated with the comprehensive risk assessment for the application of this technology should be driven by the stakeholders at the proposed field site and areas that could be affected by this intervention strategy.

Host-pathogen interaction in arthropod vectors: Lessons from viral infections

Haematophagous arthropods can harbor various pathogens including viruses, bacteria, protozoa, and nematodes. Insects possess an innate immune system comprising of both cellular and humoral components to fight against various infections. Haemocytes, the cellular components of haemolymph, are central to the insect immune system as their primary functions include phagocytosis, encapsulation, coagulation, detoxification, and storage and distribution of nutritive materials. Plasmatocytes and granulocytes are also involved in cellular defense responses. Blood-feeding arthropods, such as mosquitoes and ticks, can harbour a variety of viral pathogens that can cause infectious diseases in both human and animal hosts. Therefore, it is imperative to study the virus-vector-host relationships since arthropod vectors are important constituents of the ecosystem. Regardless of the complex immune response of these arthropod vectors, the viruses usually manage to survive and are transmitted to the eventual host. A multidisciplinary approach utilizing novel and strategic interventions is required to control ectoparasite infestations and block vector-borne transmission of viral pathogens to humans and animals. In this review, we discuss the arthropod immune response to viral infections with a primary focus on the innate immune responses of ticks and mosquitoes. We aim to summarize critically the vector immune system and their infection transmission strategies to mammalian hosts to foster debate that could help in developing new therapeutic strategies to protect human and animal hosts against arthropod-borne viral infections.

Lessons learned from the introduction of genetically engineered crops: relevance to gene drive deployment in Africa

The application of gene drives to achieve public health goals, such as the suppression of Anopheles gambiae populations, or altering their ability to sustain Plasmodium spp. infections, has received much attention from researchers. If successful, this genetic tool can contribute greatly to the wellbeing of people in regions severely affected by malaria. However, engineered gene drives are a product of genetic engineering, and the experience to date, gained through the deployment of genetically engineered (GE) crops, is that GE technology has had difficulty receiving public acceptance in Africa, a key region for the deployment of gene drives. The history of GE crop deployment in this region provides good lessons for the deployment of gene drives as well. GE crops have been in commercial production for 24 years, since the planting of the first GE soybean crop in 1996. During this time, regulatory approvals and farmer adoption of these crops has grown rapidly in the Americas, and to a lesser extent in Asia. Their safety has been recognized by numerous scientific organizations. Economic and health benefits have been well documented in the countries that have grown them. However, only one transgenic crop event is being grown in Europe, and only in two countries in that region. Europe has been extremely opposed to GE crops, due in large part to the public view of agriculture that opposes "industrial" farming. This attitude is reflected in a highly precautionary regulatory and policy environment, which has highly influenced how African countries have dealt with GE technology and are likely to be applied to future genetic technologies, including gene drives. Furthermore, a mistrust of government regulatory agencies, the publication of scientific reports claiming adverse effects of GE crops, the involvement of corporations as the first GE crop developers, the lack of identifiable consumer benefit, and low public understanding of the technology further contributed to the lack of acceptance. Coupled with more emotionally impactful messaging to the public by opposition groups and the general tendency of negative messages to be more credible than positive ones, GE crops failed to gain a place in European agriculture, thus influencing African acceptance and government policy. From this experience, the following lessons have been learned that would apply to the deployment of gene drives, in Africa:It will be important to establish trust in those who are developing the technology, as well as in those who are making regulatory decisions. Engagement of the community, where those who are involved are able to make genuine contributions to the decision-making process, are necessary to achieve that trust. The use of tools to facilitate participatory modeling could be considered in order to enhance current community engagement efforts.Trusted, accurate information on gene drives should be made available to the general public, journalists, and scientists who are not connected with the field. Those sources of information should also be able to summarize and analyze important scientific results and emerging issues in the field in order to place those developments in the proper context. Engagement should involve more opportunities for participation of stakeholders in conceptualizing, planning, and decision-making.Diversifying the source of funding for gene drive research and development, particularly by participation of countries and regional bodies, would show that country or regional interests are represented.Efforts by developers and neutral groups to provide the public and decisionmakers with a more thorough understanding of the benefits and risks of this technology, especially to local communities, would help them reach more informed decisions.A better understanding of gene drive technology can be fostered by governments, as part of established biosafety policy in several African countries. Developers and neutral groups could also be helpful in increasing public understanding of the technology of genetic engineering, including gene drives.Effective messaging to balance the messaging of groups opposed to gene drives is needed. These messages should be not only factual but also have emotional and intuitive appeal.

Stakeholder Views on Engagement, Trust, Performance, and Risk Considerations About Use of Gene Drive Technology in Agricultural Pest Management

Gene drive is an experimental technique that may make it possible to alter the genetic traits of whole populations of a species through the genetic modification of a relatively small number of individuals. This technology is sufficiently new that literature on the understanding and views of stakeholders and the public regarding the use of gene drive organisms in agricultural pest management is just beginning to emerge. Our team conducted a 2-pronged engagement process with Texas gene drive agricultural stakeholders to ascertain their values, beliefs, and preferences about the efficacy, safety, and risk management considerations of gene drive technology as a potential tool for agricultural pest management. We found that a majority of stakeholders support gene drive research and its potential use for managing agricultural pests. Our work with stakeholders confirms both their willingness to be engaged and the importance they place on stakeholder and public engagement regarding these issues, as well as the need to address these issues before use of gene drive as a pest management mechanism will be accepted and trusted.

The economic value of genetically engineered mosquitoes as a Malaria control strategy depends on local transmission rates

This paper assesses the economic value of genetically engineered (GE) Anopheles gambiae mosquitoes as a malaria control strategy. We use an epidemiological-economic model of malaria transmission to evaluate this technology for a range of village-level transmission settings. In each setting, we evaluate public health outcomes following introduction of GE mosquitoes relative to a "status quo" baseline scenario. We also assess results both in contrast to-and in combination with-a Mass Drug Administration (MDA) strategy. We find that-in low transmission settings-the present value (PV) public health benefits of GE mosquito release are substantial, both relative to status quo dynamics and MDA. In contrast, in high transmission settings, the release of GE mosquitoes may increase steady-state infection rates. Our results indicate that there are substantial policy complementarities when GE mosquito release is combined with local MDA-the combined control strategy can lead to local eradication.

Hybrid mosquitoes? Evidence from rural Tanzania on how local communities conceptualize and respond to modified mosquitoes as a tool for malaria control

Background

Different forms of mosquito modifications are being considered as potential high-impact and low-cost tools for future malaria control in Africa. Although still under evaluation, the eventual success of these technologies will require high-level public acceptance. Understanding prevailing community perceptions of mosquito modification is, therefore, crucial for effective design and implementation of these interventions. This study investigated community perceptions regarding genetically-modified mosquitoes (GMMs) and their potential for malaria control in Tanzanian villages where no research or campaign for such technologies has yet been undertaken.

Methods

A mixed-methods design was used, involving: (i) focus group discussions (FGD) with community leaders to get insights on how they frame and would respond to GMMs, and (ii) structured questionnaires administered to 490 community members to assess awareness, perceptions and support for GMMs for malaria control. Descriptive statistics were used to summarize the findings and thematic content analysis was used to identify key concepts and interpret the findings.

Results

Nearly all survey respondents were unaware of mosquito modification technologies for malaria control (94.3%), and reported no knowledge of their specific characteristics (97.3%). However, community leaders participating in FGDs offered a set of distinctive interpretive frames to conceptualize interventions relying on GMMs for malaria control. The participants commonly referenced their experiences of cross-breeding for selecting preferred traits in domestic plants and animals. Preferred GMMs attributes included the expected reductions in insecticide use and human labour. Population suppression approaches, requiring as few releases as possible, were favoured. Common concerns included whether the GMMs would look or behave differently than wild mosquitoes, and how the technology would be integrated into current malaria control policies. The participants emphasised the importance and the challenge of educating and engaging communities during the technology development.

Conclusions

Understanding how communities perceive and interpret novel technologies is crucial to the design and effective implementation of new vector control programmes. This study offers vital clues on how communities with no prior experience of modified mosquitoes might conceptualize or respond to such technologies when deployed in the context of malaria control programmes. Drawing upon existing interpretive frames and locally-resonant analogies when deploying such technologies may provide a basis for more durable public support in the future.

A Review: Wolbachia-Based Population Replacement for Mosquito Control Shares Common Points with Genetically Modified Control Approaches

The growing expansion of mosquito vectors has made mosquito-borne arboviral diseases a global threat to public health, and the lack of licensed vaccines and treatments highlight the urgent need for efficient mosquito vector control. Compared to genetically modified control strategies, the intracellular bacterium Wolbachia, endowing a pathogen-blocking phenotype, is considered an environmentally friendly strategy to replace the target population for controlling arboviral diseases. However, the incomplete knowledge regarding the pathogen-blocking mechanism weakens the reliability of a Wolbachia-based population replacement strategy. Wolbachia infections are also vulnerable to environmental factors, temperature, and host diet, affecting their densities in mosquitoes and thus the virus-blocking phenotype. Here, we review the properties of the Wolbachia strategy as an approach to control mosquito populations in comparison with genetically modified control methods. Both strategies tend to limit arbovirus infections but increase the risk of selecting arbovirus escape mutants, rendering these strategies less reliable.

Opinions of key stakeholders on alternative interventions for malaria control and elimination in Tanzania

Background

Malaria control in Tanzania currently relies primarily on long-lasting insecticidal nets and indoor residual spraying, alongside effective case management and behaviour change communication. This study explored opinions of key stakeholders on the national progress towards malaria elimination, the potential of currently available vector control interventions in helping achieve elimination by 2030, and the need for alternative interventions that could be used to supplement malaria elimination efforts in Tanzania.

Methods

In this exploratory qualitative study, Focus group discussions were held with policy-makers, regulators, research scientists and community members. Malaria control interventions discussed were: (a) improved housing, (b) larval source management, (c) mass drug administration (MDA) with ivermectin to reduce vector densities, (d) release of modified mosquitoes, including genetically modified or irradiated mosquitoes, (e) targeted spraying of mosquito swarms, and (f) spatial repellents.

Results

Larval source management and spatial repellents were widely supported across all stakeholder groups, while insecticide-spraying of mosquito swarms was the least preferred. Support for MDA with ivermectin was high among policy makers, regulators and research scientists, but encountered opposition among community members, who instead expressed strong support for programmes to improve housing for poor people in high transmission areas. Policy makers, however, challenged the idea of government-supported housing improvement due to its perceived high costs. Techniques of mosquito modification, specifically those involving gene drives, were viewed positively by community members, policy makers and regulators, but encountered a high degree of scepticism among scientists. Overall, policy-makers, regulators and community members trusted scientists to provide appropriate advice for decision-making.

Conclusion

Stakeholder opinions regarding alternative malaria interventions were divergent except for larval source management and spatial repellents, for which there was universal support. MDA with ivermectin, housing improvement and modified mosquitoes were also widely supported, though each faced concerns from at least one stakeholder group. While policy-makers, regulators and community members all noted their reliance on scientists to make informed decisions, their reasoning on the benefits and disadvantages of specific interventions included factors beyond technical efficiency. This study suggests the need to encourage and strengthen dialogue between research scientists, policy makers, regulators and communities regarding new interventions.

Public health concerns over gene-drive mosquitoes: will future use of gene-drive snails for schistosomiasis control gain increased level of community acceptance?

With the advent of CRISPR (clustered regularly interspaced short palindromic repeat)-based gene drive, present genetic research in schistosomiasis vector control envisages the breeding and release of transgenic schistosome-resistant (TSR) snail vectors to curb the spread of the disease. Although this approach is still in its infancy, studies focussing on production of genetically modified (GM) mosquitoes (including gene-drive mosquitoes) are well advanced and set the pace for other transgenic vector research. Unfortunately, as with other GM mosquitoes, open field release of gene-drive mosquitoes is currently challenged in part by some concerns such as gene drive failure and increased transmission potential for other mosquito-borne diseases among others, which might have adverse effects on human well-being. Therefore, not only should we learn from the GM mosquito protocols, frameworks and guidelines but also appraise the applicability of its current hurdles to other transgenic vector systems, such as the TSR snail approach. Placing these issues in a coherent comparative perspective, I argue that although the use of TSR snails may face similar technical, democratic and diplomatic challenges, some of the concerns over gene-drive mosquitoes may not apply to gene-drive snails, proposing a theory that community consent will be no harder and possibly easier to obtain for TSR snails than the experience with GM mosquitoes. In the future, these observations may help public health practitioners and policy makers in effective communication with communities on issues regarding the use of TSR snails to interrupt schistosomiasis transmission, especially in sub-Saharan Africa.

A typology of community and stakeholder engagement based on documented examples in the field of novel vector control

Background

Despite broad consensus on the importance of community and stakeholder engagement (CSE) for guiding the development, regulation, field testing, and deployment of emerging vector control technologies (such as genetically engineered insects), the types of activities pursued have varied widely, as have the outcomes. We looked to previous CSE efforts for clarity about appropriate methods and goals. Our analysis yielded a typology of CSE, and related vocabulary, that describes distinctions that funders, organizers, and scholars should make when proposing or evaluating CSE.

Methods

We compiled available formal documentation of CSE projects, starting with projects mentioned in interviews with 17 key informants. Major features of these examples, including the initiators, target groups, timing, goals, and methods were identified using qualitative coding. Based on these examples, subcategories were developed for a subset of features and applied to the identified cases of CSE in the documents. Co-occurrence of subcategorized features was examined for patterns.

Results

We identified 14 documented examples CSE projects, which were comprised of 28 distinct CSE activities. We found no clear patterns with respect to timing. However, we found that grouping examples according to whether initiators or targets could enact the immediate desired outcome could help to clarify relationships between goals, methods, and targets.

Conclusion

Based on this analysis, we propose a typology that distinguishes three categories of CSE: engagement to inquire –where initiators are empowered to act on information collected through engagement with target groups; engagement to influence –where initiators engage to affect the actions of already-empowered target groups; and engagement to involve –where initiators engage to delegate authority to target groups. The proposed typology can serve as a guide for establishing the goals, identifying appropriate methods, and evaluating and reporting CSE projects by directing attention to important questions to be asked well before determining who to engage and how.

Mosquito borne diseases, such as malaria and dengue, are major causes of illness and death worldwide. Furthermore, it is getting harder to control mosquitoes and other disease-carrying pests because global climate change is facilitating their spread to new areas, and over time, mosquitoes develop resistance to pesticides. Scientists are therefore developing new methods for controlling mosquito vectors using new gene editing tools. However, releasing genetically engineered insects into the environment is controversial. Many experts recommend that communities and stakeholders be consulted about if or how to use these new methods, but there are few guidelines for the best way to do this. We examined published accounts of community and stakeholder engagement pertaining to novel vector control and looked for patterns across these cases. We found that many efforts were not described in published sources, but those that were could be grouped into three categories: engagement to inquire, engagement to influence, and engagement to involve.

'The mosquitoes are preparing to attack us': knowledge and perceptions of communities in south-eastern Tanzania regarding mosquito swarms

BACKGROUND

Targeting swarms of male Anopheles mosquitoes with techniques such as aerosol spraying could potentially suppress malaria vector populations and parasite transmission. Unfortunately, research on Anopheles swarming behaviours is limited, particularly in East Africa where only a handful of studies have been done. New evidence has recently emerged that such swarms are common even in Tanzania, where they could be readily identified and characterized by community-based volunteers, and potentially targeted for control. However, improved understanding of public knowledge and perceptions will be crucial for successful uptake of any interventions targeting swarms.

METHODS

Explanatory sequential mixed methods approach was used to assess knowledge and perceptions regarding mosquito swarms among community members in Ulanga and Kilombero districts, south-eastern Tanzania. A survey questionnaire was administered to 307 respondents, after which focus group discussions were conducted to clarify responses regarding mosquito swarms and malaria transmission. Findings from both study components were used to draw qualitative inferences.

RESULTS

Most community members (83%) had previously seen mosquito swarms, predominantly in farms, over long grasses or bushes, above ponds and over roofs of houses and pit-latrines. However, there was little evidence that community members could distinguish between mosquito swarms and those of other insects. Neither were they aware that swarms consisted mostly of male mosquitoes. Swarming was associated with mosquitoes preparing to attack people, foraging for food, playing or resting. Very few respondents associated swarming with mosquito mating. Nearly all community members were willing to accept interventions targeting mosquito swarms; and approximately three quarters would pay for such interventions, between 0.9 and 2.3 USD/year.

CONCLUSION

Majority of the community members recognized presence of mosquito swarms in their communities but did not associate these swarms with mosquito mating. Instead, swarming was associated with mosquitoes seeking food or planning to attack people, and thus were generally considered dangerous. This understanding created the basis for wide-acceptance of interventions targeting swarming mosquitoes. Although the likelihood of actual interventions targeting swarms is still low, such community knowledge will be crucial in future field studies of mosquito swarms and possible inclusion of community members in mosquito control efforts.

Household Dengue Prevention Interventions, Expenditures, and Barriers to Aedes aegypti Control in Machala, Ecuador

The Aedes aegypti mosquito is an efficient vector for the transmission of Zika, chikungunya, and dengue viruses, causing major epidemics and a significant social and economic burden throughout the tropics and subtropics. The primary means of preventing these diseases is household-level mosquito control. However, relatively little is known about the economic burden of Ae. aegypti control in resource-limited communities. We surveyed residents from 40 households in a high-risk community at the urban periphery in the city of Machala, Ecuador, on dengue perceptions, vector control interventions, household expenditures, and factors influencing purchasing decisions. The results of this study show that households spend a monthly median of US$2.00, or 1.90% (range: 0.00%, 9.21%) of their family income on Ae. aegypti control interventions. Households reported employing, on average, five different mosquito control and dengue prevention interventions, including aerosols, liquid sprays, repellents, mosquito coils, and unimpregnated bed nets. We found that effectiveness and cost were the most important factors that influence people's decisions to purchase a mosquito control product. Our findings will inform the development and deployment of new Ae. aegypti control interventions by the public health and private sectors, and add to prior studies that have focused on the economic burden of dengue-like illness.

Engaging scientists: An online survey exploring the experience of innovative biotechnological approaches to controlling vector-borne diseases

Background

Pioneering technologies (e.g., nanotechnology, synthetic biology or climate engineering) are often associated with potential new risks and uncertainties that can become sources of controversy. The communication of information during their development and open exchanges between stakeholders is generally considered a key issue in their acceptance. While the attitudes of the public to novel technologies have been widely considered there has been relatively little investigation of the perceptions and awareness of scientists working on human or animal diseases transmitted by arthropods.

Methods

Consequently, we conducted a global survey on 1889 scientists working on aspects of vector-borne diseases, exploring, under the light of a variety of demographic and professional factors, their knowledge and awareness of an emerging biotechnology that has the potential to revolutionize the control of pest insect populations.

Results

Despite extensive media coverage of key developments (including releases of manipulated mosquitoes into human communities) this has in only one instance resulted in scientist awareness exceeding 50 % on a national or regional scale. We document that awareness of pioneering releases significantly relied on private communication sources that were not equally accessible to scientists from countries with endemic vector-borne diseases (dengue and malaria). In addition, we provide quantitative analysis of the perceptions and knowledge of specific biotechnological approaches to controlling vector-borne disease, which are likely to impact the way in which scientists around the world engage in the debate about their value.

Conclusions

Our results indicate that there is scope to strengthen already effective methods of communication, in addition to a strong demand by scientists (expressed by 79.9 % of respondents) to develop new, creative modes of public engagement.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0996-x) contains supplementary material, which is available to authorized users.

Colonization of malaria vectors under semi-field conditions as a strategy for maintaining genetic and phenotypic similarity with wild populations

Background

Malaria still accounts for an estimated 207 million cases and 627,000 deaths worldwide each year. One proposed approach to complement existing malaria control methods is the release of genetically-modified (GM) and/or sterile male mosquitoes. As opposed to laboratory colonization, this requires realistic semi field systems to produce males that can compete for females in nature. This study investigated whether the establishment of a colony of the vector Anopheles arabiensis under more natural semi-field conditions can maintain higher levels of genetic diversity than achieved by laboratory colonization using traditional methods.

Methods

Wild females of the African malaria vector An. arabiensis were collected from a village in southern Tanzania and used to establish new colonies under different conditions at the Ifakara Health Institute. Levels of genetic diversity and inbreeding were monitored in colonies of An. arabiensis that were simultaneously established in small cage colonies in the SFS and in a large semi-field (SFS) cage and compared with that observed in the original founder population. Phenotypic traits that determine their fitness (body size and energetic reserves) were measured at 10^th generation and compared to founder wild population.

Results

In contrast to small cage colonies, the SFS population of An. arabiensis exhibited a higher degree of similarity to the founding field population through time in several ways: (i) the SFS colony maintained a significantly higher level of genetic variation than small cage colonies, (ii) the SFS colony had a lower degree of inbreeding than small cage colonies, and (iii) the mean and range of mosquito body size in the SFS colony was closer to that of the founding wild population than that of small cage colonies. Small cage colonies had significantly lower lipids and higher glycogen abundances than SFS and wild population.

Conclusions

Colonization of An. arabiensis under semi-field conditions was associated with the retention of a higher degree of genetic diversity, reduced inbreeding and greater phenotypic similarity to the founding wild population than observed in small cage colonies. Thus, mosquitoes from such semi-field populations are expected to provide more realistic representation of mosquito ecology and physiology than those from small cage colonies.