|Letter from the Guest Editor.|
Modified insects: Risk analysis and public engagement
The first special issue on transgenic insects (Volume 17, Number 3) featured two mini-reviews – Wilke et al. (2009) summarised the potential benefits of transgenesis in enabling the Sterile Insect Technique (SIT) against selected mosquito vectors, while Brelsfoard & Dobson (2009) discussed strategies to suppress or modify insect pests and disease vectors through the use of naturally occurring and genetically modified Wolbachia strains. In this special issue (Volume 18, Number 2), Morrison et al. (2010) review genetic improvements to the SIT for agricultural pests – covering both classical genetics and transgenesis. They discuss strains created through classical genetics in Dipterans (e.g. Australian Sheep Blowfly Lucilia cuprina, Mediterranean fruitfly Ceratitis capitata) and Lepidopterans (e.g. silkworm Bombyx mori, Mediterranean flour moth Ephestia kuehniella), and outline possibilities for improving the SIT through transgenesis, focusing on advances such as genetic marking, radiation replacement, transgenic sexing, and combination of these features. However, their review does not discuss oft-quoted success stories such as eradication of the New World Screwworm (Cochliomyia hominivorax) from North and Central America (Dyck et al., 2005) because SIT has been deployed against these insect pests without the need for genetic improvements thus far.
Morrison et al. (2009) correctly mention regulatory acceptance and uncertainty over public perception of genetic modification as key challenges to overcome before the technology could be successfully deployed to benefit mankind, reiterating similar observations by other authors on the importance of community engagement in research with modified mosquitoes (Curtis & Reuben, 2007; Vasan, 2009; El Zahabi-Bekdash & Lavery, 2010). Thus, in addition to scientific considerations and general issues that should be addressed in most trials involving mosquitoes (McKemey et al., 2008), there are also important ethical, social and cultural considerations for site selection (Lavery et al., 2008). This is of topical importance: Cayman Islands (British Overseas Territory) has been conducting open field trials since 2009 (Wilson, 2009) with genetically modified male Aedes aegypti mosquitoes described by Phuc et al. (2007), while Malaysia is expected to follow suit in 2010 (TropIKA, 2010). It has been reported that Australia is likely to conduct open releases of modified female Aedes aegypti infected with Wolbachia in January 2011, with subsequent open releases planned in Thailand and Vietnam (Moreira et al., 2009; Jeffrey et al., 2009; Murphy et al., 2010; Eliminate Dengue Project first e-newsletter, May 2010). As Marshall et al. (2010a) have stated, social science is increasingly relevant as the technology moves from laboratory to field. These authors recently conducted a qualitative survey of attitudes to transgenic mosquitoes for malaria control in Mali (Marshall et al., 2010b), and have built upon that work to produce a series of closed questions that could be easily adapted to measure public attitudes in other countries towards the deployment of genetically modified vectors (Marshall et al., 2010a). More such studies are needed to enable better communication of benefits and risks to the public, especially as risk assessments are now available for open releases involving the aforesaid modified and genetically modified Aedes aegypti strains (Beech et al., 2009; Murphy et al., 2010).
Beech et al. (2009) reported 31 risks of a hypothetical open field release of a self-limiting transgenic Aedes aegypti mosquito strain to combat dengue. Patil et al. (2010) have provided a useful critique of that exercise, adding two risks to the 31 identified for a bi-sex lethal strain (such as the one described in Phuc et al., 2007), and identifying eight more risks for another strain in which the penetrance is female-specific flightlessness (Fu et al., 2010). Risk assessment is seldom complete or exhaustive, and should never be a static or one-off exercise; regular re-assessment is important to ensure that it is a living document, and as comprehensive and up-to-date as possible. Patil et al. (2010) is a step in that direction for self-limiting strains, while we may expect similar refinements in the near future for self-propagating strains (e.g. Moreira et al., 2009). For instance, the 50 risks identified by Murphy et al. (2010) can be improved by considering the risk of the strain spreading beyond the proposed release sites (as single infection of one individual may lead to global conversion of an entire species – something that has probably happened thousands of times), and by making clearer distinctions between different Wolbachia strains under consideration, between different phenotypes they induce in different insects, and between limited-time trial versus limited-time release intending to result in a permanent establishment. A lot can also be learnt by comparison of risk assessments such as Beech et al. (2009), Patil et al. (2010), and Murphy et al. (2010); after all, they pertain to cognate and complementary technologies with the common objective of reducing disease burden.
S.S. Vasan, DPhil (Oxon)
Asia Pacific Journal for Molecular Biology and Biotechnology
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