Alternative vector control methods to manage the Zika virus outbreak: more haste, less speed

In their Comment in The Lancet Global Health (March, 2016),1Yakob L Walker T Zika virus outbreak in the Americas: the need for novel mosquito control methods.Lancet Glob Health. 2016; 4: e148-e149Summary Full Text Full Text PDF PubMed Scopus (127) Google Scholar Laith Yakob and Thomas Walker present the current epidemiological situation of the Zika virus outbreak in the Americas. They argue that, in the absence of a vaccine, the ongoing use of insecticides or the destruction of mosquito breeding sites provides little hope for the containment of this disease. Consequently, they highlight two novel techniques that in their view could provide imminent relief from Zika virus and other vectored diseases. The first one is the continuous mass release of genetically engineered mosquitoes that are partly sterile into the wild. The second approach relies on the use of a vertically inherited endosymbiotic bacterium to restrict arboviruses' replication in mosquitoes. Although the theoretical potential of these novel biotechnological techniques is apparent to many, an imminent role in their use to contain the Zika virus is likely to prove premature. As of yet, no scientific reports have been published on the capacity of either technique to reduce diseases in human populations. Furthermore, the direct evidence that the Release of Insects carrying Dominant Lethal genes (RIDL) approach is effective in reducing the size of the adult female Aedes aegypti population is currently based on one published study (appendix).2Carvalho DO McKemey AR Garziera L et al.Suppression of a field population of Aedes aegypti in Brazil by sustained release of transgenic male mosquitoes.PLoS Negl Trop Dis. 2015; 9: e0003864Crossref Scopus (317) Google Scholar With respect to the effect of endosymbiotic bacteria on viral replication or transmission, it is pertinent that although data exist for at least four viral species, the Zika virus is not one of them.3Johnson KN The impact of Wolbachia on virus infection in mosquitoes.Viruses. 2015; 7: 5705-5717Crossref PubMed Scopus (89) Google Scholar The proposed link to the current Zika virus situation also makes the untested assumption that either technique could be very rapidly scaled up from the very small numbers of households used in their existing experimental work and still be proven as resource efficient. Despite the pressing need for solutions to the rapidly expanding Zika virus transmission, in our opinion it is hard to posit a substantial role for either approach until direct evidence shows a reduced human disease burden.4James S Simmons CP James AA Ecology. Mosquito trials.Science. 2011; 334: 771-772Crossref PubMed Scopus (23) Google Scholar While we acknowledge that to hold novel or experimental techniques to unrealistically high standards is counterproductive, it is surely uncontroversial to suggest that diverse and credible data must be publicly available before resources and attention are diverted away from current control programmes. Furthermore, in the specific context of ongoing mosquito control it is essential that proponents of any new approaches (biotechnological or otherwise) make efforts not to undermine confidence in techniques likely to remain part of frontline responses. Increasing insecticide resistance is undoubtedly making control more difficult for some mosquito species, but the assertion that insecticides and the destruction of breeding sites cannot be part of highly successful control programmes is not supported by recent history. Use of insecticides and destruction of mosquito breeding sites had a central role in simultaneously eliminating Aedes aegypti from 18 continental countries, including Brazil, between 1947 and 1962.5Brathwaite Dick O San Martin JL Montoya RH del Diego J Zambrano B Dayan GH The history of dengue outbreaks in the Americas.Am J Trop Med Hyg. 2012; 87: 584-593Crossref PubMed Scopus (264) Google Scholar Effectively fighting mosquitoes and the diseases they transmit has generally required community participation in the application of sustainable and cost-effective approaches. Historical success and failures of vector control should be scrutinised to help avoid the allure of innovations that do not yet possess a suitably solid evidence base. New control techniques should be developed and used, but equally the value of available techniques should not be overlooked. When these available techniques are applied with strategic vision, they can yield impressive results. RGR has a patent pending (EP2013/077856) that is related to genetically engineered insects. CB declares no competing interests. Download .pdf (.21 MB) Help with pdf files Supplementary appendix Alternative vector control methods to manage the Zika virus outbreak: more haste, less speed – Authors' replyIn response to our Comment1 promoting the development of novel approaches to controlling Aedes aegypti, Christophe Boëte and R Guy Reeves argue for the continued reliance on current techniques—mosquito breeding site management and adulticidal spraying—to contain the current Zika virus outbreak. We agree that inclusion of these more traditional approaches might be justified as part of a wider, integrated, vector management programme. However, current vector control strategies for A aegypti do not appear to be stopping the rapid increase in the number of dengue cases in recent decades in Brazil (figure).