Alternative vector control methods to manage the Zika virus outbreak: more haste, less speed – Authors' reply
Authors: Laith Yakob, Thomas Walker
Journal: The Lancet Global Health (2016)

In response to our Comment1Yakob 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 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).2PAHOWHODengue: PAHO/WHO data, maps and statistics: annual cases reported of dengue.http://www.paho.org/hq/index.php?option=com_topics&view=rdmore&cid=6290&Itemid=40734Google Scholar These techniques have repeatedly proven inadequate in protecting contemporary Latin American populations. Even in well resourced mosquito control programmes, insecticides and breeding site management continue to fail in mitigating outbreaks. In Singapore, for example, a large increase in dengue incidence has been reported in the past 40 years3Struchiner CJ Rocklöv J Wilder-Smith A Massad E Increasing dengue Incidence in Singapore over the past 40 years: population growth, climate and mobility.PLoS One. 2015; 10: e0136286Crossref Scopus (88) Google Scholar despite decades of sustained and rigorously enforced national control campaigns.4Ooi EE Goh KT Gubler DJ Dengue prevention and 35 years of vector control in Singapore.Emerg Infect Dis. 2006; 12: 887-893Crossref PubMed Scopus (400) Google Scholar Globally, the number of dengue cases reported to WHO has increased steadily from an average of less than 1000 cases per year in the 1950s to more than 3 million cases per year in 2013.5Stanaway JD Shepard DS Undurraga EA et al.The global burden of dengue: an analysis from the Global Burden of Disease Study 2013.Lancet Infect Dis. 2016; (published online Feb 10.)https://doi.org/10.1016/S1473-3099(16)00026-8Summary Full Text Full Text PDF Scopus (615) Google Scholar Therefore, we welcome the support from Jérémy Bouyer and colleagues for novel mosquito control technologies in the context of the current Zika virus outbreak. We appreciate that several technologies exist for the control of A aegypti mosquitoes but are at different stages of development and testing. The focus of our Comment1Yakob 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 was on the only two approaches, to our knowledge, which have undergone preliminary field trials in Latin American countries currently with Zika virus outbreaks: the Release of Insects carrying Dominant Lethal genes (RIDL) and the release of Wolbachia-infected mosquitoes. Although both approaches have been reported to yield successful trials in Brazil,6Carvalho 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 further field trials are needed to establish whether they could have an effect on Zika virus transmission. Unpublished results suggest that Wolbachia reduces the transmission potential of the Zika virus in A aegypti and both of these novel control strategies have been endorsed by WHO to tackle the current Zika virus outbreak.7WHOMosquito control: can it stop Zika at source?.http://www.who.int/emergencies/zika-virus/articles/mosquito-control/en/Google Scholar RIDL effectiveness might be reduced due to the presence of tetracycline in some natural environments. Further research will be needed to assess the spread and concentrations of tetracycline in natural surface waters. In areas where contamination with this drug is deemed a potential threat to effectiveness of this control method, the release of a higher number of RIDL males might be needed.8Yakob L Bonsall MB Alphey L Aedes aegypti control: the concomitant role of space, competition and transgenic technologies.J Appl Ecol. 2008; 45: 1258-1265Crossref Scopus (68) Google Scholar Bouyer and colleagues suggest that the use of the Sterile Insect Technique (SIT) might provide a safer alternative to RIDL. Unfortunately, because of an absence of empirical data from field trials, theoretical analyses are the only sources to assess SIT for A aegypti control. Mathematical models indicate that significantly higher numbers of radiation-sterilised males would need to be released to match RIDL effectiveness.9Yakob L Bonsall MB The importance of space and competition in optimizing genetic control strategies.J Econ Entomol. 2009; 102: 50-57Crossref PubMed Scopus (21) Google Scholar Additionally, such models suggest that SIT releases that are insufficient to collapse wild populations might actually risk inflating wild A aegypti populations by alleviating competition pressure at the mosquito's larval stages.8Yakob L Bonsall MB Alphey L Aedes aegypti control: the concomitant role of space, competition and transgenic technologies.J Appl Ecol. 2008; 45: 1258-1265Crossref Scopus (68) Google Scholar, 9Yakob L Bonsall MB The importance of space and competition in optimizing genetic control strategies.J Econ Entomol. 2009; 102: 50-57Crossref PubMed Scopus (21) Google Scholar No mosquito control approach is likely to provide the perfect standalone solution. Furthermore, with the rapidly expanding global distribution of arboviruses and their vectors,10Furuya-Kanamori L Liang S Milinovich G et al.Co-distribution and co-infection of chikungunya and dengue viruses.BMC Infect Dis. 2016; 16: 84Crossref PubMed Scopus (154) Google Scholar different control tools and combinations are more likely to be more suitable in different ecological and epidemiological settings. An independent body dedicated to impartial assessment of the many up-and-coming technologies alongside the traditional approaches to mosquito control is needed to inform a modernised, integrated vector management approach for the containment and mitigation of public health emergencies, such as the ongoing Zika virus outbreak. We declare no competing interests. Alternative vector control methods to manage the Zika virus outbreak: more haste, less speedIn their Comment in The Lancet Global Health (March, 2016),1 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. Full-Text PDF Open AccessAlternative vector control methods to manage the Zika virus outbreak: more haste, less speedAs stated by Laith Yakob and Thomas Walker,1 the need for efficient and novel mosquito control methods in the context of the Zika virus outbreak is undisputed. However, technologies such as Release of Insects carrying Dominant Lethal genes (RIDL) are not flawless. Transgenic Aedes aegypti larvae die if they are not fed with a diet supplemented with an antibiotic (tetracycline). However, deprivation of the mosquitoes from the antibiotic results in 5% survival of transgenic larvae,2 resulting in the uncontrolled diffusion of the transgene in large-scale deployment in the field. Full-Text PDF Open Access