Aedes aegypti OX3604C is a female-flightless RIDL strain. When mosquitoes are reared without the antidote, tetracycline, adult females cannot fly or mate. Flightless females in the wild cannot seek hosts or mates, find a blood meal or spread disease. They are likely to be rapidly eaten by predators so this trait is equivalent functionally to a lethal condition. Continual releases of sufficient numbers of RIDL males will reduce the target population to below the level needed to transmit disease. The lethality is clearly late enough to reap the benefits of larval competition for resources. The strain contains the DsRed and AmCyan markers which are clearly visible in larvae, a useful tool for quality control in production and effective monitoring in the field. OX3604C is available in a Mexican and Asian genetic background.
The advantage of this strain is that there is no need for manual sex separation, which leads to some damage from handling. The strain also offers greater flexibility in distribution because eggs, as well as adults and pupae, can be distributed. Individuals, as well as government vector control teams, in disease endemic communities can participate in the control.
OX3604C has been developed in a consortium led by the University of California at Irvine, administered by FNIH on behalf of the Bill and Melinda Gates Foundation Grand Challenges for Global Health Initiative. Other members include Cornell University, University and California at Davis and Colorado State University (CSU). Prof W. Black and M. Wise-Valdez at CSU have introgressed OX3604C into a Mexican Genetically Diverse Laboratory Strain (GDLS) background and evaluated it in indoor cage suppression trials. The Instituto Nacional de Salud Pública (INSP) in Mexico, another consortium member, evaluated the strain in large scale outdoor cages in Chiapas in 2010. The INSP will publish the results of this evaluation shortly.
CSU performed a trial to test the ability of OX3604C to suppress a population of mosquitoes in large cages under laboratory conditions. Wild type populations of Aedes aegypti were established in six cages of approximately 200 cubic ft for three months then OX3604C was released weekly into three of the cages. Three were used as controls. The wild type population of Aedes aegypti mosquitoes in all three experimental cages was eradicated over a 20-week period following the introduction of RIDL males, while in the control cages the adult population remained stable. The pattern of suppression and decline observed was closely correlated with that predicted by simulation models.
Fu, G., Lees, R.S., Nimmo, D., Aw, D., Jin, L., Gray, P., Berendonk, T.U., White-Cooper, H., Scaife, S., Phuc, H.K., Marinotti, O., Jasinskiene, N., James, A.A. and Alphey, L. A female-specific flightless phenotype for mosquito control. PNAS, Vol. 107, No. 10, 4550-4554. http://www.pnas.org/content/108/12/4772.full.pdf+html
Wise de Valdez, M.R., Nimmo, D., Betz, J., Gong, H.F., James, A.A., Alphey, L. and Black IV, W.C. Genetic elimination of dengue vector mosquitoes. PNAS Vol. 108, No. 12, 4772-4775. http://www.pnas.org/content/108/12/4772.full