Okamoto Kenichi W, Robert Michael A, Lloyd Alun L, Gould Fred
Department of Entomology, North Carolina State University, Raleigh, North Carolina, United States of America.
Department of Mathematics and Biomathematics Graduate Program, North Carolina State University, Raleigh, North Carolina, United States of America.
PLoS One. 2013 Dec 20;8(12):e81860. doi: 10.1371/journal.pone.0081860. eCollection 2013.
Two basic strategies have been proposed for using transgenic Aedes aegypti mosquitoes to decrease dengue virus transmission: population reduction and population replacement. Here we model releases of a strain of Ae. aegypti carrying both a gene causing conditional adult female mortality and a gene blocking virus transmission into a wild population to assess whether such releases could reduce the number of competent vectors. We find this "reduce and replace" strategy can decrease the frequency of competent vectors below 50% two years after releases end. Therefore, this combined approach appears preferable to releasing a strain carrying only a female-killing gene, which is likely to merely result in temporary population suppression. However, the fixation of anti-pathogen genes in the population is unlikely. Genetic drift at small population sizes and the spatially heterogeneous nature of the population recovery after releases end prevent complete replacement of the competent vector population. Furthermore, releasing more individuals can be counter-productive in the face of immigration by wild-type mosquitoes, as greater population reduction amplifies the impact wild-type migrants have on the long-term frequency of the anti-pathogen gene. We expect the results presented here to give pause to expectations for driving an anti-pathogen construct to fixation by relying on releasing individuals carrying this two-gene construct. Nevertheless, in some dengue-endemic environments, a spatially heterogeneous decrease in competent vectors may still facilitate decreasing disease incidence.
种群减少和种群替代。在此，我们对携带一种导致成年雌蚊有条件死亡的基因以及一种阻断病毒传播的基因的埃及伊蚊品系释放到野生种群中的情况进行建模，以评估这种释放是否能减少易感病媒的数量。我们发现，这种“减少并替代”策略在释放结束两年后可将易感病媒的频率降低至50%以下。因此，相较于仅释放携带杀雌基因的品系（这可能只会导致种群暂时受到抑制），这种联合方法似乎更可取。然而，抗病原体基因在种群中固定下来的可能性不大。小种群规模下的遗传漂变以及释放结束后种群恢复的空间异质性，使得无法完全替代易感病媒种群。此外，面对野生型蚊子的迁入，释放更多个体可能会适得其反，因为更大程度的种群减少会放大野生型迁入者对抗病原体基因长期频率的影响。我们预计这里给出的结果会让人对依靠释放携带这种双基因构建体的个体来使抗病原体构建体固定下来的期望有所迟疑。尽管如此，在一些登革热流行的环境中，易感病媒在空间上的异质性减少仍可能有助于降低疾病发病率。
