What is known about modified insects for disease prevention?: a systematic review
The modification and release of insects to suppress or replace natural insect vectors constitutes a promising tool for vector control and disease prevention, facing the unprecedented global emergence of vector-borne diseases. Little is known regarding these innovative modification strategies and available evidence is not standardized turning it difficult to reflect on their actual efficacy and eventual effects. This work conducted a systematic review, gathering and analyzing research articles from PubMed and Biblioteca Virtual em Saúde databases whose results directly report efficacy and effects of the use of modified insects for disease prevention until 2016. Within more than 1500 publications that were screened a total of 349 where analyzed. A total of 12/3.4% reported field-based evidence, and 41/11.7% covered modification stretagies’ efficacy after insects’ release, their epidemiology impact or its long-term efficacy. Examples of successful results were the replacement of natural field populations by wolbachia-infected mosquitoes in 5 weeks, and the elimination of a population in laboratory cages after transgenic mosquitoes release over 10–20 weeks. Variability in the effective results were described (90/25.7%) questioning its reproducibility in different settings. We also found 38/10.9% publications reporting reversal outcomes, such as an increase of vector population after release. Ecological effects such as horizontal transfer events to non-target species (54/15.5%), and wolbachia-induced worsening pathogenesis on mammal filarial diseases (10/2.9%) were also reported. Present work revealed promising outcomes of both suppressing and replacing approaches. However, it also revealed a need of field-based evidence mainly regarding epidemiologic and long-term impact of insect modification strategies. It pointed out some eventual irreversible and important effects that must not be ignored when considering open-field releases, and that may constitute constraints to generate the missing field evidence. Moreover, the level of variability of existing evidence suggests the need of local/specific evidence in each setting of an eventual release.