The race to extinguish insect pests by enlisting their own kind

Abstract

The race to extinguish insect pests by enlisting their own kindThe unheralded success of a massive operation to control the insidious screwworm offers lessons learned and cautionary tales for mosquitoes and other insect scourges. John Carey, Science WriterOn a Friday in the fall of 2016, John Welch got an email he'd been dreading-a picture of a mystery insect sent from the Florida Keys. "I knew immediately what it was-and that it was bad," the United States Department of Agriculture (USDA) entomologist says. He immediately hopped on a plane to Florida. There he found dozens and dozens of endangered Key deer dead or staggering around blind with the tops of their heads or eyes eaten away or terrible wounds on their bodies. "It was horrific," Welch recalls.And the clues suggested a threat to far more than just deer. The culprit was screwworm, a fly that lays its eggs in open wounds or in moist areas like eyes and noses of warm-blooded mammals, from dogs to people. When the eggs hatch, the larvae start dining. Without aggressive immediate treatment, "it's pretty much a death sentence, being eaten alive by the maggots," says Welch.The stakes were high. In the past, screwworm had devastated the livestock industry all across the US South before the pest was eradicated. Now it was back. Could science win the battle again?The fight had further implications for battles against a host of destructive and disease-carrying insect pests-mosquitoes in particular. Such fights are likely to intensify. In May 2018, the Centers for Disease Control and Prevention reported that between 2004 and 2016 the number of reported cases of illnesses caused by mosquito, tick, and flea bites tripled in the United States, to more than 640,000; in the same time period, nine new germs spread by mosquitoes and ticks were discovered or introduced into the United States (1).Inspired by the success of the decades-old screwworm-control effort and buoyed by a variety of new biotechnologies, researchers in dozens of academic and company labs are working to conscript the bugs themselves as weapons against their own kind. The idea: tinker with genes or parasites to create insects that carry a lethal cargo to their wild counterparts or that cripple the ability to transmit disease.Field trials in South America and the Cayman Islands of a transgenic Aedes aegypti mosquito created by a British company called Oxitec, for example, show that wild populations of the denguecarrying bug can be almost completely wiped out if enough gene-altered bugs are let loose. Another company, MosquitoMate, is rearing hundreds of thousands of mosquitoes infected with a bacterial parasite, Wolbachia; the company is looking for similar effects, with trials in California and Florida. A gene-engineered version of the crop-destroying diamondback moth has been successfully tested in the field. And researchers are experimenting with gene alterations that don't just kill insects or slow disease transmission but that also spread through wild populations via gene drive, eliminating the nee...

Discovery of Early-Branching Wolbachia Reveals Functional Enrichment on Horizontally Transferred Genes

“…Reproductive manipulating Wolbachia phenotypes include male-killing, parthenogenesis induction, feminization, or cytoplasmic incompatibility (CI), wherein infected males mating with uninfected females fail to produce progeny ( Werren, 1997 ; Taylor and Hoerauf, 1999 ; Werren et al, 2008 ). Whereas Wolbachia is widespread in insects, its discovery in PPNs has significant implications, given the ecological importance of PPNs: if these Wolbachia are obligate mutualists like filarial nematode Wolbachia , then disruption of the symbiosis could reduce the PPN burden on plants, whereas if they are reproductive parasites conferring CI as in many insects, this phenotype could be harnessed for biocontrol analogous to Wolbachia -based control programs in mosquitoes ( Caragata et al, 2016 ; Carey, 2018 ).…”