Symbiosis Marks Innovative Front In Battle To Control New World Screwworm

V. TODD MILLER

 BATON ROUGE, LOUISIANA

Symbiotic relationships come in many harmless forms throughout nature: clownfish and anemones, whales and barnacles, and bees and flowers to name a few. Two LSU AgCenter scientists are studying how to use symbiosis to potentially control a dangerous pest that is anything but harmless — the New World screwworm.

AgCenter entomologists Honglin Feng and Kristen Healy recently were awarded a U.S. Department of Agriculture Animal and Plant Health Inspection Service grant totaling $691,000 to conduct research focusing on engineered microbial symbionts that express lethal double-stranded RNA to control the New World screwworm (Cochliomyia hominivorax). The hope is to strengthen protection of livestock and wildlife and enhance U.S. preparedness against the pest’s recent reemergence.

The idea is to piggyback on the sterile insect technique, which entails releasing genetically modified sterile male insects into targeted areas to mate with females. Since females typically mate only once per life cycle, the technique results in a mass die-off. This was the method first used to eradicate the New World screwworm in the U.S. in the 1960s, then again in the 1980s.

The Feng/Healy research focuses on culturing, engineering and testing defined, tractable symbionts, organisms that rely on hosts to live, using a secondary screwworm, thus establishing a symbiont-based RNA interference (RNAi) control platform that complements existing sterile insect technique programs. The secondary screwworm (Cochliomyia macellaria) larvae feed on dead or decaying flesh, so are not a danger to livestock.

In layman’s terms, Feng explained that the technology he is developing can be applied on top of the sterile insect technique by engineering symbionts that will attach to sterile male secondary screwworm hosts. This will eliminate the need to inoculate millions of insects repeatedly before releasing them into the wild.

“They’ll naturally live with the New World screwworm, and so the symbionts can produce the RNA interference elements,” he said. “We inoculate them once in the facility before release. The symbionts will then spread naturally throughout the population, where they continuously produce RNAi elements that specifically target and kill female screwworms.”

Although his expertise is in insect microbial symbiosis, Feng said this is his first time working with the New World screwworm, which is where Healy comes in.

Healy, a medical entomologist, is an expert in insect larvae and is nationally recognized for her work in environmentally safe methods of mosquito control. She says that her years of experience in that realm has informed her current research.

“We have a new campaign in the mosquito control world called ‘yesterday’s threats, today’s solutions,’ and it very much sums up what we are experiencing with the New World screwworm,” she said. “While it’s an old threat that has returned, we can implement new and innovative solutions to ensure we maintain the health and safety of all humans and animals while also protecting the environment.”

AgCenter Extension veterinarian and Louisiana Beef Quality Assurance Program coordinator Christine Navarre is enthusiastic about the new front in battling the harmful pest.

"The sterile insect technique has been very successful for New World screwworm control, but new biological technologies offer a powerful complementary approach to enhance preparedness against future outbreaks,” she said. “New techniques have the potential to improve efficiency and decrease costs associated with New World screwworm control.”

AgCenter Extension livestock specialist Ashley Edwards believes the grant is a sign of the national importance of the LSU AgCenter and its researchers in combatting real world issues affecting both producers and consumers.

“This grant demonstrates the critical role of AgCenter research in protecting the economic sustainability of Louisiana’s livestock producers,” Edwards said. “This project will increase the number of innovative technologies that we have to combat New World screwworm, as well as provide solutions that help ensure long-term resilience and biosecurity of the livestock industry in Louisiana and across the U.S.”  ∆

V. TODD MILLER

LSU AGCENTER