The red imported fire ant (Solenopsis invicta) is an invasive species from South America that is damaging to agriculture and wildlife and known for its painful, venomous sting. That venom, however, is now a promising tool for entomological researchers in fighting back against S. invicta and limiting its spread.
Throughout the southeastern United States, shipments of certain materials and plant matter are quarantined by the US Department of Agriculture until they’re inspected and found to be free of S. invicta. Currently, the methods for identifying S. invicta are taxonomic and typically require expert training, meaning shipments found with ants could be delayed hours or even days while samples are sent to labs.
But soon that could change, thanks to entomologists at the USDA Agricultural Research Service’s Center for Medical, Agricultural and Veterinary Entomology (CMAVE) and the USDA Animal and Plant Health Inspection Service (APHIS). They’ve developed a portable, on-the-spot test kit for identifying red imported fire ants that requires no specialized training and takes just 10 minutes to complete.
“The test is similar to pregnancy tests you can buy at the drugstore,” says Steven Valles, CMAVE research entomologist and lead developer on the project.
Valles and colleagues Charles Strong at CMAVE and Anne-Marie Callcott at APHIS developed antibodies that bind to a specific protein in the red imported fire ant’s venom, and they used those antibodies to create the test kit, known as a “lateral flow immunoassay”—a six-year effort detailed in “Development of a lateral flow immunoassay for rapid field detection of the red imported fire ant, Solenopsis invicta (Hymenoptera: Formicidae),” in the July 2016 issue of Analytical and Bioanalytical Chemistry.
“You simply macerate the ants in a provided solution, place a detection strip in the solution and wait 10 minutes,” Valles says. “Two bands indicate a positive response for red imported fire ants, a single band is negative for red imported fire ants.”
Crucially, the test kit is specific to S. invicta, and testing showed the antibodies in the immunoassay did not bind with venom proteins from other Solenopsis ant species. Identifying that specific protein, and assuring it also occurred sufficiently within S. invicta to be useful in testing, was a significant challenge, Valles says.
In the quest to manage invasive species, lessening the burden of quarantines and inspections on the movement of goods is critical. The test kit for red imported fire ants will be a valuable tool in that effort. Valles says a partnership for production and distribution of the kit is in the works.