Fast Test Identifies Red Imported Fire Ants

The red imported fire ant is more than a nuisance. Its painful sting packs a powerful venom, which is life-threatening to some people and deadly to small animals. Control costs and damage to U.S. urban, agricultural, wildlife, recreational, and industrial areas are estimated at $6 billion per year.

The U.S. Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) has imposed a quarantine, mainly in southeastern states, to help limit the fire ant's spread. The ants have infested 300 million acres since they were introduced into the United States in the 1930s. A quick way to identify these invasive pests is sorely needed.

Agricultural Research Service (ARS) scientists at the Center for Medical, Agricultural and Veterinary Entomology (CMAVE) in Gainesville, Florida, and APHIS in Biloxi, Mississippi, have a solution.

Entomologist Steven Valles, who works in CMAVE's Imported Fire Ant and Household Insects Research Unit, developed novel antibodies that bind to a protein in the fire ant's venom. Working with APHIS laboratory director Anne-Marie Callcott and CMAVE entomologist Charles Strong, Valles used these antibodies to develop a portable, easy-to-use test kit that identifies red imported fire ants in 10 minutes.

Currently, identifying ants found at inspection stations takes hours or even days, because samples are typically sent to a lab.

"Trucks carrying hay, nursery stock, soil-moving equipment, or other items are inspected when they leave a quarantine area and head for an area not under quarantine,” Valles says.

If ants are detected, the shipment must remain within the inspection or holding area until ants are identified. If the wait is long, perishable loads could spoil.

"The wait could be hours if an expert has to identify the ant species from a photo, or it could take days if an ant sample has to be sent to a lab," Valles says. "The new test fixes that problem."

The test kit does not require any special training to use. It contains a plastic tube, a pestle to mix in ants, and a test strip that detects red imported fire ant venom. If the strip has two lines, the test is positive. If it has one line, it is negative.

This technology was developed primarily for APHIS's use at truck inspection stops, but could be used at other locations where cargo is imported or exported, Valles says. Other countries where red imported fire ants are a problem, such as Australia, Taiwan, and New Zealand, have expressed interest in this technology.

The USDA has obtained a biological material license for the test's antibodies, which specifically identify red imported fire ants. — By Sandra Avant, ARS Office of Communications.