REDFIELD, Iowa (DTN) -- New World screwworm (NWS) has led to a closure of live cattle imports from Mexico to the U.S., but veterinarians and entomologists say it is important to stay aware and prevent the insects from entering the country.

"In my honest opinion, the good news is NWS was found at Mexico's southern border, so it's a substantial distance from the U.S.," said Robin Pruisner, Iowa's state entomologist. "When found in the U.S., the USDA considers something that must be eradicated to protect American agriculture as well as human health, so producers will not have to take action as the USDA would work to eradicate the insect."

CONTACT VETERINARIAN IF DISEASE IS SUSPECTED

As with any disease that causes distress in U.S. livestock herds, the Animal and Plant Health Inspection Service (APHIS) stresses the importance of contacting the herd veterinarian if a disease is suspected.

According to APHIS, screwworm refers to the maggot's feeding behavior as they burrow into wounds, feeding as they go like a screw being driven into wood. Symptoms in mammals and birds include irritated behavior, head shaking, smell of decay, evidence of fly strike and presence of fly larvae in the wounds.

Pruisner said, decades ago the logistics and efficacy of releasing sterile male NWS worked well, and the process was used less than 10 years ago in Florida to eradicate the problem. "The sterile insect technique (SIT) involves sterilizing millions of male insects using ionizing radiation before releasing them into the wild to mate with wild females," she said. "As no offspring can be produced, the SIT leads to drastic reduction in the wild populations of the disease carrier while minimizing the use of pesticides." Since the female only mates once, this helps eliminate the population. The SIT process has been used in Latin America this year.

US HAS DEALT WITH NWS PREVIOUSLY

In 2016, NWS was discovered to have a population in the southern Florida Keys, infesting Key deer, according to an Entomological Society of America report. The report said the source is uncertain, but the use of SIT eradicated the population.

In 1994, Panama and the U.S. created the Commission for the Eradiation and Prevention of Screwworm (COPEG)to plan, design, construct, equip and operate a sterile fly production plant for New World screwworms, as well as to eradicate and prevent its reinfestation.

Some pests have been controlled using parasitic wasps. Pruisner doubts this would be used to eradicate NWS, as that type of control is best suited for a pest where the population is trying to be lowered, not completely eradicated.

The life cycle of the insect lasts about 21 days in warm weather and slightly longer in cooler climates. The adult female mates only once and lays her white, elongated eggs along the edges of wounds on warm-blooded animals. Producers who suspect a screwworm problem should notify their veterinarian immediately for assistance in treating the problem.

APHIS says NWS can threaten the livelihood of livestock producers, causing millions of dollars' worth of production losses and economic damage. The importation of live cattle from Mexico remains restricted until further information is received from Mexican veterinary authorities on the scope of the problem.

Updates and information about NWS can be found at www.aphis.usda.gov.

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

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