Veterinarian Larry Friedman was just a year into his practice when he joined the Department of Agriculture in 1962 with the intention of working in Wyoming. Instead, he was sent to Texas to help eradicate the new world screwworm (NWS).
For five months, he drove to remote Spanish-speaking ranches to identify and destroy the dangerous flesh-eating larvae that can kill cattle and can also get on people.
By 1966, the efforts of the USDA were successful and the screwworm had been exterminated from American soil.
This parasite is again a potential threat to American livestock, but Friedman told Cowboy State Daily that if the USDA follows the protocols put in place more than 60 years ago, the insect can once more be eliminated.
This parasite kills livestock and other warm-blooded animals by laying eggs in open wounds on the host animal, and when the larvae hatch, they feed on the host's living flesh.
According to the USDA, in the 1950s the agency’s Agricultural Research Service (ARS) developed an effective remedy: the sterile fly technique, which released sterile (infertile) screwworm flies into infested areas so they would mate with wild screwworm flies that could then not produce offspring. The practice saves U.S. livestock producers at least $900 million annually.
ARS and USDA's Animal and Plant Health Inspection Service continue to collaborate on a sterile fly-rearing facility in Panama to create a barrier in Central America that prevents the spread of screwworms from South America.
But in 2016, screwworms were detected at two sites in Florida, on wildlife in the Florida Keys and later on a stray dog miles away in Homestead.
Nearly 154 million sterile flies from the Panama facility were released in southern Florida. By April 2017, just 6 months after the infestation was discovered, the screwworm had been successfully eradicated in Florida.
The 1960s Outbreak
During that outbreak in the 1960s,Friedman was assigned to a small town in Texas, about 200 miles south of San Antonio and 60 miles from the border to help in the efforts to eliminate the screwworm.
“My job was to go out and get on these ranches and check for screwworms and any infected calves,” Friedman said. “I had to set up things so that we had permission to drop these sterile flies on the ranches along the border.”
Most of the ranches he visited 62 years ago were Spanish speaking, but he was able break down the language barrier and explain how vital his work was to their livelihoods.
“I would go to each ranch, and I would talk to them,” Friedman said. “They'd show me the cattle that had the infections, and I would find the little beasts, generally, in the umbilicus of the calves.”
At the time, all the infestations and wounds Friedman observed were caused by the larva of the screwworm.
“It was a big problem we were having, and it was infecting and killing a lot of calves, which cost a lot of money to the ranchers,” he said. “They affected the meat supply, but the ranchers didn't understand what we were doing about flying in the sterile flies.”
Friedman had to explain that by bringing in the sterile flies, it would help eliminate the larva because over time all the eggs would eventually be sterile and there would be no more pests eating their cattle live.
“It was quite a job,” Friedman said. “But they all agreed because they were losing money. I always used the muscle of the government, but we wanted to explain why we're doing it and tell them why this is such a benefit to you.”
The ranchers were reluctant to allow the release of new flies into their ranchlands, but Friedman said they ultimately agreed because they were losing money with the loss of their calves.
62 years ago, Larry Friedman worked for several months in Texas to eradicate the deadly screwworm before moving to Wyoming to help in the fight against brucellosis. The screwworm has been found in Mexico, prompting an immediate closure of the border into the United States. (Courtesy Photo) 
A fly laying eggs in the wound of a livestock animal. The larvae that hatch become screwworms, which can eat an animal or person alive. (U.S. Department of Agriculture) 
Screwworm maggots. (U.S. Department of Agriculture) 
New world swrewworms can be a devastating livestock parasite that also can affect humans. (Getty Images)
Saving The Livestock
Within a short time, Friedman was able to identify the screwworm larva by sight and help save the calves who were infected.
“It was just a matter of seeing these larva and knowing the difference between them and other flies that would lay their eggs there,” Friedman said. “The other flies wouldn't cause an infection. The screwworms on the other hand, beveled down and chewed into the tissue around the navel.”
If the infection was caught in time, the ranchers would be able to save the calves. However, with large herds it was impossible to treat every calf, and they were losing too many.
“Once you've got them convinced that it's okay to drop the sterile flies, you drop sterile flies. They mate with the females, and then they make sterile eggs,” Friedman said. “Within several months, all the screwworms are gone.”
By then, Friedman had learned of an opening in Evanston and managed to get transferred to his dream state of Wyoming. There, he worked for several months in a program to control brucellosis before going into private practice.
Current Infestation Threat
The technique for eliminating the screwworm remains the same as in the 1950s, and Friedman believes that vigilance is the key.
“You need to overwhelm the area with sterile flies,” Friedman said. “They found one case but it's unlikely that it is the only one because flies are everywhere. It only takes but one infected animal to be imported into the United States for that to possibly start an epidemic here.”
In their fight against the screwworm, the United States has closed the Mexican border to livestock importations and are monitoring the herds along the border.
Jackie Dorothy can be reached at jackie@cowboystatedaily.com.
