Meat-eating screwworms found in Texas cows: outbreak explained
This is the first time the meat-eating parasite has been detected in U.S. cattle since 1966, raising concerns among Texas agriculture officials.
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The U.S. Department of Agriculture has confirmed an outbreak of New World screwworm in southern Texas.
Wednesday night’s confirmation came hours after the Department of Agriculture announced earlier in the day that there was a possible case in South Texas and that the National Veterinary Services Laboratory in Ames, Iowa, was working to confirm it.
The parasitic fly has been detected in a 3-week-old calf in Zavala County, Texas, making it the only detection in the United States so far, according to the USDA. Larvae were found in the calf’s navel.
On Wednesday night, USDA Secretary Brooke Rollins said in a social media post that the USDA is working with Texas officials to “contain and eradicate the pest,” reinforcing her statement that the U.S.’s “food supply is 100% safe.”
This new detection, the first since the 1960s, prompted federal and Texas agencies to work together to take the following steps to combat screwworms.
- An integrated incident command team with the Texas Animal Health Commission was formed and response personnel were dispatched to the area.
- A 20km infection zone was established around the detection area, and quarantine, movement restrictions and surveillance were implemented in this area.
- In addition to the 4 million airborne releases of sterile flies per week already in the region, the targeted release of sterile NWS flies was accelerated by the immediate deployment of ground release rooms in the region.
- Increased capture of NWS flies along the border and just outside the spray area.
- Implemented monitoring and management strategies for NWS in wildlife.
- We conducted awareness-raising activities targeting the local community.
Additionally, USDA says the National Veterinary Stockpile stands ready to assist and will provide resources to the response, including treatment, equipment, and logistical support as needed.
All ports of entry in the southern United States are currently closed to livestock trade, and preventive measures began even before the detection in Zavala County.
Where is Zarba province?
Zavala County is located southwest of San Antonio, between the city of San Antonio and the border.
According to the 2020 U.S. Census, the population is 9,670.
Texas Department of Agriculture asks people to report suspected cases of New World screwworm
According to the USDA, if you suspect your animal is infected with screwworms, immediately contact your state animal health authority or your USDA regional veterinarian.
The Texas Parks and Wildlife Department also details who individuals can contact in certain situations.
USDA noted that NWS maggot infestations typically affect livestock and other warm-blooded animals, and cases of human infection are rare. Flies most often enter an animal through an open wound and eat the animal’s live flesh.
How does the New World screwworm spread and infect animals?
According to the USDA, the New World screwworm (NWS) is a parasitic fly that affects livestock, pets, wildlife, and rarely people and birds. Fly larvae feed on the living tissue of warm-blooded animals.
USDA reports that the current risk to animals and people in the United States remains very low and NWS is not contagious.
Rather, screwworm parasitism begins when a female fly lays eggs in a wound or body opening. The eggs hatch into larvae, which burrow into the wound and feed on living tissue. After about 7 days of feeding, the larvae fall to the ground, burrow into the soil, and pupate.
Adult screwworm flies emerge from the soil after 7 to 54 days.
Mateo Rosiles is a Texas Connect reporter for USA TODAY and local Texas newspapers. Do you have any news tips for him? Email us at mrosiles@usatodayco.com.
