After more than a week without any new detections, USDA confirmed four additional cases of New World screwworm since June 20 — all in Texas.
On June 20, the agency confirmed a screwworm infestation in a Crockett County sheep. The following day, two head of cattle in Edwards County tested posted for NWS. On June 22, USDA confirmed an additional case in a Terrell County goat. That case was detected in a castration site wound.
In response to these detections, USDA launched additional sterile fly dispersal flights over the newly impacted areas. The Edwards County cases occurred in an area previously designated by the agency as an affected area.
Since June 3, 16 cases of screwworm have been confirmed in the U.S. Thirteen remained active as of June 23, all in Texas.
How is USDA reporting cases?
Confirmation dates reported on USDA’s website reflect the date a case is confirmed by the National Veterinary Services Laboratories. The time between potential detection and official confirmation depends on both the condition of the test sample and the number of samples waiting to be evaluated.
In some instances, testing can be completed the same day a sample arrives at USDA’s laboratory. If questions arise regarding initial results, samples are shipped overnight to the NVSL lab in Ames, Iowa, for additional testing.
To speed confirmation of cases in Texas, the Animal Health and Plant Inspection Service deployed an NVSL entomologist to USDA’s research laboratory in Kerrville in south-central Texas. APHIS also set up a mobile animal disease laboratory in the state to allow for initial confirmations closer to detection sites. However, samples submitted by mail still go to Ames.
According to a USDA spokesperson, federal and state officials are investigating numerous reports of suspected NWS. Because not all suspected cases test positive, USDA reports only confirmed detections.
“This helps to ensure accuracy and avoids unnecessary confusion or unintended consequences such as trade disruptions or other impacts before we have definitive results,” the spokesperson said.
Is USDA making progress?
In a June 20 social media post, USDA noted no new cases had been discovered for more than a week, despite having about 8,000 traps deployed near the U.S.-Mexico border. This, according to USDA, indicates an NWS infestation is not widespread in the United States. Still, the threat of more invasive flies remains.
According to the latest information from the Mexican government, the country has 1,785 active cases of NWS. That’s 136 fewer cases than the previous report. However, according to USDA data, the number of Mexican cases within 100 miles of the U.S. border had increased from 50 to 62 as of June 18.