The four most recent cases of the New World screwworm have been confirmed on the same Texas property, marking the largest cluster of detections to be reported since the parasite was found in the US earlier this month.
Three cattle and one goat were detected to have screwworm in Terrell County, which is adjacent to Mexico, according to the US Department of Agriculture. All were from a single premises, the Texas Animal Health Commission said in a Wednesday email.
That brings the total number of cases in the US to 19 since early June when the screwworm was originally detected in a calf in Zavala County, Texas. The outbreak is the first in the US in a decade and the first in livestock in about 50 years, threatening the nation’s largest cattle state at a time when the country’s herd has already shrunk.
The screwworm is a fly whose larvae burrow into the wounds of warm-blooded animals, and it usually spreads via the movement of infested animals. Infestations are treatable but can cause death if undetected. The screwworm poses no threat to the safety of the US food supply.
Epidemiological investigations have not yet been completed on the Terrell County cases, but tracebacks are currently underway to determine how the infestations occurred, the commission said. There is currently a quarantine in parts of more than a dozen Texas counties, according to the commission.
Copyright 2026 Bloomberg.
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