The new case in Zavala County was detected on a ranch 5.6 miles from the first positive case ​of screwworm in Texas, which the USDA confirmed on Wednesday.

The infection, which ​the USDA said was in a one-month-old calf, was reported earlier on ⁠Friday by Reuters, citing sources.

The USDA discovered the second infestation “after testing a number ​of suspect cases,” the department’s Animal and Plant Health Inspection Service said in a press ​release.

APHIS and Texas Animal Health Commission officials are continuing to “collect and test other samples from the surrounding area, which have come back negative,” it said.

Friday’s case and the initial detection in nearby La ​Pryor, a town roughly 30 miles northeast of the US-Mexico border, have ​dealt a setback to US cattle ranchers, who have been preparing for the arrival of the pest ‌as ⁠it has moved north through Mexico over the past year.

Screwworms are parasitic flies that deposit eggs in open wounds or mucous membranes of warm-blooded animals. After hatching, the larvae penetrate living tissue, feeding on the host and potentially causing fatal damage if not ​treated.

An outbreak in ​US border states in ⁠the 1960s devastated wildlife and inflicted heavy financial losses on ranchers.

A widespread resurgence now could pose a significant economic threat in ​Texas, the country’s largest cattle-producing state, through animal deaths as well ​as higher ⁠labour and treatment costs.

To limit the risk, Washington has kept the US-Mexico border closed to live cattle imports for more than a year and has spent millions of dollars ⁠to curb ​the pest’s northward spread, including funding sterile fly ​production, expanding trapping programmes and stepping up livestock monitoring.