Brewster County dog brings the US screwworm count to 53, with three cases still active

A dog in Brewster County, Texas, confirmed on 2 October, is the latest New World screwworm case in the United States and takes the national count to 53 animal infestations since the first US case on 3 June. Fifty-one of those are in Texas. Two are in New Mexico. Texas Public Radio's tracker, updated Sunday evening, lists three cases as still active.

The other active infestations are goats in Crockett County, Texas, confirmed on 26 September, and a horse in Grant County, New Mexico, confirmed on 17 September. Of the 53 animal cases, 52 have been in domestic animals. None has been confirmed in wildlife or in feral animals. Fly-trap detections are counted separately and are not inside the 53.

What the fly does

Cochliomyia hominivorax is the New World screwworm fly. The female lays eggs in a wound. The larvae eat living tissue rather than dead flesh, which is the difference from ordinary blowflies. A single untreated wound can kill a calf, a dog or a horse. The United States eradicated the fly decades ago with sterile-male releases and has treated every new detection since June as a breach of that eradication.

Brewster County is Big Bend country, on the Rio Grande. The dog is the first case the tracker has placed there. Crockett County, where the goats were confirmed on 26 September, sits to the northeast. Grant County, New Mexico, is the other side of the state line. The geography is a corridor, not a single ranch.

What owners are being told

Animal owners are being asked to check wounds and report maggots at once. The three active cases are the ones still under official watch. The other 50 are closed confirmations since 3 June. That split matters for a containment programme: sterile flies and animal checks are aimed at the active sites, while the cumulative 53 is the measure of how far the breach has already run.

No human case sits in the Sunday tally. The public instruction is still the animal one, because 52 of 53 infestations have been in domestic animals and a missed wound is how the fly moves from one pen to the next.

The number that would change the response

A wildlife confirmation would move the programme off ranches and into the desert. The tracker does not have one. A second case in Brewster County, or a case north of Crockett, would lengthen the corridor. Until either appears, the operational facts are a dog confirmed on 2 October, three active infestations, and a national count of 53 that has been rising since 3 June without a wildlife hit.