NWS Update: Sept. 19, 2026

TWA NWS Best Practices Booklet (downloadable)

Sept. 19, 2026

Dear TWA member,

The Texas Wildlife Association and its partners continue to closely monitor developments around New World screwworm (NWS) spread in Texas since the initial detection on June 3. More detections are expected and response efforts continue to build. It is essential that landowners, particularly in impacted areas, vigilantly monitor wildlife and livestock and report suspicious cases to the appropriate authorities.

To provide you with timely and relevant information related to the presence of NWS in Texas, we are sharing this bi-weekly update as of 12 p.m. on Sept. 18, 2026. Cases confirmed since our Sept. 5 update are included below.

A full list of active and inactive cases is available at the USDA Dashboard, updated daily at 5 p.m. Central.

Confirmed Date

County

Species

Status

9 Sept. 2026

Presidio, TX

Horse

Active

17 Sept. 2026

Grant, NM

Horse

Active

Active cases are those that involve ongoing disease mitigation efforts, including treatment and wound management of the infested animal until all wounds have healed.

Inactive animal cases refer to situations where mitigation activities are no longer required. Either the animal has fully recovered—with wounds healed and treatment completed—or, in cases where treatment was not performed, appropriate measures have been taken to prevent the spread of NWS, such as appropriate carcass management of a deceased infested animal.

News and updates
Infested Zone officially released
On Sept. 16, USDA’s APHIS approved the release of an NWS infested zone in Texas, meaning NWS movement restrictions have been removed. Designated areas of Bandera, Medina and Uvalde counties are no longer under mandatory NWS Movement/Treatment Certificates and required inspections are no longer necessary. However, areas of Uvalde County remain under another NWS Infested Zone still in place.

Additionally, on Sept. 18, designated areas of Jim Hogg, Starr and Zapata counties were released. Jim Hogg County is no longer under NWS movement restrictions. Areas of Starr and Zapata counties remain under anothther NWA Infested Zone still in place.

Check the Texas Animal Health Commission NWS interactive zone map to verify infested zone locations.

TWA Best Practice document now available

As you head outdoors this fall, take along the TWA Best Practices for Screwworm Detection & Reporting in Wildlife. This 12-page booklet is designed to serve as an NWS resource for TWA members, hunters, ranchers, landowners and managers, and anyone who enjoys time outdoors. We now have printed copies that will be made available at future TWA events across the state.

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What to look for

Identification

NWS are parasitic flies that lay eggs in open wounds, genitalia or mucous membranes such as the umbilical cords of newborns, the nostrils, eyes or mouths of live warm-blooded animals. These eggs hatch into parasitic larvae (maggots) that only feed on living tissue, unlike other fly larvae that prefer dead or necrotic tissue. NWS larvae only burrow or “screw” into living tissue with sharp mouth hooks, giving them a screw-like appearance. Infested wounds quickly become infected and, if left untreated, will kill infested animals.

What you can do

Regularly reviewing game cameras, observations of wildlife while hunting or viewing animals, and inspection of hunter-harvested wildlife are important tools that can be used for NWS surveillance. While all warm-blooded mammals can be infested with NWS, white-tailed deer, jackrabbits, cottontails, small mammals and turkeys are more commonly affected. Instances of live or just-harvested animals with live maggots should be reported immediately.

Texas Parks and Wildlife Department (TPWD) has established procedures for the take of certain wildlife suspected to be infested with NWS.

Inspect all harvested wild game. If a harvested animal has a suspected infection, utilize a tarp or other barrier to keep larvae from coming into contact with the soil. Report the animal to your TPWD biologist, and follow guidelines for carcass treatment and disposal. Carcasses with no sign of infestation can be disposed of through normal processes.

How to report and who to report to

Pesticides for NWS

For a list of currently registered products that meet the U.S. Environmental Protection Agency’s (EPA) efficacy data, please visit Pesticides for Control of New World Screwworm.

The EPA has approved Fyfanon® ULV AG (Malathion) for treating the ground around dead wildlife when NWS larvae have already exited the carcass to pupate in the soil.

What is being done

Sterile flies are a proven technique to eliminate this pest. It is estimated that to push the screwworms back out of the United States, 500 million flies per week will need to be produced and dispersed. The following actions are in place, or under development, to expand our sterile fly resources:

TWA statement on potential feed-through treatment for wildlife

The  Texas Wildlife Association continues to work with our state and federal partners to identify and share tools that Texas landowners can use in the prevention and treatment of NWS.

We are encouraged by the recent announcement of collaborative field trials involving the United States Department of Agriculture, the Food and Drug Administration, and the Texas Parks and Wildlife Department to evaluate the use of a feed-through treatment for wildlife applications. This research represents an important step toward developing science-based management options to protect Texas wildlife resources as the construction of vital sterile insect infrastructure moves forward.

We look forward to the results of these trials and are hopeful they will determine whether this treatment can be demonstrated to be both safe and effective in preventing NWS infestation in wildlife.

Stay updated by visiting these sites

Additional online resources