Update Note: This article reports new information involving the New World screwworm outbreak following Nature World News' earlier coverage of the first U.S. wildlife case. Latest verified figures: 116 confirmed U.S. animal cases, 56 active, per USDA data reported by Texas Public Radio on Thursday, Nov. 5, 2026.

Confirmed New World screwworm cases in the United States have climbed to 116, with 56 still active, according to U.S. Department of Agriculture data compiled by Texas Public Radio as of Nov. 5. That is nearly double the 59 cases counted on Oct. 21, and the total now includes a second wildlife detection, an elk in Jeff Davis County, Texas.

The surge arrives just as Texas' general deer season opened Saturday, Nov. 7, putting large numbers of hunters in the field across a white-tailed deer herd that the Texas Parks and Wildlife Department (TPWD) estimates at about 5.64 million. No screwworm infestation has been reported in a deer so far.

That makes this season a test — and hunters are the ones running it. Hunters and processors will handle more wild animals in the next eight weeks than at any other time of year, giving officials their best chance to learn whether the flesh-eating parasite has moved from livestock and game ranches into free-ranging deer.

A Fall Spike Across Three States

The outbreak picked up sharply in autumn. USDA logged four domestic cases in August and three in September, then 36 in October and 24 in the first days of November, according to KBTX, citing the agency's online dashboard. Recent detections include cattle in Hudspeth and Mitchell counties in Texas, a horse in Greenlee County, Arizona, and horses, cattle, and a dog in New Mexico.

Weather may be part of the reason. "As we're coming into the fall and the weather's getting milder, that's likely having an impact on fly numbers," said Aaron Tarone, a professor of entomology at Texas A&M University. USDA also counts six wild screwworm flies captured in surveillance traps, most of them since October.

Of the 116 cases, 114 involved livestock or pets. The two wildlife cases, both elk in West Texas, are listed as inactive. Officials say a rising count also reflects better detection, since more people are now checking animals and reporting wounds.

Nature World News previously reported on the first wildlife case, a hunter-harvested elk on a Pecos County game ranch announced Oct. 21, and on how hunters could inspect game before the season opener. Since then, the case count has nearly doubled, Arizona has recorded its first cases, and a second elk has been confirmed.

The History Behind Biologists' Concern for Deer

Wildlife biologists watch deer closely because screwworm has hit Texas herds before. During the last major outbreaks of the 1950s and 1960s, about half of the state's white-tailed deer population was lost, KLTV reported, and Texas Public Radio cited historical estimates that the parasite killed as many as 80 percent of newborn fawns before eradication. Those estimates come from an era with far less precise monitoring.

Researchers back then also learned to use deer as a tracking tool, watching infestations in wild herds to map how the fly moved across the state. Deer are most vulnerable during the rut, when bucks fight and suffer wounds, and as newborn fawns with fresh navels.

The danger with wildlife is that no one is checking them daily. "Unfortunately, with wildlife, there is no proven treatment," South Texas veterinarian Gaylon Wilmeth-Burleson told Texas Public Radio earlier this year. An infested deer can hide in brush and die unseen, allowing larvae to drop into the soil and mature into new flies.

Inspection Steps Before Field Dressing

TPWD is asking hunters to look over every animal before field dressing or moving it. Warning signs include large open wounds, visible maggots or larvae, a strong rotten odor, and behaviors such as rubbing against trees or fences, head shaking, and unusual irritability, KLTV reported. Check the ears, eyes, nose, mouth, genitals, feet, and any antler or fighting wounds.

"We encourage all hunters and landowners to be vigilant for signs of New World screwworm while they are out in the field this season," said Alan Cain, director of TPWD's Wildlife Division, when the first elk case was announced. Suspected wildlife cases should be reported to TPWD at 512-389-4505 or a local TPWD biologist. Livestock and pet cases go to the Texas Animal Health Commission at 1-800-550-8242.

Maggots on a carcass do not by themselves mean screwworm, since common blow flies also lay eggs on dead tissue. That is why officials want samples collected and tested rather than assumptions made in the field. Hunters should not try to treat or move a live infested animal. USDA says screwworm is not a food safety risk, but hunters should never harvest or eat an animal that appears sick.

The Sterile Fly Gap

The main weapon against screwworm has not changed since the 1960s. Factories raise and sterilize huge numbers of male flies, which are released to mate with wild females that then lay eggs that never hatch. Historically, eradication required about 500 million sterile flies a week.

Current supply falls well short of that — by hundreds of millions of flies a week. A plant in Panama produces about 100 million flies a week and one in Mexico about 40 million, KBTX reported. A new U.S. plant at Moore Air Base in South Texas is due to finish construction next April, with a goal of 100 million flies a week by this time next year. Dudley Hoskins, USDA under secretary for marketing and regulatory programs, said "we will continue to be in a response posture" until production reaches full output.

Texas A&M researchers are testing electron beams as a faster, non-radioactive alternative to the cobalt sources used to sterilize flies. "So far, the results look good," said Suresh Pillai, director of the university's National Center for Electron Beam Research. The work has not been peer reviewed, and USDA says it still must be validated.

For ranchers and deer breeders, each new infested zone brings movement restrictions, inspections and treatment costs. The next milestones are USDA's daily dashboard updates, any deer detections reported through the season, which runs through Jan. 3 in the North Zone and Jan. 17 in the South Zone, and progress on the Moore Air Base plant.

Developing Story Timeline

Nov. 7, 2026: Texas general deer season opens statewide with no screwworm cases reported in deer.

Nov. 5, 2026: USDA data show 116 confirmed U.S. animal cases, 56 active, including a second elk in Jeff Davis County.

Oct. 21, 2026: USDA confirms the first U.S. wildlife case in a hunter-harvested elk in Pecos County, Texas.

June 3, 2026: USDA confirms the first U.S. case of the current outbreak in a Zavala County, Texas, calf.

What Readers Want to Know

How many screwworm cases are there now? USDA data reported Nov. 5 show 116 confirmed U.S. animal cases across Texas, New Mexico, and Arizona, with 56 active.

Has screwworm been found in deer? Not yet. The two confirmed wildlife cases were both elk in West Texas, and both are inactive.

What should hunters look for? Open wounds with maggots or a foul smell, especially around the head, genitals, feet, and fighting wounds, plus odd behavior such as head shaking or rubbing against trees.

Who do I call about a suspected case? Wildlife cases go to TPWD at 512-389-4505. Livestock and pets go to the Texas Animal Health Commission at 1-800-550-8242.

Is deer meat safe to eat? USDA says screwworm is not a food safety risk. Do not harvest or eat an animal that appears sick or visibly infested.

When will more sterile flies be available? A new plant at Moore Air Base in South Texas is due to finish construction next April, with a goal of 100 million flies a week by late 2027.