Tracker · Updated October 2026

Screwworm in dogs: every US case, the Texas outbreak, Mexico's border cases and the symptoms to check for

USDA has confirmed New World screwworm in 5 dogs in the United States, out of 52 animal cases in Texas and New Mexico since June 3, 2026. The latest, in Brewster County, Texas, on October 2, was still active on October 10. Just south of the border, dogs make up 114 of 454 Mexican cases within about 100 miles of the US.

5 dogs

confirmed with New World screwworm in the US, out of 52 animal cases (USDA, Oct 10, 2026)

52

US animal cases, June 3 to October 10, 2026

2 active

US cases still active on October 10, one of them a dog

114

dog cases in Mexico within about 100 miles of the US

0

locally acquired human cases in the US (CDC)

By the dogeats.in Editorial Team · Published 2026-10-11 · Updated 2026-10-11 · Free to reuse with credit (CC BY 4.0)

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How many dogs have had screwworm in the US?

Five. The US Department of Agriculture (USDA) has confirmed New World screwworm in 5 dogs since the pest reached the United States in June 2026. Its public dashboard, updated October 10, 2026, lists 52 animal cases in all.

Dogs are the fourth most common host so far. Cattle account for 22 cases, sheep 16, goats 7, dogs 5 and horses 2. No wildlife case has been confirmed in the US.

Four of the five dogs lived in Texas and one in New Mexico. The most recent dog case, in Brewster County, Texas, was confirmed on October 2, 2026 and is one of only 2 active US cases.

The first dog case was confirmed on June 7, 2026. A Texas veterinarian in Andrews County first reported it, but the dog lived in Lea County, New Mexico, so USDA reclassified it as New Mexico's first case.

USDA said early reports indicated that dog had recently been in Mexico, and later said its travel and exposure history were unknown. The other four dog cases were in Pecos County (June 29), Sutton County (July 13), Crockett County (August 31) and Brewster County (October 2).

Screwworm in Texas: cases by month and county

Texas has 50 of the 52 US cases. The first was a 3-week-old calf in Zavala County, confirmed on June 3, 2026, with larvae in its umbilical area.

Cases peaked in June, with 30 confirmations. They fell to 14 in July, 4 in August and 3 in September. One case was confirmed in October, the Brewster County dog.

The cases span 19 counties, 17 in Texas and 2 in New Mexico. Crockett County has 13, a quarter of the total. Brewster, Edwards and Terrell counties have 5 each.

USDA also recorded one wild screwworm fly caught in a trap in Brewster County on September 25, 2026. It is the only fly trap detection on the dashboard.

On October 10, 2026, Texas listed movement restrictions in parts of 12 counties: Brewster, Crockett, Edwards, Jeff Davis, Pecos, Presidio, Schleicher, Starr, Sutton, Terrell, Val Verde and Zapata.

Inside an infested zone, warm-blooded animals, pets included, may not leave without prior authorization from the commission. Owners need an inspection and a movement certificate first.

Screwworm in dogs in Mexico near the US border

Dogs are a much bigger share of cases just across the border. USDA publishes a running list of Mexican cases within about 100 miles of the US, from Mexico's animal health agency, SENASICA.

The list dated October 9, 2026 holds 454 cases from September 20, 2025 to October 7, 2026. Dogs account for 114 of them, or 25%. Only cattle, with 256 cases, appear more often.

Nuevo León dominates. It has 283 of the 454 cases and 103 of the 114 dog cases. Coahuila has 8 dog cases, Chihuahua 2 and Tamaulipas 1.

Dog cases near the border rose from 4 in April 2026 to 34 in June, then eased to 25 in July, 18 in August and 14 in September. Six more were listed from October 1 to 7.

As livestock cases fell, dogs made up a larger share. They were 14 of 35 near-border cases in September, or 40%, and 6 of 18 in early October.

How close to the US the Mexican dog cases are

Most Mexican dog cases on the list were 76 to 100 miles from the US. That band holds 99 of the 114 dog cases. Only 4 dogs were within 50 miles of the border.

The closest dog case was about 18 miles from the US, in Chihuahua state, on August 14, 2026. Among all animals, the closest case was a calf about half a mile from the US, in Coahuila, on August 1.

Older dogs dominate the list. The median age is 8 years, and 46 of the 114 dogs were 10 or older. Eight were under a year old.

Eight of the 27 cases still active on the October 9 list were dogs, all in Nuevo León. The age figures describe infested dogs only and do not show which dogs are most at risk.

What are the symptoms of screwworm in dogs?

Screwworm larvae feed on living tissue, usually entering through an open wound or a body opening. USDA asks owners in affected areas to check animals daily for four signs.

If you see any of these, call your veterinarian or state animal health official the same day. Do not try to treat a suspected case yourself.

• Draining or enlarging wounds
• Maggots or egg masses in a wound or body opening
• Signs of discomfort or irritability
• Lesions around body openings such as the ears, nose and genital area

USDA's general screwworm page adds head shaking and a smell of decay to the warning signs. Adult screwworm flies are about the size of a house fly, with orange eyes, a metallic blue or green body and three dark stripes on the back.

Prevention advice from USDA is practical: watch for wounds, treat them promptly and control ticks and other parasites that cause wounds. Ask your veterinarian which preventive product suits your dog.

Which drugs are authorized to treat screwworm in dogs?

Among the FDA actions USDA has announced, 4 cover dogs. The first came on December 17, 2025, more than five months before the first US case, when FDA conditionally approved Credelio Quattro.

FDA then issued emergency use authorizations for NexGard on February 18, 2026, generic nitenpyram tablets on June 11 and Simparica TRIO on August 13. Nitenpyram is the first generic animal drug authorized against screwworm.

These are prescription or labeled products with specific weight and age limits. This report gives no doses. Your veterinarian decides whether and how to use them.

Traveling with a dog between the US and Mexico

USDA has treated Mexico as affected by screwworm since November 22, 2024. Any dog entering the US from Mexico, including a US dog coming home, needs screwworm freedom certification.

The certificate must show the dog was inspected within 5 days before travel and found free of screwworm, or treated until free. In Mexico, clinic veterinarians authorized by the government can sign it.

Since August 3, 2026, Mexico also requires an inspection certificate for pet dogs going from the US to Mexico. A USDA-accredited veterinarian must sign it no more than 5 days before entry.

Pet dog travel to Mexico was briefly halted after the first US cases. The American Animal Hospital Association reported the halt on June 8, 2026, and its lifting on June 10.

How big the outbreak is, and the risk to people

The outbreak is far larger south of the border. CDC reports more than 209,400 animal cases and more than 2,700 human cases in Central America and Mexico. The current outbreak began in Panama and Costa Rica in 2023.

In the US, CDC reports no locally acquired human case. One travel-associated case was confirmed in August 2025 in a person who had returned from El Salvador.

The US last eradicated screwworm in 1966, using sterile male flies. USDA says new investments will bring production to about 500 million sterile flies a week, the scale used in that campaign.

When the first case was confirmed, USDA was already releasing 4 million sterile flies a week by air over the area. It set a 20-kilometer infested zone around each detection.

New Mexico's zone was released on August 30, 2026, after no new case for nearly three months. A second New Mexico case, a horse in Grant County, followed on September 17.

For more on disease risks for US dogs, see our rabies statistics and veterinarians by state reports.

Frequently asked questions

Methodology and limitations

US case counts come from the USDA APHIS New World screwworm public dashboard, which on October 11, 2026 read as of October 10. We transcribed all 53 rows of its case table: 52 animal cases and 1 fly trap. We checked them against the dashboard's own totals by month, status and state, then counted species and counties in Python.

Mexican figures come from the APHIS CSV of cases within about 100 miles of the US, dated October 9, 2026, which reproduces data from Mexico's SENASICA. We downloaded it and counted species, states, months, distances and ages.

Timeline, treatment and travel details come from APHIS announcements and pages, the Texas Animal Health Commission screwworm page and the CDC situation summary updated October 7, 2026.

Sources

1. USDA APHIS, Confirmed Detections of New World Screwworm dashboard (as of October 10, 2026), All 52 US animal cases, species, counties, dates, status, fly trap detection
2. USDA APHIS, NWS Current Status and Mexico case list CSV (October 9, 2026), 454 Mexican cases within about 100 miles of the US
3. CDC, New World Screwworm Outbreak situation summary (updated October 7, 2026), Human risk, 2025 travel case, Central America and Mexico totals
4. Also consulted: USDA APHIS, first dog case, June 8, 2026, USDA APHIS, first US detection, June 3, 2026, USDA APHIS, June 8, 2026, USDA APHIS, New Mexico zone release, August 30, 2026, Texas Animal Health Commission, New World Screwworm page, USDA APHIS, Pet Travel From the United States to Mexico, USDA APHIS, Bring a Pet Dog into the United States, USDA APHIS, New World Screwworm overview, USDA APHIS repost of FDA, December 2025, USDA APHIS repost of FDA, August 13, 2026, Screwworm.gov (USDA), American Animal Hospital Association, AAHA Trends, June 2026, USDA APHIS, Export Live Animals to Mexico page.

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