06/13/2026
New World Screwworm officially reported in Tom Green County
We would like to cover the case of New World Screwworm officially confirmed on a cow today in Northern Tom Green County according to a quarantine map and Texas Animal Health Commission press release. We would like to cover a few questions and give some links to resources as well.
What are New World Screwworms, and why are they a big deal?
New World Screwworms (Cochliomyia hominivorax) is a parasitic fly native to the Western Hemisphere. The fly lays eggs next to fresh wounds in warm-blooded animals, and the larvae (aka maggots) will then feed on the living tissue causing severe wounds. If these wounds are left untreated, death will often occur as the wound will grow in size attracting more to the site. They will eat skin, muscle, and bone.
New World Screwworms are a big deal because of previous extermination for the United States and most of Central America over 40 years ago. This modern miracle was achieved via sterile male flies. They cause high death loss in livestock, native wildlife, dogs, cats, and on rare occasions people. It is considered a Foreign Animal Disease by the USDA and the CDC.
What does this mean for Tom Green County and regards of warm blooded animals in the area?
For our main clientele of domestic pets (dogs and cats), movement in the state of Texas has not been restricted yet. Travel with animals to Mexico is no longer allowed, but you can return from Mexico with a pet that has a certificate of verification of no infestation and treatment. Travel to other states may not be allowed (ex. Florida), and it is highly recommended to check the USDA Pet Travel Website for further information.
For all non-domestic pets (livestock, wildlife, etc.) in the active quarantine zone (yellow section of the map), you must contact Texas Animal Health Commission for any and all questions regarding movement, inspection, and quarantine protocols. For those in the observation area, you have no movement restrictions at this time, but you should be extremely vigilant for any and all signs. Daily inspection of all animals is highly recommended. Remember, detection is key to aid in reducing the spread and potentially additional resources such as sterile fly drops. Quarantine does not mean you can not move an animal forever, but failure to report a known case carries severe penalties of up to $5,000 per day.
For up to date information regarding ever changing quarantine zones and travel requirements, please see the following resources.
USDA Pet Travel
https://www.aphis.usda.gov/pet-travel -link-cdc-alert
Texas Animal Health General information and non-domestic animal movement
https://www.tahc.texas.gov/emergency/nws.html
Current Quarantine zones and observation areas
https://tahc.maps.arcgis.com/apps/instant/nearby/index.html?appid=8455917e956b474f995cc3b94d3ef54b&sliderDistance=1
What signs should I look for with an infestation?
The following are signs from the Texas A&M Agrilife extension:
Foul-smelling wounds with visible maggots
Animals biting or licking at wounds
Lesions in navels, ears, dehorning or branding sites
Unusual restlessness or lethargy
This link has picture of the larvae (maggot) and a wound
https://agrilifeextension.tamu.edu/new-world-screwworm-fact-sheet/
What should I do to prevent myiasis (maggots in a wound)?
The best prevention is to daily inspect your pets and animals for any and all wounds or infections to include bite wounds, skin infections, hot spots, ear infections, or any other break in the skin barrier. Look for any white grains (egg sacs) and remove them immediately from an area of concern. You should seek prompt veterinary care for any and all previously listed conditions.
For dogs and cats, there are several prescription oral and topical flea and tick preventatives available to prevent and treat New World Screwworm infections. Over the counter, Capstar has been approved to treat an active infection.
For livestock and horses, there is Exzolt (cattle only), Dectomax injectable, and Ivermectin injectable.
Please see the following link for more information
https://www.fda.gov/animal-veterinary/safety-health/new-world-screwworm-information-veterinarians
Helpful resources and quarantine zone information
If you have any questions, we would be happy to answer them for you. You can call the clinic or text the clinic at 325-284-3017. You can also email us at [email protected]
CVM is providing information to support veterinarians with the identification of animal drugs for NWS myiasis.
