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New World Screwworm (NWS) Outbreak — What Rescue & Transport Professionals Need to Know
An active NWS outbreak in Texas and New Mexico is triggering rapidly-evolving import restrictions across the country. This hub centralizes what you need to keep animals moving safely and legally.
Last Updated: June 19, 2026 18:29 CDT
All information is based on the meticulous work of a group of dedicated animal welfare leaders, staff, & volunteers.
Built at Midnight does not take any credit for the gathering of this information and is only used to build & host the information hub.
For questions or comments, please email hello@builtatmidnight.com.
The Basics
What Is New World Screwworm
Before diving into current transport rules & regulations, here's what you're actually dealing with — and why states are acting quickly.
What is the New World Screwworm?
New World Screwworm (Cochliomyia hominivorax) is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. Unlike most flies, it infests healthy tissue — not just wounds. It can be fatal if untreated.
Who is at Risk?
All warm-blooded animals, including dogs, cats, horses, and livestock. There is no evidence NWS infests fruits, vegetables, or other food sources. Companion animals remain at relatively low risk with proper preventive care in place.
Where it is right now?
Active infestations have been confirmed in Texas (quarantine and surveillance zones) and New Mexico. Florida previously had detections. The situation is evolving — check the USDA APHIS confirmed cases map regularly.
Why transport is affected?
Because rescues and shelters pull from across a state, they can inadvertently move animals that originated near infestation zones. States are tightening entry requirements to prevent NWS from spreading through the interstate transport pipeline.
Get to Know The Maps
Understanding the Zone System
This is the #1 source of confusion. Not all of Texas is the same — and most states' rules differ significantly depending on which zone an animal comes from.
Infested Zone
Infest / Quarantine Zone
Active confirmed NWS infestations. This is the most restricted tier. Animals from these areas face the strictest import requirements from other states — often requiring treatment documentation and special permit approval.
Shown in yellow on the TAHC interactive map.
Surveillance Zone
Surveillance / Buffer Zone
Adjacent to infested areas and under active monitoring. Also considered a quarantine area by TAHC. Animals originating here may trigger the same enhanced requirements as infested zones for some destination states.
Shown in blue on the TAHC interactive map.
Veterinary Guidance
Approved Treatments & Preventatives
Not all products are created equal — and not all will satisfy state import requirements. Here's what's FDA authorized and what to document on your health certificate.
Prevention － Dogs
FDA Authorized
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NexGard (afoxolaner)
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Credelio (lotilaner)
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Credelio Quattro
These provide ongoing protection and are the gold standard for satisfying state import requirements. Document product, date, and route of administration on the CVI.
Prevention － Cats
FDA AUTHORIZED
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NexGard Combo
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Credelio CAT
The same principle applies — document everything on the CVI. Cats are less commonly the focus of state rules but are still warm-blooded animals subject to NWS risk.
Active Infestation Treatment
Emergency Use Auth.
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Nitenpyram (generic Capstar)
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Available as Flea Assassin brand — significantly cheaper than Capstar
Important: Nitenpyram kills larvae fast but only stays active for ~24 hours. It is a treatment, not a preventative — it will not satisfy prevention requirements for interstate transport on its own.
Use with Caution
Limited / off-label
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Simparica — off-label emergency use only; may not satisfy state requirements
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Bravecto — currently approved for livestock use only
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NexGard Plus — conditionally approved; the "plus" is heartworm prevention, not the NWS treatment
When in doubt, confirm with your vet that the specific product satisfies the requirements of your destination state before transport.
Health Certificate Guidance
CVI Best Practices for Transport
A well-documented health certificate is your best protection against delays at the border. Here's what to do every time.
1
Issue the CVI within 5 days of departure
This is the safest window for the majority of states. Some (Maryland, Delaware) specifically require this. CVIs issued in GVL are visible electronically to destination states.
2
Document your preventative treatment on the CVI
Include the product name, date administered, and route of administration — even if the destination state doesn't explicitly require it. It protects you and your animals.
3
Add the standard NWS-free remark
Virginia confirmed this is acceptable language. Adding it to every CVI is now considered best practice regardless of state.
4
Confirm your vet knows how to add the NWS remark
There have been reports of vets unfamiliar with the "create new" remark field in GVL. If they're unsure, point them to the remark language below.
5
For Michigan: email the state 48 hours before transport
Send to MDARD-NWS-Permit@michigan.gov. No permit number is required — just advance notice. The HC should accompany the animal.
Recommended CVI Remark Language
"Animal originates outside of a New World Screwworm (NWS) infested or surveillance zone. Animals have been inspected by an accredited veterinarian and found free of New World Screwworm. [Product name] was administered on [date] via [route of administration] for NWS prevention."
Add this as a remark in GVL when issuing your health certificate. Virginia has confirmed this language is sufficient for entry. It's also recommended as a safeguard for all states — requirements are evolving rapidly, and having documentation in place ahead of time avoids last-minute scrambles.
Helpful Resources
Key Resources
Go to these first when you need the most current regulatory information.
TAHC NWS Zones Interactive Map
Live map of infested (yellow) and surveillance (blue) zones in Texas. Essential before any transport decision.
USDA APHIS Confirmed Cases Tracker
National map of confirmed NWS detections updated by the federal government.
Florida FDACS Emergency Rule
Florida Department of Agriculture press release on the extended and strengthened emergency rule for NWS following Texas and New Mexico detections.
Texas A&M NWS Training Course
Free online course on New World Screwworm preparedness and response education from Texas A&M AgriLife.
All information is based on the meticulous work of a group of dedicated animal welfare leaders, staff, & volunteers.
Built at Midnight does not take any credit for the gathering of this information and is only used to build & host the information hub.
For questions or comments, please email hello@builtatmidnight.com.