The New World screwworm (NWS) is a parasitic fly whose larvae (maggots) can cause serious wounds in animals and, rarely, people. Although the U.S. eliminated this pest decades ago, a Maryland resident who was recently diagnosed with a travel-related case in 2025 reminded health officials and veterinarians to be on alert for this reemerging threat.

What Is NWS

Slightly larger than a housefly with orange eyes and a metallic blue-green body with three dark stripes.

The parasitic fly lays eggs in open wounds or body openings (eyes, nostrils, mouth, genitals).

The maggots hatch quickly and feed on healthy tissue, causing painful, fast-spreading wounds.

Why It Matters

Infestations can become severe in just a few days and cause severe pain, rapid tissue destruction, and secondary infections.

Without treatment, screwworm infections can be life-threatening.

Pets, livestock, wildlife, and people can be affected.

Recent cases have been reported in Mexico, approximately 700 miles from the U.S. border

Signs to Watch For In Dogs

A wound that gets bigger, smellier, or suddenly much worse

Maggots visible in the wound

Increased licking, scratching, shaking of the head, or unusual behavior

Pain, decreased appetite, or acting “off”

What To Do

Early action saves lives. If you notice foul-smelling wounds or maggots, call your veterinarian immediately. With prompt treatment, pets typically make a full recovery.

Do not try to treat a screwworm infestation at home; removal and medications must be done safely by a vet.

Keep your pet’s wounds clean, dry, and covered until they can be seen.

Prevention Tips

Check pets regularly for any scratches or wounds, especially after outdoor adventures.

Keep living areas clean and reduce exposure to flies when possible.

Be extra vigilant when traveling with pets to high-risk areas where screwworm is present.

Dogs cannot tell us when they are hurting, but they often provide plenty of signals. Noticing these signs early can make a big difference in their comfort, mobility, and overall well-being. According to the American Veterinary Medical Association (AVMA), pain is a serious health concern that can affect a dog’s quality of life, making prevention, early detection, and proper management essential. Left untreated, chronic pain can lead to changes in behavior (such as withdrawal, irritability or reluctance to move), muscle loss, and arthritis. By recognizing pain early and taking action, owners can help slow its progression and greatly improve their dog’s quality of life.

Pain Matters

• Pain affects behavior, mobility, health, and emotional well-being.
• Chronic pain can lead to muscle loss, worsening arthritis, irritability, or withdrawal.
• Early recognition and treatment improves outcomes and prevents secondary issues.
• Dogs do not say “ouch” - recognizing subtle signs is key.

Physical / Mobility Signs

• Limping
• Difficulty getting up, jumping, or climbing stairs
• Stiffness after resting
• Change in posture: arched back, low head, shifting weight
• Shorter walks or reluctance to move

Behavioral Signs

• Less play or interest in walks and toys
• Sleep changes: more, less, or restless nights
• Avoiding touch or flinching
• Licking or chewing one spot excessively
• Whining, groaning, or other vocalizations
• Irritability or aggression

Slow, gradual changes are often easiest to miss. Knowing your dog’s normal routine helps catch those subtle signs.

Stress Signals

• Flattened ears, tucked tail, lip/nose licking, yawning
• Panting, wide eyes, raised hackles
• Pacing, restlessness, circling
• Destructive behavior, clinginess, hiding
• Appetite changes, diarrhea, vomiting, or excessive shedding

Acute vs. Chronic Pain

Acute: sudden, obvious pain from injury, surgery, or illness

Chronic: ongoing pain from arthritis, degenerative conditions, or cancer; often subtle but impactful

Owners often notice acute pain but miss chronic discomfort, which is why knowing your dog’s normal behavior is so important.

How We Can Help Our Dogs

• Being familiar with your dog’s normal behavior and movement - early detection and intervention improves comfort and mobility.
• Track changes by keeping notes or videos of concerning behavior.
• Consult your vet: early exams, diagnostics, and pain management can make a difference.
• Pain management: medications, physical therapy, weight control, and environment adjustments.
• Provide soft surfaces with good traction, easy access to favorite rest spots, a ramp for getting into car, and assist with stairs.
• Create a safe, quiet space
• Maintain predictable routines
• Provide mental enrichment like puzzle toys and sensory games
• Seek help if pain or stress persists or worsens

Conclusion

Detecting subtle signs of pain in dogs is essential for catching issues early, allowing for prompt treatment, better health outcomes, and a higher quality of life. Because dogs often instinctively hide discomfort, early clues are easy to overlook, and by the time obvious symptoms appear, the problem may have progressed. Noticing these small changes helps prevent chronic pain and ensures your dog receives timely, compassionate care.