An Old Threat Making Headlines Again

If the New World screwworm has been around for years, many pet owners are asking a reasonable question:

Why is it called "New World" if there is nothing new about it?

The answer is surprisingly simple.

The name does not mean the parasite was recently discovered. The term "New World" simply refers to the region where this species historically existed—North and South America. There is also an "Old World" screwworm found in parts of Africa, Asia, and the Middle East.

Although this parasite was successfully eliminated from the United States decades ago, recent confirmed cases near the southern border have caused renewed concern among veterinarians, livestock producers, and pet owners alike.

The good news is that awareness—not panic—is the goal.

What Exactly Is a Screwworm?

Despite its name, a screwworm is not actually a worm.

It is the larval stage of a fly. After the adult fly lays eggs, those eggs hatch into larvae.

Unlike ordinary maggots, which primarily feed on dead tissue, New World screwworm larvae feed on living tissue. This is what makes them so dangerous and why veterinarians take suspected cases seriously.

How Does a Pet Become Infected?

One of the most important things pet owners should understand is this:

The fly does not create the wound. It looks for one that already exists.

Adult female flies are attracted to the odor, moisture, drainage, blood, and irritation associated with wounds or body openings. Once they locate an appropriate site, they deposit eggs in or near the area.

After hatching, the larvae begin feeding on living tissue, causing the wound to become larger and more severe.

What Types of Wounds Can Attract Screwworm Flies?

Many pet owners immediately think of major injuries.

But sometimes the problem begins with something much smaller.

Examples include:

• Tick bites

• Hot spots

• Ear infections

• Surgical incisions

• Scratches from other animals

• Skin irritation caused by excessive licking

• Minor cuts and scrapes

• Wounds hidden beneath long hair

• Areas around the nose, mouth, eyes, or genital region

Most of us have seen our pets come inside with a small scrape and thought, "That will probably heal on its own."

Most of the time it does.

But this situation reminds us that small problems deserve attention too.

Which Animals Can Be Affected?

Dogs are certainly susceptible, but they are not the only animals at risk.

New World screwworms can affect:

• Dogs

• Cats

• Rabbits

• Horses

• Livestock

• Wildlife

• Small mammals

• Birds with wounds

In reality, nearly any warm-blooded animal can become infected if conditions are right.

Outdoor pets, barn cats, hunting dogs, livestock guardian dogs, and animals recovering from surgery may require additional monitoring.

Can Humans Become Infected?

Human cases are uncommon, but they have occurred.

Fortunately, screwworms are not spread from pet to owner like a cold or virus. You do not "catch" screwworms from your dog or cat.

The fly itself must deposit eggs into a wound or body opening.

The same common-sense wound care principles that protect our pets also help protect us.

Signs Pet Owners Should Watch For

Seek veterinary attention if you notice:

• Excessive licking or chewing at one area

• A wound that suddenly appears worse

• Drainage or a foul odor

• Swelling

• Pain or sensitivity

• Restlessness

• Head shaking or ear irritation

• Sudden behavioral changes

• A pet acting uncomfortable or "not themselves"

Pets often tell us something is wrong long before we discover the cause.

Can Screwworms Be Prevented?

Fortunately, prevention is often straightforward.

• Check wounds daily.

• Keep surgical sites clean.

• Do not ignore ear infections or hot spots.

• Look between toes and under collars.

• Inspect pets after hiking, hunting, camping, or outdoor adventures.

• Seek veterinary care promptly when wounds fail to improve.

Early treatment remains one of the best defenses.

The Bottom Line

Most pet owners will never encounter a New World screwworm infestation.

But awareness remains one of the best forms of prevention.

Perhaps the biggest lesson is this:

The fly seeks out existing problems—it does not create them.

And sometimes the small wound we barely notice is exactly the one that deserves a second look.

Because moments matter.