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New World Screwworm: What K9 Handlers Need to Know

Many of you have seen recent headlines: New World Screwworm (Cochliomyia hominivorax) has arrived in Texas from Mexico. Here’s what that means for working canine handlers and their dogs, and what you can do right now.

What is it?

Unlike most flies whose larvae (maggots) feed on dead tissue, screwworm larvae burrow into open wounds on living animals, causing severe damage that can be fatal if untreated. The pest was eradicated from the U.S. in 1966, but its return to border states warrants attention.

No need to panic — but handlers working canines in border states should act now:

Inspect and protect.

Check all animals in your care for open wounds. Apply fly-repellent ointment like SWAT around any wounds to deter infestation. Collect any maggots from wounds and submit to a veterinarian to determine if they are screwworms.

Stock up.

Keep NexGard or Simparica Trio on hand. Both are approved for treatment and are effective against screwworm infestations. Nitampyram (Capstar or other similar products) is also effective as a one dose treatment. Consult your veterinarian for dosing guidance.

Fly control matters.

Review your fly mitigation plan and make sure you’re minimizing fly access throughout your canine kennel area, facility or vehicle. See tips on controlling your fly population below.

Evaluate all dogs coming and going from the field.

Examine every incoming and outgoing animal for wounds or signs of infestation.

Transporting canines out of border states?

A few states have banned the import of pets from impacted areas such as New York, Pennsylvania, and Florida, but most states are simply requiring health certifications confirming animals are screwwormfree 3–5 days before transport and at the time of transport. Get ahead of it by coordinating with your team veterinarian now, so you’re ready when requirements go into effect. Check-in regularly with your state regarding potential importation rule changes.

By staying vigilant and working together, we can keep the animals in our care safe.

Additional educational resources:

Mitigation Tips

With the recent confirmation of New World Screwworm (NWS) in South Texas, canine handlers that deploy into this region should think about mitigation in layers.

The biggest risk factor is…

…the specific NWS female fly finding an open wound, surgical incision, draining skin lesion, tick bite, ear wound, or moist body opening where eggs can be deposited. Female flies are strongly attracted to wounds and mucous membranes.

You should already have NexGard, Simparica Trio, or Nitenpyram (Capstar) in your plan, and you should implement the following deployment mitigation priorities:

1. Aggressive Wound Management (Priority)

Conduct daily hands-on wound checks. Cover wounds whenever practical and keep all wounds clean and dry. Protect and/or remove from service until healed, all canines with:

    • Surgical incisions
    • Hot spots
    • Skin, foot or other wounds
    • Ear injuries
    • Tick attachment wounds

2. Move All High-Risk Dogs Indoors

If canines are housed outdoors or there is limited indoor housing space, prioritize:

    • Dogs with any preexisting skin, eye or ear issues
    • Dogs with skin or ear injuries, infections
    • Dogs with wounds (whether or not they are surgically repaired or small)

3. Physical Fly Exclusion

If your kennel or housing area is open air:

    • Increase air flow with fans
    • Install fine insect screening around kennels
    • Add screened shade structures
    • Add fly curtains at housing entrances if possible
    • Install fly traps or fly aversion in areas where dogs are kenneled, resting

4. Develop a Suspect Case SOP

Every team deployed with canines in the border area or quarantine zone should have a written procedure if suspicious larvae are found:

    • Isolate animal to treat
    • Photograph lesion
    • Contact veterinarian
    • Administer Nexguard/Simparica or Capstar
    • Preserve larvae samples (put in 70% alcohol to kill)
    • Document animal origin and movement history

5. Daily Screening

    • Include a visual wound inspection after search activities at the end of the day.
    • Actively record and monitor all dogs daily with cuts, scrapes and abrasions.
    • Apply fly prevention products and cover wounds if possible.
    • Keep all wounds clean and dry and monitor until fully healed.

6.Daily Surveillance Program in all Animals

Train handlers to recognize and to immediately report:

    • Enlarging wounds
    • Foul-smelling wounds
    • Bloody wound drainage
    • Unexplained pain
    • Head shaking
    • Excessive licking
    • Visible larvae

Credits

This information was made possible through a collaboration with the Bissell Pet Foundation‘s Animal Incident Management Initiative. Learn more about the Bissell Pet Foundation’s response to New World Screwworm.

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