New World Screwworm: What Pet and Livestock Owners Need to Know
The New World Screwworm is a parasitic fly larva that can affect warm-blooded animals, including our beloved family pets and farm animals. While most fly larvae only target decaying tissue, screwworms prefer to settle in small, open cuts, tick bites, or fresh wounds on living animals.
Because early identification makes a world of difference, learning the basics of screwworm prevention and care helps keep your dogs, cats, and livestock safe and comfortable. By staying proactive and checking your animals regularly, you can easily catch potential issues before they become serious.
Screwworm in Dogs
Dogs can become exposed to screwworms due to their active outdoor behavior, their likelihood of minor cuts or scrapes, and insect bites. A simple scratch, tick bite, or post-surgical incision can quickly become an egg-laying site for a female screwworm fly.
Common Symptoms in Dogs:
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Enlarged or Non-Healing Wounds: Minor wounds that expand rapidly rather than healing
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Foul-Smelling Discharge: A reddish-brown fluid with a distinct, unpleasant odor draining from the site
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Visible Larvae: Seeing larvae burrowed inside the pocket of the wound
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Behavioral Changes: Persistent licking or biting at a specific spot, restlessness, whimpering, extreme lethargy, or loss of appetite
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Swelling and Heat: Warmth, discomfort, and pronounced swelling around the affected tissue
Screwworm in Cats
Cats—especially outdoor or free-roaming cats—are vulnerable to screwworm infestation. Feline grooming habits can sometimes obscure early signs, as cats often attempt to clean away discharge, masking the problem until the infestation is advanced.
Common Symptoms in Cats:
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Hidden Deep Wounds: Scratches from cat fights, abscesses, or surgical sites (such as spay/neuter wounds) become prime targets
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Hiding or Aggression: Cats in discomfort often hide under furniture, withdraw from social interaction, or become sensitive when touched near the infested area
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Over-Grooming: Intense licking or scratching at a localized area, frequently leading to hair loss around the wound
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Systemic Illness: Fever, rapid weight loss, dehydration, and weakness as the infestation progresses
The Importance of Prompt Treatment for Pets
Screwworm infestations in pets require prompt professional veterinary intervention. Never attempt to squeeze, crush, or pull larvae out with tweezers without professional guidance, as breaking the larvae inside the wound can trigger severe inflammatory reactions or secondary infection. Our team is here to help. Call us at (512) 596-3749 if you suspect your pet/cat is infested.
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Screwworm in Livestock
In cattle, horses, sheep, goats, and pigs, screwworm infestations can impact herd health and productivity. Calves are particularly vulnerable through the fresh umbilical cord stump immediately after birth. Other entry points include brand marks, dehorning or castration sites, barbed-wire cuts, and tick bites.
Impact on Livestock:
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Rapid Herd Contamination: A single infected animal can attract additional flies, leading to multiple overlapping infestations across a herd
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Weight Loss & Reduced Yield: Infested livestock experience discomfort and stress, leading to a decline in feed intake and milk production
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Vulnerability in Young Stock: Newborn livestock need prompt attention if umbilical infestations occur
Treating livestock for screwworm involves both immediate animal-level care and thoughtful herd-wide health protocols. Call us at (512) 596-3749 to begin a prompt treatment plan if you suspect your herd has been infested.
Key Takeaways
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Targeted Care: Screwworms target living tissue, making prompt veterinary evaluation essential
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Effective Prevention: Preventing open wounds and proactive wound management is your best line of defense to protect your pets/animals
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Maintain Year-Round Tick Control: Ticks create small, itchy bite wounds that animals scratch, opening up perfect targets for screwworms. Keeping pets on preventative flea/tick medication removes a major entry point
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Early Detection is Key: Check pets and livestock daily for fresh wounds, tick bites, or unusual discharge—especially during warm weather
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Leave Removal to Experts: Professional removal ensures the wound heals cleanly without leaving remnants behind
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Community Support: Timely reporting protects both your animals and the broader community. Screwworms are a zoonotic parasite, so protecting our pets/animals helps keep humans safe from infection, too
If you suspect your dog, cat, or livestock has been exposed to screwworms—or if you notice an unusual, non-healing wound—don't wait. Call $Hospital today at (512) 596-3749 to begin a treatment plan. For more information about screwworms, please visit the resources below.