Not All Maggots Are the Same: Why Goat Owners Should Know About Screwworm
Most livestock owners have seen maggots in a wound, on damp bedding, or around decaying organic matter at some point. In many cases, those larvae are from common blowflies feeding on dead tissue or waste.
Screwworm is different. New World screwworm larvae feed on living tissue. That difference is what makes screwworm so serious, why infestations can worsen quickly, and why suspected cases should be reported immediately.
This post is not meant to create panic. It is meant to help goat owners recognize the difference between an ordinary fly problem and a possible livestock health emergency.
The Life Cycle Matters
Understanding the life cycle explains why early detection matters.
1. Egg Stage
Adult female flies are attracted to:
- wounds
- fresh surgical sites
- navels of newborn animals
- horn bases
- ear tag holes
- scours-soiled hair
- mucous membranes (nose, eyes, vulva)
- infected hooves
A female may lay 100–300 eggs at a time.
Eggs hatch in about 12–24 hours.
2. Larval Stage (the damaging stage)
After hatching, larvae:
- burrow head-down into the wound
- feed on living tissue
- enlarge the wound rapidly
Larvae arrange themselves in a screw-like pattern, which is where the name comes from.
Over 5–7 days, the wound grows deeper and larger.
Animals often show:
- a wound that seems to get worse quickly
- intense irritation or pain
- foul-smelling or bloody discharge
- rapid tissue destruction
3. Pupal Stage
After feeding:
- larvae drop to the ground
- burrow into soil
- pupate
This stage lasts 7–10 days, depending on temperature.
4. Adult Fly
Adults emerge and can travel many miles to find new hosts.
Warm temperatures accelerate the entire cycle.
Under favorable conditions, a full life cycle can occur in about three weeks.
Goats & Other Animals at Risk
Screwworm can affect any warm-blooded animal, including:
- goats
- sheep
- cattle
- horses
- wildlife
- pets
- humans (rare but possible)
Young animals are particularly vulnerable.
Common Entry Points in Goats
Flies seek moist tissue or wounds, including:
- kidding/navel areas
- castration sites
- disbudding wounds
- ear tag holes
- horn injuries
- abscess ruptures
- cuts or scrapes
- scours-soiled hair around the tail
- infected hooves or foot rot
- vulva before & after kidding
Even tiny wounds can attract egg laying.
Warning Signs of Screwworm
Early detection is critical.
Possible signs include:
- wounds that rapidly enlarge
- tissue damage worse than expected for the size of injury
- bloody discharge
- strong foul odor
- visible larvae deep in the wound
- animals acting restless or in pain
- animals repeatedly biting or licking an area
One important clue:
Larvae are often deeply embedded in the wound, not just on the surface.
The Importance of Immediate Reporting
Screwworm is considered a foreign animal disease threat.
Reporting suspected cases allows animal health officials to:
- confirm the diagnosis
- contain spread
- deploy control programs if needed
Quick reporting protects the entire livestock community.
What You Should Do if You Suspect Screwworm
- 1. Do not ignore it.
- Contact your veterinarian immediately.
- Report to your state animal health official or USDA APHIS office.
- Keep the affected animal isolated if possible.
- Avoid moving animals off the property until guidance is given.
Do not attempt to handle the situation alone without veterinary involvement.
Prevention After a Show or Trip off the Farm
Before leaving a show or sale facility:
- Remove all bedding from the trailer.
- Sweep or scrape manure from the trailer floor.
- Avoid transporting used stall bedding.
- Knock manure and debris off hooves before loading animals.
- Inspect animals for wounds or irritated areas
After arriving home:
• Clean the trailer thoroughly
• Remove manure and organic debris
• Wash or disinfect grooming tools and equipment
• Observe animals closely for several days after travel, and quarantine new or returning animals according to your farm’s biosecurity practices
Hooves, trailers, bedding, and equipment can all carry small amounts of organic material where insects develop. Taking a few minutes to clean these areas helps prevent flies, parasites, and other hitchhikers from spreading between farms and regions.
Responsible breeders understand that good stewardship includes protecting not only their own herd, but the broader livestock community.
A clean trailer, clean hooves, and a quick post-show inspection are small habits that make a big difference.
Prevention On the Farm
Wound Management
Promptly treat and protect:
- kidding injuries
- disbudding sites
- castration wounds
- cuts or abrasions
Fly Control
Maintain strong fly management around:
- barns
- bedding areas
- manure zones
- feed areas
Hygiene
- keep animals clean and dry
- treat wounds promptly
- address scours quickly
- monitor newborn navels closely
Regular Inspections
During warm seasons, routinely check:
- tail area
- navel area of kids
- ears and horn bases
- wounds or abscess sites
- vulva before & after kidding
Why HSFGR Includes This Section
Screwworm infestations are rare, but they are serious. Because of the damage they can cause to animals and the potential impact on livestock agriculture, suspected cases should be handled with veterinary guidance and reported promptly to the appropriate animal health officials.
For goat owners, the goal is simple: know what is normal, know what is not, and act quickly when something looks wrong.
Vigilance is not alarm. It is responsible stewardship.
Good livestock care has always meant watching the little things before they become big problems. Clean trailers, sound wound care, fly control, and early reporting help protect not only our own herds, but the broader livestock community.
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