The MCS insect misting system can play a valuable role in protecting livestock from screwworm infestations by serving as a preventative measure against adult screwworm flies. Since New World screwworms lay eggs in open wounds, reducing the presence of adult flies around barns, pens, and pastures can significantly lower the risk of infestation. By using approved insecticides in a timed misting system, MCS systems help repel and kill flies before they have a chance to deposit eggs on animals. This complements other vital biosecurity practices like wound care, monitoring, and early intervention, forming a more comprehensive line of defense against this dangerous parasite.

Learn how MCS can Protect YOUR Livestock!

New World Screwworm (NWS) Overview:
Scientific name: Cochliomyia hominivorax

Nature: Parasitic fly that lays eggs in fresh wounds of warm-blooded animals.
Impact: Larvae feed on living tissue, causing severe wounds and potentially death.
Eradication History: Eliminated in the U.S. in the 1960s; still present in parts of Central and South America.
Current Concern (as of May 2025): Renewed threat; requires monitoring and control.

Signs of Infestation:
Foul-smelling wounds with maggots
Animals biting or licking wounds
Lesions (navel, ears, dehorning, branding sites)
Unusual restlessness or lethargy

Lifecycle & Damage:
Larvae burrow into wounds, enlarging and deepening them.
Mature larvae reach 17 mm and have spiraled spines.
Damage includes tissue destruction and risk of death if untreated.

Signs of New World screwworm in animals
The name screwworm refers to the feeding behavior exhibited by the maggots as they burrow (screw) into the wound. These maggots and their feeding cause extensive damage by tearing at the hosts’ tissue with sharp mouth hooks. The wound will become larger and deeper as more and more eggs hatch and larvae feed on the living tissue. This results in serious and often deadly damage to the animal if not discovered and treated.

Identification:
Larvae: Confirmed by internal breathing tubes.
Adults: Metallic blue with three stripes on the thorax, large orange eyes.
Look-alike: Cochliomyia macellaria (secondary screwworm) does not infest live animals.

Control and Treatment:
Prevention: Prompt wound treatment, sanitation.
Treatment: Topical larvicides like coumaphos or permethrin, under vet supervision.

Reporting:
Immediate Actions: Isolate suspected animals.

Contact:
Local veterinarian or wildlife biologist
Texas Animal Health Commission: (800) 550-8242
US Department Agriculture Veterinary Services: (512) 383-2400
Do not transport affected animals until advised.

Monitoring:
Regular livestock inspection and biosecurity practices are critical.

Conclusion
U.S. producers have not treated livestock for NWS in more than 40 years. Although this health threat has not been experienced in several decades, several treatment strategies exist today and should always be used in consultation with your local veterinarian.
Treatments could include:
•Preventive measures: treat wounds promptly and maintain sanitation
•After infestation: topical larvicides (e.g., coumaphos, permethrin), cleaning and removal of larvae

Visit the U.S. Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) list of potential pesticides against New World screwworm.
https://www.aphis.usda.gov/sites/default/files/pesticides-for-nws.pdf