New World Screwworm: A Threat Alpaca Breeders Should Know About
Written by the Government and Industry Relations Committee (GIRCom)
Last updated: June 15, 2026
Screwworm Update
Recent reports from the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA APHIS) confirm detections of New World screwworm (NWS) in Texas. As of this update, five animals have been affected, and no alpacas have been reported among the affected animals.
While this is not an emergency situation for alpaca owners, it is an important reminder to remain vigilant in monitoring and caring for your animals. Inspect wounds, irritated areas, and unusual conditions promptly, and contact your veterinarian immediately if you suspect an animal may be affected.
With confirmed detections in Texas, livestock owners should also expect more stringent travel requirements or restrictions for animals moving in and out of affected areas. Check with your veterinarian, state animal health officials, or event organizers before transporting livestock.
Overview
The New World screwworm (NWS) is a parasitic fly (Cochliomyia hominivorax) whose larvae feed on the living tissue of warm-blooded animals, causing a serious condition known as myiasis, or infestation by fly larvae. While this pest was successfully eradicated from the United States in the 1960s using the sterile insect technique, outbreaks in Central America and Mexico over the past few years have raised concerns about its potential re-establishment and risk to North American livestock.
Origins and History
Historically, NWS was one of the most devastating pests of livestock in the Americas. The United States eliminated the pest in the mid-20th century through a pioneering program that released millions of sterile male flies. These sterile males mate with wild females and prevent viable offspring, causing populations to collapse.
However, a major resurgence in Central America since 2023 has prompted renewed surveillance near the U.S.-Mexico border.
How Screwworm Infests Livestock
Female screwworm flies are attracted to open wounds, including cuts, tick bites, surgical sites, such as castration or ear notching, and natural openings, such as the umbilicus of newborns. They deposit hundreds of eggs at these sites, which hatch into larvae, or maggots.
These larvae burrow into and feed on living tissue, tunneling deeper as they mature. This not only physically damages muscle and connective tissues but also creates large, foul-smelling wounds that attract more flies.
Infected animals often exhibit pain, irritability, swelling, foul odor, secondary bacterial infections, fever, and loss of appetite. If untreated, deep tissue destruction can occur, ultimately leading to sepsis, severe debilitation, or death.
For alpaca breeders, even minor wounds can serve as entry points for screwworm eggs. Alpacas are susceptible because their fine fleece and social behavior, such as grooming and scratching, can make observing small wounds more difficult.
Risks Specific to Alpacas and Livestock
Although data on screwworm infestations in alpacas specifically is limited, the underlying biology suggests that any warm-blooded animal with wounds is at risk. Sheep, goats, cattle, horses, and camelids have all been affected in endemic areas.
Economically, infestations can cause:
- Loss of condition and body weight
- Reduced fertility and milk production in lactating animals
- Scarring and hide damage
- High treatment costs and labor-intensive care, if larvae must be removed and wounds disinfected
Prevention and Protection
For breeders, the best strategy is prevention and early detection.
- Inspect animals daily, especially after shearing, birthing, or handling that may cause skin breaks. Pay close attention to legs, head, neck, and abdomen.
- Practice prompt wound care. Clean and dress wounds quickly, and apply appropriate insecticides or topical veterinary products as recommended by a veterinarian.
- Minimize hazards. Reduce exposure to sharp objects in fencing and handling areas that could create wounds.
- Protect newborn crias. Treat umbilical stumps and monitor for any signs of irritation.
- Report suspicious cases to animal health authorities immediately. Early intervention can prevent establishment and spread.
Given recent geographic expansion of outbreaks and potential risk vectors, such as animal movement and wildlife, alpaca breeders, even in areas currently free of NWS, should remain vigilant, update biosecurity plans with their veterinarians, and maintain good wound management practices to reduce the risk of this destructive pest.