Colorado’s farmers and ranchers, not to mention alert pet owners, are keeping a wary eye toward the south amid reports of an increasing outbreak of New World screwworm, a highly destructive pest that feasts on animal flesh in eye-openings and wounds.
There were six confirmed reports of the pest in Texas and New Mexico as of Tuesday afternoon, according to the U.S. Department of Agriculture. Colorado agriculture officials have activated a long-prepared response to the once-eradicated bug, and say they want livestock owners to be vigilant but not panicked.
Only in rare cases has the screwworm infected humans.
Key to helping control the outbreak is to be aware of what screwworms and their damage look like, and reporting any suspicious cases immediately to a local veterinarian and state phone lines. The fly stage of the New World screwworm is larger than a housefly, with distinctive orange-tinted eyes. Damage to animals at the eyes, in wounds and other orifices is caused by the maggot stage that burrows in and causes deep distress and injury.
The Colorado Department of Agriculture is hosting webinars for livestock owners and anyone worried about the screwworm’s spread, with the next one Thursday at 6 p.m. State officials had so many questions from a previous webinar that they’ve extended the time Thursday to 90 minutes.
Sun readers can watch previous webinars or register for live ones here.
Some key points about the latest U.S. infestation of the New World screwworm:
- Untreated attacks on animals can result in death, and flies can spread eggs and larvae throughout a herd. Frequent transport of livestock opens up more avenues for infestation.
- Animal owners suspicious of a case should try to extract samples of the larvae from the wound, kill them in a sealed alcohol solution, and deliver it to state authorities or a local veterinarian for analysis.
- Owners with suspected cases or other concerns should call the state’s animal control office at 303-869-9130 or email at animalhealth@state.co.us.
- New World screwworm was eradicated from the U.S. in the 1960s, and an eradication barrier was also set up in Panama to keep it from spreading north again in the early 2000s. But outbreaks started again in Mexico in 2023, and this spring in the southwestern U.S.
- One key method of control, including in the current outbreak, is to release sterile male screwworm flies. The subsequent mating produces sterile eggs, and the population quickly dies out since females only mate once in their lifespan.