06/13/2026
This Facebook post is circulating that dogs in Texas are currently at risk due to a confirmed outbreak of the New World screwworm, which targets warm-blooded mammals. Officials have placed quarantines across parts of South and Central Texas. Counties involved: Edwards, Gillespie, Kerr, Kimble, LaSalle, Sutton, Uvalde, Vale Verde, Webb, and Zavala. While the outbreak primarily affects livestock, so far one canine case has also been documented. However, the fly lays eggs in OPEN wounds, and the hatching larvae feed on living flesh. Dogs at risk are those with open wounds, healing surgical sites, or skin injuries in areas where the parasite has been detected. Spending time outdoors can increase exposure to egg-laying flies, particularly during the daytime when adult flies are most active.
The FDA recommends Nitenpyram (Capstar) for treatments. 20 years ago, Nitenpyram was the first oral insecticide for dogs. It belongs to the neonicotinoid class, which are neurotoxic chemicals chemically similar to ni****ne. These are the serious side effects: Difficulty breathing, wheezing, or choking. Hives or severe swelling, loss of coordination, stumbling, or inability to walk. Muscle tremors or seizures, excessive drooling, or unusually large pupils. The risk of serious neurological signs (including death) is higher in smaller dogs. In 2006, my contract stated that it would void my health guarantee if Capstar was given. It's still on my list of flea treatments to NOT give your dog.
Bottom line, I think our dogs are at a low risk for screwworms. Keeping dogs inside who live in the affected areas and have open wounds will prevent screwworms.
If a dog has screwworms, ivermectin is much safer than Capstar. Ivermectin for heartworm prevention requires a microdose of 6 mcg/kg. At this level, the drug only targets immature heartworm larvae and does not kill screwworm larvae. Screwworm Treatment and Heartworm Treatment both require a higher dosage of Ivermectin.
