New Worldscrewworm affectswarm-blooded animals. | USDAOn June 3, 2026, the U.S. Department of Agriculture (USDA) confirmedNewWorld screwworm (NWS)in a 3-week-old calf in Zavala County, Texas. While noadditionalcases have beenidentified, the detection marks the pests expansion into theU.S.and prompted an immediate response from federal and state animal health officials. Because screwworm larvae can infest horses,humans,andotheranimals,veterinarians and horse owners should be familiar with the risks and signs of infestation.NewWorldscrewwormaffectswarm-blooded animals, including horses, cattle, wildlife, pets, and humans. Unlike many fly larvae thatfeed ondead tissue, screwworm larvae feed on living flesh. Adult flies lay eggs in open wounds or body openings, and the emerging maggots burrow into tissue.Infestations cause severe pain, extensive tissue damage, and foul-smelling wounds that attract more flies,andwoundsoftencontainlarvae atdifferent stages.Early detectionremainscriticalfor horse owners. Without treatment, infestations can worsen quickly andattractadditionalfliesto lay eggs. Larvaethat dropfrom woundscanpupatein the environmentanddevelop into adult flies,contributing to thepestsspread.USDA and Texas officials have begun containment and eradication efforts in the affected area. Their response includesestablishinga 20-kilometer infested zone around the detection site, implementing quarantines and movement controls, increasing surveillance, and expanding sterile fly releases(biological control).Protecting Your HorseFromNew World ScrewwormHorse owners can help protect their animals by inspecting them daily for cuts, wounds, drainageandfoul odorsfrom those lesions, orreduced appetite and weight loss, which can be a result of discomfort caused by infection.Veterinarians and researchersrecommend cleaning and protecting even minor wounds promptly because screwworm flies seek out areas where they can deposit eggs. Consistent fly control and good stable hygiene canalsoreduce risk.Owners, especially those along the U.S. southern border,should contact their veterinarianimmediatelyif a wound deteriorates rapidly, develops a foul odor, orcontainsmaggots.The USDAalso encourages livestock and pet owners in affected areas tomonitorbody openings, including theears, nose, genitalia,and(in newborn animals)navels, for signs of infestation.Take-Home MessageThe USDA confirmed a case of NWS in a Texas calf on June 3, 2026, prompting immediate containment and eradication efforts. Because screwworm larvae can infest horses and other warm-blooded animals through wounds and body openings, horse owners should practice diligent wound care,maintaineffective fly control, and contact their veterinarianimmediatelyif they notice foul-smelling wounds or maggots.