The U.S. Department of Agriculture reported confirmed cases of New World screwworm infestations in livestock and pets across Texas and New Mexico this month [1].

These parasitic outbreaks threaten the agricultural economy and animal welfare because the parasite can cause severe tissue damage and death if left untreated. The spread indicates a breach of previous containment efforts to keep the parasite from moving north from Mexico [2].

The USDA Animal and Plant Health Inspection Service is monitoring the situation to contain the outbreak [1]. Reports on the total number of cases vary among sources. One report cited five total U.S. cases [1], while another report indicated the total had reached six [3].

Recent confirmations include a calf in La Salle County, Texas [3]. Another case was reported in a dog in Andrews County, New Mexico [4]. However, there are contradictions regarding the status of the New Mexico animal; one source said the dog case was later re-classified and is no longer counted in the official total [3].

Additional activity has been noted in Zavala County, Texas, as the USDA ramps up efforts to protect livestock [2]. The agency is focusing on detection and rapid response to prevent the parasite from establishing a permanent presence in the U.S. interior [2].

New World screwworms are the larvae of flies that infest the living flesh of warm-blooded animals. Unlike common blowflies, these parasites burrow deep into the muscle and organs of the host, creating large wounds that are susceptible to secondary infections [1].

“The parasite has spread north from Mexico, prompting USDA to monitor and contain the outbreak.”

The reappearance of New World screwworms in the U.S. represents a significant veterinary and economic risk. Because the parasite targets living tissue rather than dead flesh, it can rapidly devastate cattle herds and pet populations. The discrepancy in case numbers and the re-classification of the New Mexico case suggest the USDA is currently in a volatile phase of detection and verification as it attempts to establish the exact perimeter of the infestation.