Sheep Industry News March 2025

Screwworms Top Animal Health Agenda

CAT URBIGKIT T he American sheep industry is highly focused on main taining healthy sheep flocks as it proceeds with efforts to monitor and improve health, decrease risks from foreign animal diseases, and develop preparedness and response plans to address emerging threats as producers learned during the meeting of the Animal Health Committee. Linda Detwiler, Ph.D., of the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service Veterinary Services said that while the sheep and goat industry in the United States is moving toward the ability to declare that the prion disease scrapie is extinct in this country, there is an alarming threat south of the border with the discovery of New World Screwworm in Mexico. The New World Screwworm was present in the United States in the 1960s, but has not been detected in this country for decades, according to APHIS entomologist Denise Bonilla. Unfortunately, this screwworm has now been detected in every Central American country, as well as Mexico. The United States has undertaken ag gressive efforts to stop this species from migrating further north. Bonilla provided an overview of the danger posed by New World Screwworm that has been detected in Mexico. USDA eradi cated NWS from the United States in 1966 by releasing sterile male insects and is now cooperating with other countries to keep this pest from reappearing north of the border. NWS can infest livestock, pets and wildlife. It has a 21-day lifecycle in which the fly larvae (maggots) burrow (screw) into a wound, feeding as they go like a screw being driven into wood, according to USDA. These maggots cause extensive damage to live tissue, expanding wounds as more maggots hatch and feed. The larvae have mouth hooks that are used to tear at the host tissues during feeding. Bonilla explained that NWS are not the same as other maggots that feed on dead tissue, and when it comes to detection, “before you can see it, you’ll smell the problem” as they can enter a small wound, but cause deep, infested pockets of damage under the skin. Left untreated, the damage is usually fatal in 7 to 14 days, she said, although treatment with parasiticides can be successful when detected early. NWS is not contagious from animal to animal. To maintain a barrier zone, the United States, Mexico and Central American countries partner in a program that is currently putting out more than 100 million sterile flies per week from a facility located in Panama. New World Screwworm flies are about the size of a common housefly, with orange eyes and a metallic blue or green body, with three dark stripes along their backs. Although the flies don’t move far on their own, they can be transferred into new areas with live

stock movements.

SHEEP HEALTH STUDY Dr. Natalie Urie, DVM, with APHIS provided an update on the status of the current sheep study under the National Animal Health Monitoring System. The NAHMS research is now in its data-analysis phase, using data collected from surveys and sam pling of sheep flocks nationwide. NAHMS provides a look at management and biosecurity prac tices as well as the reported occurrence of common economically important sheep diseases. The sheep study – last conducted in 2011 – provides an over view of the animal health, nutrition and management practices in the American sheep industry and can be compared to previous studies to reveal changes through time. Each NAHMS study begins with a written survey of sheep pro ducers across the country and then proceeds to on-farm sampling of representative flocks. Fecal, blood and interdigital swab samples are taken during each voluntary farm visit, and participating pro ducers receive individualized biological reports for their animals. Urie reported that customized flock health management reports should be sent in February to those who cooperated in the study, and the producer will be able to compare their flock’s information to all other operations that participated in the survey. Urie provided a sneak peek into the survey results, with about a quarter of all participants expecting to have fewer or no sheep in five years. Most of these respondents reported that retirement, lack of a successor, or other personal or family situations were driving factors leading to downsizing. While Urie cautioned that she was reporting preliminary results that hadn’t yet been finalized, the survey found: • More than a quarter of participants reported direct sales to consumers or ethnic markets. • The average number of sheep sold per operation was 127 lambs. • More than half of operations kept handwritten records. • Forty-three percent of operations had consulted a veterinarian for sheep health, productivity or management issues. DISEASE PREPAREDNESS Detwiler reported on the National Animal Disease Preparedness and Response Program, which invested more than $16 million last year in program activities. Top issues for this program in the current fiscal year include training and exercises, biosecurity, state preparedness plans, animal movement decisions, disease traceabil

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March 2025 • Sheep Industry News • 17