Evaluation of Ivermectin for Treatment of Hair Loss Syndrome in Black-Tailed Deer

Since 1997, many Columbian black-tailed deer in western Washington developed a hair loss syndrome leading to severe health issues and death. To investigate, eight affected fawns were captured in 1999. Three were treated with ivermectin, while five were untreated controls. Treated deer showed significant improvements: they gained more weight (22.4 vs. 12.6 kg), had fewer parasites, and regrew hair faster. No treated deer died, whereas two untreated deer did. The study suggested that lice, gastrointestinal nematodes, and lungworms might be key factors in the syndrome and mortality.