Treatment of Culicoides hypersensitive horses with high-dose n-3 fatty acids: a double-blinded crossover study

In this double-blinded crossover study the clinical efficacy of high dose α-linolenic acid (linseed oil) for the treatment of Culicoides spp. hypersensitivity was evaluated. Seventeen privately owned horses from north Florida, USA completed the 18-week study. Criteria for inclusion included negative dermatophyte cultures, negative skin scrapes, failure to respond to ivermectin treatment, compatible clinical signs, positive skin test to Culicoides spp.antigen and a history of seasonal pruritus consistent with Culicoides spp. hypersensitivity. Horses were randomized and each horse's feed was supplemented with 200 mL of linseed oil (n-3 source) or 200 mL of corn oil (n-6 source) per day for a 6-week period. After a 6-week washout period, each horse was crossed over to the other supplement for an additional 6 weeks. Horses were evaluated every 3 weeks. The level of pruritus was determined by counting pruritic acts in a 30-min period. Total lesional surface area was determined by computerized evaluation of scanned photographs and documented physical examination findings. There was no significant change in level of pruritus observed between the groups (P = 0.89). Additionally, lesional surface area was not significantly different between the groups (P = 0.06). However, most owners stated that horses improved while supplemented with linseed oil.