Cutaneous Habronemiasis or ‘Summer Sores’ are currently prevalent in our horse population due to the recent rain and the humid conditions of Summer and Autumn.
These lesions develop in wounds or moist areas, including the eyes, penis and sheath. The Habronema worm larvae is transported and deposited in these areas by house and stable flies. As adult Habronema worms survive in nodules within the horse’s stomach and eggs are passed in the manure; the horse itself is a source of re-infection and spread of Habronema larvae. Following introduction, the Habronema larvae migrate into the tissue and form hard, raised discoloured (brown red) nodules. The lesions will enlarge in time as soft tissue irritation and inflammation results. These lesions become irritable and painful, with the horse often rubbing or biting the area. Secondary trauma may then occur; eye ulcerations, difficult urinating, swollen sheaths, discharging and ulcerated wounds. As these wounds typically attract more flies the cycle of larvae deposition continues, and lesions continue to grow in size.