Blackfly bites: causes, symptoms, diagnosis, and treatment

Blackfly bites are lesions caused by bites of blackflies.


Causes

Blackfly, also known as buffalo gnat or turkey gnat, is 2 - 5mm in size, brown or black. Females lay eggs in clean running water, such as mountain springs, streams, rivers, and clean roadside ditches, and the eggs are adhered to water plants, branches, leaves, and rocks. The hatched larvae must live in the clean running water with sufficient oxygen, and cannot survive in the still water. The eggs or larvae overwinter in the water or under ice. The larvae develop into pupae after 5 molts. The adults in the pupae escape, flying out of the water. After copulation, the males die shortly, and the females can live for 3 - 4 weeks.


Signs and Symptoms

Blackflies pierce the skin and suck blood with their beaks, mostly on exposed areas such as the calves. Pruritus and sharp pain occur 1 - 2 minutes after bites. Local erythema, papules, vesicles occur 3 - 24 hours after bites, and petechiae are present at the bite site. Eczematoid lesions may be present as a result of scratches over time. There may be indurated lesions in the late stage. Secondary infection, erosion, and necrosis may be present due to scratches or stimulations derived from labors in the field, and the disease can persist for several weeks.


Diagnosis

If there are blackflies and clinical presentations, the disease can be diagnosed.


Treatment

Topical calamine lotion can be applied, and oral antihistamines are appropriate if there are severe hypersensitivity reactions.