Neck Threadworms (Onchocerca cervicalis)

Lifecycle: Neck threadworms have an indirect life cycle. Neck threadworm microfilariae live under the horse's skin and are picked up by the biting midge when it feeds on the horse. Microfilariae develop into infective larvae in the midge's mouth and are passed when the midge bites a horse.

How It Gets Into Your Horse: The horse is bitten by an infected midge. Larvae are deposited into the bite wound, where they migrate to ligaments in the neck, flexor tendons and suspensory ligaments.

Dangers If Left Untreated: Adult neck threadworms in the ligaments and tendons cause swelling and pain. Microfilariae may invade the lens of the eye, causing irritation, swelling and sometimes blindness. Microfilariae under the skin may cause irritation.