The larvae (which are called microfilariae) live in the tissue under the skin and are ingested by midges as they feed, they can also congregate in the eye tissue causing infections. The adult worms live in the tendons and ligaments. They are long and coiled in shape with the males being around 6cm in length and females being around 30cm in length. Neck Threadworms have to depend on an intermediate host, the biting midge - Culicoides spp. (Insecta: Diptera: Ceratopogonidae) to get to the horse. The neck threadworm microfilariae live just under the horse's skin and wait to be ingested up by a visiting midge. Once inside the midge they develop to the infective larvae L3 stage within 24-25 days. When the midge bites another horse the neck threadworms the larvae migrate to the ligaments in the neck and also to the flexor tendons and suspensory ligaments particular the forelegs.
Uveitis - This occurs when there are large quantities of dead microfilariae in the eye which causes the dead to give off large amounts of antigens which cause inflammation in the eye.
Hair loss around the head and neck area.
Swelling around Ligaments.
Swelling around tendons.
Lumps under the horses skin on the ligaments.