Anoplocephala spp are the common parasitic tapeworm of horses found worldwide. They reside in the small, and sometimes large, intestine.
Anoplocephala magna and A. perfoliata are quite small, usually 2.5-5cms long but can be up to 8cm. long and 1.2cm. wide. The anterior end, or scolex, is spherical and quite small (2-3cm) with 4 suckers. The body consists of many segments, the proglottides, which are wide and thin.
The life cycle is described in more detail in the overview at the start of the section. Larvae develop to infectivity within the oribatid mite over 2 to 4 months. After the infected mites are eaten, the tapeworms mature in about 6 weeks within the horse.
Equine tapeworms are not generally regarded as clinically significant unless a large number are present or the host is already in poor condition.
Anoplocephaliasis is the disease caused by tapeworms competing with the horse for food and vitamins. Light infections in horses cause little damage. They especially gather around the ideo-caecal valve at the entrance to the caecum. Large numbers of tapeworms may spill over into the intestine and cause irritation, producing haemorrhagic or ulcerative enteritis. Intestinal blockage or intestinal inflammation may be seen. Mild infections cause no clinical signs. Heavier infections may produce unthriftiness, colic, and diarrhoea.
Identification of square, rough embryonated eggs or segments in the faeces, or the presence of adult worms at necropsy.
Periodic treatment of horses would reduce their faecal egg output and limit the number of infective mites on the pastures, thereby limiting reinfection.