Porcine cysticercosis

Cysticercosis of farmed and wild animals is caused by the larval stages (metacestodes) of cestodes of the family Taeniidae (tapeworms), the adult stages of which occur in the intestine of humans, dogs, cats or wild Canidae and Mustellidae. Porcine cysticercosis (primarily in muscle and the central nervous system [CNS]) is caused by the metacestodes (cysticerci) of the human cestodes Taenia solium. Cysticerci of T. solium also develop in the CNS, musculature and subcutaneous tissue of humans. Gravid segments are shed by the adult tapeworms. Tapeworm eggs, within proglottids or separate, are released into the environment with the faeces. Eggs may be disseminated from faeces by physical means or transport hosts. Flies particularly ingest eggs and transport these eggs, so eggs are deposited at high intensity within 150 m of the faeces and at low intensity for 10 km. Eggs are immediately infective when passed. Animals acquire infection from ingestion of food or water contaminated with sticky eggs, ingestion of segments or faeces containing eggs. or by eating arthropods such as dung beetles that carry eggs. Humans may be infected with T. solium by eggs on vegetables, in water, etc., that have been contaminated by faeces, or food contaminated by dirty hands, by faeco-oral transmission or possibly through retro-peristalsis and hatching of eggs internally (auto-infection). Disease clusters where a human carrier exists. Most adult and larval tapeworm infections cause little or no disease. The potentially fatal human neurocysticercosis (NCC) caused by T. solium is an exception. This parasite also occasionally causes muscle or ocular signs in humans. Cysticercosis causes economic loss through condemnation of infected meat and offal. Excellent vaccines based on recombinant antigens derived from oncosphere proteins have been developed for immunising animals against cysticercosis caused by T. ovis in sheep, T. saginata in cattle and T. solium in pigs.