Humans acquire the pork tapeworm Taenia solium by eating undercooked pork or raw pork sausage. Often there are no initial symptoms other than vague abdominal complaints. The diagnosis is made by finding white translucent segments of the tapeworm in human faeces.
The eating of infected pork causes enormous suffering to millions of people in the Third World. The spread of cysticercosis is facilitated by two main factors, both of which could be controlled by human effort - inadequate sanitation, which contaminates the environment with faecal material and taenia eggs; and the breeding of pigs in unsanitary conditions, including feeding them on human waste.
Cystocercosis is a serious and sometimes fatal pork tapeworm disease. A person ingests the Taenia solium eggs, the larvae penetrate the stomach wall and invade the tissues - particularly skeletal muscle and the brain - where they mature to cyst-like masses. After several years, the cysts begin to degenerate and produce an inflammatory reaction and fibrous lesions. At this stage, epileptic convulsions may occur or, occasionally, more diffuse visual or mental disturbances will occur. Treatment includes drug therapy as well as surgical removal of cysts from the eye or brain.
Cysticercosis is a complication of Taenia solium taeniasis. T solium is the pork tapeworm; people contract taeniasis by ingesting T solium cysts in raw pork. The adult parasite is a segmented worm, generally between two and three metres long but sometimes as long as eight metres. Taenia may persist in humans for many years, with affected individuals spreading hundreds of thousands of tapeworm eggs every day both to other humans and to pigs. T solium eggs from human faeces survive in the environment (the household, pastures, water) for up to several months. Pigs become infected after ingestion of a tapeworm segment or eggs present in an environment contaminated by man. The biological cycle of T solium therefore consists of two stages in three hosts - human, pig, human. Expelled from humans, the eggs of T solium develop in pigs into cysticerci, and then humans are again infected by eating raw or undercooked meat from the pig. But humans can also infect themselves, members of their family or other people with T solium eggs, which cause human cysticercosis.
In the 1970s, cysticercosis was responsible for 28% of all neurological cases in Mexico and about one percent of all deaths. In many Latin American countries human brain cysticercosis occurs in more than 0.1% of the population; the fatality rate of untreated cerebral cysticercosis in Latin America exceeds 50%. In Africa, cysticercosis is common in Zimbabwe, Gambia, Guinea, Togo, Rwanda, Burundi, Malawi, Swaziland, Madagascar and Zaire. In Asia, it is common in northern India, where over 10% of the human population of labour colonies and slums are affected with T solium. Taeniasis and human cysticercosis are not infrequent in Indonesia and the Republic of Korea. In general, cysticercosis is prevalent in countries where people live in unsanitary conditions and in close proximity to pigs. In Moslem countries where no pork is eaten it is almost non-existent.
Pork tapeworm is common in South America, Eastern Europe, Russia and Asia.