Epidemiology
Areas in which T. solium tapeworm infection and cysticercosis
in humans are endemic include Central and South America,
Eastern Europe, Central and Southern Africa, India and
South-East Asia (39). The cycle of infection is perpetuated by
sanitary conditions which allow pigs to be exposed to human
waste, along with inadequate methods for preparing and
cooking pork. Migration of infected tapeworm carriers has
resulted in the spread of human neural cysticercosis into areas
where the disease is not considered endemic in the swine
population (e.g., cases dispersed throughout the USA).
Prevalence rates in pigs have been determined to be
l.l%-2.6% in Central and South America (23, 37, 43 , 44)
and as high as 24.6% in parts of Africa (34). Infection rates
vary regionally with a range of pig infections from 0.005% to
10% in Mexico (42). Under-reponing of swine cysticercosis
probably results from the fact that a high percentage of pigs,
particularly those prone to exposure to Taenia, art not
slaughtered through official channels. The distribution of
human cysticercosis mirrors infection rates found in swine;
for example, 0.5%-2.4% of patients tested serologically gave
positive results in studies conducted in Africa (37). A high rate
of infection in the USA (> 100 cases a year) has been reported
recently, as a result of the immigration of infected individuals
from endemic areas (40). Detection of human cysticercosis
has been improved greatly by the use of modem technology,including computer-assisted tomography and magnetic
resonance imaging; use of these methods accounts, in part, for
the increase in numbers of human cases diagnosed in recent
years.