Echinococcosis is a parasitic disease caused by infection with tiny tapeworms of the genus Echinocococcus. Echinococcosis is classified as either cystic echinococcosis or alveolar echinococcosis. Cystic echinocccosis (CE), also known as hydatid disease, is caused by infection with the larval stage of Echinococcus granulosus, a ~2-7 millimeter long tapeworm found in dogs (definitive host) and sheep, cattle, goats, and pigs (intermediate hosts). Although most infections in humans are asymptomatic, CE causes harmful, slowly enlarging cysts in the liver, lungs, and other organs that often grow unnoticed and neglected for years. Alveolar echinococcosis (AE) disease is caused by infection with the larval stage of Echinococcus multilocularis, a ~1-4 millimeter long tapeworm found in foxes, coyotes, and dogs (definitive hosts). Small rodents are intermediate hosts for E. multilocularis. Although cases of AE in animals in endemic areas are relatively common, human cases are rare. AE poses a much greater health threat to people than CE, causing parasitic tumors that can form in the liver, lungs, brain, and other organs. If left untreated, AE can be fatal.
Epidemiological data are very sparse and usually published in governamental bulletins. Human cases are not required to be reported, and surgeons do not habitually report cases to health officials. Investigating hospital registers and data from the Rio Grande do Sul Health Secretary MARDINI & SOUZA13 could identifiy 701 persons, between 1981 and 1998, which made surgery to remove hydatic cyst. Official reports from the BRAZILIAN HEALTH MINISTRY4 revealed that between 1999 and 2002, 14, 8, 32, 2 cases were registered, respectively, and none from 2003 until August 2005. There are no correct explanations that can explain this lack in official data. Some points should be given attention: one is the fact that there is no payment for hydatic surgery in the Official Brazilian Health System. This way, surgeons and hospitals have to report other procedures to be reinfunded for their expenses, and for this reason hospital records are either unavailable or unreliable. Another point to be stressed while one analyses the official data is regarded to the city in which the patient lives.
Only very few cases are localized in municipalities near endemic regions. Most of them are in surrounding areas from State Capital (Porto Alegre) or in cities far from endemic regions. It could be possible that many rural workers moved to cities where job opportunities are better and of course diagnosis was done there. But no case was identified in endemic areas during the analyzed period. In this way, official registers should be analyzed very carefully because they may no reflect the reality.