[Hydatidosis: Ultrasonographyc screening in the Río Negro Province 25 years after the first screening]

Hydatidosis (cystic echinococcosis) is endemic in Rio Negro Province, Argentina. In 1980 started a control program against the disease. In 1984 Frider et al performed the first ultrasound screening in the world at Pilcaniyeu city, later extended to other localities of Rio Negro province. The initial prevalence in asymptomatic people was 7.1% in Pilcaniyeu and 10.1% in Comallo, being all new cases and with surgical indication.The aim of this investigation was to determine the current prevalence and analyze the evolution of the disease across 25 years of the control program.In 2009 and 2010 ultrasound screening studies were conducted in both locations in all age groups.In 512 ultrasound studies at Pilcaniyeu, the prevalence was 1.5% in children (6 to 14years old) and 4.2% in adults (total 2.5%). In 770 ultrasound studies at Comallo, the prevalence was 1.1 %in children and 6.6% in adults (total 3.0%). The overall reduction in the prevalence reached 67.2%. Regarding the age distribution, rates of 1.6%-1.9% were observed in Pilcaniyeu and of 1.0-1.9% in Comallo between 0 and 30 years old, increasing significantly above 10% after 60 years old in Pilcaniyeu and after 40 years old in Comallo.The implementation of the program actions reduced the prevalence of the disease but there are still new cases, and that indicates that some bias persists in the control of the epidemiology of the disease and levels of transmission to humans as a consequence of this failures. So the search of asymptomatic cases is still important and also their management based on the follow-up by ultrasound (watch and wait) or in the treatment with albendazol.