Echinococcosis in Tibetan Populations, Western Sichuan Province, China

We screened 3,199 people from Shiqu County, Sichuan Province, China, for abdominal echinococcosis (hydatid disease) by portable ultrasound combined with specific serodiagnostic tests.Both cystic echinococcosis (CE) (Echinococcus granulosus infection) and alveolar echinococcosis (AE) (E.multilocularis) were co-endemic in this area at the highest village prevalence values recorded anywhere in the world: 12.9% were infected with one or the other form (6.8% CE and 6.2% AE).Prevalences of both CE and AE were significantly higher in female than male patients and increased with the age of the person screened.Pastoral herdsmen were at highest risk for infection (prevalence 19.0%).Prevalence of CE varied in 5 townships from 0% to 12.1%, whereas AE prevalence ranged from 0% to 14.3%.Risk factors associated with both infections included the number of owned dogs, frequency of contact with dogs, and sources of drinking water. H uman cystic echinococcosis (CE), caused by infectionwith the larval stage of Echinococcus granulosus, and alveolar echinococcosis (AE), caused by infection with the larval stage of E. multilocularis, are 2 of the most pathogenic zoonotic parasitic helminthic infections of humans in the Northern Hemisphere (1).Human CE occurs worldwide in association with herding, within which the main dog-sheep cycle for E. granulosus is transmitted (1).Human AE is a much rarer parasitic infection; transmission occurs in several regions of the Northern Hemisphere, including the United States, Europe, Central Asia, Siberia, Japan, and China (2).In China, echinococcosis occurs mainly in western regions and provinces, including Xinjiang Uygur Autonomous Region, Qinghai Province, Gansu Province, Ningxia Hui Autonomous Region, and Sichuan Province (3).A previous pilot survey showed that human echinococcosis was prevalent in western Sichuan Province, situated on the eastern Tibetan Plateau, and that both human CE and AE were present.The average prevalence was 4.0%; CE accounted for 2.1% and AE 1.9% (4).Shiqu County (longitude 97°20′00′′-99°15′28′′ E and latitude 32°19′28′′-34°20′40′′N) is located in the northwest corner of Ganzi Prefecture in Sichuan Province (average altitude 4,200 m).The county covers 25,141 km 2 , located on the eastern part of the Tibetan Plateau.Grassland covers 83.5% of this treeless area, where the weather is cold (annual average temperature -1.6°C).Ethnic Tibetans comprise 98% of the total population; they are primarily involved with livestock production and herding.The total number of livestock is >630,000.In addition, a large number of dogs, including owned dogs and strays, exist in the area (5).We conducted a village-based community epidemiologic study of human echinococcosis from 2000 to 2002 in Shiqu County, Ganzi Tibetan Autonomous Region, Sichuan Province, to further understand the epidemiology of human AE in this region. Materials and MethodsThe screening program was undertaken from 2000 to 2002; 26 villages in 5 townships in Shiqu County, were included (Figure 1).A total of 3,199 volunteers were selfselected after the purpose of the study was explained to the communities by local village leaders; volunteers were assured free diagnosis and chemotherapeutic treatment for echinococcosis, if indicated.Study participants ranged in Echinococcosis in Tibetan Populations, Western Sichuan Province, China