Widespread co-endemicity of human cystic and alveolar echinococcosis on the eastern Tibetan Plateau, northwest Sichuan/southeast Qinghai, China

Abstract

Cystic echinococcosis (CE) or hydatid disease is known to be cosmopolitan in its global distribution, while alveolar echinococcosis (AE) is a much rarer though more pathogenic hepatic parasitic disease restricted to the northern hemisphere. Both forms of human echinococcosis are known to occur on the Tibetan Plateau, but the epidemiological characteristics remain poorly understood. In our current study, abdominal ultrasound screening programs for echinococcosis were conducted in thirty-one Tibetan townships in Ganze and Aba Tibetan Autonomous Prefectures of northwest Sichuan Province during 2001-2008. Hospital records (1992-2006) in a major regional treatment centre for echinococcosis in Sichuan Province were also reviewed. Of 10,186 local residents examined by portable ultrasound scan, 645 (6.3%) were diagnosed with echinococcosis: a prevalence of 3.2% for CE, 3.1% for AE and 0.04% for dual infection (both CE and AE). Human cystic and alveolar echinococcosis in pastoral areas was highly co-endemic, in comparison to much lower prevalences in semi-pastoral or farming regions. The high ultrasound prevalence in these co-endemic areas in northwest Sichuan Province was also reflected in the hospital study, and hospital records furthermore indicated another possible highly co-endemic focus in Guoluo Prefecture of Qinghai Province, located at the border of northwest Sichuan. These chronic cestode zoonoses constitute an unparalleled major public health problem for pastoral Tibetan communities, and pose great difficulties for adequate treatment access and effective transmission control in such remote regions.

Specific IgG Responses to Recombinant Antigen B and Em18 in Cystic and Alveolar Echinococcosis in China

“…Both human CE and AE are highly endemic in northwest Sichuan Province, China (21,22), where a large number of echinococcosis cases at different stages were detected in the field through mass screening programs by portable ultrasound scan, which permitted us to analyze the correlation of specific antibody response and disease stage. Considering the natural history of cystic echinococcosis, cysts are classified into six types: CL (refers to cysts of a parasitic origin) and CE1, CE2, CE3, CE4, and CE5, indicating the different pathological/ growth activities of the parasite in human hosts (36).…”

Development of Three PCR Assays for the Differentiation between Echinococcus shiquicus, E. granulosus (G1 genotype), and E. multilocularis DNA in the Co-Endemic Region of Qinghai-Tibet plateau, China

“…3 The Tibetan pastoral lifestyles are such that close associations with domestic or wild canid definitive hosts of E. shiquicus, E. granulosus, and E. multilocularis are maintained. 16 Although the infectivity (if any) of E. shiquicus to humans is unknown, the availability of a specific copro-detection test for this fox parasite and its differentiation from the other two Echinococcus species (E. granulosus and E. multilocularis) occurring on the Tibetan plateau is useful for epidemiological studies.…”

“…1 These species occur sympatrically on the Qinghai-Tibet plateau of western China and as a result human cystic (CE) and alveolar (AE) echinococcosis are co-endemic in Tibetan pastoral communities. 2,3 In addition a new species, Echinococcus shiquicus was recently described in wildlife (Tibetan fox, Vulpes ferrilata and plateau pikas, Ochotona curzoniae). However, the zoonotic potential (if any) of this species is currently unknown.…”

A random forest approach for predicting the presence of Echinococcus multilocularis intermediate host Ochotona spp. presence in relation to landscape characteristics in western China

“…It is a highly pathogenic zoonosis with over 94% mortality in untreated patients ten years after diagnosis (Wang et al ., 2010), and is increasingly recognised as a major population health problem (Zhang et al ., 2014). The known Em range includes Europe, North America, Japan, the former USSR, Central Asia and China where new foci are being discovered (Wang et al ., 2001; Giraudoux et al ., 2013a), with prevalence rates of greater than 10% observed in Gansu and Sichuan provinces, China (Craig et al ., 1992; Li et al ., 2010). The spatial distribution of Em is highly variable, with significant regional and local differences in parasite prevalence resulting in patchy distributions generally not reflected in Em and HAE distribution maps (Eckert et al ., 2001; Giraudoux et al ., 2006; 2013a).…”

“…Pastureland degradation due to overgrazing has also been linked to increased small mammal densities, for example Ochotona spp ., Microtus spp ., Cricetulus kamensis and Myospalax baileyi (Raoul et al ., 2006) on the eastern Tibetan plateau, China, where HAE is endemic (Wang et al ., 2004; Li et al ., 2010). In Shiqu county, China, grass height was negatively related to Ochotona curzoniae burrow abundance suggesting that overgrazing in this area increased abundance of this species (Wang et al ., 2010).…”