Epidemiological characteristics and risk factors for cystic and alveolar echinococcosis in China: an analysis of a national population-based field survey.

BACKGROUND: Human cystic and alveolar echinococcosis are neglected tropical diseases that WHO has prioritized for control in recent years. Both diseases impose substantial burdens on public health and the socio-economy in China. In this study, which is based on the national echinococcosis survey from 2012 to 2016, we aim to describe the spatial prevalence and demographic characteristics of cystic and alveolar echinococcosis infections in humans and assess the impact of environmental, biological and social factors on both types of the disease. METHODS: We computed the sex-, age group-, occupation- and education level-specific prevalences of cystic and alveolar echinococcosis at national and sub-national levels. We mapped the geographical distribution of echinococcosis prevalence at the province, city and county levels. Finally, by analyzing the county-level echinococcosis cases combined with a range of associated environmental, biological and social factors, we identified and quantified the potential risk factors for echinococcosis using a generalized linear model. RESULTS: A total of 1,150,723 residents were selected and included in the national echinococcosis survey between 2012 and 2016, of whom 4161 and 1055 tested positive for cystic and alveolar echinococcosis, respectively. Female gender, older age, occupation at herdsman, occupation as religious worker and illiteracy were identified as risk factors for both types of echinococcosis. The prevalence of echinococcosis was found to vary geographically, with areas of high endemicity observed in the Tibetan Plateau region. Cystic echinococcosis prevalence was positively correlated with cattle density, cattle prevalence, dog density, dog prevalence, number of livestock slaughtered, elevation and grass area, and negatively associated with temperature and gross domestic product (GDP). Alveolar echinococcosis prevalence was positively correlated with precipitation, level of awareness, elevation, rodent density and rodent prevalence, and negatively correlated with forest area, temperature and GDP. Our results also implied that drinking water sources are significantly associated with both diseases. CONCLUSIONS: The results of this study provide a comprehensive understanding of geographical patterns, demographic characteristics and risk factors of cystic and alveolar echinococcosis in China. This important information will contribute towards developing targeted prevention measures and controlling diseases from the public health perspective.

Assessment of echinococcosis control in Tibet Autonomous Region, China.

BACKGROUND: In China the highest prevalence of echinococcosis is in Tibet Autonomous Region (TAR). The government has issued documents and implemented comprehensive prevention and control measures focusing on controlling the source of infection of echinococcosis. It was very important to understand the implementation and effect of infectious source control measures. The purpose of this study was to examine the implementation of measures to control infectious source (domestic and stray dogs) in TAR and to assess their effectiveness. METHODS: We collected data on domestic dog registration and deworming and stray dog sheltering in 74 counties/districts in the TAR from 2017 to 2019. Fecal samples from domestic dogs were collected from randomly selected towns to determine Echinococcus infection in dogs using coproantigen ELISA. We analyzed the data to compare the canine rate of infection between 2016 and 2019. The data analysis was performed by SPSS statistical to compare dog infection rate in 2016 and 2019 by chi-square test, and ArcGIS was used for mapping. RESULTS: From 2017 to 2019, 84 stray dog shelters were built in TAR, and accumulatively 446,660 stray or infected dogs were arrested, sheltered, or disposed of. The number of domestic dogs went downward, with an increased registration management rate of 78.4% (2017), 88.8% (2018), and 99.0% (2019). Dogs were dewormed 5 times in 2017, 12 times in 2018, and 12 times in 2019. The dog infection rate was 1.7% (252/14,584) in 2019, significantly lower than 7.3% (552/7564) from the survey of echinococcosis prevalence in Tibet in 2016 (P < 0.05). CONCLUSION: Between 2017 and 2019, the number of stray dogs and infection rate of Echinococcus spp. in domestic dogs decreased significantly, indicating that dogs were effectively controlled as a source of infection in TAR and reflecting a significant decrease in the risk of echinococcosis transmission.

Echinococcus spp. and genotypes infecting humans in Tibet Autonomous Region of China: a molecular investigation with near-complete/complete mitochondrial sequences.

BACKGROUND: Molecular markers are essential to identify Echinococcus species and genotypes in areas with multiple Echinococcus species to understand their epidemiology and pathology. Tibet Autonomous Region (TAR) is one of the areas worst hit by echinococcosis. However, molecular epidemiology is still missing among echinococcosis patients in TAR. This research explored the Echinococcus species and genotypes infecting humans in TAR and the population diversity and the possible origin of G1 in TAR. METHODS: Cyst samples were collected in one echinococcosis-designated hospital in TAR. Echinococcus species and genotypes were identified through a maximum-likelihood approach with near-complete/complete mtDNA using IQ-TREE. Phylogenetic networks were built with PopART, and the phylogeographical diffusion pattern was identified using a Bayesian discrete phylogeographic method. RESULTS: Using phylogenetic trees made with near-complete/complete mtDNA obtained from 92 cysts from TAR patients, the Echinococcus species and genotypes infecting humans in TAR were identified as Echinococcus granulosus (s.s.) G1 (81, 88.04%), accounting for the majority, followed by G6 of the E. canadensis cluster (6, 6.52%), E. granulosus (s.s.) G3 (3, 3.26%), and E. multilocularis (2, 2.17%). An expansion trend and a possible recent bottleneck event were confirmed among the G1 samples in TAR. Adding the other near-complete mtDNA of G1 samples globally from the literature, we identified the possible phylogeographic origin of the G1 samples in TAR as Turkey. CONCLUSIONS: Using near-complete/complete mtDNA sequences of Echinococcus spp. obtained from echinococcosis patients, a variety of Echinococcus species and genotypes infecting humans throughout TAR were identified. As far as we know, this is the first comprehensive molecular investigation of Echinococcus species and genotypes infecting humans throughout TAR. We identified, for the first time to our knowledge, the possible origin of the G1 in TAR. We also enriched the long mtDNA database of Echinococcus spp. and added two complete E. multilocularis mtDNA sequences from human patients. These findings will improve our knowledge of echinococcosis, help to refine the targeted echinococcosis control measures, and serve as a valuable baseline for monitoring the Echinococcus species and genotypes mutations and trends of the Echinococcus spp. population in TAR.

Characterizing dynamic changes of plasma cell-free Echinococcus granulosus DNA before and after cystic echinococcosis treatment initiation.

Over one million people are living with cystic echinococcosis (CE) and alveolar echinococcosis (AE). For CE, long-term albendazole treatment is often needed, which requires regular follow-up. Follow-up is mainly through imaging which is insensitive to subtle changes and subjective to experience. We investigated the changes of Echinococcus granulosus (Eg) cell-free DNA (cfDNA) in plasma of CE patients before and after albendazole treatment to evaluate its potential as an objective marker for treatment follow-up. Plasma samples of nine CE patients were collected before and after treatment. We identified Eg cfDNA from every sample through high-throughput sequencing. Eg cfDNA concentration and fragment length increased significantly after the treatment period. Ultrasound examination before and after the treatment initiation reflected the drug effects to a certain extent, as the cyst size of four patients reduced. Our findings indicated that Eg cfDNA from plasma could be a potential marker in the monitoring of CE treatment.

Identification of vulnerable populations and knowledge, attitude, and practice analysis of echinococcosis in Tibet Autonomous Region of China.

Echinococcosis is one of the 17 neglected tropical diseases recognized by the World Health Organization and causes a huge global disease burden. The Tibet Autonomous Region (Tibet) of China is the most epidemic area of echinococcosis worldwide. Echinococcosis poses an enormous threat to local public health and economic development. Identifying vulnerable populations and analyzing people's knowledge, attitudes, and practices (KAP) with respect to echinococcosis is necessary to prevent and control echinococcosis. Based on reported cases and questionnaire responses, we first used a k-prototypes clustering algorithm to identify vulnerable populations according to human demographics (including gender, age, education level, and occupation). We then used a KAP analysis to evaluate the Tibetan people's understanding of echinococcosis. The results identified three types of vulnerable population. Vulnerable population I comprised illiterate middle-aged and older women engaged in agriculture and animal husbandry. Vulnerable population II comprised illiterate middle-aged male herdsmen. Vulnerable population III comprised young male farmers with a low education level. The KAP analysis indicated that the pass rate for all participants was 72.6%, 6.4%, 95.0%, and 75.8% for KAP, K, A, and P, respectively. The pass rates were significantly different among different age and gender groups. Based on these results, it is necessary to improve public health education and professional training, and to implement effective control and management measures targeting typical hosts of echinococcosis. This study provides a direct reference for the prevention and control of echinococcosis in Tibet.

Comprehensive characterization of plasma cell-free Echinococcus spp. DNA in echinococcosis patients using ultra-high-throughput sequencing.

BACKGROUND: Echinococcosis is a life-threatening parasitic disease caused by Echinococcus spp. tapeworms with over one million people affected globally at any time. The Echinococcus spp. tapeworms in the human body release DNA to the circulatory system, which can be a biomarker for echinococcosis. Cell-free DNA (cfDNA) is widely used in medical research and has been applied in various clinical settings. As for echinococcosis, several PCR-based tests had been trialed to detect cell-free Echinococcus spp. DNA in plasma or serum, but the sensitivity was about 20% to 25%. Low sensitivity of PCR-based methods might be related to our limited understanding of the features of cell-free Echinococcus spp. DNA in plasma, including its concentration, fragment pattern and release source. In this study, we applied ultra-high-throughput sequencing to comprehensively investigate the characteristics of cell-free Echinococcus spp. DNA in plasma of echinococcosis patients. METHODOLOGY/PRINCIPAL FINDINGS: We collected plasma samples from 23 echinococcosis patients. Total plasma cfDNA was extracted and sequenced with a high-throughput sequencing platform. An average of 282 million read pairs were obtained for each plasma sample. Sequencing data were analyzed with bioinformatics workflow combined with Echinococcus spp. sequence database. After identification of cell-free Echinococcus spp. reads, we found that the cell-free Echinococcus spp. reads accounted for 1.8e-5 to 4.0e-9 of the total clean reads. Comparing fragment length distribution of cfDNA between Echinococcus spp. and humans showed that cell-free Echinococcus spp. DNA of cystic echinococcosis (CE) had a broad length range, while that of alveolar echinococcosis (AE) had an obvious peak at about 135 bp. We found that most of the cell-free Echinococcus spp. DNA reads were from the nuclear genome with an even distribution, which might indicate a random release pattern of cell-free Echinococcus spp. DNA. CONCLUSIONS/SIGNIFICANCE: With ultra-high-throughput sequencing technology, we analyzed the concentration, fragment length, release source, and other characteristics of cell-free Echinococcus spp. DNA in the plasma of echinococcosis patients. A better understanding of the characteristics of cell-free Echinococcus spp. DNA in plasma may facilitate their future application as a biomarker for diagnosis.

[Dog Fecal Contamination by Echinococcus in Cuomei County of Tibet in 2015].

Objective: To understand dog fecal contamination by Echinococcus in Lhoka Prefecture of Tibet and provide basis for development of prevention and control strategies. Methods: Survey spots were sampled around the Zhegu Village of Zhegu Town in Cuomei County of Tibet using the mechanical sampling method in May, 2015. The positions of spots, amount of dog feces, types of camps, pastures, terrains, vegetations and land cover, as well as information concerning the existence of household garbage, were recorded. The linear distance from survey spot to the center of the village was calculated. Dog feces were sampled in survey spot and examined the copro-antigen for Echinococcus contamination by ELISA. The distribution characteristics of fecal contamination were analyzed by chi-square test, Fisher's exact test, Kruskal-Wallis test and Nemenyi test. Results: Seventy-nine survey spots were selected for sampling. A total of 226 feces samples were obtained in 37 of the spots. ELISA results showed that the copro-antigen positive rate was 23.9%（54/226）, the averaged density of feces and the averaged density of positive feces were 0.317 9/100 m2 and 0.075 9/100 m2, with a maximum of 2.555 6/100 m2 and 0.555 6/100 m2 respectively. The density of feces and the density of positive feces were both higher in summer camps（0.601 9/100 m2 and 0.157 4/100 m2 respectively） than in non-camps（0.170 2/100 m2 and 0.033 1/100 m2）（χ2=18.248 4，P<0.01；χ2=15.274 3，P<0.01）. In addition, the density of feces and the density of positive feces were both higher in survey spots with household garbage（0.679 0/100 m2, 0.177 0/100 m2） than in those without household garbage （0.130 3/100 m2 and 0.023 5/100 m2）（χ2=34.634 7，P<0.01；χ2=26.109 1，P<0.01）; as well as higher in survey spots ≥10 km from the center of the village（0.403 7/100 m2, 0.107 4/100 m2） than in those <10 km（0.265 3/100 m2, 0.056 7/100 m2）（χ2=4.432 7，P<0.05；χ2=4.045 5，P<0.05）. Conclusion: The Cuomei County of Tibet is facing a serious situation of dog fecal contamination by Echinococcus. Summer camps, areas with household garbage, and districts with a ≥10 km linear distance from the village center may provide reference for determining the regions for hydatidosis prevention and control.