Abstract:

Objective To understand the epidemic situation of echinococcosis in Qinghai Province, to provide the scientific basis for optimization of prevention and control measures. Methods Echinococcosis surveillance was performed among residents, primary school students, intermediate hosts, definitive hosts, and questionnarire survey was conducted for primary school students in 39 echinococcosis endemic counties in Qinghai Province in 2020 (32 in typeⅠ and 7 in type Ⅱ). One or several nearby administrative villages (natural villages) were randomly sellected from each surveillance county as the surveiooance sites, each of which will not be repeated within 5 years. No less than 1 000 residents were surveyed at each surveillance, and examined using abdominal ultrasonography. From places near the surveillance site in the county, 1-5 primary schools were selected, in which all students in Grades 1 and 6 were examined by abdomen ultrasound scanning, with at least 500 students being examineds. A total of 300-500 cattle or sheep raised in the county were sampled from the surveillance county’s centralized slaughterhouse, and examined by inspection with naked eyes or palpation on the cystic matter or hard nodule of liver and the lung, with which autopsy was followed to determine Echinococcus infection. In each surveillance county with endemic alveolar echinococcosis, ten areas having people’s activity were selected to catch small rodents. From each selected area, no less than 50 animals were examined by dissection of livers and lungs to determine Echinococcus multilocularis infection. Ten dog owners were randomly selected from each administrative village in all epidemic townships in the surveiooance county to collect fresh domestic dog feces sample, one from each owner, while in type Ⅰ endemic county additional fecal samples of stray dogs and wild canines were collected. The Echinococcus antigen was detected using dog coproantigen detection kit. A questionnaire survey on echinococcosis prevention and control knowledge and behavior was undertaken in students of several classes selected from grade 3 to grade 6 in the schools under surveiooance scheme, with no fewer than 300 persons being surveyed in each county. Results In 2020, a total of 73 191 individuals in Qinghai Province were investigated by B-ultrasound, and 294 patients were with echinococcosis positive (including 5 new cases), with an overall prevalence of 0.40%. The prevalence in local residents and school children was 0.59% (276/46 922) and 0.07% (18/26 269), respectively. The residents and school children in type Ⅰ endemic counties had a prevalence rate of 0.70% (276/39 364) and 0.08% (18/22 646), respectively. There were no echinococcosis patients among type Ⅱ inhabitants or primary school students, showing a significant difference in the prevalence of echinococcosis between type Ⅰ and Ⅱ endemic counties (χ² = 53.32, P < 0.01). A total of 11 626 domestic animals were examined, and the total echinococcosis infection rate was 0.55% (64/11 626). The infection rate among sheep was 0.28% (18/6 491) and that among cattle was 0.89% (46/5 135). A total of 7 121 small rodents were investigated in the alveolar echinococcosis endemic county, and the infection rate of E. multilocularis was 0.38% (27/7 121). The positive rate of Echinococcus coproantigen was 0.54% (208/38 496) in 38 496 domestic dog feces samples. The positive rates of domestic dogs in type Ⅰ and Ⅱ endemic counties were 0.63% (177/27 882) and 0.29% (31/10 614), respectively, and the difference was not significant (χ² = 0.07, P > 0.05). A total of 7 253 fecal samples from stray dogs and wild canines were examined, and found coproantigen positive rate was 0.65% (47/7 253). Among them, the positive rates in type Ⅰ and Ⅱ endemic counties were 0.63% (43/6 853) and 1.00% (4/400) respectively, and the difference was not statistically significant (χ² = 0.82, P > 0.05). A total of 12 216 primary school students participated in the questionnaire survey. The awareness rate of knowledge on echinococcosis prevention was 97.8% (11 944/12 216), and the excellent rate was 88.6% (10 827/12 216). The awareness rates among students in type Ⅰ and Ⅱ endemic counties were 97.7% (9 865/10 096) and 98.1% (2 079/2 120) (χ² = 1.01, P > 0.05), and the excellent rates were 89.0% (8 986/10 096) and 86.8% (1 841/2 120) (χ² = 8.16, P < 0.01), respectively. The analysis of endemic situation of echinococcosis in different topographic areas of type Ⅰ endemic counties in Qinghai Province showed that the prevalence in people of Qingnan area, Qaidam Basin, arround the lake area and Hehuang Valley were 1.00% (261/25 980), 0.22% (21/9 354), 0.06% (10/17 200) and 0.02% (2/9 446). There was significant difference in the prevalence among residents in the four topographic areas (χ² = 271.31, P < 0.01). The positive rate of Echinococcus coproantigen from domestic dogs was 0.56% (34/6 043), 0.92% (21/2 283), 0.94% (62/6 613), and 0.46% (60/12 943) in the Qingnan area, Qaidam Basin, arround the lake area, and Hehuang Valley, respectively. The positive rate of coproantigen differed significantly between the area around the lake and Qingnan, Hehuang Valley, Qaidam Basin, and Hehuang Valley (χ² = 5.90, 15.86, 7.64; P < 0.05 or P < 0.01). The positive rates of coproantigen in stray dogs and wild canines were 0.75% (24/3 190), 0.38% (3/800), 0.72% (13/1 812) and 0 (0/1 051), respectively. There were significant differences in the positive rates of fecal antigen between street dogs and wild canines in Qingnan area, around the lake area and Hehuang Valley (χ² = 7.95, 7.58, P < 0.01). The infection rate of cattle in Qaidam Basin was the highest at 1.71% (12/700), which was significantly different from that in Qingnan area 0.87% (20/2 307) and around the lake area 0.57% (7/1 228) (χ² = 4.22, 6.58, P < 0.05). Alveolar echinococcosis endemic counties are mainly distributed in Qingnan area and around the lake area, where the infection rate of Echinococcus in small rodents was 0.39% (24/6 121) and 0.60% (3/500), respectively (χ² = 0.49, P > 0.05). Conclusion Both echinococcosis patients and new cases in Qinghai Province are distributed in typeⅠendemic counties in southern Qinghai Province, and the transmission cycle has not been entirely interrupted. The risk of infection in the population remains.

Key words: Echinococcosis, Surveillance, Qinghai Province