Prevalence of Echinococcus infection in small mammals captured from Shiqu County, Sichuan Province from 2015 to 2020

Abstract

To investigate the prevalence of Echinococcus infection in small mammals in Shiqu County, Sichuan Province from 2015 to 2020, so as to provide insights into echinococcosis control in Shiqu County. One setting with frequent activity of small mammals was sampled as the survey site from each of 9 townships where human alveolar echinococcosis was hyperendemic, in Shiqu County, Sichuan Province from 2015 to 2020. Two quadrats measuring 50 m × 50 m were assigned in each survey site during the period between July and August from 2015 to 2020 to capture all small mammals in quadrats, and the species of small mammals were identified by morphological characteristics. All captured small mammals were dissected in the field and Echinococcus infection was identified by visual examinations. The affected organs of Echinococcus - infected small mammals were collected, and Echinococcus infection was detected using PCR assay, with Echinococcus species characterized. The prevalence of Echinococcus infection was calculated in small mammals, and the trends in the prevalence of Echinococcus infection were analyzed during the period from 2015 to 2020. In addition, the prevalence of Echinococcus infection was compared in small mammals using visual examinations and PCR assay. A total of 2 692 small mammals were captured in the survey sites of Shiqu County from 2015 to 2020, and morphology characterized 1 360 Microtus fuscus (50.52%) and 1 332 Plateau pika (49.48%). The prevalence rates of Echinococcus infection were 35.63%, 19.16%, 21.41%, 8.40%, 7.68% and 4.44% by visual examinations and 18.96%, 5.36%, 5.61%, 4.58%, 3.30% and 0.37% by PCR assay in small mammals in Shiqu County from 2015 to 2020, both showing a tendency towards a decline year by year (χ2 = 215.024 and 117.045, both P values < 0.001). The prevalence of Echinococcus infection was significantly higher in small mammals by visual examinations than by PCR assay during the period from 2015 to 2020 except in 2018 (χ2= 33.597, 21.815, 51.373, 17.268 and 9.537, all P values < 0.01). PCR assay detected a reduction in the prevalence of E. multilocularis infection from 10.21% to 0.37% and a reduction in the prevalence of E. shiquicus infection from 8.75% to 0 in small mammals in Shiqu County from 2015 to 2020, both appearing a tendency towards a decline year by year (χ2 = 117.045 and 43.436, both P values < 0.001). In addition, the prevalence of E. multilocularis and E. shiquicus infections reduced from 15.19% to 0.45% and from 8.23% to 0 in M. fuscus, and the prevalence of E. multilocularis and E. shiquicus infections reduced from 7.76% to 0 and from 9.01% to 0 in P. pika in Shiqu County from 2015 to 2020. M. fuscus and P. pika were dominant species of small mammals in Shiqu County, Sichuan Province from 2015 to 2020, and E. multilocularis infection was mainly found in M. fuscus and E. shiquicus infection mainly found in P. pika. The prevalence of Echinococcus infection appeared a tendency towards a decline in both M. fuscus and P. pika year by year during the period from 2015 to 2020.