Immunodiagnosis of Human and Canine Echinococcosis and Community Studies in Northwestern China

Echinococcosis is highly endemic in northwestern China. In order to improve sero-testing in support of community screening and for hospital use, a dot immunogold filtration assay (DIGFA) for rapid serodiagnosis of human CE and AE was developed. DIGFA incorporated four antigen preparations: crude E. granulosus cyst fluid, crude extract of E. granulosus protoscoleces, E.granulosus native antigen B, and a metacestode extract (Em2) from E. multilocularis. The overall sensitivity of DIGFA in a hospital diagnostic setting using archived sera was 80.7% for human CE (n=857 samples) and 92.9% for human AE (n=42 samples). In endemic communities (Qinghe, Hobukersaier, Wenquan, Xinyuan County and Bayanbulak Pasture in Xinjiang; Xiji County in Ningxia; Ganzi County in Sichuan; Dangxiong and Dingqing County in Tibet AR) in northwest China screened for echinococcosis, the sensitivity of DIGFA ranged from 71.8% to 90.7% in comparison to abdominal ultrasound as the gold standard; specificity for CE using AgB was 94.6% and for AE using Em2 was 97.1%. This simple eye-read rapid test was judged useful for both clinical diagnostic supports, as well as in conjunction with ultrasound for mass screening in endemic CE and AE areas. An immunochromatographic assay (ICA) test for rapid E.granulosus antigen detection showed AgB detection in human cyst fluid biopsy samples had a sensitivity of 93.6%. Application of ICA for rapid coproantigen detection in dog faeces, indicated a test sensitivity and specificity generally lower (66.7%) than for coproELISA (72.2%) after 20 days post infection (dpi). A faecal sample time-course from experimental E.granulosus in dogs (n=9) indicated ICA coproantigen detection by 16 dpi and coproDNA detection by 20dpi. Epidemiological results also showed the overall ultrasound prevalence of human echinococcosis was 3.28% (615/18766), with cystic echinococcosis (CE) 2.73% (513/18766) and alveolar echinococcosis (AE) 0.54% (102/18766) respectively. Meanwhile the DIGFA serological positive rate was 22.4% (2388/10684), females had a relative higher seropositive rate (p<0.05). Relative risk factors for human CE were dog and livestock ownership, occupation as herdsman, ethnic groups as Mongolian and Kazakh. Another risk factor for seropositive might be involved with the gender as a female. This research has implications for further development of rapid tests in support of human and canine echinococcosis diagnosis and for surveillance of transmission in China and elsewhere.