[A National Survey on Current Status of the Important Parasitic Diseases in Human Population]

In order to understand the current status and trends of the important parasitic diseases in human population, to evaluate the effect of control activities in the past decade and provide scientific base for further developing control strategies, a national survey was carried out in the country (Taiwan, Hongkong and Macau not included) from June, 2001 to 2004 under the sponsorship of the Ministry of Health. The sample sizes of the nationwide survey and of the survey in each province (autonomous region and municipality, P/A/M) were determined following a calculating formula based on an estimation of the sample size of random sampling to the rate of population. A procedure of stratified cluster random sampling was conducted in each province based on geographical location and economical condition with three strata: county/city, township/town, and spot, each spot covered a sample of 500 people. Parasitological examinations were conducted for the infections of soil-transmitted nematodes, Taenia spp, and Clonorchis sinensis, including Kato-Katz thick smear method, scotch cellulose adhesive tape technique and test tube-filter paper culture (for larvae). At the same time, another sampled investigation for Clonorchis sinensis infection was carried out in the known endemic areas in 27 provinces. Serological tests combined with questionnaire and/or clinical diagnosis were applied for hydatid disease, cysticercosis, paragonimiasis, trichinosis, and toxoplasmosis. A total sampled population of 356 629 from the 31 P/A/M was examined by parasitological methods and 26 species of helminth were recorded. Among these helminth, human infections of Metorchis orientalis and Echinostoma aegypti were detected in Fujian Province which seemed to be the first report in the world, and Haplorchis taichui infection in Guangxi Region was the first human infection record in the country. The overall prevalence of helminth infections was 21.74%. The prevalence of soil-transmitted nematodes was 19.56% (including hookworm infection 6.12%, Ascaris infection 12.72% and Trichuris infection 4.63%), and the estimated number of population infected with soil-transmitted nematodes was 129 million (with 39.3, 85.93 and 29.09 million for hookworm, Ascaris and Trichuris infections respectively). The prevalence of Taenia infection was 0.28% with an infected population of 550 000. The prevalence of Clonorchis sinensis in the national survey was 0.58%. From the survey in the known Clonorchis endemic areas with a sample of 217 829, terobius vermicularis infection in children under 12 years old was 10.28%. The positive rate of serological tests for hydatid disease, cysticercosis, paragonimiasis, trichinosis, and toxoplasmosis was 12.04% (4 796/39 826), 0.58% (553/96 008), 1.71% (1 163/68 209), 3.38% (3 149/93 239) and 7.88% (3 737/47 444) respectively. In comparison to the last national survey in 1990, the prevalence of hookworm, Ascaris lumbricoides and Trichuris trichiura infections has been reduced by 60.72%, 71.29% and 73.60% respectively, and the number of infected people by soil-transmitted nematodes has declined remarkably. However, the prevalence of Clonorchis infection significantly increased in the provinces of Guangdong, Guangxi and Jilin by 182%, 164% and 630% respectively. A remarkable increase of the prevalence of Taenia infection was found in Sichuan and Tibet, by 98% and 97% respectively. Echinococcosis is important in the Western part of China. Many parasitic diseases are still highly prevalent in the rural and pastoral areas with higher prevalence, morbidity and certain case fatality in farmers and herdsmen, especially in women and children.