Increasing prevalence and intensity of foodborne clonorchiasis, Hengxian County, China, 1989-2011.

During 1989-2011, three parasitic disease surveys were conducted in Hengxian County, China, where soil-transmitted helminthiases and foodborne clonorchiasis are endemic. We compared the data and found that the prevalence of helminthiases decreased and the prevalence and intensity of clonorchiasis increased over time, especially among men. Clonorchiasis control/intervention measures are urgently needed in this area.

[Enterobius vermicularis infection status among children in 9 provinces/autonomous regions/municipalities of China].

OBJECTIVE: To investigate the infection status of Enterobius vermicularis among children in 9 Provinces/Autonomous regions/Municipalities (P/A/M) of China, and analyze its risk factors. METHOD: From April to December 2011, one provincial capital (prefecture-level city) and one county (city, district) were chosen as investigation spots from Guangdong, Guangxi, Hainan, Chongqing, Sichuan, Zhejiang, Fujian, Anhui and Guizhou, respectively. Children aged 2 to 12 were examined by using adhesive cellophane anal swab with round-bottom tube. Information of children's family condition, health behavior and school environment were collected by questionnairing. RESULTS: 14 964 children were examined, and 14 582 qualified questionnaires were collected. The total prevalence was 17.8% (2 659/14 964). Of the 9 P/A/M, the prevalence was highest in Hainan Province (51.1%, 869/1 701) and lowest in Anhui Province (0.8%, 13/1 589). The prevalence in urban areas (7.3%, 552/7 581) was lower than that of rural areas (28.5%, 2 107/7 383) (chi2 = 1156.73, P < 0.01). The highest prevalence in urban and rural areas was found in Haikou City(38.0%, 322/847) and Wanning City (64.1%, 547/854) of Hainan Province. The prevalence rate in males and females was 17.4% (1 410/8 128) and 18.3% (1249/6 834), respectively (chi2 = 2.192, P > 0.05). The highest prevalence in males (61.2%, 300/490) and females (67.9%, 247/364) was found in children of Wanning City. Multivariate logistic regression analysis showed that residence, education level of parents, occupation of parents, nail biting, types of classroom ground and type of boarding were the risk factors on E. vermicularis infection. CONCLUSION: The prevalence of enterobiasis in children is still high in many areas of China, and the prevention and control measures should be taken according to the risk factors.

Analysis of the results of two nationwide surveys on Clonorchis sinensis infection in China.

OBJECTIVE: To examine Clonorchis sinensis infection in China and evaluate the effectiveness of efforts to prevent and control it, two nationwide surveys were undertaken in 31 provinces, autonomous regions, and municipalities (PAMs) during 1988-92 (the 1990 survey) and during 2001-04 (the 2003 survey). METHODS: During the period 2001-04, two sampling methods were applied. The first method repeated the stratified cluster random sampling used in the 1990 survey; the second method applied two-characteristic stratified cluster random sampling in 27 PAMs-the 2003 endemic area (EA) survey. The Kato-Katz thick smear method was used for the nationwide survey. RESULTS: The infection rates of Clonorchis sinensis in the 1990 and 2003 surveys were 0.311% and 0.579%, respectively. The infection rate was 2.40% in the 2003 EA survey, and it was estimated that 12.49 million people in China were infected with Clonorchis sinensis. CONCLUSION: The 2003 survey showed that the standardized infection rate of Clonorchis sinensis increased by 74.85% compared with the 1990 survey. The infection rate in males was higher than in females; the infection rate among people eating raw fish or eating out frequently was higher than among those who did not.

Effectiveness of a community-based integrated strategy to control soil-transmitted helminthiasis and clonorchiasis in the People's Republic of China.

Soil-transmitted helminthiases (STHs) are caused by a group of intestinal nematode infections due to poor hygiene and environments, and clonorchiasis is a food-borne trematode (FBT) infection caused by ingestion of raw freshwater fish. Both are endemic in the People's Republic of China. To explore a suitable control strategy, integrated interventions were applied between 2007 and 2009 in ten pilot counties (eight for the STHs and two for clonorchiasis). Drug administration was used for treatment and complementary efforts to improve the situation based on health education, provision of clean water and sanitation were carried out. Significant achievements were gained as reflected by a drastic decrease in prevalence these infections were demonstrated. The overall prevalence of STHs and clonorchiasis decreased from 35.9% to 7.8% and from 41.4% to 7.0%, respectively. The reduction of prevalence and high cost-effectiveness were documented supporting large-scale application of this integrated intervention in China and elsewhere.

Current status of soil-transmitted nematode infection in China.

OBJECTIVE: To carry out national surveys for ascertaining the current status and trends of soil-transmitted nematode infections in China, providing scientific basis for further developing control strategies. METHODS: In 1988-1992 (hereinafter abbreriated as "survey in 1990"), a stratified cluster random sampling method was used in the survey. In 2001-2004 (hereinafter abbreriated as "survey in 2003"), in order to compare with the survey in 1990, two-characteristic stratified cluster random sampling method was used and 687 investigation spots were sampled from the 2848 spots selected in the survey in 1990. Kato-Katz thick smear method was used to examine the eggs of soil-transmitted nematodes in fecal samples. RESULTS: The prevalence rates were 53.6% and 19.6% for soil-transmitted nematodes, 14.6% and 6.120% for hookworms, 44.6% and 12.7% for Ascaris lumbricoides, 17.4% and 4.630% for Trichuris trichiura in survey 1990 and survey 2003, respectively. The prevalence rates of soil-transmitted nematodes were higher in 13 provinces than the average level in China in the survey in 1990, and higher in 8 provinces than the average level in the survey in 2003. The prevalence of hookworms, Ascaris lumbricoides, Trichuris trichiura and the overall prevalence of soil-transmitted nematodes were higher in females than in males. It is estimated from the results of survey in 2003 that the number of persons with soil-transmitted nematode infections in the country is about 129 million, less than that in the survey in 1990. CONCLUSION: The prevalence of soil-transmitted nematodes has declined considerably but is still relatively high in some provinces and autonomous regions. Control activities and socioeconomic development may have contributed to the decreased prevalence.

Risk factors for Enterobius vermicularis infection in children in Gaozhou, Guangdong, China.

BACKGROUND: Enterobius vermicularis infection is a prevalent intestinal parasitic disease in children. In this study, we explored the epidemiological status and risk factors for E. vermicularis infection in children in southern China. METHODS: A cross-sectional survey was carried out in Gaozhou city, Guangdong province, China, in December 2011. Children aged 2-12 years from five schools participated in the study. The adhesive cellophane-tape perianal swab method was applied to detect E. vermicularis infection, while a questionnaire was sent to each child's guardian(s) to collect demographic and socioeconomic data, as well as hygiene behaviors, pertaining to each child. Univariate and multivariate logistic regression analyses were performed to capture the potential risk factors. RESULTS: Out of the 802 children surveyed, 440 were infected with E. vermicularis, with an average prevalence of 54.86 %, and a range from 45.96 to 68.13 %. The age variable was found to be statistically significant, whereas the sex variable was not. It was found that a mother's education level (low) and not washing hands before dinner were major risk factors in all children (802). After stratification by age, a father's education level (primary or below) and biting pencils (or toys) were significant risk factors in the younger children (508), while not washing hands before dinner and playing on the ground were important risk factors in the older children (294). CONCLUSION: This study demonstrates the prevalence of E. vermicularis infection in children in Gaozhou and reveals underlying risk factors. Most importantly, it reveals that risk factors differ among the different age groups, which indicates that different control measures targeted at particular age groups should be implemented.

Epidemiological investigation on Clonorchis sinensis in human population in an area of South China.

To detect the prevalence of Clonorchis sinensis, one of the important helminthes in the human population of the Guangxi Region where Schistosoma japonicum was endemic but eliminated in the late 1980s, the Kato-Katz thick smear technique was used for examining fecal samples from selected townships in Hengxian County. Among 1,552 people examined, 491 (31.6%) were found infected with C. sinensis. By counting eggs per gram feces (EPG), it was found that the light, moderate, and heavy intensities of infection occupied 55.4, 33.0, and 11.6%, respectively, with an average EPG of 4,845 in the infected subjects. The survey revealed that the prevalence in the age groups of 0 - 9 and 10 -19 years old was less than 10% but was 45 - 50% in the groups between 30 - 39 and 60 - 69 years old. A much higher prevalence was demonstrated in the male population (41.9%) than in the females (20.5%), and heavier intensity of infection was also found in the males than in the females. These results indicated that the prevalence of this liver fluke is increasing in the past decade in that region, and there is an urgent need to further assess the epidemiological factors in reference to the area's changing socioeconomic conditions and human behavior, contamination of the environment and fish ponds, inadequate farming/fishery practices, and the infection of domestic animals.

Epidemiological profile of Clonorchis sinensis infection in one community, Guangdong, People's Republic of China.

BACKGROUND: Clonorchiasis caused by ingesting improperly prepared fish ranks among the most important but still neglected food-borne parasitic diseases, especially in the People's Republic of China (P.R. China). To promote the implementation of interventions efficiently, the demonstration of an epidemiological profile of Clonorchis sinensis infection is essential in hyper-epidemic areas. METHODS: In one community with higher levels of economic development in Guangdong province, P.R. China, villagers were motivated to provide stool samples for examining helminth eggs. Then, those infected with C. sinensis completed the structured questionnaire including demographical characteristics, knowledge and behavior. RESULTS: A total of 293 villagers infected with C. sinensis participated in questionnaire investigation. Among them, 94.54% were adult and 93.17% were indigenous. The geometric mean of C. sinensis eggs per gram of feces in the children, adult females and adult males was 58, 291 and 443, respectively. The divergence between knowledge and behavior in the adults, especially the adult males, was shown. Out of 228 persons eating raw fish, 160 did it more frequently at restaurants, the proportion of which varied in different populations, showing 25.00%, 54.88% and 80.28% in the children, adult females and adult males, respectively. CONCLUSIONS: Different interventions need to be adopted in different populations. Chemotherapy should be prioritized in the adults, especially the adult males. In addition, health education targeting the children, is essential and may play a crucial role in controlling clonorchiasis in the long term. In order to successfully control clonorchiasis, intervention in the restaurant should not be overlooked in some endemic areas.

Disability weight of Clonorchis sinensis infection: captured from community study and model simulation.

BACKGROUND: Clonorchiasis is among the most neglected tropical diseases. It is caused by ingesting raw or undercooked fish or shrimp containing the larval of Clonorchis sinensis and mainly endemic in Southeast Asia including China, Korea and Vietnam. The global estimations for population at risk and infected are 601 million and 35 million, respectively. However, it is still not listed among the Global Burden of Disease (GBD) and no disability weight is available for it. Disability weight reflects the average degree of loss of life value due to certain chronic disease condition and ranges between 0 (complete health) and 1 (death). It is crucial parameter for calculating the morbidity part of any disease burden in terms of disability-adjusted life years (DALYs). METHODOLOGY/PRINCIPAL FINDINGS: According to the probability and disability weight of single sequelae caused by C. sinensis infection, the overall disability weight could be captured through Monte Carlo simulation. The probability of single sequelae was gained from one community investigation, while the corresponding disability weight was searched from the literatures in evidence-based approach. The overall disability weights of the male and female were 0.101 and 0.050, respectively. The overall disability weights of the age group of 5-14, 15-29, 30-44, 45-59 and 60+ were 0.022, 0.052, 0.072, 0.094 and 0.118, respectively. There was some evidence showing that the disability weight and geometric mean of eggs per gram of feces (GMEPG) fitted a logarithmic equation. CONCLUSION/SIGNIFICANCE: The overall disability weights of C. sinensis infection are differential in different sex and age groups. The disability weight captured here may be referred for estimating the disease burden of C. sinensis infection.

[Study on a new prevention and control model on soil-borne parasitic diseases in rural areas of China].

OBJECTIVE: To explore a new prevention and control model on soil-borne parasitic diseases in rural areas of China. METHODS: Eight provinces and autonomous regions were selected in China as demonstration areas implementing integrated control on soil-borne parasitic diseases. The integrated control measures included authority organization and harmonization, health education, deworming, and environment modification. RESULTS: After three years, the infection rates of soil-borne parasitic diseases were significantly decreased in these areas. There were three safe guard and organization modes, three health education modes, four mass worming medication modes, and two modes of water, toilet and environment changes. CONCLUSION: The work in the various demonstration areas was summarized which pointed out a new model with efficiency and local characteristics on soil-borne parasitic disease prevention and control.

[Study on the mixed testing of serum samples in seroepidemiological survey of parasitic diseases].

OBJECTIVE: In order to accumulate experiences for improving the efficiency in serological tests, the present study on mixed testing of serum samples was performed by taking the serological test of trichinellosis and toxoplasmosis as the examples, and had proved the effects on cost-effectiveness of seroepidemiological survey of parasitic disease with method of mixed-samples test. METHODS: According to the binomial distribution principle, to develop an approach to the feasibility of mixed testing of serum samples, and to work on a cost-effectiveness analysis of one-by-one testing and mixed testing using hygienic economic analysis method was performed. For serological test of trichinellosis and toxoplasmosis, 3 kinds of mixed testing methods, namely 3 serum sample mixture, 5 serum sample mixture and 10 serum sample mixture, were performed. RESULTS: The results showed that all the 3 kinds of mixed tests of trichinellosis and toxoplasmosis showing positive result if only 1 weak positive serum sample were mixed with. When the serum samples being mixed were all negative ones, then among the 24 groups tested with each kind of negative serum sample mixture of trichinellosis (3 serum samples, 5 serum samples and 10 serum samples), they all showed negative. However, among the 12 groups tested with 2 kinds of negative serum mixture of toxoplasmosis (3 serum samples and 5 serum samples), all showed negative while among the 18 groups tested with the 10 serum sample mixture, 16 groups showed negative and 2 were positive. The mixed testing of trichinellosis and toxoplasmosis showed that the efficiency of mixed testing was related to the serological positive rate of the parasitic diseases to be examined. When serological positive rate was 10%, the efficiency of mixed testing was higher in 4 serum sample group. When serological positive rate was 1%, the efficiency of mixed testing was higher in 10 serum sample group and when serological positive rate was 0.1%, the in crease of the size of mixed serum samples could decrease the number of testing, but the prerequisite was that there must be one positive sample, so that the positivity for all the mixed tests could be detected. If mixed testing were performed on all negative samples, no positivity could be detected. CONCLUSION: The result of cost-effectiveness analysis demonstrated that for seroepidemiological survey of parasitic diseases, the cost for mixed testing was low, especially when the serological positive rate was expected low (< or = 1%, thus the mixed testing could save a large amount of the cost.