Clonorchiasis is one of the food?borne parasitic diseases. Adult parasites live in the human liver and gallbladder tube system,causing serious complications,such as gallstones,cholecystitis and cholangitis,and even bile duct cancer. The disease is very popular in our country,and the population infection rate is high. It is an important public health problem. Guang?dong Province is the earliest province being found of clonorchiasis and with serious epidemic. In the second national human para?sitic diseases distribution survey,the results showed that the average infection rate of Clonorchis sinensis in the epidemic areas in Guangdong was 16.42%. It is estimated that the population of C. sinensis infection is over 6 million. The prevention and con?trol of clonorchiasis in China is still in the initial stage currently and we face many challenges such as unclear epidemic charac?teristics and transmission mode,and lack of long?term prevention and control mechanism. This article introduces the epidemic situation of clonorchiasis and prevention and control strategies and measures in Guangdong.

Objective To study the therapeutic effect and possible adverse effects of tribendimidine enteric coated tablets in the treatment of infections due to hookworms, Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularis. Methods According to the standard clinical trial design and protocol, pearsons infected with hookworms, Ascaris lumbricoides, Trichuris trichiura, or Enterobius vermicularis respectively, were treated with tribendimidine enteric coated tablets in four counties of Guangdong and Jiangsu Provinces, albendazole was used as control. Results For hookworm infection, the curative rate (eggs negative in the faeces) were 89^5%(85/95) and 70^6%(60/85) with tribendimidine (400 mg) and albendazole(400 mg) respectively; for Ascaris infection, 97^4%(114/117) and 98^9%(91/92) with tribendimidine(300 mg) and albendazole(400 mg) respectively; for Trichuris infection,33^3%(25/75) and 56^1%(23/41) with tribendimidine(400 mg/day for 3 days) and albendazole(400 mg/day for 3 days) respectively; for Enterobius infection in children, 74^1%(60/81) and 93^0%(40/43) with tribendimidine(200 mg) and albendazole(200 mg) respectively. No considerable side effect was found. Conclusion Tribendimidine is highly active in the treatment of hookworm, Ascaris lumbricoides infections, free of major adverse effect and easy to administer. It is more effective than albendazole for the infection of Necator americanus.

Objective To understand the prevalence and epidemiological features of clonorchiasis sinensis based on inpa-tients in Zhongshan City. Methods All of the 23 town hospitals in Zhongshan City were selected as the surveillance hospitals in 2016. Among the inpatients from those hospitals,those lived in the city longer than 6 months were selected as the surveillance subjects. The stool specimens of the subjects were collected and examined by the modified Kato-Katz thick smear method for the eggs of Clonorchis sinensis. The crude infection rates of C. sinensis of the subjects were standardized according to the age and sex compositions of the population in Zhongshan City,2016. Meanwhile,the infection rates of the subjects from different towns and those combined with related clinical diseases were analyzed. Results A total of 2667 people were included in the surveil-lance,among which 219 were tested as positives,with a crude infection rate of 8.21％. For the positives,the male accounted for 81.74％(179/219),and their age ranged from 4 to 89 years with the mean value of(62.20±13.80)years. After standardization by age and sex composition,the infection rate was 3.62％for the whole population,the rates of the male and the female were 5.46％and 1.53％,respectively,and the former was 3.57 times as high as the latter. Both the infection rates of the male and the female rose as the age increasing(χ2 male=99.91,χ2 female=16.51,both P<0.01). The standardized infection rates among the subjects in different towns ranged from 0 to 10.40％,and the rates in the north towns were higher than those in the south towns. The standardized rate was 9.22％for the subjects combined with gallstone,3.40％for those not combined with gallstone,and the former was 2.71 times as high as that of the latter. Conclusion The people aged 30 years and above,with gallstone or living in towns with high C. sinensis infection rates are the key population for prevention and control of clonorchiasis in Zhongshan City.

Objective To explore the suitable chemotherapy measures in different Clonorchis sinensis infectiosity endemic ar-eas. Methods The interventional groups and control groups were set up in the heavy,moderate and light C. sinensis infectiosity areas in Guangdong Province,respectively. In the intervention groups,the chemotherapy was administered among all the residents aged above 3 years in the heavy endemic areas,the chemotherapy was given among the focus populations in the moderate endemic areas,and the chemotherapy was administered among the residents infected with C. sinensis confirmed by stool examinations in the light endemic areas. No measures were carried out in the control groups. Results One year after the interventions,the C. sinensis infection rates of the interventional groups decreased by 47.90%,86.52%and 100%,the abnormal rates of liver B ultrasonic ex-aminations decreased by 26.50%,31.00%and 100%,the ALT abnormal rates decreased by 48.70%,62.30%and 100%,and the AST abnormal rates decreased by 55.50%,39.90% and 100% in the heavy,moderate and light endemic areas,respectively. There was no decreasing trend of above-mentioned indexes in the control groups. Conclusion In the different C. sinensis infectios-ity endemic areas,the different chemotherapy measures should be carried out.

Objective To clone and express the valuable Clonorchis sinensis antigen molecules which can be applied to the diagnosis of clonorchiasis. Methods Based on the sequences (Genbank) No. AF271091 (CysA) and No.AF093242 (CysB), primers were designed to amplify the two C. sinensis cysteine proteinase genes and expressed in E.cloi. The expressed proteins were purified by affinity chromatography and then tested for their immunological characters.Results The two genes were successfully cloned and expressed. Western blot showed that CysB had strong reaction with clonorchiasis sera and very weak reaction with schistosomiasis sera, while CysA showed no reactivity with the probed sera. Immunohistochemistry showed that both proteins were mainly located in adult worm intestines and the intrauterine eggs.Conclusions The results suggested that, of the two expressed C. sinensis proteins, CysB had good antigenic reactivity against sera from patients. It is a potential candidate of diagnostic antigens for clonorchiasis.

Objective To analyze the epidemic status of principal human parasites, so as to provide scientific evidence for making prevention countermeasures for Guangdong Province in the future. Methods In 2015, a survey was performed according to the scheme of "The 3rd National Survey of Principal Human Parasites"as well as the incidence of parasites disease in Guangdong Province,the residents at 48 investiation sites in counties were surveyed. The survey of the soil-transmitted nematodes (Ascariasis, Ancylostoma, Trichuris trichiura and Enterobius vermicularis) and intestinal protozoa were performed based on the ecological regions and stratified by economic and geographic situation.The survey of food borne Clonorchis sinensis was performed along with the soil-transmitted nematodes in rural areas, and it was performed by the sample method of random cluster in cities and towns.The residents in each investigation site as the object, the ovum of the soil-transmitted nematodes, Clonorchis sinensis and other helminths were examed by the modified Kato-Katz method, test tube filter paper was used to identify Hookwormspecies, and the intestinal protozoa was checked by direct smear method. The transparent tape anal swabs method for children aged 3 - 6 years to check Enterobius vermicularis. Results Totally 12 401 residents of 48 survey sites from 22 counties were surveyed, and the total infection rate of intestinal parasites was 8.29%(1 028/12 401). The infection rate of soil-transmitted nematodes was 3.39% (420/12 401),in which the infection rate of Ascariasis, Ancylostoma, Trichuris trichiura and Enterobius vermicularis were 0.52% (64/12 401), 1.89%(234/12 401),0.46%(57/12 401),and 0.52%(65/12 401),respectively.The infection rate of Clonorchis sinensis was 4.90%(608/12 401). Nine hundred and sixty-seven children were tested for eggs of Enterobius vermicularis with the infection rate of 12.41% (120/967). The number of hook larva culture was 153, among them, 140 were hookworm larvae of America and no duodenal hookworm larvae and other nematode species were found.Totally 9 309 residents were tested for intestinal protozoa infection,and the infection rate was 0.31%(29/9 309). Conclusion In Guangdong Province, the infection rate of soil-transmitted nematodes is decreasing while the infection rate of Clonorchis sinensis is still high, and the control work of parasites still should be strengthened especially for food borne parasitic diseases.