Epidemiological Investigation Of Clonorchiasis In Guangdong Shunde From 2014 To 2015

Ⅰ. Research backgroundLiver fluke disease, a food borne parasitic disease, infected human through the ingestion of freshwater fishes and shrimps with living metacercariae of liver fluke. Clonorchis sinensis can cause serious damage to epithelial and vascular tissue in hepatic duct. The adult worms can cause a series of pathological changes, such as cholangitis, cholecystitis, gall-stone, more serious is cirrhosis that may occur in severe cases under the action of its metabolites, secretion and mechanical stimulation. Some researches show that Clonorchis sinensis infection can induce cholangiocarcinoma or hepatocellular carcinoma. It is estimated that Clonorchis sinensis infection accounted for the highest number of liver fluke infections in China and reached to 15 million in the global liver fluke infection reports. Nationwide surveys on parasitic infection status in 1990 and 2002 showed that Clonorchis sinensis infection spread most severely in Guangdong province, what’s more the rates were highest in Shunde which is affiliated to Guangdong province, located in the Pearl River Delta, widely distributed dike-pond and developed aquaculture. Shunde is a culinary world capital, the dishes are famous for fresh and mellowly smooth taste. Residents generally have a habit of eating raw and not fully cooked fresh water fishes. Therefore, the district is a highly endemic area of the liver fluke disease.It has attracted great attention of governments at all levels and health and epidemic prevention departments because of the high prevalence of liver fluke disease in Shunde. As a result lots of comprehensive prevention and control work was carried out, for example, mass screening and treatment were done in some villages, free drugs were provided from CDC, publicity columns were setted up by residential committees, the sale of sashimi was prohibited by mobilizing catering sector, fish pond toilets were dismantled, human and animal feces fed the fish was prohibited and so on. In addition, the prevalence of liver fluke disease in the region has attracted the interest of various institutions and scholars, which had conducted a amount of long-term researches on its epidemiology. These studies provide a lot of valuable research data and suggestions for the prevention and control of the disease in our country. Through a lot of investigation of these institutions and scholars and the corresponding prevention and control work, to a certain extent, it improves the people’s consciousness of preventing and curing the disease, and reduces the prevalence of the disease in the area.Although a long-term liver fluke disease prevention and control work had been taken in Shunde, we need further investigation and analysis to realize the popular trends and characteristics. This project has investigated population infection, the correlated knowledge of the public towards liver fluke infection, the changing to eating habits, the diagnosis and treatments of local medical institutions for the disease, infection of the intermediate host and so on. The analysis and comparison are given between survey data and all kinds of data reported in recent years, in order to find some popular trends and characteristics about liver fluke infection in recent years, and provide some meaningful insights and suggestions for the prevention and treatment of the disease.This topic will carry out the research and analysis through four parts. In the first part, the data of the eggs in feces of Shunde residents over the years were analyzed to understand the situation and development trend of the liver fluke infection. In the second part, the data of the questionnaire survey were analyzed which was related knowledge for the disease, living habits, medical treatment and so on in Shunde to understand their knowledge level about liver fluke and behaviors. The third part, analyzing the previous sampling survey data in Shunde, and understanding the situation of freshwater fish infected liver fluke metacercariae. In the fourth part, detection methods of local medical institutions were investigated to understanding the influence factors on detection rate.The first part:A investigation about Clonorchis sinensis infection in Shunde.1.ObjectiveThe targets are to realize the situation of Clonorchis sinensis infection and analysis the popular trends and characteristics.2.Method2.1 Selection of the survey subjects:Selecting the residents in different age stages who visited Shunde first people’s Hospital from September 2014 to June 2015, we selected five towns in the other four directions by taking the town of Le liu as the center and used stratified random sampling, and the survey subjects are those residents of origin and living for more than 5 years.2.2 Stool examinationCollecting 5g stool samples to examine the eggs by modified Kato Katz thick film screening method, we examined each faecal specimens three times with microscopic examination for the liver fluke eggs. A infectious criteria often used to make the diagnosis is finding eggs to determine the infection, at the same time the number of eggs per gram (EPG) were calculated.2.3 Literature reviewFinding out the previous published literature related to the investigation of clonorchiasis of local area, we collected the survey data related to the infection.3.Result3.1 In this survey,1536 residents accepted the fecal examination, of which 651 people are infected, and the infection rate is 42.38%; Standardized infection rate is 39.98%. Among them, male is 796 and 409 are positive, the positive rate is 51.38%. And female is 740 and 242 are positive, the positive rate is 32.70%. Among the infected people, there were more male than female, and the difference is significant(χ2=54.793, p<0.001). The lowest infection rate (5.04%) appears in the group of 0 to 10 years old, while the highest infection rate (62.62%) arise in the group of 50 to 60 years old. There are significant differences among different age groups(χ2 =272.500, p<0.001) and the infection rate increases with age.3.2 A investigation about the Clonorchis sinensis infection had been taken in Shunde in recent years:From 1982 to 2015, investigations of the infection rate of Clonorchis sinensis showed that the infection rate of Shunde area was maintained between 38.7% and 67.5% in recent 30 years. The highest one was 67.5% investigated in Guizhou in 1995, the lowest was 38.7% in Lecong in a 2008 survey.3.3 The Clonorchis sinensis infection degree(EPG) of all age stages is between 24-21600 in 651 cases of infection. The average EPG is 336, and the highest is 21600. The infections are mainly mild infections,556 patients with mild infection (EPG< 1000/g stool) accounting for 85.41%. In addition, there are 93 moderate infection patients (1000< EPG< 10000/g stool) with accounting for 14.29%, and 2 severe cases(EPG= 10000/g feces) occupy 0.30% without any ultra severe infected person. There are significant differences in the degree of infection among the different groups (χ2=1220.198, P<0.001), and the infection rate of Clonorchis sinensis (EPG) continuously increases with the increasing of age of population.4.ConclusionIn recent decades, the sickness rate of Clonorchiasis sinensis of Shunde has been maintained at a high level. Compared with that in 1970s, infection rate has declined in recent 20 years, however the infection rate decreases slightly and the trend is not obvious. Recent investigation shows that infection rate of the population of 20～40 years old has declined, infection rate of 20～30 years old is far below the average level, especially the rate of 10～20 years old is in single digits. While EPG decreased, Clonorchis sinensis infection rate and infection degree (EPG) increased with age and were higher in male than those in female.The second part:A questionnaire survey about knowledge of liver fluke disease and the medical situation of the residents in Shunde.1.ObjectiveThe targets are to learn about the residents’awareness of liver fluke disease, the eating habits, and medical situation in Shunde through the questionnaire survey,2.Method2.1 The subjects are the same as the crowd with feces examination. while the participants are examined, the investigators can make questionnaire survey.2.2 After designing questionnaire scientifically, the investigators can do one-to-one question and answer investigation which is related to he residents’ awareness of liver fluke disease, the eating habits, and medical situation.2.3By the method of literature review, looking up the published literature relating to regional clonorchiosis survey and gathering relevant data and the results of knowledge awareness and the eating habits of the participants.3.Results3.1 According to the survey,52.64% of men and 33.78% of women had ever been eating raw freshwater fish and shrimp. Both have significant difference (p< 0.001). Meanwhile, there was a rising tendency increased with age. It was relatively serious for the phenomenon that 89.95% of male and 88.24%of female ate freshwater fish which may not well-done; There was no significant difference (p> 0.05).For the times of eating raw freshwater fish and shrimp every year,71.29% of residents were in the following 5 times,15.69% in 6-10 times,5.99% in 11-20 times, only 4.10% residents more than 20 times. The times of eating freshwater fish which may not well-done were higher than the number of eating fish.25.46% of residents consumed 6-10 times a year and 29.23% of residents ate 11-20 times a year while 26.04% of residents consumed more than 20 times a year.60.94% of residents surveyed used different chopping blocks when dealing with raw food and cooked food. The residents of hearing about liver fluke disease accounted for 64.19%. 58.33%of participants knew that eating raw fish might cause having liver fluke infection. Knowing the disease caused by liver fluke roughly accounted for 47.27%. 33.33% of residents surveyed said they had contacted with publicity materials relating to liver fluke disease. The residents who knew themselves ever infected with liver fluke accounted for 7.68% of the total.9.24% of the total had received a liver fluke treatment.3.2 In the view of literature investigation in recent years, the consumption proportion of freshwater fish and shrimp which are raw or may be not well-done always remains high, but the numbers of residents eating raw freshwater fish and consumption times every year are less than 10 to 20 years ago. Moreover, more residents know about the infection approach of clonorchiasis and the disease caused by liver fluke.4. ConclusionsAfter continuous publicity and education by governments, although the consumption proportion of freshwater fish and shrimp which are raw or may be not well-done always remains high in Shunde, consumption frequency is decreased especially in the younger generation recently. there is no change for the consumption proportion of freshwater fish and shrimp which may be not well-done. Also, more residents know about the infection approach of clonorchiasis and the disease caused by liver fluke, but prevalence and treatment rates are still low. The education of primary and secondary schools students about Liver fluke disease is insufficient. The government and the prevention and control departments at all levels still need to insist on strengthening the propaganda and education relating to liver fluke.The third part:Investigation on the freshwater fish infection with encysted metacercaria of Clonorchis sinensis in Shunde1. ObjectiveThe targets are to realize the situation of freshwater infection with encysted metacercaria of Clonorchis sinensis in Shunde.2. Method2.1 The sources of being investigated freshwater fishIn October 2014-August 2015,4 species of freshwater fish including grass carp, carp, bighead carp, and dace which are made into raw or half-cooked food. For example:sashimi, sliced fish congee, and the fish fillet for hot pot and so on. The total of 156 specimens were taken from 9 trading markets in Fuyou, Huagai, Xingfu, Rongqi, Taiming,Yincheng, Sanhua,Cangmen and Chencun.2. Investigation on the infection of freshwater fish with encysted metacercaria of Clonorchis sinensis.200g flesh of the back was examined after removing fish scales, bones, internal organs from freshwater fish. The freshwater fish meat was examined the infection with encysted metacercaria of Clonorchis sinensis with digestive treatment, then calculating infection rate and infectiosity (EPG).3. Results3.1 156 freshwater fishes in 4 types sampled from various markets and restaurants in Shunde were investigated, and 19 freshwater fishes of them were found to contain metacercarias of Clonorchis sinensis. The infection rate was 12.18%, and the average infectiosity of infection-positive fish was 0.152/g. Infection rate of grass carp and crucian carp were 14.29%,13.16% respectively, and infectiosity of infection-positive fish were 0.083/g,0.116/g respectively. Infection rate of bighead carp and mud carp were 12.50%,8.33% respectively; and infectiosity of infection-positive fish were 0.265/g,0.160/g respectively.3.2 There is a declining trend on the infection rate and infectiosity of freshwater fish that farmed or sold in Shunde comparing with previous the literatures survey in recent years.4. ConclusionThe infection rate and infectiosity of freshwater fish that often seen on the dining table of Shunde residents have declined,comparing with previous reports on account of promoting of industrialization and urbanization, declining of the phenomenon that feed the fish with human excrement and animal waste, and more freshwater fish coming from non-epidemic area.The fourth part:Investigation on the examination of liver fluke infection in medical institutions in Shunde.1.ObjectiveThe targets are to realize the situation of the detection of liver fluke infection in medical institutions in Shunde and analyze influence factors.2.Method2.1 Survey population selected the people who hospitalized, had a outpatient service or took a physical examination in the First People’s Hospital of Shunde during September 2014 to August 2015 of different age stages.300 cases fecal samples and 8126 cases serum samples was collected from the residence residents more than 5 years in Shunde.2.2 Stool samples were divided into two parts, one was detected with direct smear test, and the other was detected with modified Kato’s method.2.3 Liver fluke specific antibody IgG in serum was detected by enzyme linked immunosorbent assay (ELISA).2.4 Taking a retrospective survey aims to the situation of development of liver fluke detection project and clinical detection in the First People’s Hospital of Shunde.3.Results3.1 The smear positive rate respectively is 14.0%,20.3% or 25.3%(one, two or three fecal samples) with the physiological saline direct smear method. The smear positive rate respectively is 32.7%,40.7% and 45.7%(one, two or three fecal samples) with the modified Kato s thick smear method; Two kinds of methods detected liver fluke infection with significant difference (P< 0.01) and increasing the number of fecal samples can significantly improve the detection rate of liver fluke eggs. The smear positive rate is 8.3% with the physiological saline direct smear method in clinical practice, which is quite different comparing with the two method in this experiment.3.2 17.8 million participants take a physical examination in the First People’s Hospital of Shunde during September 2014 to 2015 August, but only 8126 choose the disease antibody detection(4482 males and 3644 females).1503 people showed a positive reaction, and the positive rate is 18.50%; 1082 men were positive, and the positive rate is 24.14%.The positive reaction is 91.96% in 30 to 60 years old men reaching to 995 people, and 8.04% were detected in other age group accounting for 87 people.412 women were positive, and the positive rate is 11.3%. The positive reaction is 70.13% in 30 to 60 years old women reaching to 326 people, and 20.87% were detected in other age group accounting for 86 people.4.ConclusionSaline direct smear method is simple, but the positive rate is low in clinical liver fluke infection diagnosis. We should increase the number of samples or combine with other detection methods if we want to improve the clinical diagnosis rate of Clonorchis sinensis. There is fewer participant detecting Liver fluke infection with the specific IgG antibody, and failed to achieve satisfactory results. the health authorities at all levels should to promote the hospital to pay attention to the prevention and control of the disease, strengthened publicity and education to the residents about the knowledge of Clonorchis sinensis infection, as a result, guiding residents take a Clonorchis sinensis infection examination. The diagnosis rate of liver fluke disease was improved by the method of combination of clinical imaging, highly sensitive and specific antibody detection, cholangio and duodenal biliary drainage, except for paying attention to improve feces examination.