There are two major endemic regions in China, i. According to the results of three large-scale surveys of clonorchiasis carried out in mainland China, the prevalence of clonorchiasis increased from 0. Symptoms caused by clonorchiasis are directly proportional to worm burden [ 1 , 6 , 11 ]. Hence, patients with low infection intensity are often asymptomatic or show only mild symptoms, whereas patients with high infection intensity often show unspecific symptoms, such as asthenia, nausea, indigestion, headache or abdominal pain, especially in the right upper quadrant [ 6 , 12 ].
In addition, developmental retardation has been reported in children with heavy infection intensity. These children often present with inappetence, diarrhoea, malnutrition, anaemia and hepatomegaly [ 13 ]. Cholelithiasis is one of the most frequent complications of such infection. Previous studies discovered that a high worm burden and narrowing of the bile ducts, which might result from the accumulation of worms, cause obstruction, sequential bile stagnation, and bile pigment deposition, which may give rise to the formation of stones in bile ducts with eggs or dead worms as nuclei [ 14 — 17 ].
Additionally, C. As evidence accrued, C. Systematic reviews and meta-analyses revealed pooled odds ratios ORs for C. Additionally, in a study focusing on the relationship between liver flukes and cholangiocarcinoma, Odds Ratios OR were significantly associated with higher infection intensities [ 22 ]. In this study, we aim to explore the epidemiological characteristics of clonorchiasis in local endemic areas, with an emphasis on understanding the distribution of infection intensity and risk factors of high intensity, which can contribute to the effective and sustainable development of intervention measures.
China Fig 1. Binyang County is located at the Pearl River Basin, where has 16 towns and a population of approximately 1. The annual discretionary income per capita reached CNY for urban citizens and CNY for rural citizens in Geographic location of the Guangxi Autonomous Region in China.
Location of the study site in Binyang County [ 24 ]. Among all 16 towns of Binyang County, 7 towns were identified as the survey areas by using a random sampling method, and two villages from each town were further selected. In each survey village, residents were randomly enrolled in the survey.
The same questionnaire was used to collect the demographic information, including age, sex, education and occupation, of all enrolled study participants. Furthermore, one stool sample was collected from each participant.
Experienced and trained public health staff prepared three Kato-Katz thick smears for each sample and examined them for eggs under a light microscope [ 25 , 26 ], and each smear was examined for different people. Ten stool samples were chosen for each study village 14 for overall to be re-examined by professional staff in the high level of CDC to conduct quality control. After the faecal examination, participants who were confirmed to be infected with C.
The questionnaire contained four parts: demographic characteristics, previous illness history, knowledge and attitude towards clonorchiasis, and risk behaviours related to C. In the demographic part, sex, age, occupation and education were recorded. Four questions related to knowledge and attitudes e. Other questions about raw fish consumption, such as the duration, frequency, quantity and location of raw fish consumption, were recorded in the risk behaviours part.
Data used in our manuscript was based on the C. The main purpose of this program was to explore the re-infection rate and risk factors that influence the occurrence of C.
The first step of this program was to screen clonorchiasis patients, then cured them, and followed up them to identify the re-infection situation. Therefore, the program was focused on the infected people, and the structured questionnaire was only used in infected persons.
For the negative persons, only basic demographic information was collected. The data were double-entered and cross-checked in EpiDate 3. Analysis was performed in R Studio software Version 1. The overall infection proportion was computed by dividing the number of infected persons by the total number of survey participants, and the proportion was standardized by using different age groups of the local population in The population data used to calculate the standardized proportion were obtained from the Statistics Bureau of Nanning District.
The number of eggs per gram of faeces EPG was calculated by multiplying the egg count of every smear by 24 and then computing the average of three smears. The overall proportions of mild, moderate and heavy infections were calculated by dividing the number of mild, moderate and heavy infections by the total number of infections.
Moreover, the infection proportion and the proportions of the three types of infection intensity mild infection, moderate infection and heavy infection for different population groups by sex, age, occupation and education level were calculated and compared. Age was transformed into five categories 15, 15—29, 30—44, 45—59, and 59 years.
Univariate and multivariate logistic regression models were used to explore the relationship between raw fish consumption behaviour and high-intensity infection moderate and heavy infections. Statistical significance was determined at a p -value of 0. The objectives, procedures and potential risks were orally explained to all participants. A written consent form was also obtained from each participant with his or her own signature or the signature of a proxy, including being administrated the praziquantel to treat clonorchiasis as a medicine with off-label use.
A total of subjects response rate: The overall infection proportion was Male Of the residents who were infected with C. The age of the infected persons ranged from 3 to 88 years, with an average age of 50 years and a median age of 51 years interquartile range: 41— Most of the infected persons Additionally, 2 0.
Among the persons infected with C. Males The percentage of moderate and heavy infections increased from 7. The proportion of infected males was higher than the proportion of infected females in all age groups, except for children under 15 years old Fig 2A.
In all age groups except for children under 15 years old, the proportion of mild infection was higher than the proportion of moderate and heavy infections both in males and females Fig 2B and 2C. Infection proportion of clonorchiasis in different age groups by sex. Infection proportion of clonorchiasis for males by age group and infection intensity mild, moderate and heavy.
Infection proportion of clonorchiasis for females by age group and infection intensity mild, moderate and heavy. Among the infected persons, Among the persons who reported eating raw fish, Four hundred ninety-four Additionally, a higher percentage of males No significant differences in raw fish consumption behaviour were identified between those with different knowledge of clonorchiasis knowledge of the transmission route of clonorchiasis and that it causes cancer Table 2.
The percentage of moderate and heavy intensity of infection had increased from In this study, by analysing cross-sectional data from an endemic area in China, we found that the infection proportion of clonorchiasis was high and that a large proportion of infected persons had moderate and heavy intensity infections.
People aged 30—59 years had a higher infection proportion and a higher percentage of moderate and heavy infections than those in the other age groups.
Males experienced a higher percentage of moderate and heavy intensity infections than females, which might be attributed to the longer duration, higher frequency and greater quantity of their raw fish consumptions. Additionally, people who had been previously diagnosed with clonorchiasis or had previously taken anti-parasitics had longer durations and higher frequencies of raw fish consumptions, while no differences were identified among people with different knowledge of clonorchiasis.
Furthermore, a high frequency of raw fish consumption was a risk factor for a high intensity of infection. The distribution characteristics of infection intensity and infection proportion among the sexes and age groups except among children that were identified in this study were mainly related to living customs, i. Raw fish are often consumed in social gathering or at restaurants, and offering raw fish to guests is deemed a hospitable gesture; males have more opportunities to participate in these practices [ 8 , 28 , 29 ].
Moreover, raw fish are often enjoyed with alcoholic beverages, which is more common among males than females, except for among children [ 5 , 30 ]. Once attached, the cercariae penetrated underneath the scales and became encysted in the subcutaneous tissues and muscles as metacercariae.
Takayuki Mukoyama found immature flukes in experimental mammals as early as six hours after ingestion of infected fish, but only in the biliary tract, duodenum, and stomach. He concluded that the flukes did not penetrate the intestinal mucosa but instead migrated directly to the biliary tract.
However, when the fish were cooked in warm water for 15 minutes, the C. This led to the public health recommendations for avoidance of ingesting uncooked fish. McConnell JF. Remarks on the anatomy and pathological relations of a new species of liver flukes. Lancet ;ii, Geographic Distribution. Skip directly to site content Skip directly to page options Skip directly to A-Z link.
Section Navigation. Facebook Twitter LinkedIn Syndicate. Minus Related Pages. Life Cycle View Larger. Clonorchis sinensis eggs. Figure A: C. Figure B: C. Figure C: C. Figure D: C. Figure A: Adult of C. Figure B: Adult of C. Snail intermediate hosts of C. Figure A: Shells of Parafossarulus manchouricus , the most common snail host of C. Figure B: Bithynia sp. Laboratory Diagnosis Diagnosis is usually based on microscopic identification of eggs in stool specimens.
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