title: Trends in prevalence of clonorchiasis among patients in Heilongjiang province, Northeast China (2009-2012): implications for monitoring and control.
abstract: BACKGROUND
  Clonorchiasis is an important zoonotic parasitic disease worldwide. Past estimates showed the prevalence increased based on studies undertaken ten years or more ago. However, control strategies, changing ecology and migration may have resulted to changes in the prevalence of clonorchiasis. The purpose of the present study was to analysis the prevalence and epidemiological characterisation of clonorchiasis in Heilongjiang Province, Northeast China.
  
  
  RESULTS
  A total of 4951 clinically suspected outpatients were examined from January 2009 to December 2012. Overall prevalence of clonorchiasis was 25.93% (1284/4951) by the combination strategy of the Kato-Katz technique (KK) and enzyme-linked immunosorbent assay (ELISA), with a significant increase from 22.53% in 2009 to 34.25% in 2012. Apart from Daxinganling city, clonorchiasis was reported throughout Heilongjiang Province and mainly along the Songhua River and Nen River basin, with an increased annual prevalence. The annual prevalence in men increased significantly in 2012 and was higher than that in women over 4 years. A similar pattern was seen for the annual infection rate in rural and urban areas. Farm labourers accounted for the majority of cases (65.93%), with a higher prevalence than in other occupations. Consumption of freshwater fish was considered the strongest risk factor of clonorchiasis. The infection rates in the 40-49 and 50-59 years age groups showed a significant increasing trend in 2012. Cases of re-infection were common.
  
  
  CONCLUSIONS
  The present study revealed that clonorchiasis remained widespread and prevalent in Heilongjiang Province. An integrated control programme is urgently needed to reduce the public health impact of clonorchiasis in this endemic area.
authors.affiliation: Department of Microbiology and Parasitology, The Heilongjiang Key Laboratory of Immunity and Infection, Pathogenic Biology, Harbin Medical University, Harbin, People's Republic of China.
authors.forename: Su
authors.initials: S
authors.lastname: Han
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Zhang
authors.forename: Rui
authors.initials: R
authors.lastname: Chen
authors.forename: Jingshan
authors.initials: J
authors.lastname: Wen
authors.forename: Yihong
authors.initials: Y
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Shu
authors.forename: Hong
authors.initials: H
authors.lastname: Ling
authors.forename: Fengmin
authors.initials: F
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002681:China / Q000453:epidemiology; D003003:Clonorchiasis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D012424:Rural Population; D055815:Young Adult