Abstract:

To understand the current status of Clonorchis sinensis infection in the population of Heilongjiang Province, the survey sites were selected from 104 rural areas and 15 urban areas in the Province in April—June 2015, using stratified cluster random sampling method, in accordance to the guideline of the National Survey, Program for Key Human Parasitic Diseases. The rural areas were divided into four ecoregions: Changbai Mountain-Qianshan Mountains, the Eastern Northeast Plain, Sanjiang Plain, and Xiaoxing’an Mountain coniferous and broad-leaved mixed forest. The number of people surveyed at each survey site was no less than 250. The modified Kato thick smear method was used to examine the participants’ fecal samples (two slide-reading/sample) for C. sinensis eggs and counted. Of the 30 280 examinees, 747 were found infected, with an infection rate of 2.47%. The infection rate in rural and urban areas was 2.77% (734/26 456) and 0.34% (13/3 824) respectively, with the difference being statistically significant (χ² = 82.295, P < 0.05). Most of the infected showed mild infection (82.33%, 615/747). The infection rate was 3.05% (462/15 171) in males and 1.89% (285/15 109) in females, showing significant difference between the sexes (χ² = 42.261, P < 0.05). The highest infection rate was seen in the age group of 30-39 years (3.32%, 147/4 430), revealing significant difference between the age groups (χ² = 122.182, P < 0.05). The highest infection rate was found in farmers (animal husbandry and fishery) (3.16%, 692/21 914), with the difference between occupation groups being statistically significant (χ² = 164.846, P < 0.05). The infection rate differed significantly among the participants with different levels of education (χ² = 124.596, P < 0.05) and was highest in the group with junior high school education (3.46%, 499/14 425). The rate was significantly different between different ethnic groups (χ² = 8.395, P < 0.05), with the Han group having the highest infection rate (2.51%, 739/29 487). In rural areas, most of the infected people showed mild infection intensity (82.56%, 606/734). The infection rate was 3.39% (454/13 378) in males and 2.14 (280/13 078) in females, thus differing significantly between the sexes (χ² = 38.468, P < 0.05). The infection rate differed significantly with age (χ² = 111.315, P < 0.05) and was highest in the 30-39 year age group (3.78%, 145/3 841). Significant difference in infection rate was found also in occupation distribution (χ² = 103.863, P < 0.05), with the highest seen in the group of servants and enterprise-institution employees (5.05%, 10/198). The infection rate differed significantly in education distribution (χ² = 127.308, P < 0.05), and was highest in the group at the education level of junior high school (3.88%, 496/12 792). It also differed significantly between different ethnic groups (χ² = 8.903, P < 0.05), and was highest in the Han group (2.82%, 726/25 734). The Sanjiang Plain ecoregion showed the highest infection rate (8.75%, 575/6 574), and the rate differed significantly between ecoregions (χ² = 1 177.510, P < 0.05). In urban areas, the majority of the infected had mild infection (9/13). The infection rate in males was 0.45% (8/1 793) and that in females was 0.25% (5/2 031). The highest infection rate was detected in the age group 50-59 years (0.79%, 5/636), and among different occupations, the group of servants and enterprise-institution employees had the highest infection rate (0.97%, 4/411). In the education distribution, the illiterate group showed the highest infection rate (1.14%, 2/176). C. sinensis infection was only detected in Han ethnicity, with an infection rate of 0.35% (13/3 753). The C. sinensis infection found in Heilongjiang Province was largely mild, and the highest infection rate was seen in the Sanjiang Plain ecoregion, thus, it is imperative to actively explore feasible control strategies and measures appropriate to the actual situations in different regions in Heilongjiang Province.

Key words: Clonorchis sinensis, Infection, Survey, Heilongjiang Province