Abstract:

Objective To understand current prevalence of paragonimiasis in Hubei Province, to provide basis for formulating control strategy. Methods Surveillance sites were established in 13 counties (city, district) in Hubei Province from 2018 to 2020. One administrative village or several natural villages along water ways were selected from each surveillance site in August to October every year. All permanent residents over 6 years of age were investigated through cluster sampling, with the resident number no less than 300. Blood samples were collected from the residents at surveillance sites, and examined for antibodies against Paragonimus by ELISA. Sputum was collected from antibody-positives, and examined for Paragonimus eggs by concentrated digestion method, and the examinees were further investigated individually. For the residents who provided blood samples, questionnaire survey was conducted on general information including name, age, education level, and related behaviors as well. Stream crabs, the second intermediate host of Paragonimus, were collected in mountain pits and streams in the surveillance sites, and Paragonimus metacercaria were detected using mashing-precipitation method. Results A total of 3 947 people were investigated in 3 years, and the overall positive rate of serum antibody was 9.5% (376/3 947), while no worm egg was found in the sputum of seropositive participants. The highest seropositive rate, 72.5% (158/218), was found in Xingshan County. The seropositive rates in residents between different regions were significantly different (χ ² = 1 169.86, P < 0.01). The seropositive rate was 9.2% in males and 9.9% in females, with no statistically significant difference(χ ² = 0.516, P > 0.05). The seropositive rate were found higher among residents of age group 6-9 years old and ≥ 60 years old, being 11.1% (9/81) and 12.9% (251/1 951), respectively. The differences in seropositive rates between age groups were statistically significant (χ ² = 56.148, P < 0.01). The serum positive rates were higher in people with educational levels of college and above and primary school, being 2/14 and 12.4% (277/228), respectively. A significant difference was observed among educational levels (χ ² = 70.606, P < 0.01). The questionnaire results indicated that the serum antibody positive rate in residents drinking tap water was the highest, at 11.3% (285/2 529). Significant difference was observed among the residents groups drinking different types of water (χ ² = 28.834, P < 0.01). The seropositives found in 313 people who consume fresh crab was 11.5% (36/313); the seropositive rate in 3 643 people who had not eaten fresh crabs was 9.4% (340/3 634); with no significant difference between two groups (χ ² = 1.539, P > 0.05). The positive rate of serum antibody was 5.9% (77/1 315) in people who drank unboiled water and 11.4% (299/2 632) in those who did not drink unboiled water; the difference was statistically significant (χ ² = 30.829, P < 0.01). A total of 558 stream crabs were collected, and the positive rate of Paragonimus metacercariae was 10.4% (58/558). The intensity of infection was 7.6 metacercariae per crab. Among the 13 surveillance sites, the highest infection rate of Paragonimus metacercariae in stream crabs was found in Xingshan County, which reached 81.6% (31/38). No positive stream crabs were found in seven surveillance sites: Lichuan City, Danjiangkou City, Jianshi County, Yiling District, Tongshan County, Xuan’en County and Yingshan County. Significant difference in the infection rates of stream crabs were found between different regions (χ ² = 195.514, P < 0.01). Conclusion The positive rate of serum antibodies against Paragonimus in Hubei Province remain considerably high, especially in Xingshan County, in people ≥ 60 years of age and people with primary school education; the infection rate of metacercaria in stream crabs is comparatively high, indicative of the transmission risk remaining.

Key words: Paragonimiasis, Endemic, Surveillance, Hubei Province