Objective To understand the epidemiological characteristics of brucellosis in the population with occupational exposures to Brucella in Hangzhou, Zhejiang province, in the past 20 years and provide reference for prevention and control of brucellosis in population with occupational exposures.
Methods Brucellosis surveillance information and incidence data in the population with occupational exposures in Hangzhou from 1987 to 2023 were collected. The trend of Brucella positive rate in serological surveillance during this period and the distributions of brucellosis cases, the source of infection, the place of infection and the clinical symptoms and signs from 2004 (when the first brucellosis case was reported) to 2023 were analyzed.
Results The average positive rate of Brucella in serological surveillance was 1.56% (229/14663) in Hangzhou from 1987 to 2023.The positive rate during 2014−2023 (the second 10 years) (3.02%, 118/3907) was significantly higher than that during 2004−2013 (the first 10 years) (1.78%, 97/5452) (χ2=15.618, P<0.001) .The positive rate reached the highest in 2015 (6.32%) , and then showed a slow downward trend (trend χ2 =6.905, P=0.009) . There were 142 cases and 87 new infections from 2004 to 2023. The cases were mainly men aged 40−69 years with occupational exposures (63.38%, 90/142) . They were mainly engaged in sheep slaughtering or trading (45.07%, 64/142), milk and meat processing and trading (26.06%, 37/142) and sheep raising (18.31%, 26/142). In the diagnosed cases from 2004 to 2023, the proportion of those due to sheep raising, milk and meat processing and trading increased obviously, the proportion of those due to sheep slaughtering or trading, cattle raising decreased obviously (χ2=24.947, P<0.001) .New occupations such as dog butchering, sheep oil buying, and harmless animal disposal emerged. Winter and spring were the peak periods of the incidence of brucellosis (69.01%, 98/142) . The area affected by the epidemic expanded year by year, from sheep slaughterhouses and dairy farms to sheep farms.
Conclusion The positive rate of Brucella in serological surveillance in population with occupational exposures showed a slowly decreasing trend in Hangzhou in recent years, indicating the achievement in the prevention and control of human brucellosis. However, with the increase of livestock production and the transformation of industrial chain, the composition of occupations with high risk for Brucella exposures has changed. Therefore, it is necessary to expand the surveillance in population with occupational exposure according to the characteristics of local brucellosis situation in key areas, and strengthen the active surveillance in the season with high incidence of brucellosis.