Retrospective Analysis of the Epidemiological Evolution of Brucellosis in Animals - China, 1951-1989 and 1996-2021.

Brucellosis poses a significant threat to public health in China. This study utilized a range of epidemiological indices, including seroprevalence and the number of reported cases, to illustrate the epidemic profile of the disease. Although the seroprevalence of brucellosis in animals (including sheep, goats, cattle, and swine) steadily decreased from a severe epidemic level in the 1950s to a low endemic level by 1989, the disease reemerged in 2000. Subsequently, there has been a persistent increase in the frequency of outbreaks and the number of reported cases from 2006 to 2021, with over 98% of reported cases occurring in sheep and cattle. During this period, the culling rate declined, while infection rates increased, nearly reversing their respective trajectories. The decrease in the culling rate of positive animals coincided with an increase in infection rates, indicating that infection among these animals was persistent and circulating. In the southern regions of China, 6.34% (34,070 of 537,797) of cases were reported between 2006 and 2021, whereas in the northern regions, 93.67% (503,727 of 537,797) of cases occurred during the same timeframe. Each time cases increased in the south, they lagged 2 to 5 years behind those in the north, suggesting that stringent control measures for sheep and cattle in the north should be prioritized. These findings provide critical insights into developing control strategies to mitigate the spread of the disease.