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In the present study, surveys of case numbers, constituent ratios, conventional biotyping, and multilocus sequence typing (MLST) were applied to characterize the incidence rate and epidemiological characteristics of human brucellosis in Shaanxi Province, China. A total of 12,215 human brucellosis cases were reported during 2008–2020, for an annual average incidence rate of 2.48/100,000. The most significant change was that the county numbers of reported cases increased from 36 in 2008 to 84 in 2020, with a geographic expansion trend from northern Shaanxi to Guanzhong, and southern Shaanxi regions; the incidence rate declined in previous epidemic northern Shaanxi regions while increasing each year in Guanzhong and southern Shaanxi regions such as Hancheng and Xianyang. The increased incidence was closely related to the development of large-scale small ruminants (goats and sheep) farms in Guanzhong and some southern Shaanxi regions. Another significant feature was that student cases (n = 261) were ranked second among all occupations, accounting for 2.14% of the total number of cases, with the majority due to drinking unsterilized goat milk. Three Brucella species were detected (B. melitensis (bv. 1, 2, 3 and variant), B. abortus bv. 3/6, and B. suis bv. 1) and were mainly distributed in the northern Shaanxi and Guanzhong regions. Three known STs (ST8, ST2, and ST14) were identified based on MLST analysis. The characteristics that had not changed were that B. melitensis strains belonging to the ST8 population were the dominant species and were observed in all nine regions during the examined periods. Strengthened human and animal brucellosis surveillance and restriction of the transfer of infected sheep (goats) as well as students avoiding drinking raw milk are suggested as optimal control strategies.

What is already known about this topic? Brucellosis is one of the world’s most overlooked zoonotic diseases, and humans can easily acquire brucellosis from animals and their products. Reemerging brucellosis outbreaks are probably attributable to sociocultural factors and compounded by the lack of adequate control measures in sheep and goat rearing systems. What is added by this report? This is the first identified outbreak caused by Brucella melitensis bv.3 in Jingyang County, Xianyang City, Shaanxi Province. A total of 13 seropositve cases (7 acute patients and 6 asymptomatic persons) were identified from March to May, 2020, and the investigation indicated that sheep-to-canine-to-human was the likely transmission route. What are the implications for public health practice? Effective control of sheep brucellosis will significantly reduce the risk of human brucellosis. Priority should be given to building cooperation between all stakeholders, maintaining epidemiological surveillance to detect human brucellosis at medical centers, and making case reporting mandatory for both veterinary and public health services.

In this study, a total of 179,907 blood samples from populations with suspected Brucella spp. infections were collected between 2008 and 2020 and analyzed by the Rose Bengal plate test (RBPT) and serum agglutination test (SAT). Moreover, conventional biotyping, B. abortus-melitensis-ovis-suis polymerase chain reaction (AMOS-PCR), and multiple-locus variable-number tandem repeat analysis (MLVA) was applied to characterize the isolated strains. A total of 8103 (4.50%) samples were positive in RBPT, while 7705 (4.28%, 95% confidence interval (CI) 4.19-4.37) samples were positive in SAT. There was a significant difference in seroprevalence for human brucellosis over time, in different areas and different cities (districts) (χ2 = 2 = 32.23, 1984.14, and 3749.51, p < .05). The highest seropositivity (8.22% (4, 965/60393; 95% CI 8.00-8.44) was observed in Yulin City, which borders Inner Mongolia, Ningxia, and Gansu Province, China, regions that have a high incidence of human brucellosis. Moreover, 174 Brucella strains were obtained, including nine with B. melitensis bv. 1, 145 with B. melitensis bv. 3, and 20 with B. melitensis variants. After random selection, 132 B. melitensis were further genotyped using MLVA-16. The 132 strains were sorted into 100 MLVA-16 genotypes (GTs) (GT 1-100), 81 of which were single GTs represented by singular independent strains. The remaining 19 shared GTs involved 51 strains, and each GT included two to seven isolates from the Shaan northern and Guanzhong areas. These data indicated that although sporadic cases were a dominant epidemic characteristic of human brucellosis in this province, more than 38.6% (51/132) outbreaks were also found in the Shaan northern area and Guanzhong areas. The 47 shared MLVA-16 GTs were observed in strains (n = 71) from this study and strains (n = 337) from 19 other provinces of China. These data suggest that strains from the northern provinces are a potential source of human brucellosis cases in Shaanxi Province. It is urgent to strengthen the surveillance and control of the trade and transfer of infected sheep among regions.

What is already known about this topic? Brucellosis is one of the world’s most overlooked zoonotic diseases, and humans can easily acquire brucellosis from animals and their products. Reemerging brucellosis outbreaks are probably attributable to sociocultural factors and compounded by the lack of adequate control measures in sheep and goat rearing systems. What is added by this report? This is the first identified outbreak caused by Brucella melitensisbv.3 in Jingyang County, Xianyang City, Shaanxi Province. A total of 13 seropositve cases (7 acute patients and 6 asymptomatic persons) were identified from March to May, 2020, and the investigation indicated that sheep-to-canine-to-human was the likely transmission route. What are the implications for public health practice? Effective control of sheep brucellosis will significantly reduce the risk of human brucellosis. Priority should be given to building cooperation between all stakeholders, maintaining epidemiological surveillance to detect human brucellosis at medical centers, and making case reporting mandatory for both veterinary and public health services.

To apply the DNA barcoding technology for identification on host animal and to establish the host animal DNA bar code database on natural foci of plague in Shaanxi.139 host animals belonging to 3 orders, 6 families and 12 genera and 62 residues belonging to 7 species from 8 different parts of the province, were detected. DNA barcoding technology was used to analyze the DNA CO I gene sequence on the natural foci of plague in Dingbian county.The intra-specific genetic distance was less than 2% while the inter-specific distance ranged from 8.9% to 15.1%. Fourteen major clusters were apparently showed on a Neighbor-Joining tree. Residue samples could be detected regarding the objective gene. Alashan ground squirrel was previously noticed to carry 14 major clusters, which were previously mistakenly named as Citellus dauricus in Dingbian county.DNA barcoding technology could overcome the shortcomings caused by the morphological identification so could be used to identify the host animal and residues in the natural focus of plague.