[Epidemiological characteristics of human brucellosis in Tongliao city of Inner Mongolia Autonomous Region, 2004-2018].

Objective: To analyze the epidemiological characteristics of human brucellosis (HB), evolution and origin feature of Brucella strains in Tongliao city, Inner Mongolia Autonomous Region during 2004-2018, and to provide evidence for strategy development against the disease. Methods: Data from the reports on HB in Tongliao during 2004-2018 were extracted from the China Information System for Disease Control and Prevention before being analyzed with software Excel 2016. Epidemiologic feature was described, using the number of cases, constituent ratio and related rates. Conventional biotypes methods were used for identification of species/biovars strains while species of six Brucella strains were further verified by AMOS-PCR. Cluster analyze on six Brucella strains were performed with Bio-Numerics 5.0 software and for examining and revealing the genetic characteristics of the related strains. Results: During 2004-2018, a total of 16 704 HB cases were reported, with the incidence rate as 35.41/100 000. The incidence rates appeared as 110.51/100 000 in Jarud Banner and 67.84/100 000 in Kulun flag, which were both higher than the other areas. Most of the cases were reported in the 40-54 year olds, which accounted for 48.75% (8 143/16 704). The number of HB in farmers appeared as 14 873, which counted for 89.04% (14 873/16 704) of all the cases. Male to female ratio of incidence was 2.40∶1. Most of the reported cases appeared between March to May, which accounted for 56.30% (9 405/16 704). Peak of the disease was seen in April. Using the conventional identification method, results showed that the available six strains all belonged to B. melitensis, including three of them as B. melitensis bv.1 and others three strains as B. melitensis bv. 3. Results from the amplified AMOS-PCR showed that all the strains were B. melitensis. The six strains clustered in two MLVA-11 genotypes (111 and 116) and all belonged to the Eastern Mediterranean lineage. Based on the MLVA-16 cluster analysis, results suggested that strains from this study were having close genetic relationship with B. melitensis strains that were from Jilin and Heilongjiang provinces. Conclusions: Human brucellosis identified in Tongliao area was with greater risk in spreading the disease to the vicinity. Our findings indicated that the programs on detection and control of the disease should be strengthened.