Spatial and temporal distribution changes of human brucellosis in Inner Mongolia, China, effects of husbandry and control measures


 BackgroundInner Mongolia has the highest incidence rate, causing great public health and economic losses. A number of policies to guide the prevention and control of human brucellosis had been issued and have made some achievements. Analysis of the distribution characteristics and changes of human brucellosis is important for the targeted prevention and control of this disease.MethodsWe collected various policies and measures related to brucellosis promulgated, and comprehensively analyzed the spatial and temporal distribution of human brucellosis in Inner Mongolia from 2005 to 2019 using the Bayesian theory of space-time modeling. ResultsWith the implementation of various policies and measures, great achievements have been made and distribution trends changed. Some western regions have changed into stable or cold-spot counties, and most cities in the eastern region have become hot-spot counties during the time period. The rising trend of risk in three cities is slowing down, while the risk in two cities is growing faster than the overall trend.ConclusionThe effective prevention and control measures are essential. The analysis results of this study may provide a theoretical and scientific basis for the public health department to develop targeted effective prevention and control measures for human brucellosis.


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With the implementation of various policies and measures, great achievements have 26 been made and distribution trends changed. Some western regions have changed into 27 stable or cold-spot counties, and most cities in the eastern region have become hot-spot 28 counties during the time period. The rising trend of risk in three cities is slowing down, 29 while the risk in two cities is growing faster than the overall trend. 30

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The effective prevention and control measures are essential. The analysis results of this 32 study may provide a theoretical and scientific basis for the public health department to 33 8 it is assumed that the number of people in each township did not change during the 111 study period; 112 The second part is the process model. The logarithmic transformation of μit to the 113 disease risk allows the relative risk to be expressed as a linear combination of the 114 spatial, temporal, and spatiotemporal interaction components. The mathematical 115 expression is log( ) = + + ( 0 * + ) + * + , where α is the fixed 116 effect of the overall relative risk, describes the risk difference between the disease 117 risk in the area during the observation period and the risk in the entire study area, and 118 The third part is the parametric model. According to the Besag-York and Molliè 124 (BYM) model, the spatial structure effect is defined by the prior conditional 125 autoregressive (CAR) structure(18). In this process, a spatial adjacency matrix and a 126 temporal adjacency matrix are defined. The over-discrete parameter ε obeys the 127 normal distribution, with an average value is 0, and the variance is 2 . It is generally 128 assumed that the variance of each parameter obeys Gamma (a, b) (19). By calculating 129 the spatial relative risk probability, the probability that exp ( ) is greater than 1 is 9 divided into three categories: areas with probability> 0.6, 0.4 ~ 0.6, and <0.4 are 131 defined as hot-spot counties, stable counties, and cold-spot counties, respectively. 132 Similarly, by calculating the relative change in time, the probability of exp ( ) 133 greater than 1 is divided into 3 categories: the counties with the incidence probability 134 greater than 0.6 are considered to have a faster risk trend than the overall trend; 135 between 0.4 and 0.6 were considered to have the same risk trend as the overall trend; 136 and less than 0.4 are considered to have a slower risk trend than the overall trend . 137

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The collected case data were collated by excluding duplicate data and cases with 139 incomplete information. During the time period of 2005-2019, the number of human 140 brucellosis cases in Inner Mongolia is the largest, accounting for 29% of total number 141 in China, is more than twice that of the second (Fig. 1)  The number of cases decreased as the number of sheep increased, indicating a 170 negative correlation of human cases with sheep number (Fig. 2E). 171 The Bayesian model was processed using the WinBUGS software. The model 172 processed two chains. After a total of 20,000 iterations, the model tended to converge. 173 After the model converged, it iterated 10,000 times for parameter estimation. Hulunbeier, and Chifeng, had a higher incidence (Fig. 5A). In addition, the incidence 201 was higher in the two districts of Bayannaoer. The spatial analysis found that 40 202 districts in Hulunbuir City, Xing'an League, Tongliao City, Chifeng City and 203 Xilinguole League in northeastern Inner Mongolia were hot-spot counties, and other 204 areas were stable or cold spot counties (Fig. 5B). A total of 11 districts in Bayannaoer 205 City, Ordos City and Chifeng City had a higher risk trend than the overall trend, and 206 the risk trends in other regions were consistent with the overall trend or slower than 207 the overall trend. Among the districts and counties where the risk trend of the disease 208 13 was higher than the overall trend, only Hongshan District was a hot-spot county, nine 209 districts were cold-spot counties, and one district was a stable county (Fig. 5C). 210

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Brucellosis was firstly reported in China in 1950's. With nationwide efforts, the 212 incidence was reduced to a very low level. However, since the mid-1990s, human 213 brucellosis has re-emerged in China. The incidence of human brucellosis in Inner 214 Mongolia is the highest one and much higher than that in other provinces(20). This is 215 consistent with the fact that Inner Mongolia has the highest livestock production in 216 China. Brucellosis is mainly transmitted to humans indirectly or directly through 217 diseased animals, and has strong profession relevance. Therefore, Inner Mongolia is 218 the main epidemic area of human brucellosis in China, which is closely related to its 219 developed animal husbandry. This study conducted demographic, seasonal, and 220 spatial-temporal analysis of human brucellosis cases from 2005 to 2019, providing a 221 scientific basis for the prevention and treatment of brucellosis. 222 By analyzing the characteristics of human brucellosis cases, it is found farmer is 223 the main occupation for human brucellosis cases, while herder ranks the second, 224 which is consistent with other reports(21). Farmers use the same living space with 225 livestock, make it easy to contact sick animals. Lower awareness of the transmission 226 of Brucella by livestock, also make the farmers more likely to be infected with 227 14 Brucella(22). The incidence of herdsmen and livestock-related workers is high, 228 because they are often exposed to livestock. However, the diseased animals are not 229 quarantined, so the incidence is relatively high. This study found that human 230 brucellosis is more common in men and can occur at any age, with most cases 231 occurring between 35 and 54 years of age. In addition, human brucellosis has obvious 232 seasonality, and it occurs frequently in spring and summer. This is related to many 233 factors; one of which is that young and old men are the main labor force in China. 234 Inner Mongolia is dominated by agriculture and animal husbandry, which are related 235 to seasonal factors, such as breeding operation, precipitation, animal movement, 236 sunshine level and wind speed(23). In spring, the temperature increases, which is 237 suitable for bacterial reproduction, and animals start to move, which increases the risk and control measures, so the incidence growth is slower than the whole. However, the 358 incidence in Ningcheng County and Hongshan District has been relatively low, and 359 the awareness of human brucellosis and related measures in this area are insufficient, 360 so the risk trend increased faster than the whole. Therefore, the relevant departments 361 should pay attention to the prevention and control work in all regions, regardless of 362 the incidence rate of the area, and take timely preventive measures through the 363 analysis and prediction of the existing data. 364 In conclusion, Inner Mongolia has developed agriculture and animal husbandry, 365 and the incidence of human brucellosis is the highest in China 385 The data that support the findings of this study are available from the National 386 Notifiable Disease Surveillance System, but restrictions apply to the availability of 387 these data, which were used under license for the current study, and so are not 388 publicly available. Data are however available from the authors upon reasonable 389 request and with permission of the Plague and Brucellosis Prevention and Control 390

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