Epidemiological characteristics and spatio-temporal clusters of human brucellosis in Inner Mongolia, 2010-2021

doi:10.21203/rs.3.rs-5083017/v1

Background

Brucellosis poses a significant public health challenge in China. Inner Mongolia, characterized by its developed livestock industry, is the most severe endemic area for human brucellosis. This study aims to describe the epidemiology, explore the spatial-temporal distribution patterns, and clustering characteristics of human brucellosis in Inner Mongolia.

Methods

Data on human brucellosis cases from 2010 to 2021 were obtained from the Centers for Disease Control and Prevention in Inner Mongolia. Spatial autocorrelation analysis was used to identify high-risk areas, while spatial-temporal scan statistics were employed to detect changes in clusters over time.

Results

A total of 153,792 brucellosis cases were reported in Inner Mongolia from 2010 to 2021, with an average annual incidence rate of 52.59 per 100,000. The incidence showed a decreasing trend from 2010 to 2016, followed by a significant increase from 2016 to 2021. The disease exhibited distinct seasonality, peaking in spring and summer (March to August). Middle-aged individuals, males, and farmers/herdsmen had higher incidence rates. Spatially, incidence rates decreased from north to south and from the central and eastern regions to the west. Clear spatial clusters were observed during 2010–2013 and 2016–2021 in the global Moran’s I test. Local spatial autocorrelation analysis revealed that high-high clusters expanded from the central and eastern regions towards the west over time. Spatio-temporal scan analysis further indicated that high-risk clusters were primarily concentrated in the central and eastern regions, with a continuous expansion towards the west and south, leading to an increasingly broad geographical spread.

Conclusion

Human brucellosis cases in Inner Mongolia exhibit spatio-temporal clustering, with spatial concentration in the central and eastern regions, but also observed expansion towards the western and southern regions. The most of cases occur between March and August each year. For high-risk areas and populations, more timely and effective prevention and control measures should be implemented to mitigate the spread of brucellosis and protect public health.

Brucellosis

Inner Mongolia

Epidemiological characteristics

High-risk areas

Spatial autocorrelation

Spatiotemporal analysis

Brucellosis is a neglected zoonotic disease caused by Brucella species [1–3]. The primary sources of transmission are cattle, sheep, dogs, pigs and other animals infected with Brucella [4, 5]. Human infections are typically through direct or indirect contact with infected animals and their secretions or consumption of contaminated animal products [6]. Brucellosis is highly pathogenic and contagious, but human-to-human transmission is extremely rare [7, 8]. High-risk occupations include shepherds, breeders, slaughterhouse workers, and veterinarians, who are more susceptible to infection [1, 9]. Human brucellosis can affect multiple systems and organs, leading to complex clinical presentations. Patients in the acute phase often experience symptoms such as fever, sweating, fatigue, vomiting, headache, loss of appetite, muscle and joint pain [10, 11]. Due to the atypical clinical manifestations, brucellosis is often underdiagnosed[12, 13]. While human brucellosis is seldom fatal, insufficient and delayed treatment may progress acute to chronic, resulting in the disease more difficult to cure [6, 9]. Meanwhile, the infected livestock may exhibit symptoms which include abortion, retained afterbirth, infertility, decreased milk and meat production, further impacting the development of animal husbandry [14, 15]. Brucellosis not only poses a threat to human health and life but also causes substantial economic losses, making it a significant global public health concern [11, 13, 16].

Brucellosis is one of the most prevalent worldwide. There are more than 170 countries that have reported cases of brucellosis, with over 500000 new cases annually around the world [17, 18], especially in the Mediterranean region, Asia, the Middle East, Sub-Saharan Africa and Latin America [19, 20]. In China, the incidence rate of human brucellosis rose from 0.23 per 100000 to 3.37 per 100000, nearly a 15-fold increase from 2001 to 2020 [21]. The endemic range of human brucellosis has expanded beyond its previous boundaries, with northern epidemic areas spreading into new regions, including southern provinces that were previously unaffected. As of now, human brucellosis has been reported in all 31 provinces in China [6, 22, 23], with more than 90% of cases concentrated in the north, particularly in Inner Mongolia, which reports the highest number of cases [2, 24]. Inner Mongolia, characterized by its developed livestock industry, is the most severe endemic area for human brucellosis, with the incidence rate ranking among the top in China[6, 13, 22]. This highlights the critical state of the brucellosis epidemic in the region [17, 25]. Furthermore, the ongoing presence of brucellosis sources, inadequate quarantine practices, a shortage of personnel for prevention and control, and low protective awareness, contribute to the challenges in managing brucellosis[26–28]. In this study, we aim to analyze the epidemiological characteristics, explore the spatial-temporal distribution patterns, and detect high-risk areas of human brucellosis at the county level in Inner Mongolia from 2010 to 2021, provide a scientific adjusting prevention and control strategies.

Methods

Study area

Inner Mongolia, situated in northern China, borders with Russia to the northeast and Mongolia to the north. The region spans a narrow, elongated shape from the northeast to the southwest, covering approximately 1.183 million square kilometers. Known for its vast grasslands, Inner Mongolia has a total grassland area of about 780,000 square kilometers, which constitutes 67% of the total area[29]. These extensive grasslands provide ideal conditions for the development of animal husbandry, which produces meat, dairy products, wool, and leather.

Inner Mongolia experiences a variety of regional climates. Arid and semi-arid conditions dominate the northern and western parts, while the northeast has a humid continental climate[29]. Livestock distribution varies by area, with sheep and cattle predominantly raised in the cooler, relatively moist central and eastern areas, whereas camels are more common in the warm, arid desert areas[30]. According to Ning et al.[31], sheep are the primary source of infection in Inner Mongolia, with significant regional differences in sheep populations (Additional file: Figure S1).

As of the end of 2022, Inner Mongolia had a permanent population of 24.01 million[32]. Economic disparities lead to significant variations in population distribution, with higher concentrations in economically developed areas and urban clusters[33]. Administratively, Inner Mongolia consists of 12 municipal-level administrative units, and 103 counties (Additional file: Figure S2). In this study, spatial distribution, spatial autocorrelation analysis, and spatio-temporal scan statistics were conducted at the county level, with the 103 counties serving as the geographic units of analysis.

Data Source

Data on human brucellosis cases from January 1, 2010, to December 31, 2021, including case numbers, age, gender, occupation, month of onset, and location were obtained from the Centers for Disease Control and Prevention in Inner Mongolia. A total of 153,792 patients were included in this study. Demographic data were extracted from the Inner Mongolia Statistical Yearbook, and geographical information was acquired from the National Basic Geographic Information Center. Human brucellosis incidence rate = number of cases of brucellosis in a given year/population at the end of the same year ×100,000[6, 12, 34].

In China, all suspected or confirmed cases of human brucellosis must be reported by clinical practitioners to local Centers for Disease Control and Prevention (CDC). The diagnostic criteria of human brucellosis are based on standard protocols (Diagnostic Criteria for Brucellosis in China, WS 269–2007/ WS 269–2019). Suspected cases are confirmed through a combination of epidemiologic history, clinical signs, and positive results from screening laboratory tests, including the rose bengal plate test (RBPT), gold immunochromatography assay (GICA) and enzyme linked immunosorbent assay (ELISA), as well as confirmatory tests such as the serum agglutination test (SAT), complement fixation test (CFT) and Coomb’s test [20].

Data Source

Data on human brucellosis cases from January 1, 2010, to December 31, 2021, including case numbers, age, gender, occupation, month of onset, and location were obtained from the Centers for Disease Control and Prevention in Inner Mongolia. A total of 153,792 patients were included in this study. Demographic data were extracted from the Inner Mongolia Statistical Yearbook, and geographical information was acquired from the National Basic Geographic Information Center.

In China, all suspected or confirmed cases of human brucellosis must be reported by clinical practitioners to local Centers for Disease Control and Prevention (CDC). The diagnostic criteria of human brucellosis are based on standard protocols (Diagnostic Criteria for Brucellosis in China, WS 269-2007/ WS 269-2019). Suspected cases are confirmed through a combination of epidemiologic history, clinical signs, and positive results from screening laboratory tests, including the rose bengal plate test (RBPT), gold immunochromatography assay (GICA) and enzyme linked immunosorbent assay (ELISA), as well as confirmatory tests such as the serum agglutination test (SAT), complement fixation test (CFT) and Coomb’s test [19].

Ethical Statement

No research involving human subjects was conducted in this study. Data collection was granted by the Inner Mongolia Center for Disease Control and Prevention. All data were anonymized to protect patient privacy.

Data Analysis and Statistics

1.1.1 Spatial Autocorrelation Analysis

Spatial autocorrelation analysis is used to examine the spatial distribution of a variable and to determine whether there is a pattern of similarity or dissimilarity among neighboring locations, which can help identify infectious disease clusters. Moran’s I is a commonly used measure for assessing spatial autocorrelation [25]. The global spatial autocorrelation (global Moran’s I) was employed to measure overall spatial autocorrelation among the 103 counties in Inner Mongolia. Moran’s I ranges from -1 to 1. A value of I>0 signifies a positive spatial correlation, indicating that areas with similar spatial attributes tend to cluster together. Conversely, I<0 signifies negative spatial correlation, indicating that areas with dissimilar spatial attributes cluster together. If I approaches 0, it implies a random distribution of spatial attributes. The larger the absolute value of I, the stronger the correlation. When |Z|>1.96, it is considered statistically significant (P<0.05), indicating the presence of spatial autocorrelation [22, 23]. The local spatial autocorrelation (local Moran's I) was employed to evaluate the correlation between individual target regions and their neighboring areas, thereby identifying local clusters of human brucellosis [26]. Local indicators of spatial association (LISA) cluster maps were used to depict four types of local correlations: high-low outlier, low-high outlier, high-high cluster and low-low cluster. High-high area refers to the cluster with high incidence of brucellosis, while low-low area refers to the cluster with low incidence of brucellosis. High-low and low-high areas indicate a significant difference in incidence between the target area and its neighboring areas [2, 13].

1.1.2 Spatio-Temporal Scan Analysis

Spatio-temporal scan analysis, also known as space-time scan statistics (STSS), is a method used in epidemiology and other fields to detect clusters or unusual patterns in space and time [27]. In this study, it can help to identify whether the temporal and spatial clustering of human brucellosis is attributable to random variation or not [28]. This method utilizes a dynamically cylindrical scanning window, with its circular base corresponding to the geographical area and its height corresponding to the time dimension, systematically moving across the study area and time period. Under the assumption that the incidence rate of brucellosis follows a Poisson distribution, the null hypothesis of the model is that incidence rates inside and outside the scanning window are equal [21, 22]. Based on the observed and expected numbers of cases, the log-likelihood ratio (LLR) and relative risk (RR) were calculated to test the hypothesis for each scanning window. The P-value was determined by Monte Carlo simulation. The window with the maximum LLR value was defined as the most likely cluster, while other windows with statistically significant LLR values (P < 0.001 in this study) were considered secondary clusters. The larger LLR value, the higher likelihood being a clustered region [9, 23]. Given the 12-year timeframe of our study, we conducted 12 annual scanning analyses to mitigate the impact of temporal trends. The temporal unit was measured in months, the spatial unit was set at the county level. The spatial scanning size was set at 30% of the total population, with the length of time equivalent to half of the timeframe (default value). Monte Carlo simulations were run 999 times.

1.1.3 Statistical Methods

Microsoft Excel 2010 was used to illustrate the epidemiological characteristics, the temporal distribution and seasonal pattern of human brucellosis in Inner Mongolia from January 2010 to December 2021. The spatial distribution and spatial autocorrelation analysis were conducted using ArcMap 10.8(ESRI, Redlands, CA, USA). Spatial-temporal scan statistic was performed using SaTScan software (v10.1.3, Boston, MA, USA).

Demographic Characteristics

From 2010 to 2021, a total of 153792 cases of brucellosis were reported in Inner Mongolia, with no fatalities. The average annual incidence rate was 52.59 per 100,000 persons. The incidence rate among males was significantly higher than among females throughout the study period, with a male-to-female ratio of 2.31:1(Table 1). Cases were reported across all age groups, with the majority occurring in the 40 to 59 age range, accounting for 54.06% of all reported cases (Figure 1). The average annual incidence rate for the 40-59 age group was 84.09 per 100,000 persons, the highest among all age groups. Farmers (116095 cases) and herders (20565 cases) were the most common high-risk occupations, representing 75.49% and 13.37% of all cases, respectively. Following were individuals engaged in housework or unemployment (6011 cases) accounting for 3.91% of cases (Figure 2).

Table 1 Human brucellosis incidence on gender and age group in Inner Mongolia,2010-2021

Characteristic	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020	2021	Average
Gender
Male	103.75	101.91	69.49	51.40	58.61	40.29	35.95	42.81	54.77	78.86	91.63	124.69	71.18
Female	49.37	43.14	30.16	23.17	26.10	18.57	17.34	20.10	27.89	37.02	43.92	56.41	32.77
Male to female ratio	2.27	2.55	2.48	2.39	2.41	2.32	2.22	2.27	2.09	2.26	2.18	2.31	2.31
Age group
0-9	8.05	8.09	5.28	3.16	4.28	2.74	2.61	1.98	3.09	4.83	7.46	7.23	4.90
10-19	14.92	12.31	8.14	5.50	6.55	4.05	2.98	4.07	5.11	7.28	10.59	11.66	7.76
20-29	62.77	55.83	36.49	26.78	29.14	18.68	15.90	18.57	24.50	33.74	38.86	46.40	33.97
30-39	94.89	92.05	61.78	44.61	46.85	29.89	23.10	31.70	44.42	62.93	72.38	90.38	57.92
40-49	117.03	113.01	78.92	60.39	66.49	46.90	41.92	52.66	69.03	97.19	108.06	139.51	82.59
50-59	125.62	120.64	81.56	62.53	71.26	50.55	46.60	51.30	65.63	91.65	107.44	152.18	85.58
60-69	92.33	90.76	64.99	46.70	62.82	44.70	46.40	48.47	57.05	75.67	84.48	119.78	69.51
>70	37.20	26.80	20.92	14.11	17.66	13.54	14.17	13.74	16.81	24.04	32.90	45.80	23.14

Temporal Distribution

As shown in Figure 3 the annual incidence rate of human brucellosis in Inner Mongolia declined overall from 2010 (19187 cases,77.61 per 100000 persons) to 2016, when it reached its lowest point with 6,567 cases (26.96 per 100000 persons). Since then, the rate has steadily increased, reaching a peak in 2021(21910 cases, 91.29 per 100000 persons) over the 12-year period. Human brucellosis exhibited a significant seasonal pattern in Inner Mongolia. Although cases occurred throughout the year, the peak incidence was concentrated from March to August, accounting for 64.43% of cases from 2010 to 2021(Figure 4).

Spatial Distribution

Over the 12-year period, human brucellosis cases were reported in all 12 municipal-level administrative units and 103 counties of Inner Mongolia. The highest average annual incidence rate, 369.57 per 100,000, was observed in Sunitezuo Banner from 2010 to 2021, with 1,513 cases reported, accounting for 0.98% of all cases. The other five counties with higher incidence rates were located in the central and eastern regions of Inner Mongolia: Darhan Muminggan Joint Banner (3553 cases), Xianghuang Banner (866 cases), Dongwuzhumuqin Banner (1844 cases), Horqin Right Front Banner (8051 cases), and Xin Barag Zuo Banner (1102 cases), with average annual incidence rates ranging from 199.99 to 276.37 per 100,000. The incidence rates of human brucellosis gradually decreased from northern to southern and from the central and eastern to the western regions. The affected regions have showed an expanding trend, spreading from the central and eastern to the western regions (Figure 5).

Spatial Autocorrelation Analysis

The global spatial autocorrelation analysis revealed that during the periods 2010-2013 and 2016-2021, the global Moran’s I values were positive, with Z values exceeding 1.96 (all p<0.05). This indicated a positive spatial autocorrelation in the incidence rates of brucellosis, suggesting a clear spatial clustering distribution. The highest degree of clustering was observed in 2010 (Moran’s I=0.453), while the lowest was in 2021 (Moran’s I=0.173). In 2014-2015, there was no spatial autocorrelation (|Z| <1.96, p>0.05), implying a statistically random distribution of brucellosis incidence (Table 2).

Table 2 Global spatial autocorrelation analysis of human brucellosis in Inner Mongolia, 2010-2021

Year	Moran’s I	Z-value	P-value	Year	Moran’s I	Z-value	P-value
2010	0.453	7.818	<0.001	2016	0.228	3.562	<0.001
2011	0.419	6.699	<0.001	2017	0.259	4.017	<0.001
2012	0.323	5.023	<0.001	2018	0.324	5.026	<0.001
2013	0.316	5.014	<0.001	2019	0.222	3.511	<0.001
2014	0.016	0.482	0.627	2020	0.187	3.012	0.003
2015	0.034	0.671	0.502	2021	0.173	2.785	0.005

The LISA cluster distribution map of brucellosis incidence rates showed that from 2010 to 2021, Inner Mongolia consistently exhibited "hotspots" (high-high clusters) of brucellosis, involving 6-12 counties, except for 2 counties in 2014 and 3 in 2015. The high-high clusters were concentrated in the central and eastern parts, mainly including Dongwuzhumuqin Banner, Abag Banner, Zhengxiangbai Banner, Sunitezuo Banner, and Zhenglan Banner of Xilin Gol League, Horqin Right Front Banner, Horqin Right Middle Banner, and Tuquan County of Hinggan League, and Horqin Left Middle Banner of Tongliao City. Among these, Dongwuzhumuqi Banner and Abag Banner were consistent “hotspots” over the years. Low-low clusters were concentrated in the western parts, mainly including Alxa Left Banner of Alxa League, Haibowan District, Hainan District, and Wuda District of Wuhai City. The distribution of high-high cluster areas also showed a trend of expanding from the central and eastern to the western regions (Figure 6).

Spatio-Temporal Scan Analysis

The spatial-temporal scan analysis revealed a spatial-temporal clustering distribution of human brucellosis in the studied region. The most likely clusters in Inner Mongolia displayed relatively stable spatio-temporal patterns, concentrated from February to August, mainly located in the central and eastern regions, with a trend of spreading eastward and northward. However, in 2015 and 2016, there was a retreat toward the west and a spread toward the south (Table 3 and Figure 7).

The secondary clusters of brucellosis cases in Inner Mongolia covered a relatively wide range, from east to west and from south to north, but were primarily concentrated in the central-eastern and central-western regions (Figure 7).

Table 3 The most likely clusters of spatio-temporal scan analysis for human brucellosis in Inner Mongolia, 2010-2021

Year	Cluster center/Radius(km)	Centroid (County)	Cluster counties	Cluster Time	RR	LLR	P-Value
2010	(43.86N,113.65E)/333.25	Sunitezuo Banner	21	2010/3 to 2010/8	4.55	3006.13	<0.001
2011	(43.86N,113.65E)/367.95	Sunitezuo Banner	25	2011/2 to 2011/7	3.83	2403.66	<0.001
2012	(48.67N,116.82E)/587.86	Xin Barag You Banner	29	2012/2 to 2012/7	3.56	1777.47	<0.001
2013	(48.67N, 116.82E)/587.86	Xin Barag You Banner	29	2013/2 to 2013/7	2.78	790.51	<0.001
2014	(45.51N, 116.97E)/391.10	Dongwuzhumuqin Banner	23	2014/2 to 2014/7	2.58	621.22	<0.001
2015	(40.39N, 111.88E)/0	Helinger County	1	2015/1 to 2015/6	10.71	441.26	<0.001
2016	(40.86N, 113.84E)/174.10	Xinghe County	13	2016/5 to 2016/6	5.04	484.22	<0.001
2017	(46.07N, 122.07E) / 251.70	Ulanhot City	11	2017/3 to 2017/8	3.88	881.64	<0.001
2018	(45.06N, 121.48E) / 119.07	Horqin Right Middle Banner	4	2018/3 to 2018/8	5.88	1166.07	<0.001
2019	(45.38N, 121.57E) / 337.56	Tuquan County	20	2019/3 to 2019/8	3.31	1907.53	<0.001
2020	(44.64N, 120.86E) / 213.05	Jarud Banner	15	2020/3 to 2020/8	3.78	2512.83	<0.001
2021	(45.38N, 121.57E) / 323.18	Tuquan County	19	2021/3 to 2021/8	2.80	2007.90	<0.001

Inner Mongolia remains the most severely affected region for human brucellosis in China, with a persistently high incidence rate [6, 16, 21]. According to the results of this study, the incidence of human brucellosis in Inner Mongolia decreased from 2010 to 2016, but significantly rebounded from 2017 to 2021, peaking at 91.29/100,000 persons in 2019. This resurgence could be linked to the joint human-animal brucellosis prevention and control project initiated in 2010 [29]. During this period, enhanced control measures, including systematic screening, quarantine, slaughter control, and immunization, were implemented. Increased health awareness among susceptible populations also contributed to the initial decline in incidence. However, rising beef and lamb prices since 2016, coupled with increased demand, led to more people engaging in breeding, transportation, trading, and slaughtering activities [6]. This increase, combined with high livestock mobility and inadequate quarantine measures, likely drove the rapid rise in incidence.

The demographic characteristics of human brucellosis in Inner Mongolia were similar to those of the whole country and other provinces [4, 6, 9, 11, 21, 22, 30-32], showing the higher incidence among middle-aged men, particularly those aged 40–59, who are primarily engaged in farming or herding. This is due to the fact that in rural or pastoral regions, most middle-aged men are engaging in activities that have more contact with livestock, such as livestock breeding, transportation, trading, slaughter, fur, milk and meat processing [30, 32].. They are frequently exposed to infectious sources and have weak personal protective awareness, making them a high-risk group for brucellosis.

Our temporal analysis revealed that brucellosis cases peaked between March and August, consistent with findings from other regions in China [4, 6, 22, 33, 34] and other Asian countries [3, 5, 10, 13, 17]. This seasonality aligns with the lambing season when livestock owners are in close contact with potentially infectious materials, such as placental tissues [9, 23, 33]. Additionally, as temperatures rise, livestock owners or workers begin shearing the wool, increasing the risk of exposure. Furthermore, the suitable temperatures and sufficient sunlight during this time may prolong the survival time of Brucella in the environment [16, 33, 35].

Given the spatial distribution map and spatial autocorrelation analysis, the incidence of brucellosis in Inner Mongolia exhibited clear clustering at the county level between from 2010 to 2013 and again from 2016 to 2021. However, in 2014 and 2015, the incidence was randomly distributed, likely due to a temporary relaxation in prevention and control measures during a transitional period, leading to insufficiently timely and comprehensive epidemic monitoring and case reporting.

Our research found that from 2010 to 2021, there have been consistent high-high clusters of brucellosis in Inner Mongolia, with the exception of 2014 and 2015, each containing between 6 to 12 counties. Moreover, there has been a trend of expansion from the central and eastern regions towards the western regions. During 2010-2016, these high-high clusters were concentrated in Xilin Gol League and Ulanqab City of the central regions, Hulunbuir City, Hinggan League, and Tongliao City of the eastern regions, with these high-high clusters mainly located in agricultural, pastoral, or semi-agricultural and semi-pastoral areas. However, after 2016, the counties within high-high clusters began to emerge in western regions, mostly in Hohhot City, Ordos City, and Bayannur City. Compared to the western regions, the central and eastern regions of Inner Mongolia have experienced faster development in animal husbandry, larger livestock populations, and denser populations, causing frequent contacts between susceptible individuals and livestock in daily production and life [23, 35]. Moreover, the long-term existence and frequent cross-regional flow of infection sources, inadequate quarantine measures, weak supervision, irregular livestock management, and low rates of self-protection behavior among farmers and herdsmen have contributed to the sustained high incidence of brucellosis in these central and eastern regions [29]. Particularly in Xilin Gol League, as a crucial agricultural and livestock product base in China with naturally abundant grasslands and a favorable climate conducive to the development of animal husbandry, the area has remained an old epidemic and serious outbreak area for brucellosis, with consistently high incidence rates among the 12 municipal level administrative units in Inner Mongolia [33]. In recent years, "hotspots" have gradually emerged in the western areas as well, possibly due to the fact that these counties were originally mainly engaged in agriculture and animal husbandry. With the acceleration of population mobility and frequent exchanges in trade and animal husbandry, there has been an increase in the inflow of infected animals, compounded by difficulties in surveillance and regulation, bringing about an upward trend in human brucellosis in the western areas.

Our spatio-temporal scan analysis further confirmed that the most likely clusters were concentrated in the central and eastern regions [6, 21, 23, 35], with a trend of expansion toward the west and south over the 12-year study period. The risk was highest from February to August each year, highlighting the need for targeted interventions during these months.

Overall, the situation of brucellosis in Inner Mongolia is extremely severe, necessitating strengthened prevention and control measures. In high-risk areas, it is essential to enhance joint prevention and control mechanisms involving multiple departments to ensure that all preventive and control measures are in place [36]. The animal husbandry department should strengthen quarantine and immunization for livestock, promptly slaughter diseased animals, and disinfect the environment of infected animals. The finance department should increase funding allocation, improve the facilities of grassroots prevention and control departments, enhance remuneration for personnel involved in epidemic prevention and control at the grassroots level, and provide subsidies to breeders with diseased animals. The market supervision department should strictly enforce laws against the sale of non-quarantined livestock products to eliminate food safety hazards. The Department of Health should continue to promote health education campaigns and behavioral interventions for high-risk populations [13, 37]. Furthermore, there should be an emphasis on strengthening medical personnel training to effectively improve the diagnostic capabilities for brucellosis, achieving early detection, diagnosis, and timely treatment to reduce the harm to public health.

While this study provides valuable insights into the epidemiology of brucellosis in Inner Mongolia, it has several limitations. Although the data quality of the Inner Mongolia Center for Disease Control and Prevention Information System may be highly reliable, the atypical nature of early symptoms and signs of human brucellosis may still lead to misdiagnosis and underreport, potentially resulting in an underestimation of the true incidence. Additionally, the space-time scan method used for detecting clusters may have overlooked irregular cluster shapes due to its reliance on circular scanning windows. Lastly, the lack of data on medical resources and socio-economic factors limits our understanding of the full scope of spatio-temporal clustering factors.

Brucellosis in Inner Mongolia poses a significant challenge, with cases exhibiting spatio-temporal clustering, particularly in the central and eastern regions, and an expanding trend toward the western and southern areas. The majority of cases occur during the spring and summer months. For high-risk areas and populations, more timely and effective prevention and control measures should be implemented to mitigate the spread of brucellosis and protect public health.

LLR

Likelihood Rate

RR

Relative Risk

LISA

Local indicators of spatial association

Consent for publication

Not applicable.

Data Availability Statement

The data supporting the findings of this study are available within the article. Any additional data or inquiries can be requested from the corresponding authors upon reasonable request.

Competing Interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Funding

This study was supported by Natural Science Foundation of Inner Mongolia (2023QN07004), Inner Mongolia Autonomous Region Science and Technology Major Project, Inner Mongolia Autonomous Region Science and Technology Achievement Transformation Project (2021CG0032), Key Project of Inner Mongolia Medical University (YKD2022ZD014), Inner Mongolia Higher Education Institutions Innovation Project (NMGIRT2303), and Science and Technology Innovation Team Project of Inner Mongolia Medical University (Brucellosis Epidemiology Team).

Author Contributions

SS, SB, XW, and SL: conceptualized and designed this study. XW: collected the data. SL: conducted the analysis and wrote the manuscript. SS, SB, and XW: revised the manuscript. All authors have read and approved the final version of the manuscript.

Acknowledgments

We would like to express our sincere thanks to Suan Sunandha Rajabhat University and Inner Mongolia Medical University for invaluable help throughout this research.

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No competing interests reported.

Epidemiological characteristics and spatio-temporal clusters of human brucellosis in Inner Mongolia, 2010-2021

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