Open access Original research BMJ Open: first published as 10.1136/bmjopen-2019-031206 on 2 January 2020. Downloaded from Epidemiological features of human brucellosis in Tongliao City, Inner Mongolia province, China: a cross- sectional study over an 11- year period (2007–2017) Di Li,1 Lifei Li,2 Jingbo Zhai,3 Lingzhan Wang,4 Bin Zhang 5 To cite: Li D, Li L, Zhai J, et al. ABSTRACT Strengths and limitations of this study Epidemiological features of Objectives To describe the epidemiology of human human brucellosis in Tongliao brucellosis in the past decade and provide evidence ► This is the first study that was focused on the ep- City, Inner Mongolia province, of disease control in Tongliao city, which is one of the China: a cross- sectional idemiological characteristics of human brucellosis highest- risk areas of human brucellosis in Inner Mongolia study over an 11- year period during the past 11 years in Tongliao, which is one province, China. (2007–2017). BMJ Open of the highest- risk areas in Inner Mongolia, China. Design Cross- sectional study. 2020;10:e031206. doi:10.1136/ ► Demographic data, seasonality and spatiotemporal Participants Clinically and bacteriologically confirmed bmjopen-2019-031206 distribution of reported brucellosis cases were ex- human brucellosis cases. plored to provide evidence for strategies of disease ► Prepublication history and Primary and secondary outcome measures An additional material for this control in Tongliao. analysis of the reported cases of human brucellosis paper are available online. To ► The data used in the present study might be influ- during 2007–2017 was carried out to describe the age, view these files, please visit enced by under-reporting, misdiagnosis and incom- sex and occupational distributions of the cases. The time the journal online (http:// dx. doi. plete information as a result of passive public health series analysis model and the geographical information org/ 10. 1136/ bmjopen- 2019- surveillance. 031206). system were explored to describe the seasonality and ► The densities of livestock, meat yield, slaughter spatiotemporal distribution, respectively, at the county amount, environment and pathogen types were not Received 24 April 2019 level. Revised 24 November 2019 available in the present study, and these data should Results A total of 13 938 cases of human brucellosis http://bmjopen.bmj.com/ be taken into account for brucellosis transmission Accepted 25 November 2019 was collected in Tongliao from 2007 to 2017; the and prediction as risk factors. majority was aged 25 years to 59 years (85.4%) and the male- to- female ratio was 2.64:1; most of them were agriculturalists (81.9%) and pastoralists (12.4%). The incidence rates increased dramatically from 9.22/100 000 fatal, but has important impacts on the live- in 2007 to 69.16/100 000 in 2011 with an annual increase stock economy due to loss of production in of 14.99%. They decreased during 2012–2016 (annual international markets.3 Human brucellosis decrease of 8.37%) and rose again in 2017 (44.32/100 is commonly transmitted from infected 000). The disease peaked during March–July, with a clear on October 2, 2021 by guest. Protected copyright. periodicity and trend of monthly anterior displacement livestock directly or indirectly, and is char- since 2012. Jarud Banner, the region located in the north- acterised by acute febrile illness, inflamma- west of Tongliao, had the highest accumulated incidence tion of the genitals, sterility, spontaneous rate (130.1/100 000) compared with other counties. The miscarriage and lymphatic system lesions, high-risk regions were spread from the north-west to the amounting to more than half a million new south and east of Tongliao during the past decade. cases annually worldwide.4 It has been a Conclusions The prevalence of human brucellosis in huge problem for hyperendemic northern © Author(s) (or their Tongliao was aggravated during the past decade and China since the first report in 1905.5 There employer(s)) 2020. Re- use peaked during March–July. High- risk areas were mainly was nationwide reporting of human brucel- permitted under CC BY-NC. No concentrated in the counties with extensive prairies and losis in China in the 1960s, and the inci- commercial re- use. See rights livestock. and permissions. Published by dence was quite severe before the 1980s, BMJ. followed by a decrease for 15 years due to For numbered affiliations see INTRODUCTION the domestic animal brucellosis control end of article. Brucellosis is a highly contagious zoonotic and eradication programme.6 However, Correspondence to disease caused by Brucella spp and poses the epidemic situation of the disease has Dr Bin Zhang; great challenges to public health, particu- increased sharply since 1995, and about 20 binz361@ 126. com larly in developing countries.1 2 It is rarely 000–50 000 new cases are reported every Li D, et al. BMJ Open 2020;10:e031206. doi:10.1136/bmjopen-2019-031206 1 Open access BMJ Open: first published as 10.1136/bmjopen-2019-031206 on 2 January 2020. Downloaded from year with an annual increase of 7.8% during the last 10 Information on human brucellosis cases in Tongliao years in China.7 Increased livestock trading, the growing city was collected from January 2007 to December 2017 demand for meat consumption, absence of quarantine according to the monthly reports of surveillance, a period or pasteurisation of livestock products, and rapid move- that the complete data could be available and was consis- ment of people during the past decade has given rise tent with the national conditions of China’s 10- year statis- to increased risk of infection among the population tics for the formulation of control strategies for the next having direct or indirect contact with livestock.8 decade. All the data in the current study were publicly Inner Mongolia is the most important province in open and supplied in an anonymous format, without north- east China for livestock husbandry, and has been violation of any personal privacy. contributing about 40% of new cases of human brucellosis Human brucellosis was diagnosed through a combi- annually.9 New focus on human brucellosis has been spread nation of epidemiological exposure (contact history of all over Inner Mongolia, and the incidence increased from Brucella or living in endemic areas) and clinical mani- 0.34 per million in 2002 to 3.33 per million in 2006.4 10 Most festations (undulant fever, fatigue, sweats, arthritis, of the patients in Inner Mongolia are farmers or herdsmen, arthralgia, myalgia, splenomegaly, hepatomegaly, etc), and are commonly infected from Brucella melitensis infected and confirmed by positive results of presumptive labo- sheep (92%).11 Besides, Tongliao, a semiagricultural and ratory tests (plate agglutination test, Rose Bengal plate semipastoral area located in eastern Inner Mongolia, has test, serum agglutination test, bacterial isolation, etc), been one of the most high-risk areas of human brucellosis according to the ‘2007 Diagnostic Criteria of Brucel- with an incidence of 10–100 per 100 000 during 2006– losis (WS268-2007)’ of the Chinese Ministry of Health. 2010.9 It is reported that the incidence of human brucel- losis among the high-risk groups (population engaged Statistical analysis in agricultural cultivation, grazing, slaughtering, etc) in The data were entered into a Microsoft Excel spread- Tongliao city was as high as 11.4–49.8% from 2010 to sheet, and the demographic data were analysed using 2014.12 Previous research has expounded the spatiotem- simple descriptive statistics. The cumulative incidence poral distribution of human brucellosis in Inner Mongolia; was explored to describe the prevalence and frequency however, few studies have explored the high- risk areas at of the disease during the study period. The spatiotem- the county level in recent years. In addition, since human poral distribution maps of human brucellosis based on brucellosis is strongly associated with work and seasonality, county were plotted using a geographical information the characteristics of the new human brucellosis epidemic system through R- Project software (MathSoft, Auckland, in Tongliao should be known, so as to provide evidence for New Zealand). The monthly number of human brucel- disease control strategies. losis cases was drawn on a thermograph to analyse the In the present study, information on the reported seasonality. All further statistical analyses were conducted by SPSS V.18.0 (SPSS, Chicago, USA). cases of human brucellosis at the county level in http://bmjopen.bmj.com/ Tongliao, Inner Mongolia province, China, from 2007 to 2017 were collected, and their epidemiological Patient and public involvement features were analysed. Patients were not involved in the present study. The results of the main study were presented to study participants at the National Disease Prevention Information System of METHODS China through a monthly report. Study area Tongliao (42°15′−45°41′ N and 119°15′−123°43′ E) is on October 2, 2021 by guest. Protected copyright. located in the equatorial zone in eastern Inner RESULTS Mongolia in China, at an altitude of 120–1400 m and Demographic data of human brucellosis in Tongliao continental area of 59 835 km2. It is divided into eight A total of 13 938 cases of human brucellosis from January counties with a total population of 3.16 million. It has 2007 to December 2017 was reported in Tongliao, with an annual precipitation of 305–485 mm, and its average an average of 1268±555 cases per year. For all of the annual temperature is 0°C–6°C. The region is a major diagnosed cases, 72.9% (n=10 162) and 30.2% (n=4214) foodstuff and livestock (mainly sheep, cattle and pigs) of patients were confirmed by serological tests and production zone in China, and the husbandry contrib- bacterial culture, respectively. The median age of the utes to 42.4% of the total revenue of Tongliao.