|Year : 2020 | Volume
| Issue : 1 | Page : 22-28
Study on epidemiological status, spatial and temporal distribution of human brucellosis in kohgiluyeh and Boyer-Ahmad Province during 2011–2017
Sajjad Rahimi Pordanjani1, Ali Atamaleki2, Masoud Amiri3, Zaher Khazaei4, Hossein Fallahzadeh5, Ruhalla Alayi6, Hasan Naemi7, Hasan Askarpour6
1 Department of Epidemiology, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran; Department of Public Health, Research Center for Health Sciences and Technologies, School of Health, Semnan University of Medical Sciences, Semnan, Iran
2 Department of Environmental Health Engineering, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3 Department of Disease Management, Deputy of Health, Shahrekord University of Medical Sciences, Shahrekord, Iran
4 Department of Public Health, School of Medicine, Dezful University of Medical Sciences, Dezful, Iran
5 Department of Statistics and Epidemiology, School of Public Health, Yazd Shahid Sadoughi University of Medical Sciences, Yazd, Iran
6 Department of Disease Management, Deputy of Health, Yasuj University of Medical Sciences, Yasuj, Iran
7 Department of Public Health, Iranian Research Center on Healthy Aging, Sabzevar University of Medical Sciences, Sabzevar, Iran
|Date of Submission||08-Feb-2019|
|Date of Decision||17-Jul-2019|
|Date of Acceptance||20-Aug-2019|
|Date of Web Publication||03-Jan-2020|
Department of Disease Management, Boyer Ahmad Health Care Network, Yasuj University of Medical Sciences, Yasuj
Source of Support: None, Conflict of Interest: None
Background: Brucellosis is one of the most common diseases between humans and livestock. The purpose of this study was to investigate the epidemiological characteristics and determine the risk factors related to spatial distribution of human brucellosis in Kohgiluyeh and Boyer-Ahmad Province. Materials and Methods: This is a descriptive-analytic and cross-sectional study, in which 741 brucellosis patients were entered in the study during 7 years. Arc geographic information system version 10.2 software was used to create a spatial distribution map. The analysis of this study was performed using the SPSS software version 24 using Chi-square, independent t-test and ANOVA with a statistical significance level of P = 0.05. Results: Seasonal pattern of brucellosis was observed in this province with significant increase in spring and summer (P < 0.001). The highest incidence rate was found in ranchers (40%) and housewives (33.6%) (P < 0.001). The highest incidence of the disease (20/10,000 people) was observed in Kohgiluyeh city which was centred in Dehdasht. Furthermore, seven disease prevalence centres (A, B, C, D, E, F and G) were detected by Kernel density analysis in terms of prevalence rate per square kilometre that the western density centre (Centre C) was identified as the main centre of the disease incidence (P < 0.05). Conclusion: According to the findings of this study, it can be said that climatic features affect the incidence of brucellosis. Due to the high prevalence of brucellosis in male rancher and rural housewives and the identification of density centres of diseases incidence of in Kohgiluyeh and Boyer-Ahmad province, it is necessary prevention and control of brucellosis measures should be taken seriously in high-risk areas.
Keywords: Brucellosis, geographic information system, incidence, Kohgiluyeh and Boyer-Ahmad, spatial distribution
|How to cite this article:|
Pordanjani SR, Atamaleki A, Amiri M, Khazaei Z, Fallahzadeh H, Alayi R, Naemi H, Askarpour H. Study on epidemiological status, spatial and temporal distribution of human brucellosis in kohgiluyeh and Boyer-Ahmad Province during 2011–2017. Adv Hum Biol 2020;10:22-8
|How to cite this URL:|
Pordanjani SR, Atamaleki A, Amiri M, Khazaei Z, Fallahzadeh H, Alayi R, Naemi H, Askarpour H. Study on epidemiological status, spatial and temporal distribution of human brucellosis in kohgiluyeh and Boyer-Ahmad Province during 2011–2017. Adv Hum Biol [serial online] 2020 [cited 2022 Dec 1];10:22-8. Available from: https://www.aihbonline.com/text.asp?2020/10/1/22/275085
| Introduction|| |
Brucellosis is a common zoonotic disease in the worldwide., The disease is caused by a bacterium of the Brucella genus, which consists of four species of the germ, including Brucella melitensis (transfer of sheep and goats), Brucella abortus (transfer from cattle), brucella kanis (transfer from dog) and Brucella Switzerland (transfer from pig) are pathogens for humans. Symptoms of the disease in humans appear as fever, night sweats, arthralgia and loss of appetite and weight loss., Even in pregnant women, it can cause abortion. The main sources of infection in humans are contaminated foods such as unpasteurised milk or cheeses, direct contact with infected animals and occupational exposures. Brucellosis transmission from humans to humans is very rare., Farmers and rancher, slaughterhouse workers, dairy workers, veterinarians and laboratory personnel are occupations, which are at the high risk of brucellosis. The incidence of brucellosis in susceptible areas can be affected by climatic variables and geographic location. Brucellosis has caused heavy and severe economic burdens in almost all parts of the world.
The prevalence of brucellosis in some parts of the world is much more common than in other areas.
These include the Mediterranean Sea countries, some parts of Latin America, Southwest Asia and south of Saharan Africa., One way to stop brucellosis transmission to humans is through education and behaviour change, promoting the level of health and safety of food, as well as the use of personal protective equipment. Iran is ranked 4th in the world in terms of the incidence of brucellosis and in the Eastern Mediterranean region ranked the first. The average incidence of this disease in Iran is between 98 and 130 cases/100,000 people, 79% of which are in rural areas and the rest are in urban areas. The highest incidence of brucellosis was observed in the 10–19 age groups.
Between 2004 and 2014, the incidence of brucellosis in China between 1.48 and 2.89/100,000 population.
In a study done by Wang et al. in 2014, the incidence of brucellosis incidence of 53.23/100,000 and in 2016 was 52.12/100,000 populations. In a study by Lemos et al. based on the number of cases in each year, the incidence of HB in the state of the Parana' was 0.49, 0.42, 0.20 and 0.59 cases/100,000 population, in 2014, 2015, 2106 and 2017, respectively.
In a study by Zhu et al., brucellosis incidence was 0.40/100,000 in Zhangzhou and 0.32/100,000 in Nanping.
In a study by Li et al. in China, seasonal brucellosis prevalence was followed a significant linear pattern in the spring and summer, especially in May, and reported cases were higher in men than in women. The spatial distribution map of the place showed that brucellosis was higher in the north and North-eastern of China. The spatial pattern of the disease incidence also showed that human brucellosis was significantly related to the number of sheep, goat and pigs in meadow areas at an average height, monthly incidence also was significantly related to climatic variables such as temperature, precipitation in all provinces.
Entezari et al. conducted a study titled spatial distribution and the effect of geographical factors of brucellosis in Chaharmahal and Bakhtiari Province; they concluded that the prevalence of brucellosis is correlated with some of the climatic variables. Therefore, prevalence increased in warm months with low rainfall and high temperatures.,
Since rural life, agriculture and rancher, unsanitary slaughter of livestock and consumption of contaminated dairy products are common in Kohgiluyeh and Boyer-Ahmad province, and because households keep their livestock near their own homes and most urban households have close relationship with the villagers, determination of high-risk areas for brucellosis in this province could be effective in focussing disease prevention programmes, including health education, special health financing and vaccination of livestock. Therefore, the aim of this study was to determine the epidemiology and risk factors related to spatial and temporal distribution of human brucellosis in Kohgiluyeh and Boyer-Ahmad provinces from 2011 to 2017.
| Materials and Methods|| |
Characteristics of the studied area
Kohgiluyeh and Boyer-Ahmad province with an area of 15,504 square kilometres is located in the southwest of Iran (30° 09'-31° 32'N and 49° 57'-51° 42'E). According to the national census of Iran in 2016, the population of the province is estimated to be 713,052 representing 56% of the province's population as urban population. Furthermore, 80% of the province is mountainous, such a way that from north-east to southwest side altitude, rainfall and humidity severely reduced.,, The average of rainfall and temperature in this province is estimated to be 863 mm and 14°C, respectively. The location of this province in Iran and some of its climatic and geographical characteristics are shown in [Figure 1].
|Figure 1: Climatic and geographical characteristics of the studied area (a) situation of Kohgiluyeh and Boyer Ahmad in Iran (b) climate covered by the province (c) rainfall contour line in the province (d) contour line of digital elevation from the sea level in the province.|
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Type of study
The present study is a cross-sectional descriptive-analytic, in which 741 patients' data were used to investigate the epidemiological characteristics and risk factors related to spatial and temporal distribution of human brucellosis in Kohgiluyeh and Boyer-Ahmad provinces during 7 years.
Inclusion and exclusion criteria
The criteria for including in to the study were definition and guidelines criteria of the National Brucellosis Committee in the Ministry of Health and Medical Education of Iran, which included; (1) suspected case: The presence of clinical symptoms compatible with brucellosis associated with an epidemiological relationship with suspected or definitive cases of brucellosis or animal contaminated products; (2) possible case: A suspected case whose wright test has a titre equal to or >1/80; (3) confirmed case: suspected or possible case including: (a). Separating Brucella from the clinical specimen, (b). 2ME titre-higher than 1.40 and (c). quadruple increase or more of the Brucella agglutination titre by 2 weeks after the initial test.
Source of data collection
In this study, three sources of data collection were used: the first source, including the standard epidemiological form, was a monthly survey of brucellosis cases, which were recorded, monthly (non-urgent report) in the province health centre for each patient during the years 2011–2017. The second source was related to meteorological data of five synoptic stations at the provincial level, which included data such as annual rainfall and temperature of studied areas. The third source of data collection was related to the geographic information of the studied area, such as the geographic coordinates of the villages and their altitude from the sea level.
Meteorological data (rainfall and temperature) from five synoptic stations in the province were collected and in geographic information system (GIS) software converted to contour lines. Information about the elevation digits of the studied areas was also created using the digital elevation model map prepared by the mapping organisation of the country. Furthermore, a spatial dataset was created using the georeferenced from urban and rural areas of Chahar Mahal and Bakhtiari province, southwest of Iran in ArcGIS 10.2.2 software.
Finally, information about the incidence frequency of disease in different rural and urban areas was classified in descriptive tables of this layer and its map was prepared. Then, Kernel analysis was used to determine the incidence density of brucellosis in a unit area (square kilometre) and the Hotspot analysis was used to determine the ultimate incidence centre in the province. Furthermore, to evaluate the incidence of the disease during 2011–2017, using the software, the frequency of disease in different seasons was obtained, and then, the 7-year process of the disease was drawn during 2011–2011.
At the end of the study, relation of some demographic variables with brucellosis disease was analysed using the SPSS software version 24 using Chi-square and independent t-test with a significance level of P < 0.05.
| Results|| |
The incidence of human brucellosis in Kohgiluyeh and Boyer-Ahmad province was 741 cases in total which was registered by the health centre of the province during a 7-year period (2011–2017) and confirmed by Yasuj University of Medical Sciences. The mean age in men was 39.14 ± 18.18 and in women was 38.22 ± 16.64. The mean age difference in men and women was not statistically significant (P = 0.47). The annual incidence in a 7-year period with a seasonal pattern of the disease with a significant increase in the spring and summer is shown in [Figure 2] (P < 0.001).
|Figure 2: Annual incidence process and seasonal pattern of brucellosis in a 7-year period.|
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The demographic data of brucellosis patients are given in [Table 1] for the studied years. As it is seen, male account for 51% of patients and female 49% of patients, the difference in male-to-female ratio was not statistically significant (P > 0.6). Furthermore, 82.6% of the patients living in the village and 17.4% of the patients living in the city (P < 0.001). In terms of occupation, the highest incidence was attributed to ranchers (40%) and housewives (33.6%) (P < 0.001). About 91.1% of patients had a history of contact with the livestock and 91.4% of them reported a history of using non-pasteurised dairy products (P < 0.001). There was a statistically significant relationship between sex and job (P < 0.001) and also between sex and place of residence (P > 0.03).
The results of patient tests are shown in [Table 2]. As seen, most patients have the Wright tests result 1.320 (22.6%) and the result of 2ME test 1.80 (21.4%), respectively (P < 0.001). There was a positive correlation between the result of Wright test and 2ME of patients, and hence that with the increase of the titre of Wright test, the 2ME test titre also increased, and vice versa (r = 0.3 and P < 0.001). Furthermore, Chi-square test showed that there is a significant correlation between 2ME test and frequency of annual incidence, and hence that in 2014, with the highest incidence of disease, the 2ME test had a tangible increase (P < 0.05).
The numbers of 741 studied patients were assigned to 171 rural and urban areas in GIS software. Data related to the nearest neighbour analysis showed that the dispersion of incidence points does not follow the normal state and have a clustered dispersion (P < 0.001). Furthermore, according to the results of this analysis, the average distance between the incidence areas was determined 3986 m.
Geoclimatic characteristics and the incidence rate of the disease in each county are shown in [Figure 3] and [Table 3]. According to these results, the highest incidence of the disease in the Kohgiluyeh city was observed in the Dehdasht centre.
|Figure 3: The prevalence rate of the disease in the cities of Kohgiluyeh and Boyer Ahmad province.|
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|Table 3: Climatic characteristics and prevalence rate of disease by county|
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Frequency distribution of Brucellosis disease in different climates is shown in [Table 4] and [Figure 4]. According to the obtained results, it was observed that most cases of brucellosis in this province occurred in semi-arid, Mediterranean, semi-humid and very humid and humid climates, respectively, which is statistically significant by ANOVA test (mean square between = 95.58, mean square within = 33.74, F = 2.83, P = 0.026).
|Table 4: Frequency distribution of brucellosis disease in different climates|
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|Figure 4: Frequency distribution of disease prevalence in different climatic regions of Kohgiluyeh and Boyer Ahmad.|
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Furthermore, seven disease prevalence centres (A, B, C, D, E, F and G) were detected by Kernel density analysis in terms of prevalence rate per square kilometre. Among these, the west prevalence centre (C centre) was considered as the main centre of the disease prevalence at the provincial level. The results of the Hotspot analysis [Figure 5] showed that the prevalence of disease in the western centre was significantly higher than other centres (P < 0.001).
| Discussion|| |
The present study was conducted to determine the epidemiological status and spatial and temporal distribution of human brucellosis, along with the assessment of the risk factors related to spatial distribution in Kohgiluyeh and Boyer-Ahmad provinces during 2011–2017. In this study, the average age difference between male and female was not statistically significant (P > 0.05), meaning that the age of brucellosis disease in men and women was almost the same in this province. In a study conducted by Fouskis et al. in Greece, the age distribution of patients with brucellosis was significantly different between male and female. In a study conducted by Hasanjani Roushan et al. in Babol city, Iran, the average age of female was 38.5 and the average age of male was 35.9.
Our results showed that the peak of human brucellosis prevalence in this province was during the spring and summer seasons which was statistically significant (P < 0.05), since the spring season is the breeding season for livestock, as a result, contact with animals, especially with foetal substances increase and thereafter, milk production and dairy products will increase in summer, which probably increased the consumption of non-pasteurised dairy products and the high incidence of disease in these seasons. A similar result was obtained in previous studies. Similar results were also obtained in a study by A Gur in Turkey  and another study by Mohammadian et al. in Tiran and Karan, Isfahan Province.
In this study, there was no statistically significant difference in the sex ratio of the disease. Our results showed that there is a significant relationship between sex and job (P < 0.05). There was also a significant relationship between sex and place of residence (P < 0.05). According to the results of this study, men who lived in the village and their jobs were rancher, more likely developed brucellosis. Housewives living in the village were also prone to a higher risk of disease. In a study conducted by Gür in Turkey, 51% of males and 49% of females were affected by disease and it was consistent with the current study. However, in a study by Pérez-Rendón González et al. in Spain, 66.27% of patients was male and 38.2% were female.
In a study conducted by Farahani et al. at Arak 60% of patients were male and 40% of female. Perhaps due to the fact that women in the province are involved in most rancher work in this province, and there is a high level of contact with livestock, women in our study made up a large percentage of patients. Our results showed that 91.1% of patients had a history of contact with the livestock, as well as 91.4% of patients had a history of non-pasteurised dairy consumption, which was statistically significant. Probably, because traditional animal husbandry is being used in this province and the people of this province are interested in using traditional dairy products. Two important ways of brucellosis transmission in this province are contact with livestock and non-pasteurised dairy products. In a study conducted by Ali et al. in Pakistan, contact with livestock and raw milk consumption were a powerful way of brucellosis transmission. In a study by Guler et al. in Turkey, the use of non-pasteurised dairy products was the most important transmission way.
In this study, the results of the Wright test were found to be 1.320 in the majority of patients. In a study by Kassiri et al. the result of 1.320 was observed more than the other titre which was in consistent with the idea that most of the results of the Wright test were in endemic areas of the 1.320 titre  Furthermore, in relation to the results of the 2ME test, titre 1.80 was found more than other titre, which was in consistence with the study of Hashtarkhani et al. in Khorasan Razavi  Furthermore, in this study there was observed a positive correlation between the result of wright and 2ME tests and vice versa. This means that with increasing the titre of wright, patients with the 2ME titre also increased and vice versa. This means that with increasing the titre of wright test in patients, the 2ME titre also increase and vice versa.
In this study, we tried to show the effect of variables such as altitude, temperature and precipitation on human brucellosis using the spatial and temporal model. Our results showed that most of the patients were in semi-arid, Mediterranean, semi-humid, and very humid and humid climate, which was statistically significant. A study conducted by Zhang et al. in China showed that in zoonotic diseases changes in environmental factors affected the amount of contamination and exposure of humans to infected animals. In a study conducted by Entezari et al. in Chaharmahal and Bakhtiari province, there was a positive and significant correlation between the precipitation and increase of prevalence of brucellosis. Furthermore, in the study of Li et al. in China, the low temperature provided an opportunity to increase the prevalence of brucellosis. The study of Ahmadkhani et al. in Iran showed that low temperature and high rainfall provides the basis for brucellosis transmission. In this study, we showed that the prevalence points in the province have clustered dispersion and do not follow normal and random distribution which was matched by a study conducted in California. Our results showed that 9 points in the western centre have a significant relationship with the prevalence of the disease and high clustering of the patients in this area has led to the formation of the main centre of disease prevalence in the province. A study by Ron et al. in Ecuador showed that there was a relationship between gradual increases in the incidence of brucellosis with the southern cluster.
| Conclusion|| |
The present study shows that there is a relationship between the prevalence of brucellosis and the desired climatic characteristics in such a way that the prevalence of brucellosis in semi-arid regions was higher with high temperature and rainfall and low humidity. The western centre (C), which is located south of Kohgiluyeh, has the same climatic characteristics. Regarding the findings of this study and considering the high prevalence of this disease in spring and summer season, regular and periodic vaccination of livestock is necessary to prevent the disease and reduce the prevalence rate in these seasons. Due to the high prevalence of brucellosis in men rancher and rural housewives and the identification of major centres and incidence in Kohgiluyeh and Boyer-Ahmad province, it should be taken prevention and control measures for brucellosis in severely and high risk areas.
At the end of study, the authors gratefully acknowledge and thanks from health department of Kohgiluyeh and Boyer Ahmad for cooperation and coordination in data collection and implementation of this study. The code of ethics of this study: IR.SSU.SPH.REC.1398.071.
Financial support and sponsorship
Conflict of interest
This study has no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4]