Introduction
Bovine tuberculosis (bTB) is a chronic infectious disease that primarily affects cattle [Reference Garcia-Saenz1, Reference Moustakas and Evans2]. The main causative agent of this disease, Mycobacterium bovis (M. bovis), has a global distribution and a wide host range, including wildlife and humans [Reference Alvarez3–Reference Reis5]. The negative impact of bTB on both animal and public health, combined with the socio-economic losses it causes, raises serious global concerns [Reference Chang6, Reference Ciaravino7].
Globally, tuberculosis (TB) is the world’s leading cause of death from a single infectious agent and among the top ten causes of death, with an estimated 10.7 million people suffering from TB in the year 2024 and 1.23 million people dying from this disease in 2024 [8]. In Türkiye, a total of 9156 TB cases in people were reported in 2021, and 9851 cases in 2022 [9]. While M. bovis is estimated to account for approximately 10% of human TB cases in developing countries [Reference Chang6], this rate was found to be 5.3% in Türkiye [Reference Bayraktar10]. The World Health Organization (WHO) estimated approximately 143000 zoonotic TB cases worldwide in 2018, caused by M. bovis [11]. Similarly, the European Food Safety Authority reported 111 zoonotic TB cases in the European Union in 2021, caused by M. bovis or M. caprae, and to date, zoonotic TB still poses a serious threat to public health [Reference Bezos12] in countries in which bTB is prevalent and socio-cultural factors facilitate transmission of Mycobacterium tuberculosis complex (MTBC) species between cattle and people.
bTB is endemic in cattle populations in many countries, negatively impacting economic development and leading to significant financial burdens for breeders and taxpayers [Reference Allen, Ford and Skuce13–Reference Madden15]. It is estimated that the disease infects over 50 million cattle worldwide, resulting in annual economic losses of approximately US$3 billion [Reference Chang6, Reference Buddle16]. The reported socio-economic loss in Türkiye is estimated to range from approximately US$15 million to US$59 million annually [Reference Cosivi17]. The total population of cattle in Türkiye is approximately 17 million, and a previous study [Reference Çakır and Yakar18] shows that 0.8% of premises (herds) had a bTB outbreak for the period 2017–2021. The national bTB control programme in Türkiye established in 2024, is based on slaughterhouse surveillance, followed by tuberculin skin testing (TST) of cattle on premises where infected cattle had been identified at slaughter and kept during the previous 6 months. Cattle that test positive are conditionally slaughtered with compensation paid to breeders, and affected premises remain under quarantine until the infection has been cleared. In addition, financial support is provided to premises officially recognised as free from bTB to encourage the maintenance of disease-free status.
Spatiotemporal epidemiological studies are essential for understanding the distribution and dynamics of bTB, which can subsequently be used to identify potential risk factors and support evidence-based disease control strategies. By integrating geographical data with mapping and spatial analytical methods, spatiotemporal studies provide valuable insights into disease patterns and facilitate the identification of high-density areas [Reference Garcia-Saenz1, Reference Moustakas and Evans2, Reference Madden15, Reference Allepuz19–Reference Conteddu21].
Geographic Information Systems (GIS) are an effective tool for spatial epidemiological research to describe distribution, patterns, and to evaluate risk factors of diseases within a population. The collection, organization, and analysis of data from disease-affected areas based on designated spatial epidemiological units are vital [Reference Garcia-Saenz1, Reference Madden15]. While research on the use of GIS for animal diseases in Türkiye remains limited, it has begun to increase recently. Most studies that have used GIS in Türkiye have primarily focused on visualizing diseases through maps, with a few exceptions involving spatial analyses [Reference Çiçek22–Reference Bayir25]. In the study by Çakır and Yakar Reference Çakır and Yakar[18], which mapped the spatial distribution of bTB in Türkiye for the period 2017–2021, the authors demonstrated the spatial distribution of bTB outbreaks and how this distribution changed over the 5-year period. However, the study by Çakır and Yakar [Reference Çakır and Yakar18] did not include any spatial analyses to determine whether bTB outbreaks exhibited a high-density area tendency, among other aspects of spatial distribution.
Therefore, the aim of this study was to describe the spatial and temporal patterns of bTB outbreaks in Türkiye between 2017 and 2023 using GIS-based spatial analysis methods. In this study, in addition to mapping the spatial distribution of bTB outbreaks in Türkiye between 2017 and 2023 (two additional years of data compared to the spatial distribution), spatial analyses using buffer analysis (BA) were used to determine distances from premises with bTB outbreaks to livestock bazaars for all bTB outbreaks between 2017 and 2023.
Methods
Study area
Türkiye is located in the Northern Hemisphere, consisting of 81 provinces and 973 districts, with an area of 780580 km2 (Figure 1). The country’s diverse climate, altitude, topography, and vegetation support extensive agricultural and livestock production systems. There are approximately 16.6 million head of cattle on 1.1 million cattle premises across the country [26, 27].
Map of Türkiye’s administrative division.
Figure 1. Long description
A geographical map of Türkiye.
Surrounding Geography:
- North: Black Sea, Bulgaria, and Georgia.
- West: Aegean Sea, Greece, and the Marmara Sea.
- South: Mediterranean Sea, Syria, and Iraq.
- East: Armenia and Iran.
- A north arrow and a scale bar (0 to 200 Km) are located in the bottom-left.
Internal Divisions:
- The map displays thick black lines for Province Borders and thin grey lines for District Borders.
- Each province contains a two-digit numerical code ranging from 01 to 81.
- Major water bodies within the landmass, such as Lake Van and Lake Tuz , are shaded light blue.
Legend and Province List:
- A table in the bottom-right titled Province Codes and Names lists all 81 provinces numerically.
- 01 Adana, 02 Adıyaman, 03 Afyon, 04 Ağrı, 05 Amasya, 06 Ankara, 07 Antalya, 08 Artvin, 09 Aydın, 10 Balıkesir.
- 11 Bilecik, 12 Bingöl, 13 Bitlis, 14 Bolu, 15 Burdur, 16 Bursa, 17 Çanakkale, 18 Çankırı, 19 Çorum, 20 Denizli.
- 21 Diyarbakır, 22 Edirne, 23 Elazığ, 24 Erzincan, 25 Erzurum, 26 Eskişehir, 27 Gaziantep, 28 Giresun, 29 Gümüşhane, 30 Hakkari.
- 31 Hatay, 32 Isparta, 33 İçel (Mersin), 34 İstanbul, 35 İzmir, 36 Kars, 37 Kastamonu, 38 Kayseri, 39 Kırklareli, 40 Kırşehir.
- 41 Kocaeli, 42 Konya, 43 Kütahya, 44 Malatya, 45 Manisa, 46 K. Maraş, 47 Mardin, 48 Muğla, 49 Muş, 50 Nevşehir.
- 51 Niğde, 52 Ordu, 53 Rize, 54 Sakarya, 55 Samsun, 56 Siirt, 57 Sinop, 58 Sivas, 59 Tekirdağ, 60 Tokat.
- 61 Trabzon, 62 Tunceli, 63 Ş. Urfa, 64 Uşak, 65 Van, 66 Yozgat, 67 Zonguldak, 68 Aksaray, 69 Bayburt, 70 Karaman.
- 71 Kırıkkale, 72 Batman, 73 Şırnak, 74 Bartın, 75 Ardahan, 76 Iğdır, 77 Yalova, 78 Karabük, 79 Kilis, 80 Osmaniye, 81 Düzce.
Data collection
The data on bTB outbreaks used in this study were obtained from the Veterinary Information System (VIS), a module within the Agricultural Information System (AIS) under the Republic of Türkiye, Ministry of Agriculture and Forestry (MoAF). The data in VIS were entered directly into the system by veterinary officials working in the Provincial and District Directorates of MoAF (https://hbs.tarbil.gov.tr/Main/InternalUser).
The bTB dataset recorded in VIS includes address information and geographic coordinates of the premises identified as having a bTB outbreak across the country. Additionally, the database included field-collected information (Table 1) regarding the source of infection for bTB identified by official veterinarians. These epidemiological data are important for understanding potential risk factors for bTB outbreaks identified by field veterinarians as part of field epidemiological outbreak investigations. Seventeen categories were recorded and include (but are not limited to): (1) Latent/subclinical infection within the premises, (2) purchase of infected animals, (3) local pasture, (4) purchase of contaminated vehicles/equipment, (5) recurrent infection within the premises. These data were used for descriptive purposes in our study after the category ‘being investigated’ was removed (Table 1).
Sources of bTB infection identified through epidemiological investigations of affected cattle premises in Türkiye (2017–2023)
Table 1. Long description
The table consists of 12 columns: Number, Epidemiological category/Year, annual columns from 2017 to 2023, a 2017–2023 total, General %, and Known %.
Key data rows include:
1. Being investigated: 3006 total cases, 23.2% general.
2. Other: 2341 total cases, 18.1% general.
3. Direct contact with wildlife: 4 total cases, 0.0% general, 0.1% known.
4. Indirect contact with wildlife: 22 total cases, 0.2% general, 0.3% known.
5. In the transport vehicle: 17 total cases, 0.1% general, 0.2% known.
6. Iatrogenic transmission: 34 total cases, 0.3% general, 0.4% known.
7. Infected bull: 29 total cases, 0.2% general, 0.4% known.
8. Contaminated animal feed: 30 total cases, 0.2% general, 0.4% known.
9. Vectorial transmission: 40 total cases, 0.3% general, 0.5% known.
10. Animals distributed from the young farmer project: 30 total cases, 0.2% general, 0.4% known.
11. In the livestock bazaars: 62 total cases, 0.5% general, 0.8% known.
12. Neighbour village/premises: 67 total cases, 0.5% general, 0.9% known.
13. Recurrent infection within the premises: 231 total cases, 1.8% general, 3.0% known.
14. Purchase of contaminated vehicles/equipment: 348 total cases, 2.7% general, 4.6% known.
15. Local pasture: 803 total cases, 6.2% general, 10.5% known.
16. Purchase of infected animals: 1494 total cases, 11.5% general, 19.6% known.
17. Latent/subclinical infection within the premises: 4412 total cases, 34.0% general, 57.9% known.
The total number of bTB outbreaks across all categories from 2017 to 2023 is 12970.
Source: [26].
In addition, the number of animals sent to conditional slaughter or culled from premises with outbreaks between 2017 and 2023 due to the disease and the compensation amounts paid for these animals were also obtained from VIS.
This study covered the period 2017–2023, with data for each year. This study used the exact coordinates of the affected premises for point-based mapping. Thus, the spatial pattern of the disease was mapped at the highest possible precision, and descriptive spatial analyses were performed accordingly.
The geographic coordinates of livestock bazaars in Türkiye were obtained from MoAF with the necessary permits and incorporated into the study. These data enabled the analysis of the distance between livestock bazaars and the location of premises with bTB outbreaks. The coordinate data for both bTB outbreaks and livestock bazaars were verified, and any missing or erroneous records identified were corrected using Google Maps searches based on the addresses of the relevant premises. Duplicate notification reports were also removed from the dataset after reviewing the disease notification number, record, and approval dates.
Finally, since bTB is a notifiable disease in Türkiye, the necessary legal permissions for data access and publication of the results were obtained from the MoAF. This descriptive study only included data on affected premises with a bTB outbreak during 2017–2023, and data on unaffected premises were not available.
Data analysis
Kernel density analysis
Kernel Density Analysis (KDA) was performed using the Spatial Analyst tool in ArcGIS Pro version 3.6 on thematic maps of the outbreaks [28].
KDA was used to visualize and evaluate spatial data. This analysis shows the density of the data points, identifies hotspot and coldspot areas, and highlights locations where bTB outbreaks occur more frequently.
Buffer analysis
BA creates zones around a specified point, line, or polygon at defined distances. This analysis is used to identify the impact area or regions within a certain distance of a particular location. In this study, livestock bazaars were used as reference points in the BA to assess spatial proximity of bTB outbreaks to these locations. The distribution of bTB outbreaks was determined within buffer zones of <25, <50, <75, <100, and <125 km from livestock bazaars. The distribution of bTB outbreaks within each buffer zone was then determined using the Buffer tool in ArcGIS Pro version 3.6 [29].
Results
Temporal distribution of bTB outbreaks
From a population of approximately 1.1 million cattle premises in Türkiye, a total of 12970 bTB outbreaks were identified during the study period (2017–2023), and 107929 cattle were sent for conditional slaughter or were culled due to the disease. The total compensation paid to breeders amounted to ₺1052824716.48 (approximately US$24.2 million) during the study period (Table 2).
Total number of cattle and bTB disease data in Türkiye (2017–2023)
Table 2. Long description
The table contains seven columns: Year, Number of bTB outbreaks, Number of cattle (head), Number of cases (head), Incidence (Per 100000), Number of cattle compensated (head), and Amount of compensation paid in Turkish Lira.
* 2017: 1220 outbreaks, 16105025 cattle, 11763 cases, 73.0 incidence, 10553 compensated, 42080777.19 Turkish Lira.
* 2018: 1629 outbreaks, 17220903 cattle, 11035 cases, 64.1 incidence, 11412 compensated, 56163211.90 Turkish Lira.
* 2019: 2248 outbreaks, 17872331 cattle, 16781 cases, 93.9 incidence, 23567 compensated, 121083274.08 Turkish Lira.
* 2020: 1877 outbreaks, 18157971 cattle, 19471 cases, 107.2 incidence, 17991 compensated, 114029486.83 Turkish Lira.
* 2021: 2052 outbreaks, 18036117 cattle, 18579 cases, 103.0 incidence, 17312 compensated, 136565536.10 Turkish Lira.
* 2022: 2099 outbreaks, 17023791 cattle, 17206 cases, 101.1 incidence, 14884 compensated, 190818833.06 Turkish Lira.
* 2023: 1845 outbreaks, 16583005 cattle, 13040 cases, 78.6 incidence, 12210 compensated, 392083597.32 Turkish Lira.
* Total: 12970 outbreaks, 107875 cases, 107929 compensated, 1052824716.48 Turkish Lira.
Epidemiological investigation of bTB outbreaks
Official veterinarians who detected outbreaks of bTB in the field also investigated the most likely epidemiological transmission route of the disease and entered their findings into VIS. The data obtained from this epidemiological investigation were collected at the national level and were important for understanding the dynamics of bTB disease.
In the epidemiological investigation on 12970 premises with a bTB outbreak (Table 1), 3006 (23.2%) were excluded from this analysis since no findings were identified, and these premises were recorded as ‘being investigated’, leaving 9964 premises with completed epidemiological investigations. Among those with a completed epidemiological investigation, for 2341 (18.1%) premises the source of infection was classified in the ‘other’ category, with the remaining 7623 premises classified in one of 15 categories (Table 1) with a ‘known’ source of infection. Five of these 15 categories accounted for nearly the entirety, 7288 (95.6%), of the premises (7623) with a ‘known’ source of infection. The top five categories were: (1) latent/subclinical infection within the premises 4412 (57.9%), (2) purchase of infected animals 1494 (19.6%), (3) local pasture 803 (10.5%), (4) purchase of contaminated vehicles/equipment 348 (4.6%), and (5) recurrent infection within the premises 231 (3.0%). The remaining ten categories accounted for 335 (4.4%) premises with completed epidemiological investigations and a ‘known’ source of infection (Table 1).
Spatial distribution of bTB outbreaks
Maps showing the spatial distribution of bTB outbreaks between 2017 and 2021 were previously published by Çakır and Yakar [Reference Çakır and Yakar18]. However, they are updated here to illustrate the temporal distribution of outbreaks, adding new data for the years 2022 and 2023 and to serve as a basis for the KDA and BA, which were not previously conducted. Although there are variations in the distribution pattern by year, the main provinces where higher numbers of bTB outbreaks were observed in 2022–2023 are Erzurum, Elazığ, Sivas, Çorum, Tokat, Samsun, Çankırı, Kastamonu, Bolu, Bartın, Düzce, Kütahya, Aydın, Denizli, Burdur, and Edirne (Figure 2).
Spatial and temporal distribution of bTB outbreaks (2017–2023).
Figure 2. Long description
The figure consists of seven maps of Türkiye, each titled distribution of bTB by cattle premises followed by the year. Red dots represent one cattle premises each, defined as an epidemiological unit village or neighborhood.
1. 2017: Red dots are scattered across the country with higher concentrations in the Northwest near the Marmara Sea and the West.
2. 2018: Shows a similar distribution to 2017 with a slight increase in density in the Central and Northeast regions.
3. 2019: Displays a notable increase in red dots, particularly in the Central and Southern coastal regions.
4. 2020: Shows dense clusters in the Northwest, West, and Central regions, with dots spreading further into the East.
5. 2021: The density remains high, with significant clusters in the Central-North and Western regions.
6. 2022: Shows a substantial increase in the density of red dots across the entire country, especially in the East and Northeast.
7. 2023: This is the largest map at the bottom. It shows the highest density of bTB outbreaks. Large, dense red clusters are visible in the Northwest near the Marmara Sea, the West near the Aegean Sea, the Central region, and a very high concentration in the East near the borders of Armenia and Iran.
Each map includes geographical labels for surrounding bodies of water: Black Sea to the North, Aegean Sea to the West, and Mediterranean Sea to the South. Neighboring countries labeled include Bulgaria, Greece, Georgia, Armenia, Azerbaijan, Iran, Iraq, and Syria. A scale bar indicating 0, 100, and 200 kilometers is located at the bottom left of each map.
Kernel density analysis
Figure 3 shows the KDA results for 2017–2023. The maps in Figure 3 show the spatial distribution of bTB outbreaks and illustrates temporal changes in high-density outbreak areas of across different regions of Türkiye.
Distribution of bTB outbreaks according to KDA (2017–2023).
Figure 3. Long description
A multi-panel series of seven maps of Türkiye. The first six panels are arranged in two columns and three rows at the top, representing the years 2017, 2018, 2019, 2020, 2021, and 2022. The seventh, larger panel at the bottom represents 2023. Each map displays black dots representing cattle premises with bTB outbreaks and color-coded heat map zones indicating density per square kilometer. The color scale ranges from light green (2) to dark red (up to 25).
* 2017 to 2018: Shows moderate clusters in the West and Northeast, with peak densities reaching 14 and 13 respectively.
* 2019 to 2020: Shows an intensification of clusters, particularly in the Southwest and Central-East regions, with peak densities rising to 19 and 15.
* 2021 to 2022: Shows a significant expansion of high-density red zones in the East and Northeast, with the 2022 peak reaching 21.
* 2023 (Large bottom panel): The most intense distribution. A massive, dark red high-density cluster is concentrated in the East-Northeast. Significant secondary clusters are visible in the Southwest and Central regions. The density scale for this year peaks at 25.
All maps include geographical labels for the Black Sea to the North, the Mediterranean Sea to the South, the Aegean Sea to the West, and neighboring countries including Bulgaria, Greece, Georgia, Armenia, Azerbaijan, Iran, Iraq, and Syria. Map legends include a North arrow, a scale bar from 0 to 200 kilometers is located at the bottom left of each map.
The density of bTB outbreaks in zones surrounding these high-density areas varies over time. A prominent high-density area identified in this analysis includes a group of premises in the Thrace region, encompassing the provinces of Edirne, Kırklareli, and Tekirdağ. Another high-density area, occasionally expanding, was detected in the Aegean and Mediterranean regions, covering the provinces of Aydın, Denizli, and Burdur. A crescent-shaped high-density region was identified to the east and south of the Gulf of İzmit, including the provinces of Kocaeli, Sakarya, Düzce, Bolu, Bartın, Kütahya, and Bursa. Provinces with increasing outbreak densities over the years are primarily located in Central Anatolia, including Kayseri, Sivas, Yozgat, Çankırı, Aksaray, Niğde, and Konya, and in the Black Sea region, including Tokat, Amasya, Çorum, Kastamonu, and Samsun. Additionally, bTB outbreak concentration is observed in Erzurum, Erzincan, and Elazığ, extending to Adıyaman and Adana.
Buffer analysis
The thematic maps in Figure 4 show the distribution of bTB outbreaks overlaid with livestock bazaar variable as an additional layer. The BA was applied for each year separately between 2017 and 2023 to investigate the relationship between livestock bazaars and bTB outbreaks. The number of bTB outbreaks within each specified distance range/zone from each livestock bazaar was calculated and mapped (Figure 4). Of the total 12970 bTB outbreaks reported between 2017 and 2023, 7604 (58.6%) were found within <25 km, 11428 (88.1%) within <50 km, 12596 (97.1%) within <75 km, 12887 (99.4%) within <100 km, and 12926 (99.7%) within <125 km distance from livestock bazaars. An examination of the maps showing the distribution of bTB outbreaks in relation to livestock bazaars indicates that livestock bazaars are located in close proximity to areas with a high density of bTB outbreaks (Figure 4 and Table 3).
Distribution of bTB outbreaks by livestock bazaars buffer zones (2017–2023).
Figure 4. Long description
A multi-panel figure containing seven geographical maps of Türkiye. The first six panels are small maps arranged in two columns and three rows, representing the years 2017, 2018, 2019, 2020, 2021, and 2022. The seventh panel is a large, detailed map at the bottom representing 2023.
Each map displays:
* Red stars representing individual livestock bazaars.
* Black dots representing cattle premises with bTB outbreaks (epidemiological units like villages or neighborhoods).
* Concentric colored buffer zones around the bazaars: light blue (less than 25 kilometers), yellow (50 kilometers), pink (75 kilometers), green (100 kilometers), and purple (less than 125 kilometers).
Spatial distribution across all years:
* Livestock bazaars (red stars) are distributed throughout the country but show higher density in the West (Marmara and Aegean regions), Central Anatolia and Northeast.
* Cattle premises with bTB outbreaks (black dots) are heavily concentrated in the Northwest near the Marmara Sea, the West coast, Central Anatolia, and the Northeast near the border with Georgia and Armenia.
* The buffer zones overlap extensively, covering almost the entire landmass of Türkiye by the 125 kilometer mark.
* In the 2023 focal map, a significant cluster of black dots is visible in the East ( Erzurum, Elazığ and Kars), Central Anatolia (Sivas, Tokat, Amasya, Çorum, Çankırı, Kastamonu, Bartın, Karabük, Bolu and Düzce), West (Aydın, Denizli, Burdur and Kütahya) and the Northwest (Edirne, Tekirdağ and Kırklareli).
Map legends include a North arrow, a scale bar from 0 to 200 kilometers, and labels for surrounding bodies of water (Black Sea to the North, Aegean Sea to the West, Mediterranean Sea to the South) and neighboring countries (Bulgaria, Greece, Georgia, Armenia, Azerbaijan, Iran, Iraq, and Syria).
Distribution of bTB outbreaks by livestock bazaar buffer zones (2017–2023)
Table 3. Long description
The table consists of 12 columns: Year, five pairs of count and percentage columns for distance buffers, and a total column. The distance buffers are less than 25 km, less than 50 km, less than 75 km, less than 100 km, and less than 125 k m.
* 2017: 738 outbreaks (60.5 percent) within 25 km; 1089 (89.3 percent) within 50 km; 1173 (96.1 percent) within 75 km; 1209 (99.1 percent) within 100 km; 1212 (99.3 percent) within 125 km; total 1220.
* 2018: 996 outbreaks (61.1 percent) within 25 km; 1447 (88.8 percent) within 50 km; 1583 (97.2 percent) within 75 km; 1615 (99.1 percent) within 100 km; 1622 (99.6 percent) within 125 km; total 1629.
* 2019: 1361 outbreaks (60.5 percent) within 25 km; 1965 (87.4 percent) within 50 km; 2184 (97.2 percent) within 75 km; 2233 (99.3 percent) within 100 km; 2239 (99.6 percent) within 125 km; total 2248.
* 2020: 1090 outbreaks (58.1 percent) within 25 km; 1647 (87.7 percent) within 50 km; 1815 (96.7 percent) within 75 km; 1863 (99.3 percent) within 100 km; 1873 (99.8 percent) within 125 km; total 1877.
* 2021: 1150 outbreaks (56.0 percent) within 25 km; 1812 (88.3 percent) within 50 km; 2002 (97.6 percent) within 75 km; 2042 (99.5 percent) within 100 km; 2044 (99.6 percent) within 125 km; total 2052.
* 2022: 1185 outbreaks (56.5 percent) within 25 km; 1825 (86.9 percent) within 50 km; 2043 (97.3 percent) within 75 km; 2090 (99.6 percent) within 100 km; 2095 (99.8 percent) within 125 km; total 2099.
* 2023: 1084 outbreaks (58.8 percent) within 25 km; 1643 (89.1 percent) within 50 km; 1796 (97.3 percent) within 75 km; 1835 (99.5 percent) within 100 km; 1841 (99.8 percent) within 125 km; total 1845.
* Total (2017 to 2023): 7604 outbreaks (58.6 percent) within 25 km; 11428 (88.1 percent) within 50 km; 12596 (97.1 percent) within 75 km; 12887 (99.4 percent) within 100 km; 12926 (99.7 percent) within 125 km; grand total 12970.
Discussion
The increasing use of advanced tools in veterinary epidemiology and the digital recording of geographically referenced data in Türkiye have enabled the application of various GIS-based analyses to different animal diseases [Reference Conteddu21]. The spatiotemporal analyses and maps of bTB outbreaks generated in this study were made possible by the recording of geographic coordinates by the MoAF, specifically for premises with confirmed bTB outbreaks, together with the integration of veterinary epidemiology and geographical expertise.
The use of GIS has made it possible to produce thematic disease maps showing temporal changes in bTB, identify disease patterns and dynamics, detect areas with a high density of bTB outbreaks, visualize spatial relationships to facilitate the interpretation of epidemiological data, and evaluate the stability of infection risk [Reference Garcia-Saenz1]. Analysing the spatial distribution of disease across multiple scales is essential for understanding disease distribution, temporal changes, and transmission dynamics within the population [Reference Conteddu21]. This highlights the importance of prioritizing areas exhibiting spatial clustering in disease control efforts. Geographically targeted disease management and control programmes can contribute to reducing the overall disease burden (prevalence) and minimizing contact between at-risk animals in these areas and the broader cattle population [Reference Pereira4].
Previous studies on the spatial distribution of bTB in Türkiye covering the period 2005–2021 showed that the identification of bTB outbreaks was not evenly distributed across the country. These studies also indicated an increasing trend in the identified number of bTB outbreaks in Türkiye [Reference Çakır and Yakar18, Reference Çakır, Yakar and Keskin30]. Our findings in this study suggest that this increasing trend persisted in 2022 and 2023. Furthermore, a recent study published in 2023 mapped the distribution of cattle population at the district level alongside the national distribution of bTB outbreaks in 2021. The correlation analysis conducted in this study revealed a weak positive association between cattle population density and the number of bTB outbreaks [Reference Çakır and Yakar18].
There is a growing recognition that a better understanding of spatial patterns, the identification of high-density bTB outbreak areas, and the analysis of their relationships with other variables are essential for improving disease control. In this study, two additional years (2022 and 2023) of data were incorporated, allowing the analysis of bTB outbreaks over the 2017–2023 period. Furthermore, spatial and temporal changes in bTB outbreaks were evaluated using KDA and BA for the first time in Türkiye.
The number of identified bTB outbreaks is influenced by the characteristics of the slaughterhouse surveillance system, including the frequency of testing, the diagnostic performance of the TSTs, and the effectiveness of local veterinary authority activities. Under the national bTB control programme, the detection of a positive case during slaughterhouse surveillance is legally followed by epidemiological investigation and tuberculin testing of epidemiologically linked premises. The imperfect sensitivity and specificity of TSTs (single intradermal test: 68.1% sensitivity and 96.7% specificity [Reference Akçay31]; comparative intradermal tuberculin test: 69.8% sensitivity and 98.0% specificity [Reference Sayın32]), together with the persistence of M. bovis in manure and slurry for up to 6 months and environmental contamination, are likely to contribute to the persistence of bTB on affected premises [Reference Allen, Ford and Skuce13, Reference Fielding33]. Furthermore, Çakır et al. reported that at least 45.1% of infected premises had another bTB-affected premise within the same settlement [Reference Çakır34]. Consistent with this finding, ‘latent/subclinical infection within the premises’ was the most frequently identified category in the field epidemiological investigations in the present study (57.9%), suggesting that infection may contribute to the persistence of high-density bTB outbreak areas.
The KDA results showed that the spatial distribution of bTB outbreaks in Türkiye varied across the seven-year study period (2017–2023), while high-density outbreak areas persisted in several provinces across western, central, and eastern Türkiye (Figure 3). The persistence of high-density areas across successive years indicates that, despite temporal changes in the overall distribution of outbreaks, their spatial concentration remained relatively stable in certain regions. These findings suggest that KDA can help identify areas that may warrant greater attention in bTB control programmes and support the prioritization of geographically targeted surveillance and control measures.
Given the role of livestock bazaars as hubs for animal movement and the potential for infected animals to facilitate disease transmission between premises, examining the spatial proximity of bTB outbreaks to these locations is epidemiologically relevant [Reference Çakır34]. In the present study, 88.1% of bTB outbreaks were located within 50 km of livestock bazaars (Table 3). This finding, together with the epidemiological investigation results showing that the ‘purchase of infected animals’ was the second most frequently reported source of infection (19.6%) (Table 1), highlights the potential importance of livestock trade in bTB transmission. Premises proximity to livestock bazaars should be further investigated as a potential factor impacting the spatial distribution of bTB outbreaks in Türkiye, as the location, distance, and role of bazaars play a role not only in animal movements but also in other forms of contact with bazaar environments. For example, frequent visits to livestock bazaars by livestock owners may provide opportunities for indirect transmission through contaminated clothing, equipment, vehicles, or other fomites, even in the absence of direct animal purchase or movement [Reference Çakır34]. Therefore, strengthening biosecurity measures at livestock bazaars, including controls on animal entry and exit, regular cleaning and disinfection, and measures to minimise direct contact during animal trading, may contribute to reducing the risk of bTB transmission. Additional measures, such as pre-sale testing, verification of negative TST status, online or premises-to-premises sales, and quarantine of newly purchased animals, may further reduce transmission risks associated with livestock trade.
Overall, integrating the spatial distribution of bTB outbreaks with the identification of high-density areas, temporal changes in outbreak identification, and epidemiological investigation findings provides an important evidence base for developing more targeted bTB control strategies in Türkiye. The identification of persistent spatial areas, particularly in regions with a high concentration of bTB outbreaks, highlights the value of incorporating spatial epidemiological information into routine surveillance and control planning. In this context, prioritising surveillance and biosecurity measures at livestock bazaars, strengthening the monitoring of undocumented animal movements, and improving the traceability of cattle movements may help reduce opportunities for disease transmission. Spatially targeted interventions could also facilitate more efficient allocation of limited veterinary resources by directing surveillance and control activities towards areas where the risk of disease persistence and distribution is greatest.
Future research should incorporate complementary datasets and multidisciplinary approaches to improve understanding of bTB transmission and inform control strategies in Türkiye. Nationally and regionally representative surveys are needed to update estimates of infection prevalence and to assess its current epidemiological and socio-economic burden. More comprehensive analyses incorporating detailed animal movement data would also help clarify the contribution of animal movements and livestock bazaars to disease spread. Further research should evaluate the performance of existing diagnostic tests and explore the potential value of complementary diagnostic approaches. Finally, involving relevant stakeholders and breeders’ organisations in future research and control programmes, together with targeted training and awareness activities, may facilitate stakeholder engagement and improve the implementation of bTB control measures.
This descriptive study has several limitations. First, the limited number of previous studies on the epidemiology of bTB in Türkiye, together with the lack of recent data on the national prevalence and socio-economic burden of the disease, limited our ability to incorporate these aspects into the present analysis. Second, comprehensive spatial data on all cattle premises in Türkiye (approximately 1.1 million premises) were not available [26]. Consequently, we could not conduct spatial ‘clustering’ analyses that accounted for the population at risk, including premises without reported bTB outbreaks. This limitation is particularly relevant when interpreting the spatial distribution of bTB outbreaks, as the observed distribution may partly reflect the underlying distribution and density of cattle premises, rather than the risk of bTB outbreaks. Furthermore, detailed animal movement data were not available, limiting our ability to directly assess transmission pathways and to distinguish the contribution of livestock bazaars from other movement-related factors. Therefore, the spatial associations identified in this study should not be interpreted as evidence of causal relationships (or risk) for a given area, nor between proximity to livestock bazaars and bTB transmission.
Conclusion
Beyond describing the spatiotemporal distribution of bTB outbreaks, the spatial analyses performed in this study, including mapping, KDA, and BA, identified areas with a high density of outbreaks and demonstrated the distance between bTB outbreaks and livestock bazaars. These findings were interpreted alongside epidemiological investigation data and evidence from the existing literature, providing a broader perspective on the spatial epidemiology of bTB in Türkiye. In addition, the economic burden of bTB during the study period was characterised based on compensation payments associated with animals subjected to conditional slaughter or culling.
The findings of this study highlight the need for a coordinated and effective national bTB control strategy to further evaluate and reduce the risk of continued disease transmission and spread among susceptible cattle and premises. Beyond its impact on cattle health and production, bTB remains a public health concern because of the potential zoonotic transmission of M. bovis and other members of the MTBC, particularly in rural settings where cattle infection is prevalent and socio-cultural practices that increase the risk of zoonotic transmission of MTBC, such as the consumption of unpasteurized dairy products, may occur. Effective control of bTB is therefore important not only for reducing disease transmission but also for mitigating the associated socio-economic and operational burdens, particularly in rural communities.
The findings of this study provide important evidence to inform decision-making and policy development for national bTB control strategies, support the efficient allocation of public resources, identify areas for further work, and guide the management and monitoring of disease control efforts. By integrating spatial analysis with epidemiological investigation data at the national level, this study also provides a basis for future spatial epidemiological research on bTB in Türkiye and may contribute to a better understanding of the spatial epidemiology of the disease at the international level.
Data availability statement
The data that support the findings of this study are available from the corresponding author upon request.
Acknowledgements
As authors, we would like to thank the personnel of the MoAF for providing the data for this research and Assoc. Prof Dr Derya Karataş Yeni for proofreading the manuscript.
Author contributions
Analysing: Ş.Ç., F.O-P.; Data curation: Ş.Ç.; Drawing of maps: M.Y.; Editing: Ş.Ç., M.Y., F.O-P.; Investigation: Ş.Ç.; Methodology: Ş.Ç., M.Y.; Proofreading: F.O-P.; Spatial analyses: M.Y.; Translation: Ş.Ç.; Writing – original draft: Ş.Ç., M.Y., F.O-P. All authors reviewed the results and approved the final version of the manuscript.
Funding statement
The authors did not receive financial support from any institution within the scope of the study.
Competing interests
The authors declare that there are no competing interests.
Ethical standards
Ethical approval was not required for this study.
Declaration of generative AI and AI-assisted technologies in the writing process
During the preparation of this manuscript, the authors used ChatGPT (OpenAI) solely to proofread and improve the language of selected sentences in the revised manuscript. Tables and figures were not written/created by AI or AI-assisted technologies. Following the use of this tool, the authors carefully reviewed and edited the content as necessary and assume full responsibility for the accuracy and integrity of the published manuscript.
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