Animal tuberculosis (TB) is a zoonotic disease caused by acid-fast bacteria belonging to the
Earlier reports noted the presence of TB in wild boar in a few European countries (15, 16, 27). Its role in the transmission of TB is not always clear; however, it is believed to depend on various conditions, such as population density, the presence of tuberculosis in other species, feeding and climate (20). Most European cases of tuberculosis in boar have been reported in the Iberian Peninsula. This high incidence is probably related to the prevailing environmental and climatic conditions of the area; for example, during the dry summers typical of the region, animals tend to gather near water pockets and feeding grounds, which is conducive to infection (8). In France, most cases of boar tuberculosis are in areas where bovine tuberculosis has also been diagnosed; hence, the wild boar population is believed to be the key aetiological agent in this environment (21).
The first infection with TB (
The number of wild boar samples tested in 2013–2020 and the number of confirmed TB cases
Year | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | Total |
---|---|---|---|---|---|---|---|---|---|
Number of wild boar tested | 21* | 27** | 2 | 8 | 29 | 1 | 15 | 1 | 104 |
Number positives of ( |
9* | 14** | 2 | 5 | 9 | 1 | 5 | 1 | 46 |
* 2013 – including one wild boar from the Leski county (bordering the Bieszczady county)
** 2014 – including one wild boar from the Przemyśl county (bordering the Bieszczady county)
Another wild boar was obtained from the Bieszczady county
The lymph nodes were removed, cut into small pieces, and then processed for 3 min in an Interscience homogeniser (Schaffhausen, Switzerland). The tissues were then flooded with 5% oxalic acid solution and mixed thoroughly. The supernatant was pipetted into a separate 50 mL Falcon tube (Bionovo, Legnica, Poland) and incubated at 37°C for 20 min. The sample was then centrifuged for 10 min at 3500 ×
The obtained sediment was also used for microscopic examination. The samples were stained using a Gram Staining Kit (Merck Life Science, Darmstadt, Germany) according to the manufacturer’s protocol.
The strains grown on S media were identified using a MGIT TBc kit (Becton Dickinson, Franklin Lakes, NJ, USA), which is an immunochromatographic mycobacterial growth indicator tube (MGIT) test for detecting the MPT64 protein fraction secreted by MTBC cells during cultivation.
The isolates were identified to the species level using the GenoType MTBC test (Hain Lifescience, Nehren, Germany) according to the manufacturer’s protocol (24). The strain was identified by spoligotyping using a genotyping kit (Gentaur Molecular Products, Kampenhout, Belgium) following the manufacturer’s recommendations. This method detects polymorphisms in the chromosomal direct repeat region which are present only in the MTBC genome.
In 22 of the 46 TB positive wild boar (47.8%), tuberculous nodules ranging in size from 2 to 4 mm were found to be present in the submandibular lymph nodes. In the mediastinal lymph nodes, the changes were larger, reaching diameters of approximately 10 mm (Fig. 1), but less common, being present in only four individuals (8.7 %). In all wild boar with tuberculous lesions in the mediastinal lymph nodes, nodules were also visible in the submandibular lymph nodes.
The mycobacteria showing growth on the S medium were initially classified as
Description of SB2391 spoligotype
Pattern | Octal code | Hex code | Spoligotype | Animal of strains) (number |
---|---|---|---|---|
□■□□□□□□□□□□□□□□■■■■■■■■■■■ □■■■■■■■■■□□□□□□ | 200003777377400 | 20-00-1F-7E-FF-40 | SB2391* | wild boar (46) |
* — Assigned by the
In wild boar, control of TB is not mandated by national or European Union regulations. Pursuant to the provisions of the Act of March 11, 2004 (9) on the protection of animal health and combating infectious animal diseases, TB caused by
Control measures apply to outbreaks of TB as a category B disease in cattle, buffalo, and bison, both as livestock and free-living animals. However, among other species of even-toed ungulates, including wild boar, the disease is classified as category D or E and no such control is needed; category D makes it obligatory only to meet specific requirements and standards in the trade of animals, especially in international trade, and category E imposes only the surveillance and notification of identified outbreaks of such diseases.
Most
The problem of TB in the wild boar population in the Bieszczady Mountains is growing, and it is possible that the disease is endemic in the Lutowiska district, as implied by the number of confirmed infections among hunted animals. Animal tuberculosis in the Bieszczady Mountains affects not only bison and wild boar, but also other species of free-living animals. In this area,
The distribution and prevalence of the disease are also driven by the dynamic growth of the bison population in these areas, which is highly susceptible to infection with bovine tuberculosis (3, 12, 22, 29).
There is a pressing need to continue current administrative activities, including live monitoring of the health of wild boar and other free-living animals in the natural environment. In addition, passive monitoring is needed for tuberculosis in predators, especially wolves, which function as indicator species of tuberculosis infections in free-living animals in the Bieszczady Mountains (17). Additionally, considering that the problem of TB in wild boar in this region is related to the occurrence of infections in European bison, it may be worth introducing active monitoring of the bison population. This could consist of limited annual random shooting and examination of at least 10% of bison from each separate subpopulation,
It should be noted that, in accordance with Commission Delegated Regulation 2020/689 (5), a confirmation of MTBC infection in animal populations other than farmed cattle does not affect the TB-free status of a Member State or MTBC-free zone, provided that effective measures are implemented and periodic assessment is undertaken to prevent transmission of MTBC infection to farmed cattle. The endemic nature of tuberculosis in free-living animals in the Bieszczady Mountains poses a real risk of infection to local cattle and may hence have a direct impact on the official TB-free status of Poland (2). Planned action must be taken to monitor the disease, prevent further transmission of infection and minimise threats to public health.
Following the discovery of tuberculosis in wild boar in the Bieszczady region, a potential threat to both human and animal health, the Provincial Veterinary Inspectorate in Krosno carried out a risk analysis and subsequent administrative measures; these efforts were supported by subordinate veterinary services, State Forests and the Polish Hunting Association. The following
The local media were also informed, in order that information about the threat could be disseminated to the local population and tourists. Medium-term and long-term activities were undertaken, which were the preparation and distribution of information leaflets and general materials about the prevalence of tuberculosis in free-living animals. Training was also provided for hunters and employees of the State Forests and the Bieszczady National Park: in 2013, 14 such training sessions were held for a total of 411 participants. Hunters were issued recommendations for dealing with hunted wild boar in areas at immediate risk of tuberculosis outbreaks as well as adjacent areas (Bieszczady, Lesko, Sanok and Przemyśl counties).
In the Bieszczady county, the wild boar population was monitored passively, all samples from dead animals were tested for tuberculosis, and wild boar with suspicious organ changes were monitored actively. With the consent of the Chief Veterinary Officer, the requirement that a fifth of the herds in the Bieszczady county should undergo annual surveillance for tuberculosis was changed to a blanket requirement applying to all the county’s cattle herds until 2019. Other species of free-living animals, especially bison and predators of protected species,