Serological Study of Exposure to Selected Arthropod-Borne Pathogens in European Bison (Bison bonasus) in Poland

Abstract

Bison bonasus is an indigenous species of Central and Eastern Europe with the largest wild population inhabiting Białowieża Primeval Forest; however, free-living and captive European bison are reared in many countries around the world. Despite that the European bison was rescued from the extinction after the First World War, it remains as endangered species. Changing environment as well as human activity may have contributed to the observed increase of the risk of the emergence and re-emergence of pathogens. The aim of the survey was to establish the distribution of four pathogens transmitted by arthropods including three arboviruses [Bluetongue disease virus (BTV), Epizootic haemorrhagic disease virus (EHDV) and Schmallenberg virus (SBV)] and a bacteria (Francisella tularensis) in the main populations of European bison in Poland. A total of 251 European bison originating from eight main populations were included in the study and sampled between February 2011 and December 2014. Serum samples originated from chemically immobilized, eliminated or dead by natural causes animals. Additionally, 65 cervids from Białowieża Forest were tested to compare the seroprevalences of other ruminants inhabiting the same environment. The antibodies to SBV and BTV were found in 76.1% and 24.7% of European bison, respectively. In autumn 2012, simultaneous emergence of SBV and BTV in European bison was observed; however, while SBV has spread in all populations scattered around the country, BTV infections were observed only in the north-eastern part of Poland, where BTV cases have been previously reported in domestic ruminants. European bison age was found to be the only significant risk factor for SBV and BTV seroprevalences; however, this association was connected to the animal size, rather than to the length of exposure. None of the animals tested positive for antibodies against EHDV or F. tularensis. SBV exposure rate of cervids was much lower (35.4%) than in European bison, while BTV seroprevalence was comparable in both groups.

Infectious Disease Monitoring of European Bison (Bison bonasus)

“…During the epizootics more than 30% of European bison kept in Hardehausen died, and the surviving animals received a vaccine containing homologous inactivated BTV-8 [69]. BTV-8 epizootics did not reach Poland; however another strain, BTV-14, was detected almost simultaneously in cattle and in European bison at the northeast of Poland, near the Belarusian and Lithuanian borders [11,70].…”

“…Therefore, combining this with the dynamics of geographical spread of BTV-14 in Poland, use of some illegal vaccine containing or contaminated with this BTV strain was suggested [71]. Serosurveillance of BTV in European bison showed that the infections occurred only in the eastern populations [11]. Interestingly, despite that the discovered BTV-14 has been described as attenuated strain causing only subclinical infection in cattle, significant association between health status of European bison and the presence of specific antibodies was observed [11].…”

“…Serosurveillance of BTV in European bison showed that the infections occurred only in the eastern populations [11]. Interestingly, despite that the discovered BTV-14 has been described as attenuated strain causing only subclinical infection in cattle, significant association between health status of European bison and the presence of specific antibodies was observed [11]. The exposure rate to BTV in selectively eliminated and fallen animals in respect to healthy ones was clear; however multivariable analysis has not confirmed the health status as a risk factor.…”

“…Additionally, the occurrence of epizootic hemorrhagic disease virus (EHDV) infections transmitted by Culicoides spp. in European bison in Poland was also ruled out [11]. However, since some diseases of wildlife considered so far as absent in certain geographic areas such as African swine fever in wild boar or chronic wasting disease (CWD) in cervids become endemic in Europe, the threat of EHD in the future should also be considered real [9].…”

“…Therefore, the establishment of commercial American bison farms disqualifies the immediate vicinity as potential places for the release of European bison into the wild. Moreover, the presence of American bison poses a critical epizootic risk to the European cousin, since they can transmit the pathogens threating European bison health, which are absent or emerging in Europe [9], for example, Fasciola magna invasions [10] or epizootic hemorrhagic disease, caused by EHDV [11]. The close interspecies relationship does not ensure similar susceptibility to diseases.…”