Wild boar (Sus scrofa) as a possible vector of mycobacterial infections: review of literature and critical analysis of data from Central Europe between 1983 to 2001

Abstract

Infected animals in the wild, which can act as a reservoir and/or vector for the origin of bovine tuberculosis, are a great problem for national programmes seeking to free herds of cattle from the infection. The circulation of Mycobacterium bovis in the wild animal population might cause a slow-down in the progress of control programmes through the reinfection of herds of livestock. The Eurasian badger (Meles meles) and red deer (Cervus elaphus) living in the wild in Great Britain and Ireland, brushtail possum (Trichosurus vulpecula), ferrets (Mustela putorius f. furo) in New Zealand and wild buffalo (Bubalus arnee) in Australia are among already known reservoirs and vectors of bovine tuberculosis. In 7 countries of Central Europe (Bosnia and Herzegovina, Croatia, Czech Republic, Hungary, Poland, Slovakia and Slovenia) bovine tuberculosis in ca􀄴le was controlled as part of national control programmes more than 20 years ago. In the last decade M. bovis has been diagnosed extremely sporadically in cattle and other domestic animals as well as in wild animals held in captivity or living in the wild. This favour­able situation could be threatened by the mycobacteria spreading via the wild boar (Sus scrofa) which is susceptible to mycobacterial infection and very abundant in Central Europe. According to available literary data, mycobacteria were detected in 361 wild boar originating from countries other than those of Central Europe, such as Australia, Bulgaria, Germany, the Hawaiian island of Molokai, Italy and Spain. M. tuberculosis complex (33.9%) and M. bovis complex (39.8%) isolates were most frequently detected in the faeces and/or parenchymatous organs of wild boar. Of other mycobacterial species, M. intracellulare (3.8%), M. avium subsp. avium (3.8%), M. terrae (2.4%), M. fortuitum (2.2%), M. scrofulaceum (2.2%), M. gordonae (0.8%), M. simiae (0.5%), M. szulgai (0.5%), M. xenopi (0.5%), M. smegmatis (0.2%), M. vaccae (0.2%), fast-growing, further unspecified species (0.2%) and unidentified mycobacteria (8.8%) were isolated. Following the analysis of literary data and our own results, it was found that, in the area covered by the above-mentioned 7 countries of Central Europe, a total of 431 wild boar were examined for mycobacterial infections in the years 1983–2001. Tuberculous lesions in parenchymatous organs were found in 43 (10.0%) animals. M. bovis was identified in 22 (5.1%) animals, M. a. avium in 2 (0.4%), M. a. paratuberculosis in 1 (0.2%) animal and atypical mycobacteria in 27 (6.3%) animals. The wild boar may therefore represent, under certain unfavourable epizootio­logical conditions, a vector of some mycobacterial infections in not only animals, but also humans.