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Serum samples were collected from 385 wild boars between 2010 and 2013 to examine the seroprevalence of influenza A virus (IAV) in Japan. Antibodies against IAV were identified using a commercial kit in 13 wild boars (3.4%). To identify the serotypes, positive sera were examined by virus-neutralization test using representative serotypes and strains. Three wild boars in Yamaguchi and four in Tochigi showed the highest antibody titers against the pandemic H1N1 2009 virus and classical swine H1N1 virus strains, respectively. These data indicate that wild boars may have close contact with humans and domestic pigs and therefore that there is potential for IAVs to reassort in wild boars as they have been shown to do in pigs.

Increasing game meat consumption in Japan requires the dissemination of safety information regarding the presence of human pathogens in game animals. Health information regarding the suitability of these animals as a meat source is not widely available. In this study, we aimed to evaluate the safety of game meat and detect potential human pathogens in wild deer (Cervus nippon) and boar (Sus scrofa) in Japan. Fecal samples from 305 wild deer and 248 boars of Yamaguchi, Kagoshima, and Tochigi prefectures collected monthly for 2 years were examined for the prevalence of Shiga toxin-producing Escherichia coli (STEC) and Campylobacter spp. STEC was isolated from 51 deer consistently throughout the year and from three boars; O-antigen genotype O146, the expression of stx2b, and eaeA absence (n = 33) were the major characteristics of our STEC isolates. Other serotypes included the medically important O157, stx2b or stx2c, and eaeApositive (n = 4) and O26, stx1a, and eaeA-positive strains (n = 1). Campylobacter spp. were isolated from 17 deer and 31 boars. Campylobacter hyointestinalis was the most common species isolated from 17 deer and 25 boars, whereas Campylobacter lanienae and Campylobacter coli were isolated from three and two boars, respectively. Seasonal trends for the isolation of these bacteria were not significant. This study demonstrates that wild game animals carry human pathogens; therefore, detailed knowledge of the safe handling of game meat is needed to prevent foodborne infections.

After wild boar arrived at the Japanese Islands during the Middle-Late Pleistocene, its distribution had spread nationwide, except Hokkaido. Afterwards in the latter half of 19th century, it had shrunk to western part of Japan by the change of the socioeconomic structure of Japan. However, the energy revolution and the economic growth of Japan in 1960's have led to the distribution recovery of wild boar and to increase in agricultural damage by the species. Now the damage by wild boar amounts over 5 billion yen per year in recent years. To solve agricultural problem by wild boar 43 prefectural governments, as of 2019, have planned the Specified Wildlife Management Plan involving feedback system. But few plans adopt ecological investigations and fulfill its feedback system function. As a result, agricultural damage by wild boar have not been decreasing. In addition to the agricultural problem, in September 2019, an outbreak of the C.S.F. in wild boar population is confirmed. The Japanese government is concerned about expansion of its infection and the immediate enforcement of the C.S.F. is required. However, the general public does not understand the ecological characteristic of the wild boar correctly. As a result, when people carry out various wild boar measures, inappropriate technique tends to be used. Therefore, in this paper, I will comment on the ecological characteristic of the wild boar and show the C.S.F. prevention of epidemics from a point of view of the ecology of wild boar.