Toward better control of classical swine fever in wild boars: susceptibility of boar-pig hybrids to a recent Japanese isolate and effectiveness of a bait vaccine

Fukai, Katsuhiko; Nishi, Tatsuya; Yamada, Manabu; Ikezawa, Mitsutaka

doi:10.1186/s13567-020-00821-w

Cited by 13 publications

(24 citation statements)

References 17 publications

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“…After each oral vaccination, wild boars with an antibody response induced by the oral vaccine were obtained in a proportional range of between 40% and 50% in weekly time points, describing the maintenance of the antibody-positive population in CSF affected areas. This statement demonstrates that the efficacy of the oral vaccine in wild boar supports the results of experimental studies of oral vaccines [ 21 , 30 ]. In terms of antibody response, wild boars assumed as being at a recovery status increased apparently after vaccination from 9% to 26%.…”

Section: Discussionsupporting

confidence: 76%

Efficacy of Oral Vaccine against Classical Swine Fever in Wild Boar and Estimation of the Disease Dynamics in the Quantitative Approach

Bazarragchaa

Isoda

Kim

et al. 2021

Viruses

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Classical swine fever virus (CSFV) in the wild boar population has been spreading in Japan, alongside outbreaks on pigs, since classical swine fever (CSF) reemerged in September 2018. The vaccination using oral bait vaccine was initially implemented in Gifu prefecture in March 2019. In the present study, antibodies against CSFV in wild boar were assessed in 1443 captured and dead wild boars in Gifu prefecture. After the implementation of oral vaccination, the increase of the proportion of seropositive animals and their titer in wild boars were confirmed. Quantitative analysis of antigen and antibodies against CSFV in wild boar implies potential disease diversity in the wild boar population. Animals with status in high virus replication (Ct < 30) and non- or low-immune response were confirmed and were sustained at a certain level after initial oral vaccination. Through continuous vaccination periods, the increase of seroprevalence among wild boar and the decrease of CSFV-positive animals were observed. The epidemiological analysis based on the quantitative virological outcomes could provide more information on the efficacy of oral vaccination and dynamics of CSF in the wild boar population, which will help to improve the implementation of control measures for CSF in countries such as Japan and neighboring countries.

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Section: Discussionsupporting

confidence: 76%

Efficacy of Oral Vaccine against Classical Swine Fever in Wild Boar and Estimation of the Disease Dynamics in the Quantitative Approach

Bazarragchaa

Isoda

Kim

et al. 2021

Viruses

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“…However, while the prevalence after vaccine distribution in Germany and France was less than 1% [ 12 , 32 ], 10% of animals in Japan remained infected after 1 year of vaccine distribution. Given the higher prevalence in Japan and lower pathogenicity of the causative strain [ 19 ], there would be a need for greater immunization levels to allow CSF eradication in the wild boar population in Japan.…”

Section: Discussionmentioning

confidence: 99%

“…Since infected wild boars pose a major infection risk to pig farms [ 18 ], there is a need to control CSF spread in wild boars to prevent its introduction to pig farms. An artificial infection study revealed that the recent Japanese isolate of the CSFV in wild boars was moderately virulent; moreover, the effectiveness of the bait vaccine was confirmed through an experimental CSFV challenge using boar-pig hybrids as a wild boar alternative [ 19 ]. However, characteristics of the affected wild boar population and the field effectiveness of the oral bait vaccination remained unclear.…”

Section: Introductionmentioning

confidence: 99%

Epidemiological analysis of classical swine fever in wild boars in Japan

et al. 2021

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Background Classical swine fever (CSF) is a contagious disease of pigs and wild boars that is transmitted through direct/indirect contact between animals or CSF virus-contaminated fomites. When the disease re-emerged in 2018 in Japan, a CSF-infected wild boar was reported shortly after the initial pig farm outbreak; subsequently, the disease spread widely. To control the disease spread among wild boars, intensive capturing, fencing, and oral bait vaccination were implemented with concomitant virological and serological surveillance. This study aimed to describe the disease spread in the wild boar population in Japan from September 2018, when the first case was reported, to March 2020, based on the surveillance data. We conducted statistical analyses using a generalized linear mixed model to identify factors associated with CSF infection among wild boars. Moreover, we descriptively assessed the effect of oral bait vaccination, which started in March 2019 in some municipalities in the affected areas. Results We observed a faster CSF infection spread in the wild boar population in Japan compared with the CSF epidemics in European countries. The infection probability was significantly higher in dead and adult animals. The influence of the multiple rounds of oral bait vaccination was not elucidated by the statistical modeling analyses. There was a decrease and increase in the proportion of infected and immune animals, respectively; however, the immunization in piglets remained insufficient after vaccination for 1 year. Conclusions Conditions regarding the wild boar habitat, including forest continuity, higher wild boar population density, and a larger proportion of susceptible piglets, were addressed to increase the infection risk in the wild boar population. These findings could improve the national control strategy against the CSF epidemic among wild boars.

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“…However, despite strenuous control efforts, almost 2 year after the initial CSF notification, the lack of success in controlling the outbreak is concerning. The continuous notification of CSF in the area might have been attributed to wide spread of the virus within wild boar populations favored by free animal movements, as well as to the emergence of epidemiologically related domestic pig farms [ 76 , 230 ].…”

Section: Emergence Of New Csfv Subgenotype In Endemic Regions Undementioning

confidence: 99%

A Critical Review about Different Vaccines against Classical Swine Fever Virus and Their Repercussions in Endemic Regions

et al. 2021

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Classical swine fever (CSF) is, without any doubt, one of the most devasting viral infectious diseases affecting the members of Suidae family, which causes a severe impact on the global economy. The reemergence of CSF virus (CSFV) in several countries in America, Asia, and sporadic outbreaks in Europe, sheds light about the serious concern that a potential global reemergence of this disease represents. The negative aspects related with the application of mass stamping out policies, including elevated costs and ethical issues, point out vaccination as the main control measure against future outbreaks. Hence, it is imperative for the scientific community to continue with the active investigations for more effective vaccines against CSFV. The current review pursues to gather all the available information about the vaccines in use or under developing stages against CSFV. From the perspective concerning the evolutionary viral process, this review also discusses the current problematic in CSF-endemic countries.

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Toward better control of classical swine fever in wild boars: susceptibility of boar-pig hybrids to a recent Japanese isolate and effectiveness of a bait vaccine

Cited by 13 publications

References 17 publications

Efficacy of Oral Vaccine against Classical Swine Fever in Wild Boar and Estimation of the Disease Dynamics in the Quantitative Approach

Efficacy of Oral Vaccine against Classical Swine Fever in Wild Boar and Estimation of the Disease Dynamics in the Quantitative Approach

Epidemiological analysis of classical swine fever in wild boars in Japan

A Critical Review about Different Vaccines against Classical Swine Fever Virus and Their Repercussions in Endemic Regions

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