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Experimental infection of European wild boars and domestic pigs with pseudorabies viruses with differing virulence

Thomas F. MüllerInstitute for Epidemiological Diagnostics, Institute of Epidemiology, Federal Research Centre for Virus Diseases of Animals, Seestraße 55, D-16868 Wusterhausen, Germany.

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Jürgen TeuffertInstitute for Epidemiological Diagnostics, Institute of Epidemiology, Federal Research Centre for Virus Diseases of Animals, Seestraße 55, D-16868 Wusterhausen, Germany.

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Robby ZellmerInstitute for Epidemiological Diagnostics, Institute of Epidemiology, Federal Research Centre for Virus Diseases of Animals, Seestraße 55, D-16868 Wusterhausen, Germany.

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Franz J. ConrathsInstitute for Epidemiological Diagnostics, Institute of Epidemiology, Federal Research Centre for Virus Diseases of Animals, Seestraße 55, D-16868 Wusterhausen, Germany.

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Abstract

Objective—To determine susceptibility of European wild boars (Sus scrofa) to infection with pseudorabies virus (PrV) and to characterize the virulence of a wildboar PrV isolate for wild and domestic pigs.

Animals—18 wild boars and 16 domestic pigs.

Procedure—Three groups of 4 wild boars were inoculated with PrV Bartha, Kaplan, and a wild-boar isolate (BFW1) and housed with uninfected pigs. Two groups of domestic pigs (4 and 8 pigs/group, respectively) were inoculated with various doses of BFW1. Animals were observed daily for clinical signs, and samples were tested for PrV excretion and homologous antibodies. After reactivation of latent infection by induced immunosuppression, PrV was detected in tissues of necropsied animals, using cell culture and a polymerase chain reaction (PCR).

Results—Clinical signs depended on virulence of the PrV strain and dose of inoculum. Only infection with PrV Kaplan resulted in severe disease and death. Virus was isolated from nasal and genital swab specimens. Antibodies were first detected on day 7 after inoculation; a specific humoral immune response was delayed in BFW1-infected animals. Virus was isolated from various tissues of Kaplan-infected wild boars, whereas mainly viral DNA was detected in a few tissues of Bartha- and BFW1-infected animals, using PCR after immunosuppression.

Conclusions and Clinical Relevance—European wild boars are susceptible to transmission of PrV infection from domestic pigs and vice-versa. The PrV isolate BFW1 is of low virulence and seems to be adapted to the wild boar population from which it was isolated. (Am J Vet Res 2001;62:252–258)

Abstract

Objective—To determine susceptibility of European wild boars (Sus scrofa) to infection with pseudorabies virus (PrV) and to characterize the virulence of a wildboar PrV isolate for wild and domestic pigs.

Animals—18 wild boars and 16 domestic pigs.

Procedure—Three groups of 4 wild boars were inoculated with PrV Bartha, Kaplan, and a wild-boar isolate (BFW1) and housed with uninfected pigs. Two groups of domestic pigs (4 and 8 pigs/group, respectively) were inoculated with various doses of BFW1. Animals were observed daily for clinical signs, and samples were tested for PrV excretion and homologous antibodies. After reactivation of latent infection by induced immunosuppression, PrV was detected in tissues of necropsied animals, using cell culture and a polymerase chain reaction (PCR).

Results—Clinical signs depended on virulence of the PrV strain and dose of inoculum. Only infection with PrV Kaplan resulted in severe disease and death. Virus was isolated from nasal and genital swab specimens. Antibodies were first detected on day 7 after inoculation; a specific humoral immune response was delayed in BFW1-infected animals. Virus was isolated from various tissues of Kaplan-infected wild boars, whereas mainly viral DNA was detected in a few tissues of Bartha- and BFW1-infected animals, using PCR after immunosuppression.

Conclusions and Clinical Relevance—European wild boars are susceptible to transmission of PrV infection from domestic pigs and vice-versa. The PrV isolate BFW1 is of low virulence and seems to be adapted to the wild boar population from which it was isolated. (Am J Vet Res 2001;62:252–258)