Short communicationSeroprevalence of pestivirus in four species of alpine wild ungulates in the High Valley of Susa, Italy
Introduction
The family of pestiviruses contains three viruses that cause important livestock diseases: Classical Swine Fever Virus (CSFV), Bovine Virus Diarrhea Virus (BVDV) and Border Disease Virus (BDV). To control CSFV a compulsory eradication program is implemented in the whole European Union. Similarly, in several countries in Europe compulsory and voluntary eradication programs exist for BVDV in cattle herds (Bitsch and Ronsholt, 1995, Greiser-Wilke et al., 2003, Moennig and Greiser-Wilke, 2003). In Italy and France, voluntary BVDV control programs for cattle have been described (Dufour et al., 1999, Ferrari et al., 1999). No BDV control programs for sheep have been described in Europe. However, Border Disease is considered an economically important disease in sheep farming (Nettleton et al., 1998).
The harbouring of infectious agents by wildlife is recognized as a risk for domestic livestock (Frölich et al., 2002). Wildlife, once infected, can serve as a reservoir of infectious diseases that form a constant threat of infection to livestock. Knowledge of CSFV prevalence in wild boar (Sus scrofa) is of major importance for the control of this disease in Germany (Laddomada, 2000) and Italy (Zanardi et al., 2003). To make control and eradication programs successful on the long-term, presence of pestivirus in wildlife populations should be monitored. Several surveys to estimate the seroprevalence of pestiviruses in wildlife have been performed in the past decade (Baradel et al., 1988, Depner et al., 1991, Frölich and Hofmann, 1995, Frölich and Flach, 1998, Schmitt and Wittkowski, 1999). In a study performed in 1988 in the French Alps, a low BVDV seroprevalence was found in roe deer (0.7%) and chamois (5.6%), while no red deer were seropositive (Baradel et al., 1988). In a more recent survey, performed in the northern Alps of Italy, none of 145 chamois was BVDV seropositive (Citterio et al., 2003). Epidemics of Classical Swine Fever have been reported in wild boar in the Lombardy region of the Italian Alps between 1998 and 2002 (Zanardi et al., 2003).
Sometimes pestivirus isolates from wildlife may reveal a new subtype or strain (Hamblin and Hedger, 1979, Depner et al., 1991, Frölich and Hofmann, 1995). Virus neutralization tests (VNT) to detect and study pestivirus antibody in Chamois have not been performed before. The use of the VNT to analyze pestivirus seropositive chamois can give an indication for the existence of a new subtype or strain of pestivirus.
Although overlap exists between habitat of wildlife and pastures used for domestic livestock, such as sheep and cattle (Mussa et al., 2003), and pestivirus transmission between domestic livestock and wildlife could easily occur, an estimation of pestivirus seroprevalence in the four wild ungulate species examined in this study has never been performed in the north-western part of the Italian Alps.
The goal of this study was, therefore, to investigate the seroprevalence of pestivirus in four alpine wild ungulates: red deer (C. elaphus), roe deer (C. capreolus), wild boar (S. scrofa) and chamois (Rupicapra rupicapra) and to determine titers using VNT for four strains of pestivirus in chamois and wild boar.
Section snippets
Area
All samples were collected from alpine game in the area of the High Valley of Susa (Alta Valle di Susa), north-west Italy. The area is naturally bordered in the north by the French border (Haute Morienne-Savoye), in the east by the lower part of the Susavalley, in the west by the Hautes Alpes and in the south by Chisone Valley (Valle del Chisone). The heights vary between 800 and 3500 m above sea level. The vegetation is a mixture of pine and foliage trees and alpine pasture, some parts are bare
Results
In total 375 samples were screened for pestivirus antibodies by ELISA (Table 1). No antibodies were found in the 73 samples of roe deer, while 7 (12.5%) and 8 (5.9%) of 56 and 136 samples of wild boar and red deer were ELISA-positive, respectively. The highest number of ELISA-positive samples were found in chamois: 28 (25.5%) of 110 samples.
The level of neutralizing antibody titers in chamois were in the same range when tested against representatives of four different pestivirus groups. Titers
Discussion
In this study, we found seropositivity of antibodies against pestivirus in three out of four investigated species of large alpine game. The highest prevalence was found in chamois: 25.5%. Baradel et al. (1988) have found a pestivirus antibody prevalence in chamois of 5.6% (4 out of 72 positive). In our study, prevalence of pestivirus antibody in wild boar was lower than in chamois: 12.7%. However, in earlier surveys among wild boar in the same area the prevalence was lower: 5.0% (Rossi, L.,
Conclusion
Pestivirus antibodies were found in three out of four large alpine ungulates in the High Valley of Susa. Seroprevalence was particularly high in chamois. More samples are needed to isolate and characterise the pestiviruses that circulate in these animals.
Note added to proof
Recent work by Arnal et al. (2004) and Hurtado et al. (2004) suggest that a pestivirus strain, found in death and diseased Pyrenean chamois (Rupicapra pyrenaica pyrenaica) could be typed as a separate strain, BDV-4, closely related to BDV. This supports the hypothesis of the possibility of a unique pestivirus strain in this population of chamois in the Italian Alps.
Acknowledgements
Dr. Luca Rossi, Dario Dominici, Manuela Ferra and the hunters of the Comprensorio Alpino TO 2 are gratefully acknowledged for the help in collecting the blood samples. The authors thank Metje Koopmans, CIDC-Lelystad, Wageningen University and Research Centre, for her skilful technical assistance and Dr. P. Becher, Institute of Virology, Justus-Liebig University, Giessen, Germany, for investigating the sera for the presence of pestivirus.
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