BVD in Free-ranging Wild Ruminants in Switzerland
In the frame of an eradication program for bovine viral diarrhea (BVD) in Swiss livestock, the question was raised whether free-ranging wildlife could threaten the success of this sanitary measure.
13 February 2013
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Therefore, we conducted serological and virological investigations on BVD virus (BVDV) infections in the four indigenous wild ruminant species (roe deer, red deer, Alpine chamois and Alpine ibex) from 2009 to 2011, and gathered information on interactions between wild and domestic ruminants in an alpine environment by questionnaire survey.
Results
Thirty-two sera out of 1’877 (1.7%, 95% confidence interval [CI] 1.2-2.4) were seropositive
for BVDV, and a BVDV1 sub genotype h virus was found in a seropositive chamois (0.05%,
95% CI 0.001-0.3). The seropositive animals originated from sub-alpine or alpine regions and
significantly more seropositive red deer, chamois and ibex than roe deer were found.
There
were no statistically significant differences between sampling units, age classes, genders, and sampling years. The obtained prevalences were significantly lower than those documented in
livestock, and most positive wild ruminants were found in proximity of domestic outbreaks.
Additionally, BVDV seroprevalence in ibex was significantly lower than previously reported
from Switzerland. The survey on interspecific interactions revealed that interactions expected
to allow BVDV transmission, from physical contacts to non-simultaneous use of the same
areas, regularly occur on pastures among all investigated ruminant species.
Interactions
involving cervids were more often observed with cattle than with small ruminants, chamois
were observed with all three domestic species, and ibex interacted mostly with small
ruminants. Interactions related to the use of anthropogenic food sources were frequently
observed, especially between red deer and cattle in wintertime.
Conclusions
To our knowledge, this is the first report of BVDV RNA isolated from an Alpine chamois.
Nevertheless, our results suggest that BVDV infections are only sporadic in Swiss wild
ruminants, despite regular occurrence of interactions with potentially infected livestock.
Overall, serological, virological and ethological data indicate that wildlife is currently an
incidental spill-over host and not a reservoir for BVDV in Switzerland.
