Experimental Exposure of Naive Alpacas to Different Genotypes of Bovine Viral Diarrhea Virus Isolated from Cattle and Alpacas
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Recent outbreaks of bovine viral diarrhea virus (BVDV) have involved alpacas and evidence demonstrates that alpacas can contract and propagate the virus. The objective of this research was to compare and characterize clinical signs, viremia, nasal shedding, and seroconversion resulting from intranasal inoculation of alpacas with genotype BVDV 1b and BVDV 2 isolated from cattle and genotype 1b of alpaca origin. Three groups of six alpacas were inoculated with a different genotype of BVDV (1b [Group 1], 2 [Group 2], and 1b alpaca-strain [Group 3]). All three genotypes of BVDV induced viremia, nasal shedding and seroconversion in naïve alpacas. No clinical illness was detected in any group. The onset of viral detection in serum was significantly different among groups; the mean onset was 4.0, 2.3, 7.5 d for Groups 1, 2, and 3 respectively. Onset and duration of viral detection in white blood cells was significantly different among groups with onset at 3.0, 2.3, and 4.7 d and cessation at 13.0, 10.0, and 12.3 d, respectively. The mean onset of viral nasal shedding was 6.9 d and was not significantly different between groups. Virus was detected post-inoculation until an average of 8.9 d in nasal secretions and 9.4 d in serum. A decrease in mean leukocyte count was observed in all three groups; however, statistically significant reductions in mean total leukocyte counts were detected only in group 1 between pre-inoculation day -7 and post-inoculation days 4 (p=0.0003), 6 (p<0.0001), and 8 (p=0.0006). Results demonstrate that genotype 1b and 2 strains of BVDV cause alpacas to exhibit viremia and nasal shedding of virus in a temporal pattern that is similar to the outcome of acute infection of cattle.