Systemic distribution of viral antigen in alpacas persistently infected with bovine pestivirus.

Recently, confirmed occurrences of persistent bovine viral diarrhea virus (BVDV) infection in North American alpacas have raised concerns about the role of persistently infected (PI) alpacas in transmission of virus among herds, yet only limited pathological descriptions of persistent infections in alpacas have been reported. The objective of this study was to characterize BVDV antigen distribution in 10 PI alpacas of varying age and to compare viral antigen distribution and localization in tissues of PI alpacas with 5 PI calves of varying age. Ocular dysplasia was evident in 1 PI alpaca, constituting the first reported congenital ocular lesion in PI alpacas. Viral antigen was widely distributed in alpaca tissues and was prominent in neurons, endothelial cells, and vascular tunica media myocytes but had limited distribution in lymphoid tissues and moderate distribution in epithelium of several organ systems of alpacas. Macrophages in the alpaca gastrointestinal system submucosa and lymph node medullary sinuses often had prominent labeling. In addition, only 1 alpaca had antigen labeling in the bone marrow in contrast to PI cattle. Labeled cells in calf tissues were more widely distributed, occurring prominently in lymphoid and epithelial tissues. Common features of the 2 host species were widespread antigen labeling and absence of lymphoid depletion.

Long-term clinicopathological characteristics of alpacas naturally infected with bovine viral diarrhea virus type Ib.

BACKGROUND: Substantial bovine viral diarrhea virus (BVDV)-related production losses in North American alpaca herds have been associated with BVDV type Ib infection. OBJECTIVES: To classify and differentiate the long-term clinicopathological characteristics of BVDV type Ib infection of alpaca crias, after natural virus exposure. We hypothesized that persistently infected (PI) alpacas specifically demonstrate growth retardation, clinicopathological evidence of opportunistic infections, and early mortality. ANIMALS: Thirty-five crias naturally exposed to BVDV (18 acute, 3 chronic, 14 PIs), and 19 healthy cohort controls of 5 northeastern alpaca farms were prospectively evaluated over 2 years (September 2005-September 2008). METHODS: Observational cohort-control study. RESULTS: Chronically (viremia >3 weeks) and PI crias demonstrated significantly lower birth weights, decreased growth rates, anemia, and monocytosis compared with control animals. Common clinical problems of PI alpacas included chronic wasting, diarrhea, and respiratory disease. Median survival of PI alpacas that died was 177 days (interquartile range, 555) with a case fatality rate of 50% within 6 months of life. Transplacental infection was confirmed in 82% (9/11) of pregnant females on 1 farm, resulting in the birth of 7 PI crias (7/10 deliveries; 1 animal was aborted). Mean gestation at the beginning and end of BVDV exposure was 64 and 114 days, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: Natural BVDV type 1b infection during early pregnancy resulted in a high incidence of PI offspring. Although PI alpacas may have distinct clinical characteristics, verification of persistent viremia in the absence of endogenous, neutralizing antibodies is essential to differentiate persistent from chronic infection.

Virulence markers in the 5' untranslated region of genotype 2 bovine viral diarrhea virus isolates.

Virulence markers to distinguish high from low virulence bovine viral diarrhea virus genotype 2 isolates have not been previously reported. The objective of this study was to identify virulence markers by evaluating the primary and secondary structures of the 5'-untranslated region of low and high virulence bovine viral diarrhea virus genotype 2 isolates. The nucleotide sequences of the entire 5'-untranslated region mRNA of eight bovine viral diarrhea virus genotype 2 isolates, four of high virulence and four of low virulence, and two genotype 1 reference isolates were determined using a polymerase chain reaction and a 5' Rapid Amplification of cDNA Ends System. Two nucleotide substitutions were identified in the internal ribosomal entry site that distinguished the high virulence from the low virulence genotype 2 isolates. The low virulence isolates had a cytosine at position 219, whereas the high virulence isolates had a uracil. At position 278, a uracil or cytosine was found in the low and high virulence groups, respectively. The substituted bases are virulence markers that were used to identify bovine viral diarrhea virus genotype 2 isolates of high virulence.