title: Long-term clinicopathological characteristics of alpacas naturally infected with bovine viral diarrhea virus type Ib.
abstract: BACKGROUND
  Substantial bovine viral diarrhea virus (BVDV)-related production losses in North American alpaca herds have been associated with BVDV type Ib infection.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  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
  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.
authors.affiliation: Department of Clinical Sciences, Cummings School of Veterinary Medicine at Tufts University, North Grafton, MA 01536, USA. daniela.bedenice@tufts.edu
authors.forename: D
authors.initials: D
authors.lastname: Bedenice
authors.forename: E
authors.initials: E
authors.lastname: Dubovi
authors.forename: C L
authors.initials: CL
authors.lastname: Kelling
authors.forename: J N
authors.initials: JN
authors.lastname: Henningson
authors.forename: C L
authors.initials: CL
authors.lastname: Topliff
authors.forename: N
authors.initials: N
authors.lastname: Parry
mesh_terms: D000818:Animals; D002161:Camelids, New World; D016022:Case-Control Studies; D015331:Cohort Studies; D030241:Diarrhea Virus 1, Bovine Viral / Q000145:classification*; D005260:Female; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary; D018182:Pestivirus Infections / Q000473:pathology / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D011247:Pregnancy; D011446:Prospective Studies; D013997:Time Factors; D014766:Viremia / Q000662:veterinary