Interpretive Summary: Infection with bovine viral diarrhea viruses (BVDV) is a source of major economic loss to U.S. cattle producers. BVDV can cause both acute and persistent infections. Both types of infections result in producer losses. Many tests are available to screen herds for animals persistently infected with BVDV. This study was designed to determine if these tests can also be eemployed to detect acute infections. We acutely infected 16 animals with one of six different BVDV strains and evaluated two tests commonly used in diagnostic laboratories for screening for persistently infected animals. We found that these tests did not reliably detect acute infections with any of the six strains. This suggests that acute infections are commonly missed in BVDV screening programs. This is a major problem when you are trying to eliminate BVDV from a herd. These studies also suggest that acute BVDV infections are under reported. This, in turn, leads to an underestimation of the effects of BVDV on animal production.

Technical Abstract:
Bovine viral diarrhea viruses (BVDV) can cause both acute and persistent infections. Diagnostic tests have been designed to detect animals persistently infected (PI) with BVDV. It is not known how reliably these tests detect acute BVDV infections or conversely whether acute BVDV infections are confused with persistent infections in surveys for PI animals. In this study two tests presently in use in diagnostic laboratories, polymerase chain reaction amplification followed by probe hybridization (PCR/probe) of serum samples and immunohistochemical detection of viral antigen in skin biopsies (IHC) were evaluated for their ability to detect acute BVDV infections. Six different BVDV strains were used to infect 16 colostrum deprived, BVDV free and BVDV antibody free calves. Clinical signs, seroconversion and virus isolation indicated that inoculated animals did replicate virus. None of the acutely infected animals were positive by IHC. Virus could be detected in 19% (3/16) of acutely infected animals by the PCR/probe technique. These results indicate that these two methods, commonly used to screen herds for PI animals, will not reliably detect acute outbreaks of BVDV.