Bovine Viral Diarrhea Virus (BVDV)
(NY) A female, 3-month-old Ayrshire calf presented in late October for a 1-week history of inappetence, low-grade fever, and mucoid diarrhea. She was drooling excessively and was exhibiting signs of pain including bruxism and an arched back. The calf came from a small, well-vaccinated herd that regularly tests show cows for Bovine Viral Diarrhea Virus (BVDV) using ACE testing. This calf was the only animal displaying clinical signs. The herd overwinters with another small herd, and the dam of the sick calf had lived there during the gestational stage that corresponds with persistent infection (PI) of BVDV in the fetus. Within 24 hours of birth, the calf was removed from the dam and raised with 3 male goats. A number of antemortem tests were performed including a fecal float, salmonella culture, and bovine coronavirus PCR on feces, and PCRs for Bluetongue virus, Malignant Catarrhal Fever, and Epizootic Hemorrhagic Disease on EDTA whole blood. All results were negative. The calf began exhibiting catarrhal nasal discharge and the diarrhea had become profuse and mildly hemorrhagic. Due to the calf’s worsening condition despite broad-spectrum antimicrobial treatment, the decision was made to euthanize. A field necropsy revealed inflammation throughout the gastrointestinal tract and enlargement of the mesenteric lymph nodes. BVDV PCR on the intestine yielded a high positive result, which was corroborated by gross and histologic lesions of the gastrointestinal tract. These findings were consistent with acute mucosal disease.
Acute mucosal disease is an uncommon, but fatal, presentation of BVDV in PI cows. PI calves are a result of BVDV infection with a noncytopathic strain at days 45-125 of gestation, causing the fetus to become immunotolerant of the virus. If these calves become superinfected with a cytopathic strain of BVDV, either through mutation of the persistently infected noncytopathic strain or an external source such as a modified live vaccine, they can develop mucosal disease. Clinical signs include pyrexia, depression, anorexia, profuse diarrhea, decreased milk production, ptylism, mucopurulent oculonasal discharge, and oral erosions. While it is a rare presentation of BVDV, especially in well-managed herds, mucosal disease should remain on the differential list for acutely ill calves refractory to treatment.
Smith, Bradford P. Large animal internal medicine-E-Book. Elsevier Health Sciences (2014): 957-962