Congenital Infection of Cattle with the Herpesvirus Causing Malignant Catarrhal Fever

Abstract

Summary Nine pregnant cows, which were infected with malignant catarrhal fever virus (MCFV) in late pregnancy, developed the acute disease but virus was not demonstrable in their foetuses 5 to 10 days after onset. Two further cows, which recovered from the experimental disease, produced uninfected calves 2 to 8 months later. A third animal gave birth to 2 calves 14 and 22 months after recovery and both of these showed a delayed reaction to challenge at the age of 31 and 7 weeks respectively. One cow produced her third calf 44 months after inapparent infection with MCFV; thyroid monolayers prepared from this calf developed extensive cytopathic effects which were shown to be due to MCFV of undiminished virulence. The same cow gave birth to 3 further calves, the last being born 80 months after initial infection. All these were shown to be infected with MCFV, one being born with the disease, whereas another did not develop clinical signs of MCF until the age of 17 weeks. The behaviour of passively-acquired neutralizing antibody to MCF and rinderpest viruses was investigated in 2 calves. Antibody to MCFV was partially sensitive to 2-ME treatment and probably had a half-life of 7 to 8 days, whereas rinderpest antibody was catabolized 3 to 5 times more slowly and was not sensitive to 2-ME. It is suggested that the former may have been of the IgG1 class. Colostral antibody did not protect congenitally-infected calves against virus multiplication.