Biologie de l'infection des bovins par le Pestivirus responsable de la maladie des muqueuses

The virus BVD/MD belongs to the genus pestivirus from the family Flaviviridae, as well as viruses responsible for hog cholera and border disease. BVD/MD virus is responsible for two distinct disease entities in cattle: bovine virus diarrhoea (BVD), which is characterized by high morbidity and low mortality, and mucosal disease (MD) which is sporadic but highly fatal. BFV/MD virus exists under two biotypes among which antigenic pairs: a non cytopathic and a cytopathic biotypes. These biological characters are purely cultural and do not correspond to the in vivo pathogenic behaviour. Recent experiments from our group show that the two biotypes of a same antigenic pair differ by their biological properties in the target animal. The cytopathic strain, contrary to the non cytopathic one, induces belated both humoral and cellular immune responses. Only non-cytopathic strain produces viraemia and nasal excretion. These results confirm the fact that non-cytopathic strains represent an epidemiological dead end. These results also permit to envisage a logical modelisation of the infection at a population level.