Pneumonia in pigs infected with pseudorabies virus and Haemophilus parasuis serovar 4

Six HPCD (hysterectomy-produced, colostrum-deprived) pigs were inoculated endobronchially with pseudorabies virus (PRV) in the right caudal lobe by means of a bronchoscope. Two pigs, killed on days 5 and 7, had severe purulent pneumonia in the right caudal lobe, associated with an accidental Haemophilus parasuis serovar 4 infection. The three surviving animals were treated with antibiotics. The pigs infected with PRV had necrotizing bronchiolitis and alveolitis. PRV antigen was closely associated with necrotic foci, and was sometimes surrounded by profuse H. parasuis antigen. PRV antigen and IgG- and IgA-containing cells were also detected in bronchioalveolar lavage fluid. These results suggested that the PRV infection destroyed respiratory epithelial cells and allowed H. parasuis to proliferate in the lungs.