Experimental Infection of Calves with Bovine Adenovirus Types 1 and 2

Abstract

Summary Colostrum-deprived calves were inoculated by the respiratory route with 20 ml. suspension of the prototype strain of either bovine adenovirus type I (strain bovine No. 10) or type 2 (strain bovine No. 19). The mean infectivity titres of the virus suspensions were 103.9 TCID50 per ml. and 102.1 TCID50 per ml. respectively. Each calf was inoculated within 24 hours of birth and examined at necropsy when 4 or 7 days old. All calves except one showed a limited clinical response, consisting of nasal and ocular discharges accompanied by moderate diarrhoea, but with no overt clinical pneumonia. One calf died following an acute clinical pneumonia and enteritis after inoculation with type 2 virus. At necropsy, gross lesions of pneumonia were present in all calves but such lesions were discrete and consisted of collapse and consolidation accompanied by emphysema. Significant histopathological changes were seen in the respiratory tract tissues and consisted of mild proliferative bronchiolitis and alveolar collapse. Intranuclear inclusions were found in cells of bronchioles, alveolar cells and in reticulum cells of associated lymph nodes; these inclusions were more numerous 7 days after infection. Virus was recovered from swabs of nasal mucosa, conjunctiva and from faeces of all calves following inoculation up to the time of necropsy. Calves which were inoculated with maintenance medium of uninfected bovine kidney cultures as controls remained normal and free from virus up to the time of necropsy 7 days later.