Canine Adenovirus Pneumonia in 2 puppies- CAV-2

Canine Adenovirus Pneumonia in 2 puppies- CAV-2

History: Two English Bulldog puppies (1, and 3 weeks old) had trouble breathing in the morning and by noon had died.

Gross Necropsy Findings:

Lungs: Diffuse dark red to purple, edematous.

Histologic Findings:

Lung: At low power, centered around bronchioles and extending into the interstitium are cellular infiltrates. Bronchiolar epithelium is sloughing off the basement membranes

Lung: At higher power, centered on a bronchiole there is necrosis and sloughing of respiratory epithelium. Epithelia contain nuclear inclusions which fill the nucleus or marginate the chromatin (arrow)

Lung, bronchiole at high power: Intranuclear inclusions are visible, and the lumen of the bronchiole contains necrotic cell debris and degenerate neutrophils, indicating a bacterial component secondary to loss of epithelial defenses.

Lungs, alveolar spaces: The lung is collapsed, alveolar capillaries are congested, and there is necrosis of type 1 pneumocytes, and intranuclear inclusions. There are a few neutrophils present.

Lungs: Multifocal necrosis of bronchiolar respiratory epithelium and alveolar pneumocytes. Alveolar septa are expanded by moderate numbers of macrophages, lymphocytes, plasma cells, and neutrophils (degenerate and intact). Respiratory epithelia contain large basophilic intra-nucelar viral inclusions that displace the chromatin. There is diffuse vascular congestion.

Liver: There are multifocal areas of hepatocellular necrosis with small numbers of macrophages. There are small numbers of macrophages in the portal areas. There is diffuse vascular congestion.

Morphologic Diagnosis: 

Lungs: Multifocal to coalescing broncho-interstitial pneumonia, necrotizing, lymphoplasmacytic and neutrophilic, severe, with intraepithelial intra-nuclear viral inclusions.

Liver:  Multifocal, random, hepatic necrosis, moderate

Bacterial cultures: Small numbers of  non-hemolytic E coli were cultured from the lungs and liver, and small numbers of Klebsiella spp were cultured from the lungs.


The features of the pneumonia are diagnostic for Canine Adenovirus type 2.  This disease affects unvaccinated juvenile dogs and is distinct from disease caused by Canine Adenovirus type 1 (Infectious Canine Hepatitis).  Infections may be mild particularly in vaccinated animals, and limited to the upper respiratory tract, producing a serous or catarrhal rhinitis or tracheitis.  Disease in the lungs is severe when complicated by bacterial pneumonia.  In this case the disease was peracute, the lesions are necrosis with only moderate cellular infiltrates, and no type 2 pneumocyte hyperplasia which takes at least 3-4 days to appear. Bacterial cultures indicate a possible complication with bacterial pneumonia. Common bacterial causes of pneumonia in dogs do include E coli, particularly in newborn pups, as well as Klebsiella pneumoniae, Bordetella bronchiseptica, Pasteurella spp, and Streptococcus spp.  Multifocal hepatic necrosis indicates bacterial sepsis and likely contributed to the acute death in these pups.


Lopez, Alfonso. Respiratory System, Chapter 9 in Pathologic Basis of Veterinary Disease 4th edition, McGavin, M.D., and Zachary, J.F. editors. 2004 Mosby Elsevier.

About Brian

Anatomic Pathologist, VetPath Services, Stone Ridge, NY- musculoskeletal, oral/dental, and sinonasal diseases
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