Bronchiectasis is primarily a disease of the bronchi and bronchioles involving a vicious circle of transmural infection and inflammation with mediator release (Barker, 2002). In a large, retrospective study about the demographic, clinical, and radiographic features of bronchiectasis in dogs, conducted in the United States, bronchiectasis was often secondary to known diseases (chronic bronchitis, pulmonary fibrosis) and affected dogs were older (>10 years old). Rottweiler dogs were not considered to have an increased risk (Hawkins et al., 2003). Reports of diffuse bronchiectasis in dogs usually refers to congenital diseases of cilia, e.g., primary ciliary dyskinesia or syndromes similar to Kartagener's syndrome (bronchiectasis, sinusitis, and situs inversus or partial lateralizing abnormality).

This report is based on six cases of severe diffuse bronchiectasis in Rottweiler dogs. All dogs had a history of chronic cough, respiratory distress, and progressive weight loss. The duration of clinical signs prior to admission ranged from days to one year. Dogs weren't related, and were from different localities from the state of São Paulo.

Physical examination findings included respiratory distress and coarse crackles on thoracic auscultation. Hyperthermia was not common finding. The most common hematological findings were leukocytosis with neutrophilia, mild eosinophilia and lymphocytosis. Serum biochemical analyses were unremarkable. All dogs were receiving antibiotics at the admission.

Thoracic radiographic abnormalities were very similar. Initially were observed, large lung opacities, suggestive of mass or lung lob consolidation. Mild pleural effusion was observed in two dogs. After some weeks of treatment lungs were "cleared" and bilateral, diffuse saccular bronchiectasis could be easily identified in all dogs. Trans-tracheal wash samples were obtained from three patients, and cytological evaluation predominantly neutrophilic inflammation. No bacterial or fungal organisms were observed or isolated by culture.

Dogs were treated initially with n-acetylcysteine (300 mg/dog q8h, PO), slow-release theophylline (200 mg/dog q12h, PO), and a 14-day course of amoxicillin-clavulanate (500 mg/dog q8h). Except for antibiotic therapy, all other drugs were maintained life-long; daily exercise (leash walking) was also recommended. Antibiotics were further administered when an acute exacerbation of the disease was suspected (e.g., worsening of respiratory distress, leukocytosis).

Dogs lived for 3 days to 28 months after diagnosis. In all cases, airways were dilated, thickened, and filled with thick, viscous fluid. The most prominent histopathological finding was a constrictive cellular bronchiolitis associated with acute bronchiolitis, characterized by an inflammatory cell infiltrate involving the terminal and respiratory bronchioles, and mucostasis. A remodeling process was also present and characterized by fibrous tissue involving the airway wall resulting in sub-occlusion and bronchiectasis. The cause of death of the animals was a diffuse alveolar damage. Lung specimens of one case were examined by electron microscopy; no ciliary abnormalities were detected.

There is one report of a very similar case of bronchiectasis in a 2 year-old Rottweiler with primary ciliary dyskinesia (Hoover, Howard-Martin & Bahr, 1989). Electron microscopy was performed in just one of our cases, and ciliary abnormalities, other than those attributed to chronic respiratory disease were not detected. Thus, more ultrastructural studies are still necessary.

The syndrome here described is uncommon but it is recognized by the authors and many other veterinarians in Brazil for more than one decade. To our knowledge it has not been described elsewhere. Apparently, males and females are equally affected and Rottweiler-"mixed" dogs are not affected. The age of presentation varies widely.

This syndrome is an idiopathic constrictive bronchiolitis and may represent a unique lung disease in Rottweiler dogs.

References

1.  Barker AF. Bronchiectasis. N Engl J Med. 346(18): 1383-93, 2002.

2.  Hawkins EC, Basseches J, Berry CR, Stebbins ME, Ferris KK. Demographic, clinical, and radiographic features of bronchiectasis in dogs: 316 cases (1988-2000). J Am Vet Med Assoc. 223(11): 1628-35, 2003.

3.  Hoover JP, Howard-Martin MO, Bahr RJ. Chronic bronchitis, bronchiectasis, bronchiolitis, bronchiolitis obliterans, and bronchopneumonia in a Rottweiler with primary ciliary dyskinesia. J Am Anim Hosp Assoc. 25(4): 297-304, 1989.