What Is Canine Tuberculosis

1 How dogs catch and show the disease

The sources of infection are people, cattle, or cats with active tuberculosis. The bacteria spread mainly through the respiratory and digestive tracts. Crowded, damp, or poorly ventilated housing, fatigue, poor nutrition, and other lung problems all make a dog more likely to fall ill. The incubation period is highly variable – days, months, or even years – depending on the dog’s health, diet, and age, and the course is typically long.

In the early stage there are few obvious whole-body signs: the dog may simply eat erratically and tire or weaken easily, later losing weight steadily and looking depressed. Where the lesions form decides the symptoms. Lung involvement brings a short dry cough at first that later produces thick, mucus-filled sputum. Abdominal organ disease causes poor digestion, weight loss, and anemia. Uterine disease enlarges the belly and yields a pale, gritty discharge streaked with blood, while skin disease produces painless, ulcerated nodules, often around the throat and neck.

Under the microscope the disease is marked by granulomas and cheese-like (caseous) calcified nodules in various organs. The center of each nodule often dies and is surrounded by immune cells, and acid-fast tuberculosis bacteria may be seen as short chains or beads inside the affected cells.

2 When to suspect and how it is confirmed

Unexplained, progressive weight loss, coughing, abnormal lung sounds, stubborn diarrhea, or swollen surface lymph nodes in a group of dogs are reasons to suspect tuberculosis. Microbiological testing should be performed when needed to confirm.

3 Treatment and control

To remove the source of infection, open cases and dogs that test positive on the tuberculin reaction are generally euthanized, and the contaminated premises, tools, and other items are thoroughly disinfected. Dogs of breeding value may be tried on a course of antituberculosis drugs, though success is limited.