Zoonotic TB: Signs and symptoms

Not all M.bovis infections progress to TB disease, there might be no symptoms at all. The symptoms of TB disease caused by M.bovis are similar to the symptoms of TB caused by M.tuberculosis, which includes fever, weight loss, anorexia, night sweats, etc. Since, the symptoms of Bovine TB are similar to MTB, the clinical picture of sick animal can help in confirmation of diagnosis. 

Clinical Presentations in animals:

• In many animals the course of the infection is chronic, and signs may be absent, even in advanced cases when many organs may be involved. Subclinical signs include weakness, dyspnoea, anorexia, emaciation, enlargement of lymph nodes, and cough, particularly with advanced tuberculosis.
• Lesions are commonly observed in the lymph nodes mainly of the head and thorax, lungs, intestines, liver, spleen, pleura, and peritoneum. Head and neck lymph nodes may become visibly affected, sometimes rupture, drain, and in advanced cases may be greatly enlarged and may obstruct air passages, alimentary tract, or blood vessels.
• Clinical signs vary with the involvement of the lung manifested through cough, dyspnoea, and other signs of low-grade pneumonia which can be induced by changes in temperature or manual pressure on the trachea.
• Digestive tract involvement is manifested by intermittent diarrhoea or constipation, extreme emaciation, and acute respiratory distress may occur during the terminal stages of tuberculosis.
• In the late stages, common symptoms include progressive emaciation, a low–grade fluctuating fever, weakness and inappetence. Animals with pulmonary involvement usually have a moist cough that is worse in the morning, during cold weather or exercise, and may have dyspnea or tachypnea

Clinical Presentations in human:

• M. bovis infection in humans has similar clinical forms as those caused by M. tuberculosis. Most of the symptoms in humans is associated with the extra-pulmonary form of the disease; however, about half of the post-primary cases involve the lung which is responsible for human-to-human transmission of tuberculosis due to M. bovis.
• The common clinical signs of zTB include loss of appetite, diarrhoea, weight loss, intermittent fever, intermittent hacking cough, large prominent lymph nodes, weakness, and so on. Young children infected with M. bovis typically have abdominal infections and older patients suffer from swollen and sometimes ulcerated lymph glands in the neck.
• Pulmonary disease is more common in people with reactivated infections, and this would occur only when some of the animals had active tuberculosis. The symptoms may include fever, cough, chest pain, cavitation, and haemoptysis. The pulmonary form of tuberculosis occurs less frequently and is usually occupationally related.