Tuberculosis is a chronic mycobacterial infection. It primarily attacks the lungs in more than 80% of the cases, leading to pulmonary tuberculosis. Extra pulmonary tuberculosis occurs in less than 20 percent of cases and affects various organs such as lymph nodes, bone and joints, the uro-genital tract, the meninges, the larynx, eye, intestine, peritoneum etc.
Based on the result of the sputum smear, pulmonary tuberculosis can further be classified as smear positive and smear negative. The disease is present in all parts of the world. In most developing countries the incidence is increasing rather than decreasing and varies from 50-150 smear positive cases per 100,000 of general population with mortality rate ranging from below 5 to 100 deaths in 100,000 of the population.
Recently the disease has been associated with HIV/AIDS and tuberculosis has been recognized as one of the most frequent opportunistic infection in person with HIV infection, due to compromised immunity of such persons. Similarly, the incidence of tuberculosis has increased in places where tuberculosis and HIV infection are highly prevalent.
Although there are no reliable data on the true incidence of tuberculosis in Nigeria, observations have shown that the disease has been on the increase over the past few years. The situation is not different in many other developing countries with dwindling economy and poor living standard and may continue to be so in the fore seeable future unless an intensive control program is embarked upon by such countries.
Mycobacterium tuberculosis (human and bovine strains)
RESERVOIR OF INFECTION: Human and cattles .
MODE OF TRANSMISSION: Transmission of infection is mainly air- borne by droplets, droplet nuclei and dust; thus it is enhanced by over crowding in poorly ventilated accommodation. Infection may also occur by ingestion, especially contaminated milk and infected meat.
SIGNS AND SYMPTOMS OF TUBERCULOSIS
- Weight loss
- General malaise
- Persistent cough for more than 4 weeks
- Chest pain-
PATHOPHYSIOLOGY AND PROGNOSIS
PRIMARY COMPLEX; on first infection, the patient develops primary complex which consist of a small parenchymal lesion and involvement of the regional lymph node, in the lungs, this constitutes the classical Ghon focus, with a small lung lesion and invasion of the mediastinal lymph node- in most cases primary complex heals spontaneously, with fibrosis and calcification of the lesions but the organisms may persist for many years within this focus.