Tuberculosis (TB) is a chronic, infectious disease, caused by the bacillus Mycobacterium tuberculosis. It usually affecting the lungs and lymph nodes, but also the abdomen, the urinary and genital organs, the bones, the brain and virtually any organ and tissue in the body. The disease is called tuberculosis because of the formation of characteristic small nodules, which consist mainly of chronic inflammatory cells. There are over 5 million cases of TB in the world, and it is still among the world's leading killers.
Patients with TB usually have chronic weight loss and fever. Other symptoms depend upon the organ affected, with cough being the common complaint because of involvement of the lungs. The doctor can usually pick up an enlargement of the lymph nodes. Because of certain laboratory staining properties TB bacteria are often called "acid fast bacilli", or AFB. There are very few other bacteria which have similar properties, therefore the demonstration of AFB on examination of tissue is virtually diagnostic of TB infection
Diagnosis of TB is not always easy. Lung TB may show typical lesions usually described as cavities. TB of the abdomen does not easily show on X-rays, and ultrasound as well as barium studies are needed. In bone TB there may be destruction of the bones, seen on X-rays. TB of the brain usually needs a CAT scan or MRI for diagnosis. Some immunological tests are available for TB, but none is foolproof. ELISA and SAFA are of questionable utility. Many physicians never get these tests done. The Mantoux (tuberculin) test is usually positive in about 75-90% of cases. Microbiological tests can be done, and include demonstration of AFB* and the polymerase chain reaction (PCR). Unfortunately demonstration of AFB either on a tissue sample, or bacterial culture is often unsussessful since tissues do not usually contain large quantities of bacteria. The PCR is the test of the future. Presently it is not standardized, therefore interpretation is difficult. Moreover it is available in very few places. Endoscopy may be of some value in diagnosis of TB of the gastrointestinal tract, and the urinary tract. If diseased tissue can be biopsied, it must be examined under a microscope (histopathology). Histopathology provides the final diagnosis. If a mass is present, a fine needle aspiration cytology may be performed to harvest tissue, which is then examined under the microscope.
The treatment for all forms of TB is antitubercular therapy ("ATT"). ATT is the treatment for the infection, and is needed in all patients with TB. If the patient has to be operated, ATT may be started before surgery, although this is not mandatory. ATT will be required for 6 months, whether or not surgery has been performed. ATT consists of administration of a combination of drugs. The usual drugs and their side effects are:
Isoniazid (or INH) 300
mg once daily ( occasional liver toxicity)
Rifampicin 450 mg once daily (colours the urine orange, occasional liver toxicity)
Ethambutol 800 mg once daily (eye toxicity)
Pyrazinamide 750 mg twice daily (liver toxicity, may cause stomach upset)
Four drugs are given for 2 months, then the first two for another four months. Other regimes are also used. Most patients have an excellent outcome from abdominal TB, if treated in time.
Filariasis is a chronic illness caused by the
worms Brugia malayi, Wuchereria bancrofti, and less often Loa
loa. It is probably the single commonest chronic infection in the
world, with over 100 million persons affected. Filariasis is seen
in developing countries, especially in south-east Asia, and is
rare in the west. The larva of the worm is called a microfilaria,
and is transmitted by the bite of mosquitoes of various species.
The microfilariae cause an illness called acute filariasis. The
time from mosquito bite to development of acute filariasis is
usually a few months. Acute filariasis is characterized by fever
and other symptoms. During this phase, blood examination
sometimes shows microfilariae, especially if the blood is taken
at night. Later the larval forms grow into adult worms which
reside in the lymph nodes, causing a block in the lymphatic
system drained by the node. This results in chronic filariasis,
with resultant lymphedema in that part of the body.
Acute filariasis is treated with medicines. Diethyl carbamazine (DEC) is the drug most often used. In India, it has even been added to common salt, to lower the incidence of filaria. DEC kills the adult worm, but not the microfilariae. Another drug that is effective in filariasis is ivermectin.