You have been working in a poultry farm and have had a cough several times in the year. You have been worried if it was due to occupational exposure to poultry. You have often heard about wearing masks but are not sure why these are used. Indeed you need to know more about the possible infections, and their treatments and prevention.
Understanding histoplasmosis
Histoplasmosis is an infection caused by the fungus Histoplasma capsulatum. It is mainly an infection of the lungs but can spread to other parts of the body.
The fungus is found in damp soil which has organic matter from droppings of birds and bats. Birds themselves are not affected by the fungus as their body temperatures are high, though bats are an exception due to the lower temperatures. The fungus may be found in the feathers of wild birds and can contaminate their droppings. Domestic birds like canaries and parakeets are not affected. One however does not get any infection directly either from bats or from another infected person. The infection is acquired by the air-borne spores of the fungus.
Spores are a dormant and resistant reproductive form of the fungus that enables it to tide over and survive in adverse environmental conditions. When the spores find favourable environmental conditions, they form the active forms of the fungus. Spores are extremely light and remain suspended in air or may drift into the air when dirt or other contaminated material is disturbed. The microscopic spores when inhaled can travel along the respiratory passages to reach the lungs. Here these are trapped by cells called macrophages which are defence cells which eat away any harmful material entering the body. These macrophages then travel to the lymph nodes through special channels.
The lymph nodes are special rounded structures that form a part of the immune system. The spores multiply in the nodes and cause inflammation and enlargement of the nodes. The enlarged nodes in the chest can press upon other surrounding structures like the food pipe and air passages to cause obstruction. If the spores escape destruction by the immune system in the nodes, the infection reaches the bloodstream and spreads in the body. Repeated infections can occur though the ones that follow successively are milder than the first one.
Risk factors
Anybody who is exposed to the fungus can be infected. Risk is highest for those who work with infected soil or have close contact with bird or bat droppings. Thus, farmers, pest control workers, gardeners, archaeologists, and geologists are at higher risk. People engaged in poultry, and construction workers working in old buildings, roads, and bridges are also at risk. A more generalized, widespread, and serious infection develops in those who have a weak immune system, the defence system in the body. Thus, babies and young children, elderly, and cancer and organ transplant patients taking drugs to suppress the immune system, and patients with AIDS are more likely to acquire the infection.
Symptoms
Histoplasmosis may range from an entirely asymptomatic mild infection to a fatal serious one. Symptoms appear around 3 to 17 days after exposure. The severity of the disease is dependent upon the number of spores inhaled. Acute symptomatic pulmonary histoplasmosis is a type of illness that may cause fever, headache, chills, sweats, cough, body aches, and loss of appetite. In some cases, there may be arthritis, pain and inflammation in the joints or pericarditis, an inflammation in the sac surrounding the heart. These occur as a result of the heightened response mounted by the immune system to infection.
Spelunker’s lung is a condition characterized by sudden and severe difficult breathing that develops in people exposed for long to bat excrement stirred up by explorers in caves. When the infection has been present for long periods it is called chronic pulmonary histoplasmosis. This mainly occurs in people with an underlying lung problem. The symptoms may be low grade but present for long periods, sometimes years.
Disseminated histoplasmosis occurs when the infection spreads in the body via the bloodstream. In addition to the usual symptoms, one may develop a large liver and spleen, meningitis (an inflammation of the membranes covering the brain), and ulcers in the mouth, tongue, and gut. The lung tissue may be extensively damaged leading to pneumonia and there may be poor function of the adrenal gland, a gland situated close to the kidneys that produces natural steroids, chemical entities that help to combat infections. There may be a rash or nodules on the skin.
Diagnosis
The most definitive diagnostic test for histoplasmosis is a fungal culture. This involves the isolation and growth of the fungus in laboratory conditions from the samples collected for this purpose. Samples may be taken from blood, sputum, mucus or tissue of lymph nodes, lungs or bone marrow. This test takes around 4 weeks and is hence not useful in acute conditions. The samples may be stained and observed under a microscope to identify the fungus. Samples of the urine and blood may be tested for antibodies which are a type of proteins produced by the immune system in response to the infection. The same may be tested for antigens that are the component proteins of the fungus. An X-ray of chest, CT scan of brain, ultrasound of abdomen, and echo or ECG of heart may be done according to the sites involved in infection.
Treatment
Mild cases may not need treatment but the chronic and disseminated disease needs to be treated with antifungal medicines to clear the fungal infection. These include amphotericin B, itraconazole, or fluconazole. These may be given as injection or infusion into the vein, the superficial blood vessel. The duration of treatment will depend upon the severity of the condition.
Prevention
Precautions are needed to prevent exposure to the fungus, especially in regions where the infection is rampant. The contaminated soil or barn should be sprayed with water before handling it. This can prevent the spores from rising into the air. People at risk of exposure should wear face masks when working in caves or poultry, and other areas that have the potential of contamination with bird or bat droppings. These precautions are more important in those with weak immune systems. Histoplasmosis should be treated in time and prevented by taking due precautions. People with occupational risks should be more vigilant.
