Fungal lung infections are difficult to treat, because fungal cells are very similar to human cells (eukaryotic). This makes it challenging to find drugs to attack the pathogen, without doing harm to the host. Pathogenic fungi are often dimorphic, meaning they can grow either as moulds or yeasts, depending on temperature, they thrive at human body temperature and they do well in the moist conditions found in human tissues. Fungal lung infections are often mistaken for something else such as bacterial pneumonia, tuberculosis, influenza or even cancer. Sometimes a fungal infection can exist for some time before a correct diagnosis is made (although this does not happen as often as it used to). No matter what fungus is involved, the symptoms are very similar.
Endemic Fungal Infections
Endemic invaders have special adaptations and characteristics allowing them to infect just about anyone who is exposed. People inhale dozens, hundreds or even thousands of fungal spores every day, depending on environmental conditions. Immunity to fungi is generally strong, but a few species can establish growth in the lung tissue of healthy hosts.
The endemic species are associated with specific geographic locales, and specific substrates (such as bird droppings). Examples of endemic pathogenic fungi and the mycoses they cause are: Coccidioides immitis (coccidiomycosis), Histoplasma capsulatum (histoplasmosis) and Blastomyces dermatitidis (blastomycosis).
Opportunistic Fungal Infections
Opportunistic fungal pathogens rarely cause disease in healthy hosts. They may be established by breathing in spores, injection into the body through a traumatic injury or by colonising severely damaged or burnt tissues.
People with weakened immune systems are susceptible to infection by opportunistic fungi. Cancer patients, immunocompromised patients suffering from HIV/AIDS or those who are on a course of immunosuppressive drugs before and after organ transplant, or bone marrow transplant, are at risk. Often encountered opportunistic fungi and the mycoses they cause include: Aspergillus spp. (aspergillosis) and Cryptococcus neoformans (cryptococcosis).
Symptoms of Coccidiomycosis
Lesions of coccidiomycosis can appear almost anywhere on the body, but in most cases, the place of origin is from a lung infection. From the lungs, the disease can spread throughout the body. It is important to identify and treat the infection (this goes for any fungal infection) while it is still localised to lung tissue. Primary lung infection can remain at a low level with minimal symptoms for a long time before advancing to a full-blown mycosis. Often the lung infection clears spontaneously, leaving the host with immunity to future infection.
Coccidiomycosis should be suspected if a person has visited an area where the disease is known to occur, and does not respond to treatments aimed at bacterial infections. Although the disease is endemic, it is more likely to proceed to an advanced phase in those with weakened immune systems. Symptoms include: • Cough (maybe bloody) • Difficulty in breathing • Chills • Chest pain • Joint and muscle pain • Rash on legs
Chest X-rays may show spots or cloudy regions in the lung. Diagnosis is made by observing characteristic fungal spherules containing endospores in sputum or by an antibody test.
Symptoms of Histoplasmosis
Histoplasmosis is contracted by inhaling spores that have been stirred up from contaminated soil. Visitors or workers in caves, roosts, barns or other areas where bats or birds leave large quantities of droppings are especially prone to infection. Symptoms include:
• Coughing (with or without mucous) • Chest pain • Fever • Hoarseness • Fatigue • Weight loss • Night sweats • Joint pain
A chest X-ray may show numerous small, well-defined and widely distributed lesions, diffuse masses--or nothing at all. Diagnosis is made by culturing the organism from infected tissue or by an antibody test.
Symptoms of Aspergillosis
Aspergillus spores are common in the air everywhere, and everyone breathes them in all the time without harm. For the immunocompromised patient, however, Aspergillus is a dangerous pathogen. The agent most often seen is A. fumigatus although others are reported. If the infection spreads from the lungs to other organs, death is a common outcome. Typical symptoms include:
• Cough (may be bloody) • Breathing difficulty • Headache • Fever • Chest pain • Night sweats
A chest X-ray may show a peculiar and distinctive mass known as a "fungus ball" in the lung. Diagnosis is made by culturing the organism from infected tissue, by microscopic examination of lesions and by antibody tests--preferably all three.
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