Description

Histoplasmosis is a fungal disease caused by Histoplasma capsulatum that affects both dogs and humans. The disease in dogs usually affects the lungs and small intestine.

Symptoms

If symptoms of histoplasmosis infection occur, they will start within 3 to 17 days after exposure; the average is 12–14 days. Most affected individuals have clinically silent manifestations and show no apparent ill effects.  The acute phase of histoplasmosis is characterized by non-specific respiratory symptoms, often cough or flu-like. Chest X-ray findings are normal in 40–70% of cases.  Chronic histoplasmosis cases can resemble tuberculosis;  disseminated histoplasmosis affects multiple organ systems and is fatal unless treated.  While histoplasmosis is the most common cause of mediastinitis, this remains a relatively rare disease. Severe infections can cause hepatosplenomegaly, lymphadenopathy, and adrenal enlargement.  Lesions have a tendency to calcify as they heal. Ocular histoplasmosis damages the retina of the eyes. Scar tissue is left on the retina which can experience leakage, resulting in a loss of vision not unlike macular degeneration.

Diagnosis

Histoplasmosis can be diagnosed by samples containing the fungus taken from sputum, blood, or infected organs. It can also be diagnosed by detection of antigens in blood or urine samples by ELISA or PCR. It can also be diagnosed by a test for antibodies against Histoplasma in the blood. Histoplasma skin tests indicate whether a person has been exposed, but do not indicate whether they have the disease.  Formal histoplasmosis diagnoses are often confirmed only by culturing the fungus directly.

Prevention

It is not practical to test or decontaminate most sites that may be contaminated with H. capsulatum, but the following sources list environments where histoplasmosis is common, and precautions to reduce a person's risk of exposure, in the three parts of the world where the disease is prevalent. Precautions common to all geographical locations would be to avoid accumulations of bird or bat droppings.

• The government of the USA provides a document, Histoplasmosis: Protecting Workers at Risk, which contains information on work practices and personal protective equipment that will reduce the risk of infection.
• Histoplasmosis is common in some Spanish speaking regions; the above document is also available in Spanish: La Protección de los Trabajadores que Tienen un Riesgo de HISTOPLASMOSIS.
• Authors at the University of Nigeria have published a review which includes information on locations in which histoplasmosis has been found in Africa (in chicken runs, bats and the caves bats infest, and in soil), and a thorough reference list including English, French, and Spanish language references.

Treatment

Antifungal medications are used to treat severe cases of acute histoplasmosis and all cases of chronic and disseminated disease. Typical treatment of severe disease first involves treatment with amphotericin B, followed by oral itraconazole.  Treatment with itraconazole will need to continue for at least a year in severe cases.

In many milder cases, oral itraconazole or ketoconazole is sufficient. Asymptomatic disease is typically not treated. Past infection results in partial protection against ill effects if reinfected.

Wikipedia and GNU

The content of this entry is from the Wikipedia article "Histoplasmosis" licensed under the GNU Free Documentation License.