Histoplasmosis is not, at this time, proven to be carried by ticks or transmitted by ticks, however, patients with Lyme disease have also tested positive for histoplasmosis.

Histoplasmosis is caused by the fungus Histoplasma capsulatum. Symptoms can vary, but the disease often affects the lungs. Other organs can be affected with disseminated histoplasmosis. The disease can be fatal if untreated. Histoplasmosis is common among patients with immune system dysfunction, such as chronically ill patients and AIDS patients.

H. capsulatum fungus grows in soil and material contaminated with bird or bat droppings. The fungus has been found in caves, poultry houses, bat habitats and bird roosting areas. Histoplasmosis is reported to not be contagious, but is contracted by inhalation of the spores from disturbed soil or animal droppings.

The early phase of histoplasmosis can produce respiratory symptoms, with often a cough or flu-like presentation. It is reported that chest X-rays are normal in 40–70% of cases of histoplasmosis. Chronic histoplasmosis can appear to be a tuberculosis-like illness. Disseminated histoplasmosis affects multiple organ systems and is fatal unless treated.

Histoplasmosis is the most common cause of mid-chest inflammation (mediastinitis). It can also cause a nondescript rash and systemic symptoms.

Severe infections can cause hepatosplenomegaly (both liver and spleen enlargement), lymphadenopathy (swollen lymph nodes), and adrenal enlargement. Lesions caused by histoplasmosis have a tendency to calcify (harden) as they heal.

Ocular (eye) histoplasmosis damages the retina and forms scar tissue, which can experience leakage resulting in a loss of vision (similar to macular degeneration).

Diagnosis and Treatment

Samples containing fungus taken from blood, sputum or infected organs can be used to detect the infection. ELISA, antibody or PCR blood tests are also available.

Antifungal medications can be used to treat severe and chronic and disseminated disease cases. Treatment with itraconazole should continue for at least a year in severe cases. In milder cases, oral itraconazole or ketoconazole is generally recommended.