Histoplasmosis has not yet been proven to be transmitted to humans by ticks, however, patients with Lyme disease have also tested positive for histoplasmosis after having one or more tick bites.

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 Lyme 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).

Testing for Histoplasmosis



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.

Important- Treat the patient, not the test!

Antifungal medications can be used to treat severe, 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.

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Brief History of Histoplasmosis in Maryland

[Selected quotes were extracted from Med-Chi Newsletter- 2014]

Histoplasmosis, commonly shortened to “Histo” in medical parlance, is endemic to the Potomac River valley. The fungus grows in the soil and is enriched by bird and bat excrement. Birds are not infected by the fungus and do not transmit the disease.

When the soil is disturbed, spores can be inhaled causing infection in the lungs.

Persons in certain dust-generating inhaled causing infection in the lungs.

Persons in certain dust-generating occupations, such as construction or farming, are at risk for acquiring Histoplasmosis.

Mild pulmonary symptoms may resolve without treatment, and more serious pulmonary symptoms may present as pneumonia. In endemic areas, 10% to 25% of HIV-infected people will develop disseminated Histoplasmosis.

Although found throughout Maryland, the presence of Histoplasmosis in western Maryland is highlighted here because of the large number of studies conducted on Histoplasmosis in this region.

Histoplasmosis in this region. In 1991, the last article on Histoplasmosis was published by our predecessor, the Maryland Medical Journal. The 1991 article described what was then a relatively new phenomenon, disseminated Histoplasmosis in AIDS patients.

Today, Histoplasmosis is established as the most common endemic fungal infection

in humans in the United States.

In the 1960s and 1970s, Maryland initiated several important studies establishing the prevalence of Histoplasmosis infection.

Histoplasmosis testing of lifetime resident Montgomery County high

school students reported 71% had been infected.

In Frederick County, 42% of sixth grade students reacted to histoplasmin, as did 55% of high school students in Washington County. A study of Navy recruits revealed that more than 50% of lifetime residents of Washington, Frederick, and Harford Counties had been infected.

In 1970, a Histoplasmosis skin testing survey was conducted in Walkersville among persons aged thirteen years and older. Seventy-four percent of the population participated.

Fifty-nine percent were Histoplasmosis reactors, and 15% had pulmonary calcifications on a chest X-ray.

Skin testing is no longer recommended as a diagnostic or screening test for Histoplasmosis.

In 1979 an outbreak of Histoplasmosis affecting nine of nineteen Maryland state bridge maintenance workers was reported.

The workers had disrupted bat guano during bridge maintenance. Additionally, four epidemiologic investigators became ill with Histoplasmosis following collection of the bat guano.

More recently, outbreaks of Histoplamosis have been reported in neighboring Virginia and Pennsylvania among travelers returning home from church mission trips to South America. The travelers had been renovating churches and engaged in dust-generating activities, such as cleaning indoors and outdoors, and electrical and plumbing activities. The overall attack rate was 61%.

Physicians should consider the possibility of Histoplasmosis among patients presenting with pulmonary symptoms returning from travel abroad.

Histoplamosis is not a reportable disease in Maryland, and thus no prevalence or incidence rates are available.

Maryland Health Services Cost Review Commission data report only three hospital discharges in Maryland from 2010 to 2012, with a principle discharge diagnosis of Histoplasmosis. Thus, it appears that Histoplasmosis is primarily treated on an outpatient basis.

The Eastern Shore of Maryland is occasionally in the route of hurricanes as they spiral up the east coast with their attendant flooding.

While no reports of increased fungal infections related to flooding in the United States exist, there is anecdotal evidence.

Theoretically, infection with fungal species that contaminate buildings, occupants, and the environment could occur. The CDC advises that while Blastomycosis is a potential problem because it can cause serious disease even in persons with normal host defenses, Histoplasmosis is unlikely to be increased as a result of fungal contamination after major hurricanes or floods.

From the Mason-Dixon line to Point Lookout, from Assateague Island to Backbone Mountain, Maryland physicians must be vigilant for a unique melding of regionally prominent and globally associated diseases.

*The views expressed are strictly those of the author and do not represent those of the Washington County Health Department or the Maryland Department of Health and Mental Hygiene. Information for this article is in part from public domains, such as the Centers for Disease Control and Prevention, U.S. National Library of Medicine, the National Oceanic and Atmospheric Administration, and the Maryland Department of Health and Mental Hygiene websites.

Full article HERE.

Last Updated- February 2019

Lucy Barnes