Histoplasmosis
Histoplasmosis is a fungal infection primarily affecting the lungs, often resulting in respiratory illness. It is caused by inhaling spores from the fungus *Histoplasma capsulatum*, typically found in bird and bat droppings. Individuals at risk include those working in environments where they may encounter these droppings, such as construction or agriculture, as well as residents of specific regions in the United States and other parts of the world where the fungus is prevalent. Symptoms can vary widely; many people remain asymptomatic, while others may experience fatigue, fever, cough, chest pain, and in severe cases, hemoptysis (coughing up blood) or vision loss.
Diagnosis involves a combination of medical history, physical examination, and various tests, including cultures and imaging studies. Treatment generally requires antifungal medications, with options like amphotericin B and itraconazole being common. Preventative measures are crucial for those at risk, particularly by minimizing exposure to environments associated with bird and bat droppings. While histoplasmosis was once thought to be limited to specific geographic areas, its presence has now been documented in broader locations, highlighting the importance of awareness and prevention.
Histoplasmosis
- ANATOMY OR SYSTEM AFFECTED: Lungs, respiratory system
Definition
Histoplasmosis is a fungal infection that often causes a respiratory illness.
Causes
Histoplasmosis is caused by a fungal infection of the lungs. Humans become infected by exposure to bird and bat droppings.
Risk Factors
Risk factors for histoplasmosis include work that involves contact with bird or bat droppings (such as in an aviary); activities that put one in contact with bird or bat droppings (such as cave exploration); keeping birds as pets; living along river valleys; living in the states of Mississippi, Ohio, Kentucky, Illinois, Indiana, Missouri, or Tennessee; living in eastern Canada, Mexico, Central or South America, Southeast Asia, or Africa; travel to a location where histoplasmosis is common; and having a medical condition, such as human immunodeficiency virus (HIV) infection, that weakens the immune system. Individuals who work in construction, demolition, agriculture, and landscaping may also be at risk for histoplasmosis due to contact with birds and bird droppings. Histoplasma spores may be able to live in the body for decades, according to a case study published in the journal BMJ Case Reports in 2017. The case report described a seventy-year-old man who was diagnosed with histoplasmosis despite having rarely left his home state of Arizona, a region in which Histoplasma spores are not typically found. The man is thought to have inhaled the spores during a brief visit to North Carolina thirty years before he began displaying symptoms of histoplasmosis. While once believed to be relegated only to the geographic areas previously mentioned, in the twenty-first century, histoplasmosis is believed to affect a far greater area than previously thought as Histoplasma capsulatum was detected in soil in Antarctica.
Symptoms
Many people do not have symptoms, but those who do have symptoms include weakness, headache, achy muscles, joint pain, fever, chills, malaise (a feeling of discomfort or uneasiness), hemoptysis (coughing up blood), chest pain, cough, shortness of breath, weight loss, mouth sores, enlarged liver and spleen, skin rashes, and loss of vision.
Screening and Diagnosis
A doctor will ask about symptoms and medical history and perform a physical exam. Tests may include blood tests, a blood culture, a sputum culture, a pulmonary function test, skin testing, urine antigen testing, X-rays of the chest or abdomen (or both), and bone marrow tests.
Treatment and Therapy
Treatment includes the use of antifungal medications, which may include amphotericin B or itraconazole. Newer antifungal medications, such as posaconazole and voriconazole, may also be prescribed. Persons with acquired immunodeficiency syndrome (AIDS) may require treatment with an antifungal medication for the rest of their lives to prevent further attacks of histoplasmosis. However, in the twenty-first century, this may no longer be true for AIDS patients on regular antiretroviral therapy.
Prevention and Outcomes
Persons anticipating being exposed to bird or bat droppings should wear face masks, and persons with weakened immune systems should avoid bird and bat droppings.
Bibliography
"Clinical Practice Guidelines for the Management of Patients with Histoplasmosis: 2007 Update by the Infectious Diseases Society of America." Clinical Infectious Diseases, vol. 45, 2007, p. 807.
Conover, Michael R., and Rosanna M. Vail. Human Diseases from Wildlife. Boca Raton: CRC, 2015.
Des Jardins, Terry R., et al. Clinical Manifestations and Assessment of Respiratory Disease. 7th ed., St. Louis: Mosby Elsevier, 2016.
Hospenthal, Duane R., and Michael G. Rinaldi. Diagnosis and Treatment of Fungal Infections. 2nd ed., Cham: Springer, 2015.
Kaufman, C. A. "Histoplasmosis." Clinics in Chest Medicine, vol. 30, 2009, p. 217.
Longo, Dan L., et al. "Histoplasmosis." Harrison’s Principles of Internal Medicine. 19th ed., New York: McGraw-Hill, 2015.
Mason, Robert J., et al., eds. Murray and Nadel’s Textbook of Respiratory Medicine. 5th ed., Philadelphia: Saunders/Elsevier, 2010.
Myers, Adam. Respiratory System. Philadelphia: Mosby/Elsevier, 2006.
Papadakis, Maxine, et al., editors. Current Medical Diagnosis and Treatment 2015. 54th ed., New York: McGraw-Hill, 2015.
"Treating and Preventing Histoplasmosis." American Lung Association, 7 June 2024, www.lung.org/lung-health-diseases/lung-disease-lookup/histoplasmosis/treatment. Accessed 27 Sept. 2024.
Trilles, Luciana, and Maria Deane. "Molecular Detection of Histoplasma Capsulatum in Antarctica." CDC, Oct. 2022, wwwnc.cdc.gov/eid/article/28/10/22-0046‗article. Accessed 27 Sept. 2024.