Description

Histoplasmosis is a disease caused by the fungus Histoplasma capsulatum (1). The fungus usually grows in soil enriched with accumulations of bat or bird droppings. The disease is acquired via inhalation of spores (conidia) from soil contaminated with bat or bird droppings.

Occurrence

In the United States, H. capsulatum var. capsulatum is found along the Ohio and Mississippi River valleys, mostly in the central and southeastern states (1). Its occurrence has been described on every continent except Antarctica (1,2). Autochthonous human cases have been reported throughout North, Central, and South America, the Caribbean, parts of the Middle East (Iran and Turkey), parts of Asia (Pakistan, India, China, Thailand, Indonesia, Vietnam, Malaysia, Philippines, Burma, and Japan); parts of Europe (northern Italy, Bulgaria, Spain, Hungary, Austria, France, Portugal, Romania, the countries of the former Soviet Union, Great Britain, Ireland, and Norway); parts of Africa; and Australia. Overall, histoplasmosis is rare among returning travelers. Surveillance data on illness in returning travelers from GeoSentinel, a communications and data collection sentinel provider network of 33 tropical and travel medicine clincs, determined that fewer than 0.5% of travelers presenting ill to clinics were diagnosed with histoplasmosis (3,4).

Risk for Travelers

Persons who visit endemic areas and are exposed to accumulations of bat guano or bird droppings are at increased risk for infection (5-8). Not all sources of exposure are obvious when visiting endemic areas (9,10); however, activities such as spelunking, mining, construction, excavation, demolition, roofing, chimney cleaning, farming, gardening, and installing heating and air-conditioning systems are known to be associated with disease (high-risk activities). Other activities may become better recognized as ecotourism and adventure tourism become more common in endemic areas of Central and South America (4,9). While in caves or mines, spending time close to the ground or kicking up dirt infested with bat guano containing H. capsulatum can increase the risk of infection. Histoplasmosis is not transmitted directly from person to person.

Clinical Presentation

Ninety percent of infections are asymptomatic or result in a mild influenza-like illness (2,11-12). Some infections, however, cause acute pulmonary histoplasmosis, manifested by high fever, headache, nonproductive cough, chills, weakness, pleuritic chest pain, and fatigue. Symptoms occur 3-17 days after exposure, and most persons recover spontaneously 2-3 weeks after symptom onset, although fatigue may persist longer. Dissemination, especially to the gastrointestinal tract and central nervous system, can occur in persons with severe immunocompromising conditions (e.g., HIV infection). Reinfection can occur with sufficient exposure, and in these individuals, the incubation period can be shorter.

Prevention

Persons at increased risk for severe disease should be advised to avoid high-risk areas, such as bat-inhabited caves. If exposure cannot be avoided, persons should be advised to decrease dust generation in infested areas by watering the areas before engaging in dust-generating activities and to wear masks and special protective equipment (1). Hosing off footwear and placing clothing in airtight plastic bags to be laundered after engaging in high-risk activities could also decrease the potential for exposure. Further details about protective equipment can be obtained from http://www.cdc.gov/niosh/docs/2005-109/. Transportation of soil, guano, and other potential fomites should be avoided. No effective vaccine for histoplasmosis is currently available.

Treatment

The Infectious Diseases Society of America has developed guidelines for the management of histoplasmosis. Antifungal treatment is not usually indicated for healthy, nonimmunocompromised persons with acute, localized pulmonary infection, because this form of the disease is self limited, often resolving within 3 weeks (12). Persons with persistent symptoms beyond 1 month can be treated with itraconazole or Amphotericin B. All persons with severe disease, including diffuse pulmonary and disseminated histoplasmosis, should be treated with either itraconazole or Amphotericin B. For those persons with immunodeficiency or chronic diseases, treatment may be required for longer periods. Newer azoles may be useful for refractory disease (13,14). Pregnant women for whom treatment is indicated, should be given Amphotericin B. Consultation with an infectious diseases specialist is advised.

References

1. Cano MVC, Hajjeh RA. The epidemiology of histoplasmosis: a review. Semin Respir Infect 2001;16:109-18.
2. Wheat LJ. Histoplasmosis: a review for clinicians from non- endemic areas. Mycoses. 2006;49(4):274-82.
3. Freedman DO, Weld LH, Kozarsky PE, Fisk T, Robins R, von Sonnenburg F, et al.; GeoSentinel Surveillance Network. Spectrum of disease and relation to place of exposure among ill returned travelers. N Engl J Med. 2006;354:119-30.  
4. Panackal AA, Hajjeh RA, Cetron MS, Warnock DW. Fungal infections among returning travelers. Clin Infect Dis. 2002;35:1088-95.
5. Valdez H, Salata RA. Bat-associated histoplasmosis in returning travelers: case presentation and description of a cluster. J Travel Med. 1999;6:258-60.
6. Nasta P, Donisi A, Cattane A, Chiodera A, Casari S. Acute histoplasmosis in spelunkers returning from Mato Grosso, Peru. J Travel Med. 1997;4:176-178.
7. Buxton JA, Dawar M, Wheat LJ, Black WA, Ames NG, Mugford M, et al. Outbreak of histoplasmosis in a school party that visited a cave in Belize: role of antigen testing in diagnosis. J Travel Med. 2002;9:48-50.
8. Centers for Disease Control and Prevention. International notes. Cave-associated histoplasmosis—Costa Rica. MMWR Morb Mortal Wkly Rep. 1988;37:312-3.
9. Weinberg M, Weeks J, Lance-Parker S, Traeger M, Wiersma S, Phan Q, et al. Severe histoplasmosis in travelers to Nicaragua. Emerg Infect Dis. 2003;9:1322-5.
10. Morgan J, Cano MV, Feikin DR, Phelan M, Monroy OV, Morales PK, et al.; Acapulco Histoplasmosis Working Group. A large outbreak of histoplasmosis among American travelers associated with a hotel in Acapulco, Mexico, spring 2001. Am J Trop Med Hyg. 2003;69:663-9.
11. Wheat LJ. Laboratory diagnosis of histoplasmosis: update 2000. Semin Respir Infect. 2001;16:131-40.
12. Wheat J, Sarosi G, McKinsey D, Hamill R, Bradsher R, Johnson P, et al. Practice guidelines for the management of patients with histoplasmosis. Clin Infect Dis. 2000;30:688-95.
13. Restrepo A, Tobon A, Clark B, Graham DR, Corcoran G, Bradsher RW, et al. Salvage treatment of histoplasmosis with posaconazole. J Infect. 2006 [Epub ahead of print].
14. Wheat LJ, Connolly P, Smedema M, Durkin M, Brizendine E, Mann P, et al. Activity of newer triazoles against Histoplasma capsulatum from patients with AIDS who failed fluconazole. J Antimicrob Chemother. 2006;57:1235-9.