Seventeen students (mean age, 24 years; range, 20-40 years) entered the cave to observe the bats and photograph a small boa constrictor feeding on them. The students were in the cave an average of 26 minutes (range, 3-90 minutes). Fifteen (88%) of the 17 students became acutely ill within 9-24 days (mean, 14.4 days);* 12 remained ill 14 days after onset of symptoms. One student, who did not enter the cave, did not become ill. Signs and symptoms among the 15 ill persons included fever (93%), headache (87%), cough (80%), dyspnea (80%), chest pain (73%); and myalgia (53%). Two patients were hospitalized, but all recovered without antifungal treatment.
Chest x-rays were obtained for 12 of the 15 patients; 10 had bilateral diffuse fluffy nodular parenchymal infiltrates. Late acute-phase and early convalescent-phase serum specimens (3 and 5 weeks after exposure to the cave) and urine specimens (5 weeks after exposure) were obtained from all 15 patients. Twelve of the 15 patients had evidence of histoplasmosis by complement fixation test, immunodiffusion test, or urinary antigen detection test (1,2). Reported by: JE Johnson, RN, BSN, JD Kabler, MD, Univ Health Svc, Univ of Wisconsin- Madison; MF Gourley, MD, DJ D'Alessio, MD, Univ of Wisconsin-Madison Medical School; RW Dodge, MS, R Golubjatnikov, PhD, Wisconsin State Laboratory of Hygiene; JP Davis, MD, State Epidemiologist, Wisconsin Dept of Health and Social Svcs. LJ Wheat, MD, Indiana Univ School of Medicine, Indianapolis. DH Janzen, PhD, Univ of Pennsylvania, Philadelphia. Pan American Health Organization. Div of Field Svcs, Epidemiology Program Office; Immunology Br, Div of Mycotic Diseases, Center for Infectious Diseases; Respiratory Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases, CDC. Editorial Note: Histoplasmosis is caused by inhalation of spores of Histoplasma capsulatum from its natural soil habitat. Growth of H. capsulatum requires moderate temperatures, high humidity, and a source of nitrates, often from decomposing feces of bats or birds. H. capsulatum has been isolated from both bat caves and bird roosts, and human infection has been associated with exposure to both sources (3).
This outbreak is typical of bat-cave-associated histoplasmosis (4). The high attack rate (88%) could be explained by the relatively young age of the persons entering the cave or by exposure to a large inoculum of H. capsulatum spores. The extraordinarily dry ground in the cave also may have increased the dispersion of spores in the cave. H. capsulatum has been more readily isolated from caves under dry conditions than after flooding (5).
Cave-acquired histoplasmosis differs in several respects from histoplasmosis associated with bird roosts. Bats, unlike avian species, may become infected with H. capsulatum (6). Therefore, formaldehyde spraying, a useful control measure for avian-associated sources of histoplasmosis (7), may be ineffective in reducing the risk of infection in a bat cave because bats can recontaminate the cave. Furthermore, skin test surveys have shown that persons living near contaminated caves have a lower prevalence of reactivity to histoplasmin than spelunkers living in the same area (3). This finding suggests that H. capsulatum infection occurs only in persons who enter contaminated caves. In contrast, airborne dispersal of organisms from bird roosts can cause outbreaks involving at least several square kilometers (8).
Much of Santa Rosa National Park consists of mature deciduous dry forest in the relatively dry climate of northwest Costa Rica. During the rainy season (June-November), a seasonal river usually floods the cave that was associated with this outbreak and washes out the bat guano. However, flooding had not occurred because of extraordinarily low rainfall during this year's rainy season. Measured rainfall since 1978 has averaged 160 cm per year, but only 50-70 cm were recorded during 1987. The cave is accessible from a hiking trail and is commonly included on tours of the park led by local field biologists. No illness was reported among groups from the same university who entered the cave in January 1983 and January 1986. Officials of Santa Rosa National Park and field biologists in the area have been notified of the outbreak, and warning signs have been posted outside the cave. References
Kaufman L, Reiss E. Serodiagnosis of fungal diseases. In: Lennette EH, Balows A, Hausler WJ Jr, Shadomy HJ, eds. Manual of clinical microbiology. 4th ed. Washington, DC: American Society for Microbiology, 1985:924-44.
Wheat LJ, Kohler RB, Tewari RP. Diagnosis of disseminated histoplasmosis by detection of Histoplasma capsulatum antigen in serum and urine specimens. N Engl J Med 1986; 314:83-8.
Larsh HW. The epidemiology of histoplasmosis. In: Al-Doory Y, ed. The epidemiology of human mycotic diseases. Springfield, Illinois: Charles C Thomas, 1975:52-73.
Sacks JJ, Ajello L, Crockett LK. An outbreak and review of cave-associated histoplasmosis capsulati. J Med Vet Mycol 1986;24:313-25.
DiSalvo AF, Bigler WJ, Ajello L, Johnson JE, Palmer J. Bat and soil studies for sources of histoplasmosis in Florida. Public Health Rep 1970;85:1063-9.
Emmons CW, Klite PD, Baer GM, Hill WB Jr. Isolation of Histoplasma capsulatum from bats in the United States. Am J Epidemiol 1966;84:103-9.
Centers for Disease Control. Histoplasmosis control: decontamination of bird roosts, chicken houses, and other point sources. Atlanta: US Department of Health, Education, and Welfare, Public Health Service, 1979; HEW publication no. (CDC)80-8380.
DiSalvo AF, Johnson WM. Histoplasmosis in South Carolina: support for the microfocus concept. Am J Epidemiol 1979;109:480-92. *A tour member who experienced any two of the following symptoms within 30 days after returning to the United States was considered to have histoplasmosis: fever, headache, cough, dyspnea, or chest pain.
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