Vol. 17, No. 41

Monday, November 9, 1998

1. Provided by Leslie Edwards Reger, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.

Outbreaks for 11/2/98-11/6/98: 3 foodborne gastroenteritis outbreaks in a food service facilities, several cases hepatitis A isolated in a private home

2. The Johns Hopkins Hospital. Information provided by Dr. Ann Smith, Department of Pathology.

Clinical History: On a hot July evening a resident at a hospital in Virginia received a call from the emergency room. The ER physician wanted to admit eight patients to the medicine team on call. All eight patients had been brought in by van from rural Virginia (Powhattan County). All eight patients were male, between the ages of 23 and 48 years old, and complaining of similar symptoms which began between 3 to 9 days ago. The symptoms included malaise, fatigue, weakness, cough, shortness of breath, chest pain, lack of appetite, weight loss, and fevers. Leukocyte counts done in the ER ranged from 3-17,000 and chest x-rays revealed either bilateral infiltrates, hilar adenopathy, or both. The one exception was the finding of diffuse infiltrates in a patient who was known to have AIDS. While the resident on call was gathering the team and hurrying to the ER the patient with AIDS went into acute respiratory distress and bronchoscopy was done and a bronchoalveolarlavage (BAL) specimen was sent to Microbiology. When the resident arrived in the ER the first thing he noticed was that all eight patients were wearing orange jump suits.

Diagnosis: Direct microscopic examination of the BAL specimen using a silver stain (GMS) revealed yeast forms consistent with Histoplasma capsulatum. H. capsulatum is a dimorphic fungi which can be epidemic or endemic and can produce a spectrum of illness from subclinical infection to progressive disseminated and sometimes fatal disease. Laboratory diagnosis is best made by direct visualization of fresh clinical specimens (sputum, blood smears, biopsies) or in preparations of fixed specimens (bone marrow or lung biopsies). Serologic and antigen testing also play a useful role. Antigen testing by ELISA for histoplasma in urine, serum, or CSF is rapid, highly sensitive test in patients with disseminated disease. However, in patients with focal disease it has markedly decreased sensitivity. Clinically opportunistic histoplasmosis develops as a chronic pulmonary disease in those with an underlying defect such as emphysema. Patients with immunosuppressive conditions including AIDS have a much higher risk for developing disseminated disease. In cases of outbreaks or epidemics where there is a heavy inoculum or even a brief exposure to aerosolized spores of H. capsulatum an acute pulmonary infection can occur in an otherwise healthy host, resulting in fever, hypoxia, and pulmonary infiltrates.

Amphotericin B is still the recommended treatment for non-ambulatory patients with histoplasmosis while Itraconazole is an excellent alternative in ambulatory patients or those with mild to moderately severe infection.

Epidemiologic Investigation: After brief discussions with the eight patients it was discovered that they had come from the state prison where up to forty prisoners had become ill within the past week and a half. The prisoners had been sent in equal batches to various ER's in order not to "flood" one particular hospital. A call to the prison led to the discovery that the prison buildings were comprised of cell blocks with attached external walkways for prison guards. There were windows from each cell that opened onto the walkway. For many years prisoners had been throwing trash, vegetable refuse, and waste onto the walkways in order to taunt the guards. After years of accumulated buildup and bird droppings, the guards complained to the prison warden who ordered pressure washing of the walkways to clean up the debris. This aerosolized the Histoplasma that had been deposited over the years thus inoculating the prisoners and leading to the "outbreak."

Discussion: This outbreak, in addition to several others which have been reported in Maryland and nearby states, reemphasizes the fact that endemic histoplasmosis is not confined to the midwestern United States. Studies on outbreaks in Maryland bridge workers have helped to demonstrate the link between bats and human histoplasmosis by isolating H. capsulatum from specimens of bat guano. Additional studies revealed that bats can carry the fungus in their tissues and intestinal tract. Birds have also long been implicated in histoplasmosis outbreaks but have not been found to be natural carriers or successful recipients of experimental Histoplasma infection. It is believed that the contribution of birds to the epidemiology of histoplasmosis probably relates to the conditioning of the soil by their droppings which makes for a suitable environment for the fungus to grow. The fact that disturbing bird or bat droppings has been repeatedly implicated in Histoplasma outbreaks reiterates the need for inspection by local governments or health departments before any large excavation, demolition, or construction projects, etc. are initiated in urban areas where histoplasmosis is endemic.

References:

1. Bartlett PC et al. Bats in the Belfry: An Outbreak of Histoplasmosis. Am J Public Health. 72(12): 1369-72, 1982 December.

2. Bradsher RW. Histoplasmosis and Blastomycosis. Clin Infect Dis. 22 Suppl 2: S102-11, 1996 May.

3. Schlech WF et al. Recurrent Urban Histoplasmosis, Indianapolis, Indiana. Am J Epidemiology. 118(3): 301-12, 1983 September.

4. Sorley DL et al. Bat-Associated Histoplasmosis in Maryland Bridge Workers. Am J Med. 67(4): 623-6, 1979 October.