Some factors in the epidemiology of histoplasmin sensitivity in Williamson County, Tennessee

Current diagnosis of histoplasmosis

Histoplasmosis is a common infection endemic in many regions of America, Asia, India and Africa, with sporadic cases also occurring throughout the world. Although excellent laboratory methods for diagnosis are available, there are deficiencies that must be met by continued research. Clinicians and laboratory directors must be familiar with the uses and limitations of a battery of serologic and mycological tests to accurately diagnose histoplasmosis. Research is needed to reduce false-negative and false-positive results, and to improve the identification of the organism in tissues. Approaches to the diagnosis of histoplasmosis and areas that require further research will be reviewed.

Blindness from presumed ocular histoplasmosis in Tennessee

Tennessee has the highest histoplasmosis infection incidence in the United States. Over 60% of the population reacts positively to skin tests and more than 60 new patients require hospitalization for the treatment of this disorder each year. However, the presumed ocular histoplasmosis syndrome (POHS) remains an uncommon cause of blindness in this state. A retrospective analysis performed with the assistance of 173 Tennessee Ophthalmologists identified 98 new POHS cases in 1980. A similar study, performed in a prospective manner, found 44 new POHS cases in the first six months of 1981. An analysis of recipients of Aid to the Blind revealed 0.5% with POHS; while 2.8% of new applicants for Aid to the Blind had POHS.

Outbreak of acute pulmonary histoplasmosis in members of a wagon train

In August 1980, an outbreak of acute pulmonary histoplasmosis occurred among participants in a wagon train as it traveled through eastern Tennessee. Of the 85 people on the train 69 (81 percent) had evidence of infection with Histoplasma capsulatum. Fifty-four people had symptomatic disease. The source of infection was traced to the site of a former winter blackbird roost in Charleston, Tennessee, that had been partially cleared five years earlier to make a park. Fourteen of 25 soil samples from this site were culture-positive for H. capsulatum. This is the first reported outbreak to involve a large migrant group. The outbreak is unusual in that exposure occurred without excavation, construction or tree-cutting at the site.

The natural course of active choroidal lesions in the presumed ocular histoplasmosis syndrome

Eighty-two patients and 106 eyes with the POHS have been followed for one year or longer. Untreated active choroidal lesions were divided into groupings based on the distance from the center of the CFZ and the reltionship to the border of the CFZ. Twenty-three percent of untreated active choroidal lesions that were located inside the CFZ achieved 20/20 to 20/40 vision. Sixty-three percent of untreated active choroidal lesions that were located outside of the CFZ achieved a vision of 20/20 to 20/40. The active choroidal lesions with the best visual prognosis were 0.25 to 0.5 disc diamterers, demonstrated no growth, and had little or no associated choroidal bleeding. Activation of choroidal lesions in the fellow eye at the site of preexisting atrophic scars was documented in 21% of the eyes. One fellow eye developed a de novo active choroidal lesion. Eighteen percent of the cases had structurally congested nerve heads characterized by slight elevation of the disc and no physiologic depression; 3% of the eyes had drusen of the optic nerve. A relationship may exist between peripapillary scarring in the POHS and these nerve head changes.

Focal choroidopathy in experimental ocular histoplasmosis

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The status of presumed ocular histoplasmosis: including a report of a survey

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