Seroprevalence of histoplasmosis in Kampala, Uganda

Abstract

Histoplasmosis is endemic to the Midwestern United States, but cases have been reported nearly worldwide. A 1970 study found 3.8% skin test sensitivity to Histoplasma capsulatum in Uganda but no systemic study of histoplasmosis exposure has occurred since the onset of the human immunodeficiency virus (HIV) pandemic. This study investigated the seroprevalence of H. capsulatum and sought previously undetected cases of histoplasmosis in Kampala, Uganda. Serum, cerebrospinal fluid (CSF) and/or urine specimens were obtained from HIV-infected persons with suspected meningitis. Specimens were tested for H. capsulatum IgG and IgM by enzyme immune assay and Histoplasma antigen. 147 of the 257 subjects who were enrolled had cryptococcal meningitis. Overall, 1.3% (2/151) of subjects were serum Histoplasma IgG positive, and zero of 151 were IgM positive. Antigen was not detected in any serum (n = 57), urine (n = 37, or CSF (n = 63) samples. Both subjects with serum Histoplasma IgG positivity had cryptococcal meningitis. Histoplasma capsulatum IgG was detected at low levels in persons with HIV/AIDS in Kampala, Uganda. Histoplasmosis is not widespread in Uganda but microfoci do exist. There appears to be no cross-reactivity between Cryptococcus neoformans and Histoplasma antigen testing, and cryptococcosis appears to be at most, a rare cause of positive Histoplasma IgG.

Keywords: Diagnostic Techniques and Procedures; Histoplasmosis; Histoplasmosis capsulatum; Human Immunodeficiency Virus; Validation Studies; seroepidemiologic studies.

Figure 1.

Scatter plots of serum Histoplasma Enzyme Immunoassay IgG and IgM results. Note : Figure 1a displays the results of serum EIA Histoplasma IgG testing with the positive cutoff noted by a horizontal line at 15 units and the positive results at 26 and 17 units. Figure 1b displays serum IgM EIA results with the positive cutoff noted by a horizontal line at 20 units.