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Abstract

Immunologic and occupational aspects of the susceptible population exposed to Histoplasma capsulatum, the causative agent of histoplasmosis were analyzed in the Mexican State of Guerrero. Three areas were studied, Juxtlahuaca, Olinala, and Coyuca; in the first two, their populations refer contact with bat guano and/or avian excreta, which contain nutrients for fungal growth, while the Coyuca population referred no contact with the above mentioned excreta. Previous infection with H. capsulatum was determined by histoplasmin-skin test, and the response was higher in men than in women (93.87, 85.71, and 6.6% for men, and 78.94, 66.6, and 0% for women) in Juxtlahuaca, Olinala, and Coyuca, respectively. Labor activities related to a persistent contact with the fungus were considered as an occupational risk factor, histoplasmin-skin test reached 88.57 and 36.36% of positive response in individuals with high and low risk activities. A high percentage of histoplasmin responses was observed in subjects with constant contact with H. capsulatum, such as, cave-tourist guides, peasants, and game-cock handlers, and generally they developed the largest diameter of skin reactions. Genetic risk factor was determined by studying the gene frequency of the Major Histocompatibility Complex antigens in a sample of individuals and their degree relatives in Juxtlahuaca, Olinala, and Coyuca. Significant differences were found for HLA-B22 and B17 antigens in Juxtlahuaca, and for HLA-B22 in Olinala, in comparison to the usual gene frequency observed in the normal Mexican population. HLA results were important, considering that HLA-B22 was previously found to be possibly related to pulmonary histoplasmosis in Guerrero.

Distinguishing Benign Mediastinal Masses from Malignancy in a Histoplasmosis-Endemic Region

“…[15] Although non-Hodgkin lymphoma is more common in whites than blacks and genetic differences in susceptibility to histoplasmosis have been reported, these factors are unlikely to account for a difference of this magnitude. [16, 17] Residential areas in the Memphis metropolitan area had racial dissimilarity indices of 32-66% over the study period suggesting that, as previous studies have illustrated, differences in exposure or the intensity of exposure to infectious conidia in the environment at the neighborhood level might contribute to higher rates of histoplasmosis in some racial and ethnic groups. [16, 18]…”

Calcified Granulomatous Disease: Occupational Associations and Lack of Familial Aggregation

“…Outside of outbreaks, occupational associations with histoplasma exposure have been estimated using skin testing. Such studies have demonstrated higher rates of histoplamin reactivity associated with various occupations including poultry workers [29, 33], cave tourist-guides [29], guano collectors [29], and farmers [34]. To our knowledge, our study is the first to demonstrate association between the granulomatous sequelae of histoplasma exposure and occupation.…”

“…One study demonstrated higher gene frequencies of HLA-B22 and HLA-B17 observed in areas of higher rates of histoplasmin skin reactivity [29]. Numbers in this study were limited to fewer than 30 subjects per area, and association with histoplasmosis was speculative.…”

Epidemiology of Histoplasmosis

“…Patients at high risk for reactivating latent infection and developing disseminated histoplasmosis are those chronically receiving corticosteroids or chemotherapy, those receiving anti-cytokine therapies (tumor necrosis factor alpha or gamma interferons antagonists), individuals who have received solid organ transplantation, and patients with advanced HIV infection [63,67]. Additional risk factors for histoplasmosis include smoking [69], COPD [70], extreme ages (infants younger than 2 years old, elderly older than 50 years old) [71], and genetics deficiencies (IFN-γ receptor 1 deficiency or histocompatibility complex haplotypes) [72,73].…”