Histoplasmosis: an outbreak occurring among young men who visited one cave

Antibody therapy for histoplasmosis

The endemic human pathogenic fungus Histoplasma capsulatum is a major fungal pathogen with a broad variety of clinical presentations, ranging from mild, focal pulmonary disease to life-threatening systemic infections. Although azoles, such as itraconazole and voriconazole, and amphotericin B have significant activity against H. capsulatum, about 1 in 10 patients hospitalized due to histoplasmosis die. Hence, new approaches for managing disease are being sought. Over the past 10 years, studies have demonstrated that monoclonal antibodies (mAbs) can modify the pathogenesis of histoplasmosis. Disease has been shown to be impacted by mAbs targeting either fungal cell surface proteins or host co-stimulatory molecules. This review will detail our current knowledge regarding the impact of antibody therapy on histoplasmosis.

Surface architecture of histoplasma capsulatum

The dimorphic fungal pathogen Histoplasma capsulatum is the most frequent cause of clinically significant fungal pneumonia in humans. H. capsulatum virulence is achieved, in part, through diverse and dynamic alterations to the fungal cell surface. Surface components associated with H. capsulatum pathogenicity include carbohydrates, lipids, proteins, and melanins. Here, we describe the various structures comprising the cell surface of H. capsulatum that have been associated with virulence and discuss their involvement in the pathobiology of disease.

Histoplasmosis in Australia: report of 16 cases and literature review

We describe 16 previously unreported patients with histoplasmosis from Queensland and northern New South Wales, Australia, and review all previous Australian reports, providing 63 cases in total to study (17 cases of acute pulmonary histoplasmosis, 2 cases of chronic pulmonary disease, and 44 cases of systemic disease, including 17 cases of single-organ infection and 27 instances of disseminated disease). All acute pulmonary disease was acquired in Australia, with 52% of systemic disease definitely autochthonous. Most cases of single-organ disease occurred in immunocompetent patients (76%), and were oropharyngeal (53%) in location. Forty-one percent of disseminated disease occurred in patients with human immunodeficiency virus (HIV). Patients with HIV had high rates of systemic symptoms, pancytopenia, fungemia, and hepatosplenomegaly. Oropharyngeal and adrenal involvement as well as systemic symptoms were prominent in immunocompetent patients with disseminated disease, with 6 of 7 cases of adrenal involvement leading to Addison disease. Most systemic disease was diagnosed by culture of Histoplasma capsulatum. Where serology was assessed in cases other than acute pulmonary disease, it was positive in only 32%.Prognosis for patients with single-organ disease was excellent. Disseminated disease was associated with recurrence in 30% and death in 37%. The results of this study confirm several previously known patterns of disease but also provide new insights into this rare but endemic condition in Australia.

Histoplasmosis in two aboriginal patients from Australia's tropical Northern Territory

Endemic histoplasmosis occurs uncommonly in Australia and has not previously been reported in the tropical Northern Territory, nor in Aboriginal Australian patients. We report one suspected and one confirmed case of severe disseminated histoplasmosis in Aboriginal Australians from the Northern Territory. Underlying illness included chronic cardiac disease and Type 1 diabetes mellitus, respectively, and neither patient was infected with HIV. The clinical presentations resembled malignancy. Diagnosis of histoplasmosis was made on the basis of bowel histology in Case 1, demonstrating characteristic yeasts, and lymph node histology and culture in Case 2. Histoplasmosis should be considered in relevant clinical situations, even in HIV-negative patients who have not left Australia.

DIAGNOSIS OF HISTOPLASMOSIS

Endemic mycoses can be challenging to diagnose and accurate interpretation of laboratory data is important to ensure the most appropriate treatment for the patients. Although the definitive diagnosis of histoplasmosis (HP), one of the most frequent endemic mycoses in the world, is achieved by direct diagnosis performed by micro and/or macroscopic observation of Histoplasma capsulatum (H. capsulatum), serologic evidence of this fungal infection is important since the isolation of the etiologic agents is time-consuming and insensitive. A variety of immunoassays have been used to detect specific antibodies to H. capsulatum. The most applied technique for antibody detection is immunodiffusion with sensitivity between 70 to 100 % and specificity of 100%, depending on the clinical form. The complement fixation (CF) test, a methodology extensively used on the past, is less specific (60 to 90%). Detecting fungal antigens by immunoassays is valuable in immunocompromised individuals where such assays achieve positive predictive values of 96-98%. Most current tests in diagnostic laboratories still utilize unpurified antigenic complexes from either whole fungal cells or their culture filtrates. Emphasis has shifted, however, to clinical immunoassays using highly purified and well-characterized antigens including recombinant antigens. In this paper, we review the current conventional diagnostic tools, such as complement fixation and immunodiffusion, outline the development of novel diagnostic reagents and methods, and discuss their relative merits and disadvantages to the immunodiagnostic of this mycosis.

Histoplasmosis in Australia: A report of a case with a review of the literature

Histoplasmosis is a rare but serious fungal infection commonly presenting as mucosal ulceration of the oral cavity. It is increasingly recognized in Australia but the source of infection remains obscure and it is likely to be under-diagnosed. We report a case of chronic mucosal ulceration which failed to fully respond to periodontal therapy. Histology and culture of a gingival biopsy was consistent with histoplasmosis, and the patient responded favourably to treatment with oral itraconazole. Histoplasmosis may present to general dental practitioners as chronic mucosal ulceration and should be considered in the differential diagnosis of such lesions. Diagnosis is best made by culture and histology of biopsy specimens.

Phylogeography of the fungal pathogen Histoplasma capsulatum

Until recently, Histoplasma capsulatum was believed to harbour three varieties, var. capsulatum (chiefly a New World human pathogen), var. duboisii (an African human pathogen) and var. farciminosum (an Old World horse pathogen), which varied in clinical manifestations and geographical distribution. We analysed the phylogenetic relationships of 137 individuals representing the three varieties from six continents using DNA sequence variation in four independent protein-coding genes. At least eight clades were idengified: (i) North American class 1 clade; (ii) North American class 2 clade; (iii) Latin American group A clade; (iv) Latin American group B clade; (v) Australian clade; (vi) Netherlands (Indonesian?) clade; (vii) Eurasian clade and (viii) African clade. Seven of eight clades represented genetically isolated groups that may be recognized as phylogenetic species. The sole exception was the Eurasian clade which originated from within the Latin American group A clade. The phylogenetic relationships among the clades made a star phylogeny. Histoplasma capsulatum var. capsulatum individuals were found in all eight clades. The African clade included all of the H. capsulatum var. duboisii individuals as well as individuals of the other two varieties. The 13 individuals of var. farciminosum were distributed among three phylogenetic species. These findings suggest that the three varieties of Histoplasma are phylogenetically meaningless. Instead we have to recognize the existence of genetically distinct geographical populations or phylogenetic species. Combining DNA substitution rates of protein-coding genes with the phylogeny suggests that the radiation of Histoplasma started between 3 and 13 million years ago in Latin America.

An outbreak and review of cave-associated histoplasmosis capsulati

Three male college students from Florida developed acute onsets of fever, chills, shortness of breath, and cough within one day of each other, and all were eventually hospitalized for four to 29 days. All chest x-ray films showed diffuse reticulonodularities in both lung fields. Laboratory studies confirmed the diagnosis of histoplasmosis. The three students had been 'spelunking' (cave exploring) 6 to 7 days before their onset of symptoms. One of four soil samples collected in the caves was positive for Histoplasma capsulatum by the indirect mouse inoculation procedure. Of three investigators who entered the implicated caves, two developed acute febrile illness within 15-21 days. One investigator was hospitalized for 18 days with a confirmed diagnosis of histoplasmosis. Investigation identified an additional case (the person had entered the caves 6 months before this episode), but was not reported to health authorities. Spelunkers should be aware of the potential risk of histoplasmosis and how to avoid infection. Physicians should be cognizant of cave-associated histoplasmosis, inquire about spelunking in persons who develop febrile respiratory illnesses with diffuse nodularities on chest x-ray films, and report such cases to their health department. A review of 42 reported outbreaks of cave-associated histoplasmosis and the approach to environmental control of infected caves are included.

Disseminated histoplasmosis

The first reported case of disseminated histoplasmosis in Western Australia is described. The diagnosis was delayed because the clinical presentation closely resembled that of tuberculosis, the initial histoplasma serology was negative, and constant severe thrombocytopenia delayed efforts to obtain tissue required for culture and histology. Despite adequate therapy, relapse occurred on one occasion.

Oral histoplasmosis treated with miconazole

A case of localised histoplasmosis of the gingivae, with no osseous involvement is described in a 50-year-old man. The diagnosis was based on histology, growth on culture and a positive histoplasmin latex test. Therapy was commenced with intravenous amphotericin but was changed to intravenous miconazole because of serious immediate side effects and the development of marked renal impairment and moderate suppression of erythropoiesis. Rebiopsy of the gingival margin showed therapy to be effective. No source of the infection could be traced.