Histoplasmosis: Epidemiology in Latin America

Disseminated Histoplasmosis in an Indigenous Child With Malnutrition: A Case Report

Histoplasmosis is a mycosis caused by Histoplasma capsulatum, a dimorphic fungus endemic to areas with nitrogen-rich soil, like the one contaminated with bird and bat excrement. Patients with a deficient immune response are especially at risk for developing invasive infections, such as disseminated histoplasmosis, and secondary immunodeficiency can be a consequence of malnutrition. This case report presents a 15-month-old male infant with malnutrition who presented with signs and symptoms of disseminated histoplasmosis, including fever, malaise, weight loss, cough, and diarrhea. The infant came from a geographic area where histoplasmosis is endemic, and he was a member of a cultural group with a higher prevalence of histoplasmosis than the general population. On physical examination, hepatosplenomegaly, lymphadenopathy, and lung crackles were found, which are common in most patients with histoplasmosis. The keystone of diagnosis of H. capsulatum infection is antigen detection, but the criterion standard is isolation of the organism from body specimens through laboratory culture. Histological diagnosis is especially useful for rapid diagnosis. Treatment of disseminated histoplasmosis in the pediatric population consists of deoxycholate amphotericin B for four to six weeks followed by itraconazole to complete a total of three months of treatment. Despite the involvement of multiple organ systems, the patient recovered satisfactorily after the completion of amphotericin B treatment for one month and the resolution of his malnourishment.

HIV and COVID-19 in Latin America and the Caribbean

PURPOSE OF REVIEW

Latin America and the Caribbean (LAC) has been hit hard by COVID-19 due to political instability, flawed health systems, and structural inequalities. The repercussion of the pandemic on vulnerable populations, like people living with HIV (PLWH), is complex. This review aims to explore the interactions between the HIV and COVID-19 pandemics in this region.

RECENT FINDINGS

Data regarding the interactions of HIV and COVID-19 in LAC is scarce. Only case reports or small case series have been published regarding the clinical course of COVID-19 in PLWH and regarding the clinical course of COVID-19 in PLWH, which appears to be similar to the general population. The pandemic has disrupted prevention and treatment of PLWH. However, there have been country efforts to counteract those effects. There are some lessons from the HIV response which have been effectively applied in the region to address COVID-19. COVID-19 has had an unprecedented impact on the cascade-of-care among PLWH in LAC. There is a need for longitudinal studies that assess clinic implication of these pandemic interactions in LAC.

New Histoplasma Diagnostic Assays Designed via Whole Genome Comparisons

Histoplasmosis is a systemic fungal disease caused by the pathogen Histoplasma spp. that results in significant morbidity and mortality in persons with HIV/AIDS and can also affect immunocompetent individuals. Although some PCR and antigen-detection assays have been developed, conventional diagnosis has largely relied on culture, which can take weeks. Our aim was to provide a proof of principle for rationally designing and standardizing PCR assays based on Histoplasma-specific genomic sequences. Via automated comparisons of aligned genome contigs/scaffolds and gene (sub)sequences, we identified protein-coding genes that are present in existing sequences of Histoplasma strains but not in other genera. Two of the genes, PPK and CFP4, were used for designing primer sets for conventional and real-time PCR assays. Both resulted in a 100% analytical specificity in vitro and detected 62/62 H. capsulatum isolates using purified DNA. We also obtained positive detections of 2/2 confirmed H. capsulatum clinical FFPE (formalin-fixed paraffin-embedded) samples using both primer sets. Positive control plasmid 10-fold serial dilutions confirmed the analytical sensitivity of the assays. The findings suggest that these novel primer sets should allow for detection sensitivity and reduce false positive results/cross-reactions. New assays for detecting pathogenic fungi, constructed along these lines, could be simple and affordable to implement.

Progressive disseminated histoplasmosis in Latin America and the Caribbean in people receiving highly active antiretroviral therapy for HIV infection: A systematic review

Histoplasmosis is the most clinically significant mycosis in Latin America; still it has been neglected in people with human immunodeficiency virus (HIV). There is limited information about its contribution to morbidity and mortality in this population. We conducted a systematic review of scientific literature to provide an estimation of the frequency and mortality of histoplasmosis among people with HIV receiving highly active antiretroviral therapy (HAART) in Latin America, and factors associated with mortality. We searched articles in PubMed, Scopus, WHO Global health library, and Scielo using different combination of terms including "histoplasmosis" and HAART. We identified 949 articles, removed 662 duplicated; screened 287 abstracts; reviewed full text of 53 articles; and selected 15 articles that provided information on the number of patients studied, included patients receiving ART, and reported any measure of frequency estimate for qualitative synthesis. Studies were conducted in Argentina (n = 4), Brazil (n = 6), Colombia (n = 2), French Guyana and the Bahamas (=2), and Guatemala (n = 1). Heterogeneity of studies characteristics precluded any aggregated estimates. Histoplamosis was frequent in these cohort studies and mortality was high despite the use of HAART. Low CD4 counts, delayed HAART initiation and poor adherence were related to increased incidence, poor prognosis and increased mortality, respectively. Histoplasmosis may be an important contributor to mortality in people with HIV in Latin America. Diagnostic delays represent an important limitation for improving care of patients suspected to have histoplasmosis. Reducing histoplasmosis diagnostic delays and therapy initiation is needed to further decrease mortality.

Molecular detection of Histoplasma capsulatum indoors: A public health approach

BACKGROUND

Histoplasmosis, caused by the dimorphic fungus Histoplasma capsulatum, represents an important public health problem, especially in urban environments where bats and humans cohabit indoors.

AIMS

To detect the presence of H. capsulatum indoors, using samples of bat droppings collected in roost sites inside houses.

METHODS

A Real-Time TaqMan PCR assay targeting the ITS1 region of the ribosomal DNA of H. capsulatum was carried out.

RESULTS

Fifty-nine sampling points in the municipality of São Paulo were inspected, all of them located at inhabited places. H. capsulatum was isolated from nine samples.

CONCLUSIONS

The rapid identification and monitoring of sites where the fungus is present may contribute to make a more reliable database of H. capsulatum distribution.

Role of western blot assay for the diagnosis of histoplasmosis in AIDS patients from a National Institute of Infectious Diseases in Rio de Janeiro, Brazil

BACKGROUND

Histoplasmosis is a frequent fungal infection in HIV/AIDS patients, with high morbimortality rates when diagnosis and treatment are delayed. Antibody detection, which is faster than the gold standard culture test, hastens the laboratory investigation.

OBJECTIVES

To evaluate the role of WB for antibody detection in the diagnosis of histoplasmosis among HIV/AIDS patients.

PATIENTS AND METHODS

Fifty patients with proven or probable histoplasmosis were included. Clinical, epidemiological and laboratory data were described in the same population after a review of their medical records. WB was performed using deglycosylated histoplasmin.

RESULTS

About 82% of patients were adult males and the mean age was 39.3 years. CD4⁺ T lymphocyte count less than 150 cells/mm³ was observed in 62% patients. Antibodies against Histoplasma capsulatum M antigen were detected in 62% of patients, and against both M and H antigens in 28% of individuals. Sera from 10% of patients were nonreactive. Histoplasmosis was the first opportunistic infection in 38% of the cases. Disseminated and pulmonary histoplasmosis occurred in 84% and 16% of patients, respectively. The overall mortality was 16%.

CONCLUSION

WB could be useful for the histoplasmosis diagnosis in HIV/AIDS patients because of its easefulness and good sensitivity in a population where antibody production is hampered.

Multicenter Validation of Commercial Antigenuria Reagents To Diagnose Progressive Disseminated Histoplasmosis in People Living with HIV/AIDS in Two Latin American Countries

Histoplasmosis is an important cause of mortality in patients with AIDS, especially in countries with limited access to antiretroviral therapies and diagnostic tests. However, many disseminated infections in Latin America go undiagnosed. A simple, rapid method to detect Histoplasma capsulatum infection in regions where histoplasmosis is endemic would dramatically decrease the time to diagnosis and treatment, reducing morbidity and mortality. The aim of this study was to validate a commercial monoclonal Histoplasma galactomannan (HGM) enzyme-linked immunosorbent assay (Immuno-Mycologics [IMMY], Norman, OK, USA) in two cohorts of people living with HIV/AIDS (PLHIV). We analyzed urine samples from 589 people (466 from Guatemala and 123 from Colombia), including 546 from PLHIV and 43 from non-PLHIV controls. Sixty-three of these people (35 from Guatemala and 28 from Colombia) had confirmed histoplasmosis by isolation of H. capsulatum Using the standard curve provided by the quantitative commercial test, the sensitivity was 98% (95% confidence interval [CI], 95 to 100%) and the specificity was 97% (95% CI, 96 to 99%) (cutoff = 0.5 ng/ml). Semiquantitative results, using a calibrator of 12.5 ng/ml of Histoplasma galactomannan to calculate an enzyme immunoassay index value (EIV) for the samples, showed a sensitivity of 95% (95% CI, 89 to 100%) and a specificity of 98% (95% CI, 96 to 99%) (cutoff ≥ 2.6 EIV). This relatively simple-to-perform commercial antigenuria test showed a high performance with reproducible results in both countries, suggesting that it can be used to detect progressive disseminated histoplasmosis in PLHIV in a wide range of clinical laboratories in countries where histoplasmosis is endemic.

Detection of Histoplasma capsulatum in Organic Fertilizers by Hc100 Nested Polymerase Chain Reaction and Its Correlation with the Physicochemical and Microbiological Characteristics of the Samples

Histoplasma capsulatum is the causative agent of histoplasmosis and this fungus inhabits soils rich in phosphorus and nitrogen that are enriched with bird and bat manure. The replacement of organic matter in agroecosystems is necessary in the tropics, and the use of organic fertilizers has increased. Cases and outbreaks due to the presence of the fungus in these components have been reported. The Instituto Colombiano Agropecuario resolution 150 of 2003 contains the parameters set by the Colombian Technical Standard (NTC 5167) on the physicochemical and microbiological features of fertilizers, but it does not regulate the search for H. capsulatum. The aim of this study was to demonstrate H. capsulatum presence in organic fertilizers by nested polymerase chain reaction (PCR). A total of 239 samples were collected: 201 (84.1%) corresponded to organic fertilizers, 30 (12.5%) to bird excrement, and 8 (3.4%) to cave soils. The Hc100 nested PCR had a detection limit of 0.1 pg/µL and a specificity of 100%. A total of 25 (10.5%) samples were positive and validated by sequencing. Seven of the positive samples represented locations where H. capsulatum was previously detected, suggesting the persistence of the fungus. No significant correlations were detected between the physicochemical and microbiological parameters with the presence of H. capsulatum by nested PCR, indicating the fungus existence in organic fertilizers that complied with the NTC 5167. The Hc100 nested PCR targeting H. capsulatum standardized in this work will improve the evaluation of organic fertilizers and ensure the prevention of outbreaks and cases due to manufacturing, marketing, and use of fertilizers contaminated with H. capsulatum.

High Mortality and Coinfection in a Prospective Cohort of Human Immunodeficiency Virus/Acquired Immune Deficiency Syndrome Patients with Histoplasmosis in Guatemala

Histoplasmosis is one of the most common and deadly opportunistic infections among persons living with human immunodeficiency virus (HIV)/acquired immune deficiency syndrome in Latin America, but due to limited diagnostic capacity in this region, few data on the burden and clinical characteristics of this disease exist. Between 2005 and 2009, we enrolled patients ≥ 18 years of age with suspected histoplasmosis at a hospital-based HIV clinic in Guatemala City. A case of suspected histoplasmosis was defined as a person presenting with at least three of five clinical or radiologic criteria. A confirmed case of histoplasmosis was defined as a person with a positive culture or urine antigen test for Histoplasma capsulatum. Demographic and clinical data were also collected and analyzed. Of 263 enrolled as suspected cases of histoplasmosis, 101 (38.4%) were confirmed cases. Median time to diagnosis was 15 days after presentation (interquartile range [IQR] = 5-23). Crude overall mortality was 43.6%; median survival time was 19 days (IQR = 4-69). Mycobacterial infection was diagnosed in 70 (26.6%) cases; 26 (25.7%) histoplasmosis cases were coinfected with mycobacteria. High mortality and short survival time after initial symptoms were observed in patients with histoplasmosis. Mycobacterial coinfection diagnoses were frequent, highlighting the importance of pursuing diagnoses for both diseases.

Worldwide Phylogenetic Distributions and Population Dynamics of the Genus Histoplasma

Background

Histoplasma capsulatum comprises a worldwide complex of saprobiotic fungi mainly found in nitrogen/phosphate (often bird guano) enriched soils. The microconidia of Histoplasma species may be inhaled by mammalian hosts, and is followed by a rapid conversion to yeast that can persist in host tissues causing histoplasmosis, a deep pulmonary/systemic mycosis. Histoplasma capsulatum sensu lato is a complex of at least eight clades geographically distributed as follows: Australia, Netherlands, Eurasia, North American classes 1 and 2 (NAm 1 and NAm 2), Latin American groups A and B (LAm A and LAm B) and Africa. With the exception of the Eurasian cluster, those clades are considered phylogenetic species.

Methodology/Principal Findings

Increased Histoplasma sampling (n = 234) resulted in the revision of the phylogenetic distribution and population structure using 1,563 aligned nucleotides from four protein-coding regions. The LAm B clade appears to be divided into at least two highly supported clades, which are geographically restricted to either Colombia/Argentina or Brazil respectively. Moreover, a complex population genetic structure was identified within LAm A clade supporting multiple monophylogenetic species, which could be driven by rapid host or environmental adaptation (~0.5 MYA). We found two divergent clades, which include Latin American isolates (newly named as LAm A1 and LAm A2), harboring a cryptic cluster in association with bats.

Conclusions/Significance

At least six new phylogenetic species are proposed in the Histoplasma species complex supported by different phylogenetic and population genetics methods, comprising LAm A1, LAm A2, LAm B1, LAm B2, RJ and BAC-1 phylogenetic species. The genetic isolation of Histoplasma could be a result of differential dispersion potential of naturally infected bats and other mammals. In addition, the present study guides isolate selection for future population genomics and genome wide association studies in this important pathogen complex.

Histoplasmosis is a potentially severe fungal disease of mammals caused by Histoplasma capsulatum. The highest incidence of the disease is reported on the American continent, and approximately 30% of HIV and histoplasmosis co-infections are fatal. Previous studies have suggested at least 7 phylogenetic species within H. capsulatum, however by increasing taxon sampling and using different phylogenetic and population genetic methods, we detect at least 5 additional phylogenetic species within Latin America (LAm A1, LAm A2, LAm B1, LAm B2, RJ and BAC-1). These phylogenetic species are nested in the former LAm A clade. We found evidence that bats may be a cause of speciation in Histoplasma, as well-supported monophyletic clades were found in association with different species of bats. The radiation of the Latin American H. capsulatum species took a place around 5 million years ago, which is consistent with the radiation and diversification of bat species. Previous phylogenetic distribution of Histoplasma is upheld and strong support is indicated for the species delineation and evolution of this important pathogen.

Validation of western blot for Histoplasma capsulatum antibody detection assay

BACKGROUND

Histoplasmosis is worldwide systemic mycoses caused by the dimorphic fungus Histoplasma capsulatum. The isolation and identification of H. capsulatum in culture is the reference test for histoplasmosis diagnosis confirmation. However, in the absence of it, serology has been used as a presumptive diagnosis through antibody and antigen detection. The purpose of the present study was to validate an immunoassay method (western blot) for antibodies detection in the diagnosis of histoplasmosis.

METHODS

To validate the western blot (WB) a study was conducted using 118 serum samples from patients with histoplasmosis and 118 serum controls collected from January 2000 to December 2013 in residents of the Rio de Janeiro State, Brazil. Diagnostic validation parameters were calculated based on the categorization of results obtained in a 2 × 2 table and subjected to statistical analysis. In addition, the viability of deglycosylated histoplasmin antigen (ptHMIN) onto nitrocellulose membranes previously sensitized was evaluated during the same period.

RESULTS

The WB test showed sensitivity of 94.9 %, specificity of 94.1 %, positive predictive value of 94.1 %, negative predictive value of 94.9 %, accuracy of 94.5 %, and almost perfect precision. Besides, the strips have proved to be viable for using at least 5 years after ptHMIN antigen sensitization.

CONCLUSION

Western blot test using ptHMIN provides sensitive, specific, and faster results. Therefore, could be considered a useful tool in the diagnosis of histoplasmosis being used by public health system, even in situations where laboratory facilities are relatively limited.

Validation of an enzyme-linked immunosorbent assay that detects Histoplasma capsulatum antigenuria in Colombian patients with AIDS for diagnosis and follow-up during therapy

We validated an antigen capture enzyme-linked immunosorbent assay (ELISA) in Colombian persons with AIDS and proven histoplasmosis and evaluated the correlation between antigenuria and clinical improvement during follow-up. The sensitivity of the Histoplasma capsulatum ELISA was 86%, and the overall specificity was 94%. The antigen test successfully monitored the response to therapy.

Usefulness of the murine model to study the immune response against Histoplasma capsulatum infection

The present paper is an overview of the primary events that are associated with the histoplasmosis immune response in the murine model. Valuable data that have been recorded in the scientific literature have contributed to an improved understanding of the clinical course of this systemic mycosis, which is caused by the dimorphic fungus Histoplasma capsulatum. Data must be analyzed carefully, given that misinterpretation could be generated because most of the available information is based on experimental host-parasite interactions that used inappropriate proceedings, i.e., the non-natural route of infection with the parasitic and virulent fungal yeast-phase, which is not the usual infective phase of the etiological agent of this mycosis. Thus, due to their versatility, complexity, and similarities with humans, several murine models have played a fundamental role in exploring the host-parasite interaction during H. capsulatum infection.