Isolation of Histoplasma capsulatum from bats in Oklahoma

Bat-associated microbes: Opportunities and perils, an overview

The potential biotechnological uses of bat-associated bacteria are discussed briefly, indicating avenues for biotechnological applications of bat-associated microbes. The uniqueness of bats in terms of their lifestyle, genomes and molecular immunology may predispose bats to act as disease reservoirs. Molecular phylogenetic analysis has shown several instances of bats harbouring the ancestral lineages of bacterial (Bartonella), protozoal (Plasmodium, Trypanosoma cruzi) and viral (SARS-CoV2) pathogens infecting humans. Along with the transmission of viruses from bats, we also discuss the potential roles of bat-associated bacteria, fungi, and protozoan parasites in emerging diseases. Current evidence suggests that environmental changes and interactions between wildlife, livestock, and humans contribute to the spill-over of infectious agents from bats to other hosts. Domestic animals including livestock may act as intermediate amplifying hosts for bat-origin pathogens to transmit to humans. An increasing number of studies investigating bat pathogen diversity and infection dynamics have been published. However, whether or how these infectious agents are transmitted both within bat populations and to other hosts, including humans, often remains unknown. Metagenomic approaches are uncovering the dynamics and distribution of potential pathogens in bat microbiomes, which might improve the understanding of disease emergence and transmission. Here, we summarize the current knowledge on bat zoonoses of public health concern and flag the gaps in the knowledge to enable further research and allocation of resources for tackling future outbreaks.

Infection of bats with Histoplasma species

Histoplasma species infect humans and animals, notably bats. Histoplasma species are thermally dimorphic fungi existing in mycelial form in the natural environment and in yeast form in infected tissues. In this narrative literature review, we summarize the occurrence of Histoplasma spp. in different species of bat tissues (n = 49) and in soil admixed with bat guano where the species of bat dwelling nearby has been identified (an additional 18 species likely infected) to provide an up-to-date summary of data. Most positive isolations are from the Americas and Caribbean, with some studies from Thailand, Malaysia, Nigeria, Slovenia, France, and Australia. We also summarize some of the early experimental work to elucidate pathogenicity, latency, immune response, and faecal excretion in bats. Given the recent recognition of the global extent of histoplasmosis, thermal dimorphism in Histoplasma spp., and global heating, additional work on understanding the complex relationship between Histoplasma and bats is desirable.

An Hcp100 gene fragment reveals Histoplasma capsulatum presence in lungs of Tadarida brasiliensis migratory bats

Histoplasma capsulatum was sampled in lungs from 87 migratory Tadarida brasiliensis bats captured in Mexico (n=66) and Argentina (n=21). The fungus was screened by nested-PCR using a sensitive and specific Hcp100 gene fragment. This molecular marker was detected in 81·6% [95% confidence interval (CI) 73·4-89·7] of all bats, representing 71 amplified bat lung DNA samples. Data showed a T. brasiliensis infection rate of 78·8% (95% CI 68·9-88·7) in bats captured in Mexico and of 90·4% (95% CI 75·2-100) in those captured in Argentina. Similarity with the H. capsulatum sequence of a reference strain (G-217B) was observed in 71 Hcp100 sequences, which supports the fungal findings. Based on the neighbour-joining and maximum parsimony Hcp100 sequence analyses, a high level of similarity was found in most Mexican and all Argentinean bat lung samples. Despite the fact that 81·6% of the infections were molecularly evidenced, only three H. capsulatum isolates were cultured from all samples tested, suggesting a low fungal burden in lung tissues that did not favour fungal isolation. This study also highlighted the importance of using different tools for the understanding of histoplasmosis epidemiology, since it supports the presence of H. capsulatum in T. brasiliensis migratory bats from Mexico and Argentina, thus contributing new evidence to the knowledge of the environmental distribution of this fungus in the Americas.

Adherence patterns of Histoplasma capsulatum yeasts to bat tissue sections

The adherence of Histoplasma capsulatum yeasts to lung, spleen, liver, gut, and trachea cryosections of Artibeus hirsutus bats and inbred BALB/c mice (control) was studied after in vitro yeast-tissue incubations. Candida albicans yeasts were used as a well-known adherent fungal model in the mice host, and latex beads were used as a negative adherence control. Adhered yeast cells were identified by using crystal violet staining and the immunoperoxidase method with specific antibodies. H. capsulatum yeasts adhered to all tissues tested, mainly in the lung. Moreover, H. capsulatum yeasts adhered preferentially to white and red spleen pulp, in contrast to the dispersed distribution of C. albicans yeasts. H. capsulatum yeasts were mostly found on the sinusoidal face of hepatocytes. In general, the gut showed a higher number of adhered H. capsulatum yeasts than the trachea in both bats and mice. H. capsulatum and C. albicans yeasts developed high selectivity for the lamina propria of the gut. In addition, H. capsulatum yeasts interacted better with the lamina propria and adventitia of the trachea. The number of H. capsulatum yeast cells that adhered to each tissue section type was always greater than the corresponding number of C. albicans yeast cells, and latex beads never adhered to the tissue sections. Controls with anti-H. capsulatum and normal rabbit sera showed a significant blockage of H. capsulatum yeast adherence to lung tissue. This is the first study describing the patterns of H. capsulatum yeast adherence to different bat and mouse tissues.

Occurrence of Penicillium marneffei infections among wild bamboo rats in Thailand

Penicilliosis marneffei has emerged as an endemic systemic mycosis in Southeast Asia among humans and wild bamboo rats. To gain an insight into the epidemiology of this life-threatening disease, a survey of bamboo rats for natural infections by Penicillium marneffei was carried out in the central plains of Thailand during June-September, 1987. Thirty-one lesser bamboo rats (Cannomys badius) and eight hoary bamboo rats (Rhizomys pruinosus) were trapped. Portions of their internal organs were cultured to determine if they had been infected by P. marneffei. Six each of C. badius (19.4%) and R. pruinosus (75%) yielded cultures of this unique, dimorphic Penicillium species. All of the isolates were readily converted to their unicellular form that multiplies by the process of schizogony by incubating them at 37 degrees C on plates of brain heart infusion agar. Their identity was further confirmed by a specific immunological test. Among the internal organs of the positive rats, the lungs had the highest positivity (83.3%), next in decreased order of frequency were the liver (33.3%) and the pancreas (33.3%). The use and value of domestic and wild animals in locating and demarcating endemic areas of geophilic fungal pathogens are discussed. Penicilliosis marneffei is considered to be a zooanthroponosis--a disease that occurs in lower animals, as well as, humans.

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.

Isolation of Histoplasma capsulatum from tissues of bats captured in the Aguas Buenas Caves, Aguas Buenos, Puerto Rico

Of 30 bats belonging to four species, only one species, Brachyplylla cavernarum, yielded positive for Histoplasma capsulatum. Bats were collected at the Aguas Buenas Caves in Puerto Rico. The other species are: Artibeus jamaicensis, Monophyllus redmani portoricensis, and Erophylla bibombifrons; these resulted negative for the fungus.