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Post by katinka on Mar 26, 2010 5:20:55 GMT -5
I believe this is what happened in nature and for us to become infected by animal- and plant pathogens: Cryptic pathogenesisAn alternative explanation for virulence in microbes acquired from the environment is cryptic pathogenesis, whereby such microbes have animal hosts that are yet to be discovered. In such a scenario, some fraction of the microbial population is always cycling through an animal host, and consequently, attributes for persisting in animal hosts are maintained through selection. The finding that land and marine mammals in areas where Coccidioides immitis is endemic are sometimes found to be infected with this fungus is consistent with a cryptic-pathogenesis explanation. Although the possibility of cryptic pathogenesis cannot be excluded for any environmentally acquired microbe, since this would involve proving a negative, there is experimental evidence against an absolute need for animal passage in the maintenance of virulence. Avirulent strains of C. neoformans and H. capsulatum can be restored to virulence through passage in the amoeboid hosts Dictyostelium and Acanthamoeba castellanii, respectively ec.asm.org/cgi/content/full/6/12/....ourcetype=HWFIGSo, this means that certain avirulent strains of fungus can become infectious when in 'contact or encased' within Dicty and/or Achanthamoeba? If this can happen with these two types of fungus, then I believe it probably can with other types too. Kat
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Post by katinka on Mar 26, 2010 5:21:31 GMT -5
Accidental Virulence, Cryptic Pathogenesis, Martians, Lost Hosts, and the Pathogenicity of Environmental Microbes ec.asm.org/cgi/content/full/6/12/....ourcetype=HWFIGfrom above site: Population genetics of the frog-killing fungus Batrachochytrium dendrobatidis Global amphibian decline by chytridiomycosis is a major environmental disaster that has been attributed to either recent fungal spread or environmental change that promotes disease. Here, we present a population genetic comparison of Batrachochytrium dendrobatidis isolates from an intensively studied region of frog decline, the Sierra Nevada of California. In support of a novel pathogen, we find low diversity, no amphibian-host specificity, little correlation between fungal genotype and geography, local frog extirpation by a single fungal genotype, and evidence of human-assisted fungus migration. In support of endemism, at a local scale, we find some diverse, recombining populations. Recombination raises the possibility of resistant sporangia and a mechanism for rapid spread as well as persistence that could greatly complicate global control of the pathogen. Kat
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Post by katinka on Mar 26, 2010 5:22:21 GMT -5
I decided to look at this one a bit closer because I believe Kammy has a pic from a human sample showing us similarity. Histoplasma capsulatum This anamorphic fungus has a known sexual teleomorph that carries the name Ajellomyces capsulatus. Pic here: www.doctorfungus.org/Mycoses/images/histoplasma-duboisii-yeast.jpgHowever, a disseminated and potentially fatal picture is seen among immunosuppressed individuals, children less than 2 years old, elderly persons, and people exposed to very large inoculum. Since the advent of the HIV epidemic, histoplasmosis has reemerged to become one of the most frequent opportunistic diseases in those areas of the world endemic for this soil-based fungus. The infection is acquired through inhalation of Histoplasma capsulatum microconidia. The lungs are thus the most frequently affected site and chronic pulmonary disease may occur. All stages of this disease may mimic tuberculosis. Histoplasmosis may coexist with actinomycosis, other mycoses, sarcoidosis, or tuberculosis. www.doctorfungus.org/Mycoses/human/histo/histoplamosis_c.htmKat
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Post by katinka on Mar 26, 2010 5:22:50 GMT -5
Histoplasma capsulatum...This anamorphic fungus has a known sexual teleomorph that carries the name Ajellomyces capsulatus.This fungus is infecting the bats: Ajellomyces capsulatusPic here: www.doctorfungus.org/Mycoses/images/ajellomyces_capsulatus.jpgAjellomyces capsulatus causes the infectious disease histoplasmosis. The fungi releases small spores called conidia that can be inhaled and infect the lungs. The symptoms are often mild but can be severe producing illness similar to tuberculosis. The disease may also affect other parts of the body, such as the skin or eyes. The fungus is generally found living on bird or bat droppings. It appears to thrive in nitrogen rich soil. The very closely related fungus, Ajellomyces dermatidis, causes the disease blastomycosis. The symptoms of the disease are very similar to those found in regards to histoplasmosis. The fungus is often found growing in rotting wood and nitrogen rich soil.
It is generally found in areas with high humidity and near a water source, but there is little known about its natural history. Generally the only time that we hear of the fungus being mentioned is when we hear of dogs, cats or people becoming infected. Kat
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Post by katinka on Mar 26, 2010 11:04:17 GMT -5
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Post by aqt on Mar 26, 2010 17:51:44 GMT -5
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