The definitive environmental niche for C neoformans has not been determined, although there is a strong 'historic' association with weathered bird (especially pigeon) guano and more recent evidence for growth in decaying plant matter in hollows of certain trees. Interestingly, koalas seem capable of amplifying the number of cryptococci in certain environments. There is strong evidence that several of Australian eucalyptus trees provide a natural environmental niche for C bacillisporus. C n var grubii is by far the most common isolate from cryptococcosis in people and animals worldwide, although C bacillisporus is important in certain geographical regions such as Australia, Papua New Guinea, South East Asia and Central Africa. Both varieties are strongly associated with disease in immunocompromised human patients, although the same may not be true for companion animals. C neoformans can be divided into two varieties based on serotyping, C n var grubii and C n var neoformans. C neoformans has a world wide distribution, while C bacillisporus is largely restricted to tropical and subtropical climates. C neoformans and C bacillisporus differ biochemically, genetically, ecologically and epidemiologically. Recent advances in the taxonomy of the genus Cryptococcus have led to a new nomenclature that was proposed at the 5th International Conference on Cryptococcus and cryptococcosis. Historically, five serotypes (A, B, C, D, AD) have been identified on the basis of antigenic differences in capsular polysaccharide. In contrast to the other systemic mycoses, the prevalence of cryptococcosis in cats exceeds that in dogs by an order of magnitude. Cryptococcus has a worldwide distribution and, in addition to people, infects a variety of domestic and native mammals. Unlike other dimorphic fungi, the yeast phase of Cryptococcus is found under routine laboratory conditions and in infected tissues. Buds may break off when small and thus the cell population varies in size. In tissues, Cryptococcus reproduces by forming one or two daughter cells (buds) that are connected to the parent cell by a narrow isthmus. The capsule provides protection from environmental insults (e.g., desiccation) and the phagocytic response of the host. In animal tissues, Cryptococcus neoformans and C bacillisporus exists as a round, yeast-like organism, with a variably-sized polysaccharide capsule as its distinguishing feature. The importance of the perfect state is that spores resulting from sexual or asexual filamentous reproduction likely represent the infectious propagules that give rise to mammalian disease. Thus far, the filamentous phase has been demonstrated only under strictly controlled laboratory conditions, but this perfect state is likely to exist in certain natural environments. They exist in animal tissues as the yeast form ( Cryptococcus spp), but are capable of transforming under special laboratory conditions into a filamentous form ( Filobasidiella spp). C neoformans and C bacillisporus are dimorphic, basidiomycetous fungi. Elaboration of a polysaccharide capsule and the enzymes laccase and phospholipase by C neoformans and C bacillisporus are additional virulence factors that contribute to pathogenicity. The ability of C neoformans and C bacillisporus to grow at 37 oC may in part explain their pathogenicity, because other members of the genus grow poorly at this temperature. Thus, cryptococcosis is not a contagious or anthropozoonotic disease.Ĭryptococcosis is most commonly caused by two species of the genus Cryptococcus, C neoformans and C bacillisporus. The infection is thought to be acquired from the environment, with no reported cases of disease transmission from one affected animal to another. Books & VINcyclopedia of Diseases (Formerly Associate)Ĭryptococcosis is an important disease of man and animals and the most common systemic mycosis of cats.VINcyclopedia of Diseases (Formerly Associate).Diagnosis is by detection of characteristic. Symptoms include watery diarrhea with gastrointestinal and systemic symptoms. read more, Cyclospora Cyclosporiasis Cyclosporiasis is infection with the protozoan Cyclospora cayetanensis. read more, Cystoisospora belli Cyclosporiasis Cyclosporiasis is infection with the protozoan Cyclospora cayetanensis. Symptomatic disease develops predominantly in patients with AIDS and includes chronic diarrhea, disseminated infection, and corneal disease. read more, microsporidia Microsporidiosis Microsporidiosis is infection with microsporidia. The primary symptom is watery diarrhea, often with other signs of gastrointestinal distress. Oocysts of some parasites (eg, Cryptosporidium Cryptosporidiosis Cryptosporidiosis is infection with the protozoan Cryptosporidium.
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