Epidemiology
In humans, C. neoformans causes cryptococcal meningitis worldwide and is primarily associated with desiccated bird droppings in environments protected from the sun (Casadevall and Perfect 1998).
The species C. neoformans and C. gattii cause systemic infections in both immunocompromised and immunocompetent individuals (Casadevall and Pirofski 1999). Globally, more than one million people get infected with cryptococcosis worldwide every year (Holmes et al. 2003; Cogliati 2013). The disease is more common in sub-Saharan Africa and tropical countries (such as Brazil, Thailand, Malaysia, and Papua New Guinea)(Seaton et al. 1996; Laurenson et al. 1997). Among HIV-negative individuals in the USA, the average annual incidence has remained almost constant at about one case per 100,000 individuals (Pappas 2013). The incidence of cryptococcosis has increased to about 5% in Western countries, while in sub-Saharan Africa, its incidence is as high as 30% in individuals with malignancies or those receiving corticosteroids or immunosuppressive therapy (Idnurm et al. 2005). Before the advent of molecular identification techniques, it was believed that C. neoformans infections occurred mainly in immunocompromised patients. However, it has since been observed that the epidemiology of C. neoformans is far more complex. Moreover, in contrast to C. neoformans var. grubii, C. neoformans var. neoformans appears to be more prevalent in Western and Mediterranean Europe (Viviani et al. 2006; Desnos- Ollivier et al. 2010; Guinea et al. 2010).12.4.1 Animal Cryptococcosis in Australia and Asia
Veterinary studies from Papua New Guinea, Australia, New Zealand, and the Hawaiian Islands have reported the isolation of C. neoformans and C. gattii from cats, dogs, horses, koalas, ferrets, sheep, goats, kiwis, cows, African grey parrots, cockatoos, other parrots, spinner dolphins, and echidnas (Riley et al.
1992; Connolly et al. 1999; Malik et al. 2002, 2003; McGill et al. 2009; Rotstein et al. 2010). However, in Asia, C. neoformans, but not C. gattii, has been recovered from cats, dogs, bandicoot rats, and house mice (Singh et al. 2007; Okabayashi et al. 2009; Singh et al. 2017).12.4.2 Animal Cryptococcosis in Europe
The species C. neoformans has been isolated from cats, dogs, magpies, and striped grass mice (Bauwens et al. 2004; Lagrou et al. 2005; Belluco et al. 2008; Morera et al. 2014; Danesi et al. 2014a), while C. gattii has been isolated from pet ferrets and goats in Spain, with the latter occurring in association with stands of E. camaldulensis trees (Frases et al. 2009; Morera et al. 2011).
12.4.3 Animal Cryptococcosis in the Americas
The species C. neoformans has been recovered from insects, bulls, ferrets, and sheep (Lemos et al. 2007; Riet-Correa et al. 2011; de Jesus et al. 2012), while infection due to C. gattii has been reported in cheetahs, goats, and psittacine birds (Raso et al. 2004; Illnait-Zaragozi et al. 2010). Three cases of cryptococcal infection caused by C. neoformans have been reported in North American ferrets; furthermore, dogs, cats, horses, ferrets, marine mammals, and birds living on or near Vancouver Island (British Columbia, Canada) have been reported to be infected with C. gattii (Hanley et al. 2006; MacDougall et al. 2007; Bartlett et al. 2012).
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