Longitudinal study of Amphibiocystidium sp. infection in a natural population of the Italian stream frog (Rana italica)

<jats:title>Abstract</jats:title><jats:p>Mesomycetozoean-induced infections (order Dermocystida, genus<jats:italic>Amphibiocystidium</jats:italic>) in European and North American amphibians are causing alarm. To date, the pathogenicity of these parasites in field conditions has been poorly studied, and demographic consequences on amphibian populations have not been explored. In this study, an<jats:italic>Amphibiocystidium</jats:italic>sp. infection is reported in a natural population of the Italian stream frog (<jats:italic>Rana italica</jats:italic>) of Central Italy, over a 7-year period from 2008 to 2014. Light and electron microscope examinations, as well as partial 18S rDNA sequence analysis were used to characterize the parasite. Moreover, a capture-mark-recapture study was conducted to assess the frog demographics in response to infection. Negative effects of amphibiocystidiosis on individual survival and population fitness were absent throughout the sampling period, despite the high estimates of disease prevalence. This might have been due to resistance and/or tolerance strategies developed by the frogs in response to the persistence of<jats:italic>Amphibiocystidium</jats:italic>infection in this system. We hypothesized that in the examined<jats:italic>R. italica</jats:italic>population, amphibiocystidiosis is an ongoing endemic/epidemic infection. However, ecological and host-specific factors, interacting in a synergistic fashion, might be responsible for variations in the susceptibility to<jats:italic>Amphibiocystidium</jats:italic>infection of both conspecific populations and heterospecific individuals of<jats:italic>R. italica.</jats:italic></jats:p>