Occurrence of Fusarium spp. in sea turtles with and with and without shell and skin lesions

Fusarium spp. are fungi worldwide distributed in soil, plants, water and other organic substrates which sometimes act as pathogens causing superficial and or disseminated infections in humans and animals. Several skin and shell diseases have been described to occur in sea turtles but the role of Fusarium spp. as a primary cause of infections remains anecdotic. The present study was designed to investigate the occurrence of Fusarium spp. on sea turtles with or without shell and skin lesions. A total of 90 animals (i.e., 38 without and 52 with lesions) were enrolled in the study. Shell and skin scraps were collected from each turtle on three anatomical sites (i.e., carapace, flipper and plastron) examined microscopically (i.e., cytological examination with Calcofluor and scanning electron microscope -SEM analysis) and cultured. Seven (7.8%) out of 90 samples gave positive results at the microscopic examination with calcoflour (i.e., 3 animals without lesions and 4 animals with lesions). SEM analysis revealed the presence of fungal hyphae on and in the internal structures of the carapace in all samples collected from animals with lesions whereas no fungal structures were observed in animals without lesions. Fusarium spp. was isolated from 23 (44.2%) isolates collected from animals with shell and skin lesions and from 3 (7.9%) without lesions. Fusarium spp. were also isolated and identified from the sand of the filter of the rescue centres. Occurrence of lesions and recovering time spent in the rescue centre were identified as the most significant risk factors (p<0.05). Fusarium solani (7.8%), Fusarium oxysporum (5.6%), Fusarium acuminatum (0.74%) and Fusarium brachygibbosum (0.37%) were morphologically and molecularly identified. The results of this study suggest that fusariosis should be included in the differential diagnosis of shell and skin infections in sea turtles and that the diagnosis of infections should be performed using SEM analysis associated with fungal culture. Finally, in the rescue centre, management procedures (e.g., protocols of disinfection) are suggested in order to control the infections.