Identification of etiological agent for necrotizing scute disease and sensitivity in green sea turtle

Abstract:

Green sea turtle (Chelonia mydas) in captivity that suffered from necrotizing scute disease showed the symptoms of "grey-white scute", Wood lamp fluorescence phenomenon, suspected of the presence of fungal infection;One dominant fungus was isolated and purified from the edge necrosis of the carapace of the green turtles, which was numbered SDABAI. The pathogenic strain was identified by morphological observation, conidia morphology, and combined with ITS 18S rDNA sequence analysis, and the phylogenetic analysis was constructed. The results showed that the SDABAI strain(accession number:MK583351) and Fusarium solani(accession number:KU377470.1) had 99% genetic similarity, so SDABAI was determined to be F. solani, and the fungal morphology and conidia morphology were also consistent.The SDABAI strain was inoculated into a 4 mL centrifuge tube and cultured on an inclined plane for 4-5 days. After growing white flocculent fungi, the fungus was sealed on the dorsal plates of 2 healthy green sea turtles (A1 and A2) using light-curable composite resin. Each turtle had 2 germ-bearing centrifuge tubes (A1-1; A1-2; A2-1; A2-2). On the 24th day of infection, the infected symptoms of A1 appeared, with fluorescence, which produced the same symptoms as the natural disease, and Fusarium solani similar to SDABAI were isolated at the edge of shell of A1.A2 had weaker symptoms than A1.According to the whole dorsal shell of green sea turtles showing "grey-and-white scute" symptoms and the pathogen of Fusarium solani, it was named green sea turtle necrotizing scute disease.Garlic oil, wormwood oil and tea tree oil were selected for drug sensitivity test. The results showed that all of them could inhibit growth to a certain extent, and also inhibit the growth of secondary bacteria, with the best antifungal effect of garlic oil. The results showed that five drugs, including terbinafine, clomazole, miconazole, nystatin and amphotericin, had better antifungal effect on SDABAI.