Molecular and clinical evidence of Aeromonas hydrophila and Fusarium solani co-infection in narrow-clawed crayfish Astacus leptodactylus.

Co-infections occur when a host is infected by 2 or more different pathogen types, either by secondary or simultaneous infections, and are very frequent in nature. In this study, 10 narrow-clawed crayfish Astacus leptodactylus with signs of disease were collected from Haft Baram Lake (Fars province, southern Iran). Samples of fluid from inside the intact abscess and melanized lesions in the cuticle were cultured aseptically onto brain heart infusion agar and Sabouraud dextrose agar for bacterial and fungal agents, respectively. After primary colony isolation for bacterial and fungal agents, the isolates were confirmed as Aeromonas hydrophila and Fusarium solani, using specific PCR methods based on 16S rDNA and internal transcribed spacer (ITS) rDNA sequences that produced a single band of 685 bp and 600 bp, respectively. Partial sequence analysis of the F. solani ITS showed 100% sequence identity among all our samples, as well as a close genetic relationship between this isolate (GenBank accession number MG519784) and those previously reported from loggerhead sea turtle Caretta caretta in Cape Verde (FJ948133, AM412641, and DQ535186), black-blotched stingray Taeniura melanopsila in Japan (LC019016), and American manatee Trichechus manatus in Japan (AB775569). The results indicate that narrow-clawed crayfish can be infected by A. hydrophila and F. solani simultaneously, and to the best of our knowledge, this is the first report of just such a co-infection in this host. Further studies are necessary to investigate the pathogenicity of these organisms and their effects on narrow-clawed crayfish.