First description of milky disease in the Chinese mitten crab Eriocheir sinensis caused by the yeast Metschnikowia bicuspidata

Abstract

The Chinese mitten crab, Eriocheir sinensis, is an economically important crustacean species in China. A recent epidemic of “milky disease” in Panjin, China resulted in a large loss of cultured E. sinensis. Clinical signs of the disease include weak response, swollen pereopod and claw joints, opaque or whitish muscles, and milky hemolymph, culminating in tissue or organ failure and death. Histological analysis of the crabs showed a marked disorder of fibers, discrete necrotic lesions, and high yeast infiltration in the muscles, heart, gills, and other organs. The yeast cells (LNES0119) isolated from the diseased crab tissues were subjected to polymerase chain reaction analysis. The resulting product, the D1/D2 domain of 26S rDNA of the LNES0119 yeast isolate, was used to identify the pathogen for milky disease, which was found to have 98% sequence identity with the sequence of Metschnikowia bicuspidata (GenBank accession nos. U44822 and U94944), a pathogenic yeast found in aquatic invertebrates. A laboratory challenge experiment showed that the pathogen was infectious and caused the same pathological alterations in crab hosts. The present findings demonstrated that the pathogen isolated from the Chinese mitten crab with milky disease was the yeast M. bicuspidata. This study is the first description of M. bicuspidata infection in the Chinese mitten crab and thus warrants further research on the effects of M. bicuspidata in crustaceans