Protective effect of chicken egg yolk immunoglobulin (IgY) against Spiroplasma eriocheiris infection in Chinese mitten crab

The aquaculture of the Chinese mitten crab Eriocheir sinensis has become the leading and pillar of aquaculture in China. The tremor disease (TD) caused by Spiroplasma eriocheiris is the most destructive disease of E. sinensis. At present, the treatment of TD in crabs mainly depends on antibiotics. To protect the environment and the health of aquatic products, it is urgent to establish an effective and pollution-free green prevention and control technology. This study aimed to investigate the prevention and control of the TD by immunization with chicken yolk antibody (IgY). Anti-S. eriocheiris IgY was obtained by intramuscular injection of ultrasonically inactivated S. eriocheiris into chickens. After successful isolation and purification of IgY from eggs, ELISA and sensitivity tests were performed. Specific IgY was able to specifically react at a titer of 1:10,000 to antigen at a minimum concentration of 20 μg/mL and to inhibit the growth of S. eriocheiris in vitro. The affection of IgY in vivo to resist S. eriocheiris infection was demonstrated by feeding or injection of specific IgY. The copy number of S. eriocheiris in crab hemocytes with specific IgY administration was significantly less than in crabs that received normal IgY or without IgY. Meanwhile, the survival rate of E. sinensis with anti-S.eriocheiris- specific IgY using both injection and feeding methods significantly increased during S. eriocheiris infection. The electron microscope results showed that the structure of S. eriocheiris in specific IgY group was completely irregular and broken pin vivo. Finally, this study provides a reference for clarifying the potential role of specific IgY to help E. sinensis resist S. eriocheiris infection.