河蟹甲壳病是由能破坏几丁质的细菌引起的，该病的症状与虾的褐斑病相似，发病初期，病蟹甲壳出现棕色、红棕色点扶病灶，斑点中部下凹；发病晚期，斑点连结成不规则的形状，中心部溃疡很深，可见内部软组织，边缘呈黑色，此时病蟹出现肢体不全，蟹壳穿孔，并可继发细菌和真菌? Crab carapace is caused by bacteria that can destroy chitin, and the symptoms of the disease are similar to those of shrimp. At the early stage of disease, the brown and reddish brown carapace appears in the diseased crab, and the spot in the middle is concave. In the late onset, Spots into irregular shapes, the central part of the ulcer deep, showing the internal soft tissue, the edge was black, then the disease crab limb incomplete, crab perforation, and secondary to bacteria and fungi?