Shrimp do not have the same immune system as vertebrates. This characteristic has a significant impact on shrimp farm management: it prevents these crustaceans from becoming immune to disease through vaccination. Since shrimp lack an adaptive immune system, innate immunity is their essential form of defense. This immunity acts as first-line protection from the disease and mortality threats. As with all livestock species, the best way to reduce these impacts on farmed shrimp is by erecting a number of barriers so as to prevent the development of pathogens. In this respect, physical and sanitary barriers are the most effective means of prevention. (I googled sick shrimp art and found this so I'm using it)