The increasing demand for fish and shrimp as cheap and healthy food has promoted worldwide development of intensive aquaculture, which simultaneously increased the occurrence of several diseases among the farmed species. Fish and shrimp diseases pose severe economic losses and are considered as the major bottleneck for the aquaculture production and development. In this manner, there is a prime necessity for the understanding of diseases and their control which is outlined in this book which gives a new insight for the prevention of infections and their transmissions in aquaculture to support sustainable aquaculture production and product trade.