Zoonotic diseases of fish and their prevention and control

Fish and aquatic-derived zoonotic diseases have caused considerable problems in the aquaculture industry and fishery worldwide. In particular, zoonotic diseases can pose widespread threats to humans. With the world's growing population and potential global trade of aquaculture and fish, the risk of environmental contamination and development of fish and aquatic-derived zoonoses in humans are increasing. The important causes of zoonoses include bacteria, parasites, viruses, and fungi. The zoonotic bacterial agents are divided into two main groups: Gram-positive (<i>Mycobacteriaceae</i>, <i>Streptococcaceae</i>, <i>Erysipelothricaceae</i> families) and Gram-negative (<i>Aeromonadaceae</i>, <i>Vibrionaceae</i>, <i>Pseudomondaceae</i>, <i>Enterobacteriaceae</i>, and <i>Hafniaceae</i> families). The premier parasitic agents include cestodes (tapeworm; e.g. <i>Diphyllobothrium</i> spp.), trematodes (fluke; e.g. <i>Opisthorchis</i> spp.), and nematodes (round worm; e.g. <i>Anisakis</i> spp.). In addition, protozoan organisms such as <i>Cryptosporidium</i> spp. are also considered fish-derived zoonotic pathogens. Two groups of fish-associated fungi causing basidiobolomycosis and sporotrichosis also pose a zoonotic risk for humans. The majority of the fish-derived zoonotic diseases are transmitted to humans mainly via the consumption of improperly cooked or raw fish or fish products. Therefore, the incidence of zoonotic diseases can be reduced by properly processing fish and fish products, e.g. by thermal (heat/freezing) treatment. The prevalence of zoonotic agents in fishes varies seasonally and should be regularly monitored to evaluate the prevalence of pathogens in both wild and cultured fish populations. This review focuses on the fish zoonotic agents/diseases and their control and prevention.