The world fisheries production has levelled off and most of the main fishing areas have reached their maximum potential. In contrast, the global human population is increasing; thus, the demand for aquatic food products also increase. Global aquaculture production attained 90.4 million tons in 2012, generating an incomes US$ 144.4 billion, and the production of food fish was 66.6 million tons. Epitheliocystis is a serious skin and gill disease in fish, believed to be caused by pathogenic intracellular bacteria. The disease has been reported in at least 90 species of marine and freshwater fish in both the southern and northern hemisphere. It affects a number of commercially important aquaculture species, including salmon, kingfish, trout
and bream. Infection in these fish species is characterized by the development of cysts, typically in the gill epithelia, promoting the fusion of gill lamellae. This condition is usually benign; however, sometimes it can be associated with a high mortality, particularly in cultured fish. Infections can lead to respiratory distress and death, particularly in cultured and juvenile fish. While fish mortality data attributed to epitheliocystis is sparse, a remarkably broad range of 4%-100% observed mortality rates has been reported. Even with the recent molecular advances in identifying the pathogens, the reservoirs and modes of transmission of the etiologic agent(s) of this disease remain largely unknown. Bacteria belonging to the order Chlamydiales are an extremely important and diverse group of pathogens of vertebrates, which include respiratory diseases of fishes. Chlamydial infections of fish are emerging as an important cause of epitheliocystis in new and established aquaculture industries [6, 8]. However, empirical data and direct evidence relating to the etiology, treatments and epidemiology remain limited, highlighting the need for more work to better characterize this disease across the different hosts and locales affected.
Wilmore
Webley
