Immunological Control of Fish Diseases

Abstract

All metazoans possess innate immune defence system whereas parameters of the adaptive immune system make their first appearance in the gnathostomata, the jawed vertebrates. Fish are therefore the first animal phyla to possess both an innate and adaptive immune system making them very interesting as regards developmental studies of the immune system. The massive increase in aquaculture in recent decades has also put greater emphasis on studies of the fish immune system and defence against diseases commonly associated with intensive fish rearing. Some of the main components of the innate and adaptive immune system of fish are described. The innate parameters are at the forefront of immune defence in fish and are a crucial factor in disease resistance. The adaptive response of fish is commonly delayed but is essential for lasting immunity and a key factor in successful vaccination. Some of the inherent and external factors that can manipulate the immune system of fish are discussed, the main fish diseases are listed and the pathogenicity and host defence discussed. The main prophylactic measures are covered, including vaccination, probiotics and immunostimulation. A key element in the immunological control of fish diseases is the great variation in disease susceptibility and immune defence of different fish species, a reflection of the extended time the present day teleosts have been separated in evolution. Future research will probably make use of molecular and proteomic tools both to study important elements in immune defence and prophylactic measures and to assist with breeding programmes for disease resistance.

Dietary low or excess levels of lipids reduced growth performance, and impaired immune function and structure of head kidney, spleen and skin in young grass carp (Ctenopharyngodon idella) under the infection of Aeromonas hydrophila

“…Low or excess levels of lipids decrease immune function, induce oxidative damage and apoptosis and impair the antioxidant system in the skin of young grass carp Fish skin is an important immune organ, which has an essential role in protection against invasive pathogens [111]. Thus, we found a scoring system to evaluate skin haemorrhage and lesions during A. hydrophila infection, similar to that of Song et al [58].…”

Expression analysis of heat shock protein genes during Aeromonas hydrophila infection in rohu, Labeo rohita, with special reference to molecular characterization of Grp78

“…Phagocytes are major innate immune molecules which show respiratory or oxidative burst activity by releasing bactericidal reactive oxygen species (ROS) upon stimulated by PAMPs through receptors or by the uptake of pathogens (Magnadottir 2010). However, excessive production of these ROS may lead to oxidative stress in fish.…”

An Overview of the Immunological Defenses in Fish Skin

“…Its structure and function reflect the adaptation of the organism to the physical, chemical, and biological properties of the aquatic environment and the natural history of the organism. The aquatic environment is rich in pathogenic organisms [26]; hence, the skin of aquatic vertebrates is extremely important as the first line of defence against the invasion of environmental pathogens, and it is just important to the respiratory and digestive organs. Because of the intimate contact of fish with the environment, cutaneous diseases are relatively more common in fish than in terrestrial vertebrates and are one of the primary disease conditions presented to the aquatic animal practitioner [27].…”

“…Both the number of goblet cells and the composition of the mucus which they produce may vary depending on their location. On the other hand, fine structural studies have demonstrated that the epidermis of fishes may have two different types of glandular cells, namely, goblet cells and club cells [26,57]. The slipperiness of the mucus is considered to be a result of the presence of high molecular weight gel-forming macromolecules, and it is assumed that the predominant gel-forming macromolecules in mucus are glycoproteins.…”