Fish body to disease susceptibility and resistance to disease

After the pathogen enters the water body, the lack of fish and aquatic animals, the disease still does not occur, so the susceptible and resistant to the fish and aquatic animals are essential conditions for the occurrence of diseases. Such as the occurrence of hemorrhagic disease of grass carp silver carp, catfish, not a body without injury is not unboiled water mildew and susceptibility to disease in animal breeding is with the non-specific immunity and specific immunity of the strength of the two changes.
According to fish immune response to antigen targeted, divided into non specific immunity and specific immunity,
Non specific immunity, at least including physiological factors, physical defense structure of the two part.
Non – specific immunity from physiological factors, with age, body temperature, nutrition and breathing and so on. Such as cryptobiosis and Trichodina disease is fry, fingerling stage common parasite epidemics, and with the growth of the age of the fish body, even with the presence of pathogens. It is not easy to cause disease occurrence; Jiujiang Bothriocephalus acheilognathi usually not parasitic in 1 above the age of grass carp intestine, in low temperature cold northern area or in fall and winter, most microbial carbon diseases, such as hemorrhagic disease of grass carp, Bacterial Gill Rot Disease of sex, enteritis will not occur. Under the condition of hypoxia, fish are prone to disease.
The main factors that affect the immune function of non specific immunity in fish are the scale, skin and other surface barrier, and the second line of defense. Scales, skin and mucus is an important barrier for parasite invasion of the fish body resistance. Therefore, the protection of fish body surface is not damaged and without predators attack injured, pathogen could not invade, leaf spot, tail handle disease, disease and water mildew of print would not have happened. The concentration of chemical substances in the breeding water is too high, which can cause the fish to secrete a large amount of mucus, and once the excess secretion of mucus, it can not protect the role of the fish, and can not resist the invasion of pathogenic bacteria. After entering the body of the pathogen, the pathogen of the pathogen is often swallowed up by the phagocytic cells, and attracts the white blood cell to the injured site to swallow the pathogenic microorganism, which shows the inflammatory reaction. When the phagocytic cells and the phagocytic ability of white blood cells can not stop the rapid growth and reproduction of pathogenic microorganisms, the local lesions will be expanded, more than the fish body’s tolerance and lead to fish death. Therefore, health cultivation is an important measure to prevent the disease.
Specific immunity is the body of the body in the process of life to accept the foreign body to stimulate the immune system, also known as acquired immunity. According to the different ways of the different, can be divided into automatic and passive immunization. In addition to a very small number of viral and bacterial diseases can be obtained after a specific immunity, can be lifelong immunity, the vast majority of the disease’s specific immunity has a certain time limit. Such as patient Lernaea disease of silver carp and bighead carp can produce specific immunity, but not lifelong immunity of grass carp hemorrhage immune killing injections of vaccine, immunity can keep 14 months and thereafter gradually decreased. Therefore, according to the master of fish disease causes, control and improve aquaculture water environmental conditions, enhancement of fishes and aquatic economic animals body resistance is the key to the prevention and treatment of diseases of the livestock.