Disease predatory fish
The causative agent in fast-flowing water persists for long (in hours). Its virulence is low, as it usually causes disease in immunocompromised fish spawning. After amplification of their virulence by passaging in the body is weakened fish it causes disease in a large number of fish in the form of epizootic outbreaks.
Ehpizootologicheskaja data. Disease in pikes usually occurs within a few days after spawning (March – April). The most susceptible Mature individuals. The perch, bream, roach and burbot the disease recorded in the summer. The emergence of the disease contributes to cold spring, especially during the spawning period of pike. Then the flash increases and reaches maximum development during the summer months. It fades by the end of summer,
Epizootic process can continue in a large body of water (reservoir, lake) for several years and spread to other reservoirs-current water with transportable or migratory fish. The source of infection are sick and dead fish, microbiological. They are contagious from the beginning falls into the water with secretions, or the decomposition of corpses. Most researchers believe that infection occurs via povrezhdeniya the skin, mucous membranes, intestines.
Symptoms. Depending on various external factors and the body’s resistance the disease manifests itself in several forms. A form characterized by the presence of round dry spots or ulcers (5 – 10 cm) with a red border; sometimes I note the ulceration of the snout and other head injuries. When In the form of wet spots slightly bordered. When the form With red spots observed on the mucous membrane of the pharynx and the inner side of the Gill covers, on the skin in the front lower part of the body; also characterized by the absence of open sores and damp spots, no damage on the head. This form of the disease occurs in brackish waters. When the form D are formed suppurating wounds and abscesses.
The disease acute, subacute and chronic. In the acute phase observed hemorrhagic inflammation of the mucous membrane of the mouth, inner side of the Gill cover, the skin in the lower part of the body from the pectoral fins to the anus. the disease is characterized by transience and mass lesions of fish. When increased resistance of fish in summer prevails subacute, at which point necrotic collapse individual sections of the skin that look like deep scuffs. In the necrotic process involved the underlying tissue, ulcers with a red rim surrounding inflamed tissue. Often these lesions are rounded and are located closer to the rear part of the body. Sometimes inflamed eye tissues. The autopsy found hemorrhagic inflammation of the stomach and swim bladder. A chronic course occurs mainly at the end of an epizootic outbreak and is characterized by the formation on the body of diseased fish in different parts of ulcers with hemorrhagic or serous inflammation inflammation of the underlying muscle tissue that are usually naked and have focal hemorrhage. When the skin lesions usually reveal varying degrees of serous-hemorrhagic inflammation, hyperemia and necrosis of the epithelium, hemorrhage, edema and breakdown of loose connective and adipose tissues. Dense connective tissue, usually little damaged.
In other species, the disease occurs with inflammation of the skin, ulceration and aresenium scales.
The diagnosis is mainly put on the basis of clinical signs in the spawning season, and bacteriological tests. Experimentally infecting healthy fish by suspension from internal organs of diseased fish. The Guinea pike to check the virulence of the selected cultures to introduce 0.1 – 0.2 ml 2 – 5-day broth culture and were watching them for 2 to 3 weeks.
Control measures and prevention. The basis of the disease supposed to remove the source of infection from the reservoir, reducing the number of susceptible fish and the establishment of immune herds.
With the appearance of the disease produce maximum catching of pikes, and the collection and disposal of diseased fish and dead bodies. During the mass harvesting of fish daily disinfect fishing gear, tools, containers and other equipment. Do not allow the migration of infected fish in a pond from other bodies of water, and in safe waters. Gradually in the affected water body is created spontaneously immune herd, and the epidemic fades out.
In the occurrence of epizootics in fish farms is carried out the most comprehensive catching pike in the head and feeding the ponds during the autumn harvesting of the ponds. In the next two years take steps to decrease or complete elimination of pikes head in the pond and prevent their landing in the fishing ponds. All this leads to a gradual recovery of the economy.
On troubled waters or fish farms impose a quarantine. It is prohibited the import and export of sensitive fish species, and authorizes the health of their catch regardless of the season or the existing seasonal ban on fishing. All fish to be caught are subject to mandatory veterinary examination and no signs of the disease are sold through a network of public catering.
Disinfection measures in fish farms and on the fishing pond is carried out in the same way as with other highly contagious diseases of fish. The corpses of fish after disinfection buried to a depth of at least 1 m.