Ringworm disease is a common multiple gill disease that is mainly transmitted by eggs and larvae, and a large number of parasites can cause mass death of fry and fish species. The common ringworms in the feeding of fish in China are gill ringworms, bighead carp ringworms, silver carp ringworms and ring gill finger bad worms. The insect body is flattened, there are 4 black eye spots on the back of the front of the head, the mouth is near the eye point, the expanded part under the mouth is called the pharynx, and the intestinal tube after the pharynx extends to the posterior end of the body to form a ring. The posterior end of the worm body has a fixing disc consisting of 1 pair of large anchor hooks and 7 pairs of small edge hooks, which are fixed to the gills of the fish. Ringworms are hermaphrodites. There is an ovary in the posterior part of the worm body, and the sperm nest is behind the ovary. Ringworms are widely distributed, endemic in summer and autumn, and diseased fish can often have more than 60 insect bodies on a gill piece. Ringworm disease is more common at the fingerling stage and is quite lethal to juveniles, but not harmful to healthy adults.
1, Symptoms
1. The symptoms of the diseased fish are not obvious at the beginning of the disease, with the increase of parasite bodies, the gill silk tissue is destroyed, the gill filament mucus of the diseased fish increases, the gills lose blood, and the gills are all or partly dark gray or pale, which hinders the breathing of the fish, and sometimes a large number of insect bodies can be seen squeezing out of the gills.
2. The gills are significantly puffy, and the gill lid is slightly open and difficult to close.
3. Mental sluggishness, slow swimming; stop feeding in severe cases, difficulty breathing, gradual emaciation and weakness, and eventually suffocate due to breathing obstruction and suffocation.
4. Seriously infected ringworm diseased fish, the body color becomes black, very thin, swimming slowly, appetite loss, gill filament mucus increases, gill petals are gray-white, breathing difficulties; young fry, especially bighead carp fry, often show gill organ puffiness, gill cover is difficult to close the disease.
The gills increase mucus and the gills lose blood
Second, the harm
Ringworm disease is a parasitic gill valve disease common in the fry and fingerling stages, mainly harming grass carp, silver carp, bighead carp, carp, crucian carp, Tuantou bream (Wuchang fish) and goldfish. Overwintering fingerlings begin to develop diseases after the onset of spring, and the epidemic season is in late spring and early summer. Not only is it prevalent in pond fish farming, but there are also a large number of deaths in small reservoirs and lakes. It is endemic in all major fish farming areas in China, and the Yangtze River Basin is more serious.
The pathogenicity and damage of ringworms depend on the age of the host and the number and size of the parasites. Ringworms usually insert the hook on their posterior sucker (posterior fixer) into the parasitic site, causing lesions at the parasitic site, resulting in the following adverse consequences: (1) ringworms attach to the gills after the fixator, make inchworm movements, destroy the gills' epidermal cells, causing gill damage, bleeding, and mucus increase; (2) in the process of parasitic host, detachment from the host and feeding, the formation of epidermal damage, easy to cause pathogens (such as bacteria, viruses) invasion, causing inflammation, secondary diseases; (3) ringworm sucking fish blood, mucus, Stimulate the host to produce a large number of secretions, disrupt normal physiological activities, cause electrolyte imbalance, pH imbalance in the main fluid, causing a variety of complications; (4) parasitism can cause the host systemic hypoxia, exacerbate the appearance of extensive and progressive lesions in various organs, until the metabolic disorders of each system, causing multiple organ failure of fish.
Third, the role of parasites on the host
1. Nutrient capture
The parasite's source of nutrients depends entirely on the host, which can cause damage to the host. The size of the damage depends on the size and number of worms. For example, ringworms suck blood from the gills of fish, and tapeworms absorb digestive juice in the intestines of grass carp, affecting the growth and development of fish.
2. Mechanical stimulation
The parasite's mechanical stimulation and damage to the host, the parasite's attachment organs (hooks, spines, suction cups) have a mechanical stimulus effect on the host when attached, destroying mucosal and epidermal cells. Causes bacterial invasion, causing inflammation or degeneration. For example, the anchor hook of the single-limb fluke and the suction cup of the compound limb fluke have irritation and damage to the host fish.
3. Compression and blockage
In vivo parasites compress, squeeze and atrophy the internal organs of the host; when a large number of parasites gather or burrow into the narrow aisle, they will also block the lumen and cause atrophy and necrosis of the host tissue. Compression and obstruction occur in the main organs and certain parts of the host, which can lead to the death of the host.
4. Hazards during migration
Some parasitic worms migrate from one organ to another or with blood circulation when they migrate within the host, causing internal bleeding or secondary infection.
Preventive treatment
1. The pond should be completely cleared before the seed stocking, and the prevention of parasitic diseases should be done regularly in the breeding process.
2. If the mixture can be used for herbal insect repellent net, if not fed, it can be sprinkled with insect repellent powder for insect repellent, and the specific medication can be operated according to the drug instructions.
3. After the disease is controlled, the sick fish pond should be filled with about 20 cm of new water.