First, pathogen and form, life history.
There are many types of pathogens of ringworm disease, including gill ring worms and gill ringworms that parasitize grass carp; silver carp ringworms that parasitize silver carp; bighead carp ringworms that parasitize bighead carp; bad gill ringworms that parasitic carp, crucian carps and goldfish; and monozoan trematodes that belong to the heloid class in parasites.
Ringworm, small testicle quasi-ringworm, short hook quasi-ring insect, the insect body is flat, the body length is less than 2 mm, the front end of the head has two pairs of head, 4 black eye spots, the mouth is near the eye point, the expanded part below is called the pharynx, after the pharynx there are two intestinal tubes extending to the back end of the body to connect into a ring, the back end of the worm body has attached organs, consisting of a pair of large anchor hooks and 7 pairs of edge small hooks, which are fixed on the gills of the fish. The morphology of the insect body is shown in the figure below.
Ringworms are hermaphrodite parasitic trematodes. The life history is relatively simple, there is no intermediate host, adults lay eggs on the gills of the fish, hatch into ciliate larvae, larvae encounter a suitable host in the water will attach to parasitism, develop into adults on the gills of the host, and the number of eggs laid and the incubation time are closely related to water temperature. The time for incubation of larvae in eggs at 18 °C-30 °C is 3-7 days.
When the water temperature is above 20 °C, the ciliate larvae of the ringworm hatched in the water cannot find a suitable host within 24 hours and lose their infectivity. When the water temperature is below 20 ° C, as the water temperature decreases, the survival time of ciliated larvae in the water is prolonged.
Second, symptoms and epidemics, diagnostic methods.
When ringworms parasitize on gills, due to the attachment and movement of the insect body on the gills, the anchor hook and the edge hook hook the gill tissue of the host, and constantly make inchworm-like movements, thereby destroying the epidermal cells of the gill filament, stimulating the gill filament cells, thus secreting too much mucus, the sick fish breathing difficulties, swimming slowly, often floating on the surface of the water, newly diseased fish, paroxysmal wild swimming on the water, or rapidly swimming sideways at the bottom of the pool. The body color is black, and the gills of the fish are whitish and puffy. Young fry, especially bighead carp fry, often show edema of gill organs, gill lids are difficult to close, and under the mucus there are "small white dots" gathered by many ringworms. Because the gill tissue is destroyed, it is easy to cause secondary infection of pathogenic microorganisms, and at the same time, the insect body seizes the host nutrient and the anorexia of parasitic fish caused by the parasitism of the insect body causes the malnutrition of the fish body and the body is thin.
Due to the parasitism of the insect body in the gills, the breathing disorders of the diseased fish are caused, and the oxygen needs of various organs of the body are not met, resulting in a series of physiological dysfunctions.
Ringworm disease is a common parasitic disease in the freshwater fry and fingerling stages, which mainly endangers carp cultured fish such as grass carp, silver carp, bighead carp, carp, crucian carp, Tuantou bream (Wuchang fish) and ornamental fish such as goldfish. Transmission is mainly based on eggs and larvae, with overwintering fingerlings beginning to develop diseases in late spring and endemic in late spring and early summer. It is most prevalent in the 20-25°C water temperature range, and is endemic not only in pond fish farming, but also in small reservoirs and lakes. It is endemic in all major fish farming areas in China, and the Yangtze River Basin is more serious. Most species of ringworms have a strong selective effect on the host, and reproduction spreads rapidly, is harmful, and a large number of parasites can cause a large number of fish species to die.
The simplest diagnostic method of ringworm disease is microscopic examination, that is, cutting the gills suspected of ringworm infection, placing it on a glass slide, adding a drop of water, making a water-soaked tablet, placing it under a microscope for observation, and more than 5 ringworms appear in each field of view of the low magnification lens, which can be identified as ringworm disease.
Photographs of ringworms under the microscope are as follows:
Third, prevention and control recommendations.
1, before the stocking of fish fingerlings, each cubic meter of water body with 20 grams of potassium permanganate to bathe the fish fingerlings, which can kill ringworms.
2, the use of drugs to kill.
In the process of treatment, it is necessary to use drugs according to life history, you can use 80% of the refined crystal dimethadios powder, 200 grams per acre of water, or ring killer (mebendazole solution), per acre. The dosage of rice water body is 67g-100g. Take the drug 1-2 times as appropriate. When killing insects, we must pay attention to the sensitivity of related varieties to drugs to avoid drug accidents. When sprinkling, it is better to use Kunhong Albendazole for internal administration, and the dosage is 10 kg per pack of mixing ingredients for internal use for 5-7 days.
Disinfection is followed by disinfectants such as mybican (povidone iodine) or glutaraldehyde to avoid secondary infection of the wound caused by parasite parasitism. Since the drug cannot kill the eggs of the ringworm, it is necessary to use the drug again one week after the first insecticide to avoid the re-infection of the fish body by the larvae developed by the eggs that have not been killed, resulting in repeated diseases.
The fish disease is a typical gill parasite, which breeds secondary infections that cause gill mold, hyperemia of the head, treatment first requires insecticide, then removal of fungi, and repair of the water environment, controlling the breeding and reproduction of parasites and bacteria from the root.
【Suggested Method】
On the first day, ringworm drugs, such as Suyada "ring killer" containing mebendazole, pay attention to the dosage and time of medication.
The next day, the bacteria will be cleared + mold flat, mixed throughout the pool evenly sprinkled.
After 3 days, the water quality is adjusted, and the algae seed + water beauty + EM is used.
【Tracking Results】
The number of deaths on the 3rd day of medication dropped to a few, and there were basically no deaths on the 5th day.