For the vast majority of conventional aquaculture species, September and October are the last chances for rapid weight gain for fish. After nearly half a year of intensive feeding, the fish have successfully reached a larger size. However, due to feed nutrition, water quality, breeding management and other reasons, there are often more or less harmful parasites in the intestines of many fish. Basically all fish intestinal parasites rely on the nutrients of the fish body for reproduction and metabolism, and a large amount of nutrient loss will slow down the weight gain rate of our fish and increase the bait coefficient. And the reproduction and survival of parasites in fish will increase the chance of infection of various diseases. For the National Day New Year's Day temporarily do not clear the pond to sell fish ponds, intestinal parasites will be more harmful, in most provinces in the country, during the winter because the water temperature is too low, we tend to stop feeding, in the absence of enough bait supplementation, intestinal parasites will make the fish fall out of the speed of acceleration, rapid emaciation, so that in the Spring Festival fish prices are high in the case of breeding benefits but rapid reduction, facing the consequences of not making money or even loss.
Therefore, before the fish overwinter, we must do a round of intestinal deworming work on the fish.
Common fish intestinal parasites
Common symptoms of intestinal parasites: the abdomen of the sick fish is swollen like a ball of leather
1. Tāo[tāo] worm. It is also commonly known as 'noodle worm.'
There is a sense of hardness under pressure, and the long white strip of insect body can be seen wrapped around the digestive tract.................................... Tongue tapeworm disease
Pathogen: The schizophal larvae of the tongue-like tapeworm are long white bands, commonly known as "noodle worms". The English name is ligula sp. Adults parasitize the intestines of water birds, mainly gulls, and fish are its second intermediate host. Its eggs eventually host the feces of the gull bird are discharged into the water, in which they hatch hook bulbs, which swim freely in the water, and after being swallowed by a slender dart water fleas, develop into protocopods in their bodies.
Symptoms: A parasitic disease caused by the invasion of schizocephalus liae (Ligula) and diplodocus (Digramma)) into the intestines of fish. Most freshwater farmed fish and wild trash fish occur. The abdomen of the diseased fish is enlarged, the body cavity is filled with a large number of white banded insect bodies, the internal organs are squeezed, the normal function is destroyed, and the development of the fish is hindered.
Prevalence: Schizophal larvae of the tongue tapeworm usually parasitize the body cavity of crucian carp, carp, silver carp, bighead carp and other fish. It is widely distributed in Heilongjiang, Inner Mongolia and the Yangtze River Basin. But in the Gan Antarctic is rare.
Second, head groove tapeworm disease
In the foregut there are milky white translucent, flattened tapeworms .............................. Taeniasis of the head groove
1. Pathogens
Bothriocephalus gowkongensis and B. opsarijchthydis. The body is banded, segmented, and 20 to 250 mm long. The head segment has 1 distinct top disc and 2 deep suction grooves. Adults parasitize the intestines of fish, with the middle host being sword fleas.
2. Prevalence
Grass carp, tuantou bream, bluefish, silver carp, bighead carp, mullet, etc. can all be infected with the disease, and grass carp and tuantou bream species are the most seriously affected. In particular, it is the most harmful to overwintering grass carp fingerlings, with a mortality rate of up to 90%. Grass carp are most likely to suffer under 8 cm, and when the body length exceeds 10 cm, the infection rate begins to decline.
3. Symptoms and pathological changes
Sick fish are emaciated, blackened, have decreased appetite or do not feed, and their mouths are often open; Dissection shows that the foregulet is dilated into a gastric sac, which contains a large number of banded milky white worms, and the intestinal mucosa is hyperemic and inflamed.
4. Diagnostic methods
By cutting open the belly of the fish and cutting the dilation site of the foregut, the diagnosis can be confirmed by seeing the white banded segmented worm body.
3. Capillary nematode disease
It can be seen that there are transparent nematodes in the intestine, mainly in the posterior intestine............... Capillary nematode disease
cause of disease
Capillary nematode disease is a disease caused by nematodes whose causative agent is capillary nematode. The male is 1.93 to 4.15 mm long and the female is 4.99–10.13 mm long. Capillary nematode disease is a fish disease caused by capillaries parasitizing the intestines of fish. The body is linear and visible to the naked eye. Eggs are excreted into the water with the host feces, sink to the bottom of the water, or attached to aquatic weeds and debris, and are infected after being swallowed by fish.
1, Symptoms
Parasitizing in the digestive tract of fish, burrowing into the mucosal layer of the intestinal wall with the head, destroying the tissue, so that other pathogenic microorganisms in the intestine invade the intestinal wall and cause inflammation, which can cause the death of the fish in severe cases. Simple suffering from capillary nematode disease, due to the absorption of nutrients by the insect body, makes the fish body thin, and the growth and development are affected to a certain extent.
The eggs of the capillary worm begin to divide after the feces are excreted. When the water temperature is 28 to 32 ° C, it develops into larvae after 6 to 7 days. The larvae usually become infective embryonic eggs in the egg without burrowing out of the egg shell, and other fish swallow the embryonic egg and then become infected.
Prevalence
Capillaries parasitize in the intestines of green, grass, silver carp, bighead carp, carp and yellow eel, mainly endangering the fish species of that year, and are most popular in Guangdong, Hubei and other places.
【Illness】 The sick eel has a loss of appetite and a emaciated body, often sticking its head out of the water, and rolling its abdomen upwards or in a struggling manner. From June to September every year, the peak season of yellow eel capillary disease is in full swing, and the incidence of soil eel ponds with high-density hydrostatic culture is generally the majority, while cement ponds or brick eel ponds cultivated by flowing water are less common. The incidence is around 80%.
4. Echinacenococcosis
Milky white echinococcus can be seen hanging on the intestinal wall ....................................... Echinococcus disease
【Symptoms】 The appetite of the sick eel is seriously reduced, or it does not eat, the body color becomes blue and black, and the anus is red and swollen. The insect body penetrates into the intestinal mucosa with a snout, sucks nutrients, causes inflammation of the intestinal wall, and in severe cases, it can cause intestinal blockage or intestinal perforation, causing the death of yellow eels, with an incidence of about 90%.
V. Lateral trematodiasis Asymphylodorasis
It can be seen that there are sesame-like insect bodies peristalsis in the intestine............ Lateral trematodiasis
Symptoms The onset of the fry body turns black, swimming is weak, clustered in the downwind of the fish pond, do not eat, so it is called "closed mouth disease". 6 to 10 cm of fish fingerlings onset, except for a slight loss of physical fitness, there are no obvious symptoms.
Hazards Mainly harm grass carp, bluefish, silver carp, bighead carp, carp, crucian carp and other fry. Lateral trematodiasis is also common at the fingerling stage, but it only affects growth and does not cause death. The onset season is from May to June, and the harm is particularly great within 3 to 6 days after the fry descend from the pond.
Life history of Japanese side-breeding flukes
Japanese side breeder trematodes (Asymphylodora japonica Yamaguti, 1936). The worm is like a small sesame seed, with a mouth and an abdominal suction cup in the body, one testicle and one ovary visible in the back half of the worm body, and a lumpy yolk gland arranged on both sides of the body, and the penis and uterus end are opened on one side of the body, and there are small spines, egg pear-shaped and egg caps. The eggs of the lateral trematodes fall into the water with the fish droppings, hatch the trichocetes, and then enter the field snails [Viviparus (Cipangopaludina) chinensis], the swamp snails (Parafossarulus eximius and Parafossarulusstriatulus) and other bodies to develop into thunder larvae and tail cercariae. Tailed larvae are tailless, shaped like adult insects, they migrate to the antennae of snails, swallow for fry, and mature in the intestines of fish; Or it enters other snails into cystic cysts, and after swallowing snails such as bluefish and carp, cysticers develop into adults in the intestines of fish. More parasitism of insects will cause mechanical blockages in the intestines of fish bodies, affecting the feeding and digestion of fry and fish species. Intestinal blockage is the cause of "occlusion disease" in fry. Fry die as a result of failure to obtain the nutrients necessary to sustain life, resulting in exhaustion.
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