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Trypanosoma is a genus of flagellar that was first discovered in the blood of trout in 1841. Trypanosomiasis is small, parasitizing the blood, causing the fish to be mentally weak, inedible, weak, anemic, and finally dead. Since the 1950s, there have been reports of trypanosomiasis infection cream, grass, silver carp, bighead carp, carp, crucian carp, bats, yellow jaw fish, yellow eel, eel, catfish and other fish. Sick fish manifest as no food, mental stagnation, floating on the surface, slow activity, difficulty breathing, body color fading, gill silk rot, etc., initially thought to be hypoxia and gill rot disease, after taking oxygenation measures, chlorine disinfectant disinfection water, internal administration of vitamin C, furazolidone, antibiotics and other weeks are ineffective, there are constantly dead fish. Subsequent microscopic examination found that there were fluctuating insects in the gills, misidentified as gill cryptoflagellus, using a combination of ketone sulfate and ferrous sulfate (5:2) 8 mg/L soaked for 10 minutes, ineffective, switched to 250 mg/L formalin soaked for 30 minutes is still ineffective, and the number of dead fish is increasing day by day. Finally, Sichuan Agricultural University led the consultation, and through autopsy, blood smear microscopy, pathological tissue examination, etc., the diagnosis of trypanosomiasis was confirmed.
1. Pathogens
Trypanosomiasis is a flagella that lives in the blood and can cause disease in humans, domestic animals, some wild animals and fish. Trypanosoma. The body of trypanosomiasis is long, narrow, pointed at both ends, and shaped like a willow leaf, but tends to bend into an S-shape, wavy shape, or ring. Propagation is a longitudinal dichotomy. Life history includes 2 hosts, with vertebrates such as fish as the terminal host, and arthropods or leeches (also known as ants, the same below) as intermediate hosts.
Trypanosomiasis is a disease caused by trypanosomiasis parasitizing in the bloodstream of fish and, in severe cases, can cause death in sick fish. Trypanosomas are species of flagellar. The worm body is narrow and long, with a body length from 10 microns to more than 100 microns, and the two ends are thin; there is a nucleus, oblong oval, which is anterior in the middle of the worm body; the back of the worm body has 1 dynamic nucleus and 1 hair-bearing body, and 1 anterior flagella grows from the hairy body, forming a wave film along the edge of the worm body, which is free from the front end of the worm body. It is parasitic in the blood of fish and multiplied by the dichotomy. There are nearly 100 species of trypanosomiasis that parasitize in fish.
2. Prevalence
Trypanosomiasis is widely distributed in China, and pathogens can be found all year round, and are endemic from June to August. Transmitted by leeches (Johanssonis sp.). Freshwater fish can generally be infected, and a variety of marine fish, such as turbot flounder, mackerel, mackerel, ray, cod, perch, seabream and eel order can also be infected.
3. Symptoms and pathological changes
It parasitizes in the blood of fish and obtains nutrients in an osmotic manner. Usually no symptoms are visible. In severe infection, the fish can be weakened, emaciated, anemia and a continuous sporadic death occurs. A small amount of parasitism has little effect on the fish body, and when it is severely infected, it can make the fish body weak, emaciated, and anemia. Leeches that transmit fish trypanosomiasis are known to include the ulnar pedicle (Piscicola geometra).
Trypanosomiasis parasitizes the blood of fish and is mainly transmitted through leeches and is an important disease of a variety of freshwater and marine fish. A large number of infections lead to hypoxia, emaciation, and eventual death. Intermediate host leeches usually parasitize the surface of the fish, fins, gill cap trailing edges, etc., so there will be different degrees of congestion or bleeding.
On live examination, blood and saline are taken from the gills and hearts of live fish, and observed under a microscope, trypanosomiasis is seen beating lively in situ between cells, which is easy to detect; smear specimens need to be stained before they can be seen. The parasitic trypanosomiasis in anchovies generally has a low infection rate, the intensity of infection is not large, and there is no special disease on the outside. However, in carp, crucian carp and catfish, sometimes the infection intensity is very high, and the fish have the phenomenon of jumping out of the pond with irritability, but their blood pathological indicators are not detected. As for the infection of trypanosomiasis, only chinese neck leeches, inchworm leeches and marginal dipterus leeches are recorded in China, such as carp, crucian carp and catfish, and it is not clear whether these leeches are infected.
4. Diagnostic methods
Microscopic examination of the blood reveals the shape and number of insects. A drop of blood is drawn from the gill artery or heart of the fish, placed on a load slide, observed under a microscope, and when the worm body with twisted movement between the blood cells is seen, it is basically diagnostic.
(A large number of trypanosomiasis parasitize the blood of diseased fish)
Trypanosomiasis is a narrow, leafy, with 1 flagella growing from the posterior basal granule, forming a fluctuating membrane along the body and freeing to the anterior end as flagella. The sick fish is thin and weak, and there is anemia in severe cases, but it does not cause a large number of deaths, and the method of diagnosis is to suck a small drop of blood in the gill artery or heart of the sick fish and place it under a microscope.
Diagnosis is based primarily on microscopic examination of large numbers of trypanosomiasis in the blood. Trypanosomiasis infection is suspected when fish experience decreased appetite, drowsiness, and pallor of gills and enlarged spleen. The blood is further drawn, divided into two parts, one part is made of a blood smear, and the blood is stained by Jimsa to see if there are a large number of trypanosomiasis in the blood to make a final diagnosis.
(Leeches, ants)
5. Life history of trypanosomiasis
The life history of fish trypanosomiasis in fish is more complicated, with leech blood sucking infection of fish body, trypanosomiasis first experienced an incubation period, this period lasts about 1 week or so, but this period in the fish body's peripheral blood generally can not be observed in the presence of insects. This is followed by a period of development, which can last from a few days to a few weeks. As a result of the bifurcation of trypanosomiasis during this period, the slender size of a large number of flagella can be observed in the peripheral blood of the fish, and the large number of trypanosomiasis can lead to the death of the host.
6. Prevention and control methods
Because trypanosomiasis parasitizes the blood, the usual method of insecticidal treatment is ineffective, so the treatment after infection is more difficult, and it is recommended to focus on prevention.
Current control methods are mainly controlled by killing fish leeches. In shallow waters along ponds and lakes with many leeches, drugs can be used to eliminate leeches and reduce infection. It is recorded abroad that sodium aminophenylarkilate is used to kill trypanosomiasis, but it should not be used for edible fish.
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