Crucian carp prices rose across the board. It is understood that due to the small stock of large-scale fish in the current production areas, with the recovery of consumption, the demand surges, the supply is tight, and the price of fish in various places soars. Among them, Jiangsu Xinghua's various specifications of crucian carp have been significantly raised, 6 two specifications of fish rose as high as 1 yuan / jin, while 9 two sizes of fish rose from the original 11 yuan / jin to 11.5 yuan / jin; Guangdong region rose more ferociously, Jiangmen area 8 two size fish dolls 9.5 yuan / jin soared to 12 yuan / jin, Yunfu production area is raised by 0.5 yuan / jin, the latest quotation of 8 yuan / jin.
If the price of fish is good, it must also be well raised. According to reports, the current pond fish is less related to the outbreak of fish disease in the early stage, resulting in a large number of fish losses; and with the increase in temperature, another parasitic disease affecting crucian carp has also entered a high incidence period, and prevention and control should be done in advance to minimize the loss.
A large analysis of the pathogenesis of crucian carp myxosporidium
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Crucian carp myxosporidosis is a serious parasitic disease of the heterogeneous silver crucian carp, which mainly endangers crucian carp fingerlings and adults, and is common in June to July and September to October.
Biological characteristics: Myxozoans, myxozoans are a class of highly specificized epizoan parasites with invertebrates and aquatic vertebrates as the main host, generally parasitic outside the host cell, or tissue parasitism, or cavity parasitism; when tissue parasitizes, nutrients are usually located between host cells until they develop into large sporangia, and the spores mature within the sporangia.
The same myxotic animal shows obvious selectivity or host specificity for different hosts, and the same myxosome animal parasitizes different parts of the same host and causes host pathological changes, that is, the myxosome animal has strict host specificity and hisxidity.
Table 1 Crucian carp common spore worms
First, the law of pathogenesis
Myxosporidium in yancheng area that endangers crucian carp farming
(1) Honghu iodine bulbophyllum causing crucian throat spore disease
The disease generally has two peaks of incidence, the epidemic water temperature in June-July and September-October is 20-27 °C, and the infection rate and mortality rate are very high, resulting in great economic losses.
(2) Wuhan unipolar worm causing crucian skin spore disease
The disease is generally only endemic in the grow-out period of summer flower fingerlings in April and July.
(3) Wang's unipolar worm that causes gill spore disease in crucian carp
During the epidemic period of the disease, the disease is infected with Wuhan unipolar worm, fish species and adult fish, and the circulating water temperature is 20-30 °C.
(4) Wu Li iodine bubble worm that causes crucian carp bellysporidosis
The disease generally occurs in July to November, but there is no obvious seasonality, it can be found all year round, and the proportion of infections has increased in recent years.
Abdominal spore disease caused by Wuhan unipolar worm, the body surface protrusions of crucian carp are visible to the naked eye, and the spore sporangia under the scales are milky white in shape nearly round or oval.
Gill spore disease caused by the unipolar worm Wang, open the gill cavity gill filament to reveal a distinct milky white sporangia. Needle-like or linear sporangia are found under a microscope at the beginning of the disease.
In Yancheng, the economic losses are greater, and the "laryngeal spore disease" caused by the laryngeal parasitizing Honghu iodine bubble worm and the "abdominal spore disease" caused by the liver and pancreas parasitize Wu Li iodine bubble worm are the most serious, which can occur in both the seed and adult stages.
"Laryngeal spore disease" caused by Honghu iodine bulbophyllum opens the oropharyngeal cavity, and in mild cases, the upper part of the pharyngeal cavity is red and swollen, and in severe cases, the sporangia block the throat of the fish, the gill lid is turned outward, and the side of the crucian carp is protruding.
The abdomen of the diseased fish with "abdominal spore disease" caused by Wu Li iodine bubble worm was inflated, and after dissection, it was found that the sporangia of different sizes in the abdominal cavity were milky white and filled the entire abdominal cavity, seriously squeezing the liver, intestine and other organs.
Second, why is myxosporidium difficult to treat
Although the great harm of fish mussporosis has been recognized, so far no effective drug control methods for fish mussosporasis have been found. This is because once the myxosporidium forms mature spores and cysts in the fish, the tough shell of the spores makes it difficult for the drug to enter, and almost any drug is ineffective against the musosporidium at this stage.
Although there is still controversy in the academic community, most scholars tend to believe that the development process of myxosporidium is roughly as follows: the spores are swallowed by the intermediate host (generally aquatic oligochaetes) after being released from the fish body to the water body, and the spores develop into thousands of radiation sporangia in the intermediate host through asexual reproduction, and the radiosporidia are released into water, and when they encounter the fish body, they are infected, and they are divided and developed into mature spores and cysts in the fish.
The intermediate host of myxosporidium "red worm"
3. Comprehensive prevention and control
How we can be more targeted
The author believes that the prevention and control of myxosporidiosis needs to be based on the key and weak links in the epidemic, combined with the method of drug control, and put forward the key points of integrated control of fish musporidiosis according to the ecology of the myxosporidium population (including the "parasite-host" relationship), for your reference.
1. Selection of prevention and control time period
The development of fish myxosporidium is subject to the killing of the source of infection in the water body in the stage of host parasitism, radiosporidium, vegetative body and mature spores (encapsulates) and the expulsion and killing of the early stage of infection in the fish, then the myxosporidium will not survive and cause disease. Since the mature spore (encapsulated) stage is the most difficult to kill by drugs, it is not recommended to control at this stage, but should be carried out at the stage of radiosporidium and vegetative body.
2. Clear the pond
The development of fish myxosporids requires aquatic oligochaetes (water earthworms) as intermediate hosts, so measures such as pond clearance are crucial for the control of myxosporidiosis, which can eliminate water earthworms and radial spore worms in water bodies and sediments, and even kill mature spores in water bodies and sediment.
3. Avoid adding water during the onset period
The radiosporidium stage of myxosporidium and its intermediate host (water earthworm) can be transmitted by water currents (radiospores are not migratory) So water addition is avoided during the annual onset of the Yancheng area.
4. Alternating use of different drugs
According to two weak links in the developmental history of crucian carp myxosporidium: (1) radiosporidium stage; (2) myxosporidium vegetative phase. After the musporidium infects the fish body, the first formation of vegetative bodies, and then through the development of the formation of spores and cysts, the mature spores of the muscular spores have a very hard shell, the drug is difficult to penetrate, the vegetative body is a deformed body without shells, parasitic in the fish, it is easier to die, so internal administration is the focus of killing.
Seasonal dynamics and prevalence of myxosporidium disease in Yancheng region Can be killed annually in water bodies one month before the emergence of mature spores and cysts, and spore nutrients in water bodies and spore bodies in fish bodies.
External use: such as copper naphthenate, avermectin, dimethoate, etc. Because the intermediate host is difficult to completely kill, and the new radiosporidium is released into the water body again, different drugs are used interchangeably.
Internal use: Common internal Chinese medicines include 100 parts of the 100-part betel nut scatter, bitter ginseng powder, the Chinese Science Institute recommended that the end of the pen and other authors do not recommend adding chlorphenidine in the prevention, resulting in the resistance of myxosporidium.
5. Add hepatoprotective drugs to the internal administration program
The root of the treatment of fish musporidiosis is how to control its infection intensity and the practical effect of secondary bacterial diseases that may be triggered by the infection of myxosporidium shows that the effect of Western medicine is usually more direct and significant, but the toxic side effects on the fish itself are also obvious, so it is recommended to add liver protection drugs to the internal treatment regimen, or when the internal treatment regimen is stopped, that is, the use of crucian health functional materials or liver and intestines to take a course of internal treatment.
6. Regulation of water quality and substrate
Through the regulation of water quality and substrate, the pond bottom is oxidized and alkalinized. After entering the water, a small amount of fertilizer water replenishes bacteria to cultivate pond water algae, reduce pond organic matter, regularly use carbon sources and other nutrients of water bodies, maintain the good bacterial phase and algal phase of the pond, and increase the dissolved oxygen of the pond. At the same time, in terms of feeding, choose high-quality feed and feed reasonably to ensure that crucian carp can be fully fed and grow healthily.
Infection with myxosporidium can be reduced in the above way.
Reprint Statement
Source: Haida Agriculture and Animal Husbandry