In the natural environment, the vitality of fish and the ability to adapt to the environment are very strong. With the promotion and development of intensive fish farming, fish diseases have been increasing in recent years, and various new diseases have emerged. The degree of harm to production has gradually intensified, and the prevention and control of fish diseases in a timely manner has become an important link in increasing aquaculture production and ensuring a bumper harvest.
With the rise of temperature, the water temperature is also rising, the rainy season is also coming, and the activities of various pathogens are strengthened, which is easy to infect fish with various diseases, especially parasitic diseases, especially wheelworms, which are the most prone to outbreaks, causing greater losses and seriously affecting the growth of surviving individuals in the later stages. Although there are many prevention and control measures for parasitic diseases, in order to make the aquatic products that occur in line with the requirements of green food, higher requirements are put forward for the methods of prevention and treatment and medication, and the principle of "prevention first, active treatment, and prudent use" should always be adhered to. Here we briefly discuss a common link in the control of parasitic diseases - the integrated control of wheelworms.
<h1 class= "pgc-h-arrow-right" > biological habits of wheelworms</h1>
Trichodina is a type of ciliate. It is about 0.07mm in size and cannot be seen with the naked eye. Under the microscope, from its reverse surface, you can see that there is a ring of teeth arranged in a wheel shape by 18-30 tooth bodies, which looks like a wheel, especially when it rolls forward, it is indeed very similar to the large wheel of a tractor in motion.
Sometimes, when we look at it from its side, it looks like a felt hat worn on the head of an old man. It also has a large horseshoe-shaped nucleus in its body, and a small nucleus near the large nucleus. Although the small nucleus is small, it can play a greater role than the large nucleus in breeding children and grandchildren! The mouth of the wheel worm is located on the reverse side of the "wheel", and there is a large or small telescopic bubble near the mouth, which is surrounded by a membrane similar to the plasma membrane, and there is moisture and excrement dissolved in water in the bubble, and when the telescopic bubble is constantly expanding, the inclusions in the bubble will be excreted.
Wheelworms wear down the skin and gill tissue of fish with their characteristic "wheels", the constant rotation of the tooth rings, and then ingest their cell debris or parasitic blood cells.
<h1 class= "pgc-h-arrow-right" > second, the symptoms of fish wheelworm disease</h1>
Fish rotifers parasitize the body surface and gills, and fry can have symptoms of "white head and white mouth" or "running horse" (circumnavigating).
Sick fish appear as black bodies and swimming alone. Some swim wildly around the pond in groups, often causing a large number of deaths of fry and fingerlings. The chakra parasitic on the surface of the fish slides back and forth on the surface of the fish body, stripping the host's skin tissue cells and gill tissue for nutrition, destroying the skin and gill tissue, affecting the fish's breathing and normal activities.
If a large number of wheelworms are concentrated on the top and mouth of the fish, the severely worn fish can see the symptoms of white-headed white-mouthed in the water, and the fish's mouth and gills are damaged and cause feeding difficulties, shortness of breath, and even death.
When a large number of wheel worms are parasitic on the tail fin, it will affect the normal swimming of the fish, and even if the fish flicks its tail vigorously, it still cannot get rid of the entanglement of the wheel worm, so the fish shows anxiety. It has been found that a one-inch-large fry, its parasitic wheelworms, in a low-power microscope field of more than 60 to reach such a parasitic number, can be regarded as a lethal amount, the juvenile fish soon died.
Not only are the four major fish difficult to overwhelm, but even the tilapia with strong vitality, few diseases and low oxygen tolerance, as well as special breeding species such as spotted forktail backfish, yellow eel, loach, giant yellow croaker, eel and so on, are also difficult to escape the "magic hand". On the surface and gills of most fish, the wheelworm can be found all year round, but it is only a matter of the number.
<h1 class = "pgc-h-arrow-right" > third, the cause of fish death caused by the outbreak of wheelworms</h1>
1, the fish's physique is poor, there is no ability to resist.
When there is a rotifer parasite, the immune system has no ability to resist, and symptoms of weakness immediately appear, followed by death. After the fish overwinter, the physical consumption is larger. Therefore, after entering the spring when the water temperature rises and the fish begin to feed, it is necessary to pay attention to strengthening the nutrition of the fish, and choose a better compound feed to feed, but pay attention to the amount of each feeding not too much. At the same time, a part of nutrition and bile acids can be added to the feed regularly, which can restore the physique of fish quickly, greatly improve the resistance to pathogens such as external parasites, and effectively prevent the outbreak of parasitic diseases.
2, the physique of the fish is not bad, but the environment of the water body is very poor.
When the rotifer parasitizes and destroys the gills, the gills are subsequently infected with a large number of bacteria, causing secondary infectious diseases and causing death. During the wintering period, due to the less water change in the pond, the metabolic waste of various aquatic organisms accumulates in the water, and after the water temperature rises in the spring, these metabolic wastes decompose quickly and consume a large amount of dissolved oxygen in the water. When the oxygen is insufficient, a large number of toxic intermediates are produced, which greatly reduces the resistance of fish and increases the chance of contracting various diseases, including parasites.
Therefore, when entering the spring, in addition to proper water replacement, we must maintain the high dissolved oxygen of the water body and a good water quality environment, you can regularly use water quality improvers and disinfectants and drugs to improve water quality, which can effectively promote the growth of phytoplankton and the improvement of water color and fish feeding, prevent the accumulation of metabolic waste, and effectively improve the water environment in which fish live.
<h1 class= "pgc-h-arrow-right" > fourth, wheelworm control measures</h1>
The application of insecticidal drugs, Chinese herbal medicine is also effective, but can not be arbitrarily increased to prevent drug residues and insect resistance increased, to rotate the use of drugs, in order to completely kill the parasites.
Add safe Eucalyptus essential oil to the feed for parasite control. Derived from the leaves of Australia's unique multi-bract eucalyptus, Lechang Eucalyptus essential oil has 1,8 eucalyptus, monoterpenes, sesquiterpenes and other natural anti-insect repellent components, gram acts on multiple target cells, can effectively control common parasites such as wheel worms, ringworms, anchorhead loach, and melon worms. Safe and non-toxic, does not harm the water quality and fish body, can be added for a long time.
The article is transferred from the WeChat public account of the "Aquatic Insect Resistance Alliance".