It is not the most lethal pathogen, but it is the most headache-inducing master of "attrition warfare". Understanding it and preventing it is a compulsory course for every livestock farmer.
It is the little melon worm.
I. Characteristics and Hazards of the Small melon Worm
The small gourd worm, scientifically known as Ichthyophthirius multifiliis, is terrifying not in its direct killing but in its unique life pattern and the resulting control difficulties.
Strong viability: Widely present in various freshwater bodies, it has certain resistance to common disinfectants.
Astonishing reproductive capacity: After an adult matures and sheds, it can form a wrap at the bottom of the pool and split into hundreds or even thousands of infection-capable larvae.
Parasitic sites are fatal: They mainly parasitize on the skin, fin rays and gills of fish. The small melon worms on the gill filaments are hard to detect with the naked eye, but they can seriously damage the respiratory function of the gill tissues. This is the main cause of oxygen deficiency, surfacing and even "dark" death in fish schools.
Symptoms of harm
On the body surface: A large number of small white dots (pustules) visible to the naked eye appear.
Behavior: The school of fish is restless, frequently rubbing against the edge and jumping around. Loss of appetite, floating on the water surface or gathering at the intake.
Gills: Increased mucus, darker color, and difficulty in breathing. Even in water bodies with sufficient dissolved oxygen, a phenomenon similar to surfacing occurs.
Ii. How to Prevent Problems Before They Occur?
For the small melon worm, the best treatment is always prevention. Investing costs in early prevention is far less costly than treating after an outbreak.
1. Thoroughly clean the pond to eliminate potential hazards.
2. Seedling quarantine and soaking disinfection: All imported seedlings must undergo strict quarantine. Before putting the fish into the pond, soak them in a 3% to 5% salt solution or povidone-iodine solution for 15 to 20 minutes to effectively kill the insects carried on their surface.
3. Reasonable density: Excessively high stocking density is a breeding ground for parasitic diseases, which will greatly increase the difficulty of management and treatment.
4. Strengthen water quality regulation: Regularly use microecological preparations (such as EM bacteria and bacillus) to decompose organic waste, stabilize water bodies, and destroy the living environment of the small melon worm.
5. Enhance the fish's physical condition: Feed high-quality feed and regularly add liver-protecting and gallblade-protecting drugs (such as bile acids) and immune enhancers (such as astragalus polysaccharides, VC) to the feed to build the "last line of defense" for the fish's own body.
Iii. Once an outbreak occurs, how to strike precisely?
If small melon worms have already appeared in the pond, do not seek medical help in a panic. Precise strikes must be carried out based on their life history.
"Ginger and Pepper Mixture" : Use 1 kilogram of ginger and 0.5 kilograms of dried chili peppers per mu and per meter of water depth, mix and boil them into a thick juice, and then sprinkle it all over the pond. Use continuously for 2 to 3 days. This method has little irritation to the fish body, leaves no drug residue, and has a good killing effect on the larvae of the small melon worm.
2. External application of copper sulfate + ferrous sulfate: Use copper sulfate and ferrous sulfate in a ratio of 5:2. First, apply ferrous sulfate, then copper sulfate. Choose to apply it at night to ensure sufficient dissolved oxygen before sprinkling.
3. Others: During the intervals of medication, a small amount of water can be changed (10-15%) to reduce the density of larvae in the water. Picking up the floating film on the water surface in the downwind area in the early morning can effectively remove some of the fallen insect wraps.
Key operation: Within 24 to 48 hours after medication, close observation must be carried out and the aerator should be turned on to prevent the fish from being deprived of oxygen. Decide whether an additional application of medication is needed based on the insect situation to kill the newly hatched larvae.
Iv. Misunderstandings in Prevention and Control
Misconception 1: "You can stop taking the medicine once the white spots disappear." Completely wrong! The disappearance of the white spots on the body surface only means that the adult has fallen off, and the packages at the bottom of the water are multiplying wildly. It is necessary to adhere to treatment for at least 7 to 10 days, covering the entire life cycle, in order to achieve a complete cure.
Misconception Two: "Focusing only on the surface of the body while neglecting the gills." Gill infections are the "invisible killers". Once any abnormal surface of the fish is detected, the gills must be inspected immediately.