'Four no's' in disease prevention for shrimp

(Baonghean) - Given the complicated disease situation in farmed shrimp in the first crop of 2017, disease prevention and control as well as environmental protection in farming areas are urgent issues today.

In particular, implementing the "Four No's": Do not release diseased shrimp, do not supply untreated water into the pond, do not hide diseases, do not discharge untreated water or dead shrimp into the environment is a good solution that shrimp farmers need to follow.

According to the Nghe An Veterinary Department, the area of ​​shrimp infected with the disease in the first crop of 2017 as of May 10 was 69.4 hectares, mainly concentrated in the communes of Quynh Xuan and Quynh Di in Hoang Mai Town; Quynh Bang, Quynh Luong, An Hoa in Quynh Luu District; Nghi Thai Commune, Nghi Loc District; Hung Hoa Commune, Vinh City.

The disease mainly appears on whiteleg shrimp at stage 6 (60 days after stocking), most often at 20 - 49 days, the test results are mainly white spots. Therefore, for the next crop to be successful, shrimp farmers need to thoroughly implement the "Four No's" in disease prevention.

Farmers in Quynh Thanh commune (Quynh Luu) use lime powder to treat shrimp ponds. Photo: Viet Hung

First, do not supply water to the pond without treatment.

Carry out pond renovation work according to technical procedures to eliminate residual pathogens in the pond, limiting the occurrence of disease, specifically:

Step 1: Drain the pond and reservoir. Remove pests in the pond (shrimp, crab, snail, insects, miscellaneous fish, etc.). Dredge the pond bottom, repair the banks, water supply and drainage culverts.

Step 2: For soil ponds, apply agricultural lime powder and dry the pond bottom for at least 30 days. The amount of lime is 3 - 3.5 tons/ha. Harrow thoroughly so that the lime penetrates the bottom to kill all remaining shrimp, crabs, clams, snails, insects, and miscellaneous fish, kill bacteria in the mud, detoxify (heavy metals, H2S) and neutralize pH.

For ponds with tarpaulin lining: Remove the tarpaulin, clean, disinfect, wash the pond and sprinkle CaO lime mixed with thick water into the gaps between the tarpaulin.

Before supplying water to the pond, it is necessary to kill pathogens, miscellaneous fish, predatory fish, crustaceans, mollusks... Use Chlorine with a concentration of 25-30 ppm, 65-70% active type (depending on the active chlorine % ratio of Chlorine, dissolve Chlorine in water, spread evenly throughout the pond, use water fans or aerators for about 3-4 hours continuously. After 3 days of treating all the effects of free Chlorine), we can supply it to the pond.

Second, do not release disease-carrying shrimp.

Select to release shrimp of the same age with the same size: Postlarvae 15-20 (for black tiger shrimp) and P 10-15 (for white leg shrimp), the same size (no more than 10% deviation). Shape: balanced, straight whiskers, no tail curl; shrimp have light blue-gray, light brown-gray color; swim fast, cling to the tank wall, when taken out of the basin, rotate the water flow, shrimp cling around and swim upstream, do not gather in the middle of the basin when the water flow stops rotating. Observe under microscope: Shrimp intestines are full of food, intestine/muscle ratio at the sixth abdominal segment: 1/4; dorsal muscle is transparent or bright blue; there is a star-shaped pigment strip running along the edge of the abdomen; shrimp are not infected with white spot virus (WSSV), yellow head disease (YHV), MBV (if infected with MBV, the rate is < 20%); shrimp have no organisms.

Third, do not hide your illness.

When a disease occurs in a pond, it is necessary to immediately report to local veterinary officers to determine the extent of the damage so that there is a policy to support chlorine disinfection, avoiding widespread spread. Shrimp farmers need to promote their spirit and community responsibility, avoiding the situation of not reporting when a disease occurs in farmed shrimp to the local authorities but only quietly handling it themselves. That makes it difficult for the management of functional sectors, creating opportunities for the disease to spread and develop. What is more worrying is that when the pond is infected, farmers handle it themselves, so it is impossible to determine the concentration and dosage of drugs and chemicals to completely kill the pathogens. It is even more dangerous when some households do not handle drugs and chemicals but discharge wastewater directly into the environment.

Fourth, do not discharge untreated pond water into the environment.

The treatment of dead shrimp due to disease needs to be taken care of and handled thoroughly. Shrimp farmers need to collect all dead shrimp in the pond, then bury them far from the pond shore to avoid spreading, creating opportunities for viruses and bacteria to develop. Collecting dead shrimp not only contributes to protecting the environment of their own pond but also contributes to protecting the environment of the common farming area.

In addition to implementing the "Four No's" in disease prevention and control mentioned above, the stages of renovation, dredging mud after treating pathogens, and care and management must be carried out in accordance with the recommendations of the relevant authorities. Thoroughly applying the "Four No's" in disease prevention is how shrimp farmers protect themselves.

Tran Trung Thanh