Soft shell disease in whiteleg shrimp

2.5. Some common diseases and their treatments

2.5.13. White Feces Syndrome

- Pathogens:
+ It is caused by many factors, but mainly by bacteria, parasites, and environmental factors, including Pleistophora sp., microsporidian parasites of shrimp, and bacteria of the Vibrio genus.
+ In northern area of Vietnam, the disease usually occurs from April to July, and is most widespread in May and July. In Central Vietnam, the disease is scattered. In southern region of Vietnam, white feces syndrome appears around August to October. The disease usually occurs in hot and dry season when water temparature and farming density are high. Shrimp is susceptible to white feces syndrome when it is from 40 to 90 day-old. The syndrome usually appears during unusual weather period (sunny, rainy days or when the weather changes).
It occurs in both black tiger prawn and whiteleg shrimp.

- Signs:
When shrimp are infected, check feeding trays will help us see white feces on the trays. White feces can float on the water surface along the edges or pond corners (at the end of the aerators’ direction or wind direction). Shrimp with this disease will reduce eating, or stop growing. Farmers need to check shrimp intestine, which is not be full of feed and has yellow spots at the end of the intestine. Shrimp is distorted with thin shells, gradually shrinks and grows slowly.

- How to prevent:
+ To prevent this disease, it is necessary to prepare and clean farming pond from the start of the crop. Do not use feed that is moldy or has fungi; limit the use of fresh food.
+ During the farming process, strictly manage environmental factors such as pH and other water indicators. Periodically use bioproducts to clean pond environment. Change water regularly and use biocides will help limit white feces syndrome especially in prolonged hot, sunny, or rainy periods.
+ Use digestive probiotics to help shrimp absorb feed better. Vitamin and mineral supplements can help strengthen shrimp health and reduce stress. Take out dead shrimp from farming ponds to prevent the spread of the disease (healthy shrimp may eat dead shrimp infected with the syndrome).
+ On the market today, there are several types of medicines for preventions and treatments of white feces syndrome. They are mostly antibiotics. Thus, they should be used according to doses instructed in package. Avoid using medicine rushingly; avoid increasing doses or using insufficient doses. Overdose may cause drug tolerance in shrimp and can lead to the prolonged treatment time, which is expensive and inefficient.

Source: Temporary process for safe brackish-water shrimp farming in areas affected by diseases in Vietnam. According to The Official Dispatch No. 10/TCTS-NTTS. January 6th, 2015. Vietnamese Directorate of Fisheries

Viet Linh 2015. Translated by Sonia Linh V.

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