Soft-Shell Syndrome in Shrimp

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The term “soft-shell syndrome” (SSS) is used to describe a condition found in shrimp that have been cultured in intensive systems. SSS is characterized by the development of a thin, translucent shell that is easily peeled off the animal.

V. harveyi, V. alginolyticus, V. fluvialis, and V. parahaemolyticus were noted by their characteristic results and biochemical tests. It has also been observed that mineral deficiency, poor quality water, bad management practices, and association of Vibrio bacteria are the possible causes of loose shell syndrome in L. vannamei.

Causes of Soft-Shell Syndrome in Shrimp

Soft-shell Syndrome (SSS) is a shrimp disease caused by several factors, including environmental stress, bacterial infection, and viral infection.

Six pathogenic strains of Vibrio were isolated from the hemolymph, along with V. harveyi, V. alginolyticus, V. para-haemolyticus, V. anguillarum, V. splendidus, and V. vulnificus. V. harveyi was the most abundant, with a concentration of 100.

These bacteria are found in marine environments and can contaminate shrimp ponds.

It has been associated with high stocking densities, poor water quality, and stress factors such as crowding and handling. The most common cause of SSS, however, is low salinity water.

When shrimp are exposed to low salinity water for an extended period of time, the salt concentration in their blood decreases and they lose their hard shell. This leaves them vulnerable to predators and other dangers.

Signs & Symptoms of Soft-Shell Syndrome

The clinical signs are typically evident after the animals have been removed from the water for inspection or grading.

Affected animals have a thin, translucent shell that can be easily peeled off the animal. The underlying musculature and viscera are exposed and the animal appears “soft”.

It is a bacterial disease of shrimp that causes the shrimp to lose its hard shell. This can result in death if the shrimp are not able to produce a new shell quickly.

The symptoms of SSS include loss of the hard shell, swelling of the body, and discoloration.

Diagnosis of Soft-shell Syndrome

Diseases like white spot syndrome virus and yellow head virus can cause deadly disease in a short time period, as opposed to LSS, a progressive disease that leads to gradual, low-level fatalities.

The symptoms of LSS include a flaccid spongy abdomen due to muscular dystrophy, no overlap between the exoskeleton and the muscles, and a shrunken liver and pancreas.

The performance of the feed conversion efficiency was significantly diminished, and the meat quality of shrimp was poor due to impairment of the hepatopancreatic functions, as represented by the atrophy of the liver.

Shrimp lose quality due to impaired functions of their hepatopancreatic organs, such as digestion and absorption.

Histological examinations reveal shrinkage of muscle fibers and myofibrils. Histology of LSS-affected shrimp revealed shrinkage of the extensor and flexor muscle fibers with occasional hemorrhagic infiltration.

The hepatopancreas was inflamed with enlargement of intertubular spaces and scattered hemocytic infiltration, and low levels of lipid reserves were found in the R cells. The hepatopancreas was necrotic in advanced stages of LSS.

Inflammation of the hepatopancreatic tubules with GI epithelial cell hyperplasia and multifocal hemorrhages with intratubular myelocytic infiltration was observed in the hepatopancreas of the sister cell.

In more advanced stages of LSS, it was observed that the tubular epithelium was sloughed and destroyed by numerous lysosomes.

Preventive Measure To Avoid Soft-shell Syndrome

This research shows that the disease has a positive impact on the productivity of shrimp. Restoring the feed-water cycle will ameliorate culture for L. vannamei and decrease disease in shrimp.

Prevention is key and good sanitation practices are important for preventing contamination of ponds with these bacteria.

Treatment of Soft-shell Syndrome

Higher levels of calcium and phosphorus were found in hepatopancreas, hemolymph, and muscle of soft-shelled P. indicus than hard-shelled individuals; however, the exoskeleton of normal shrimps showed higher calcium and phosphorus nutrition than the soft-shelled shrimps. It is illustrated that specific nutritional and environmental solutions would resolve this tendency.

SSS can also be caused by poor water quality or a lack of food. If left untreated, SSS can kill shrimp.

There are several ways to treat SSS, including increasing the salinity of the water, adding antibiotics or antivirals to the water, or feeding the shrimp food that contains high levels of salt.

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