Prevention and Treatment of Muscle Opacity Disease and Cramp Disease in Whiteleg Shrimp Farming

Muscle opacity disease:

Causes: Sudden temperature changes are the main cause, whether the temperature is too high or too low; Vibrio infection or sporozoan parasites in the muscle.

Symptoms: The muscle of the last one or two abdominal segments turns white and loses its transparency; in some diseased shrimp the whole body turns white, and microscopic examination shows the whitened muscle is already necrotic, with disordered muscle fibers and indistinct striations. Diseased shrimp are rarely seen at the pond surface, but dead shrimp are found on the pond bottom; in the early stage of the disease feeding is normal, and after death the whitened, opaque muscle turns red first.

Prevention and treatment methods: In the hot season, take care to maintain a certain water level; stocking density should not be too high; if diseased shrimp are found, within 6 hours add an appropriate amount of fresh water to lower the temperature and adjust water quality; spread hydantoin-type or iodine preparations over the whole pond for 2—3 consecutive applications, and administer vitamins orally.

Cramp disease

Causes: Triggered by stimuli such as temperature, light intensity, pressure, and disturbance.

Harmfulness: The abdomen of the diseased shrimp bends toward the ventral side, is stiff, and cannot be straightened; in mild cases only the middle of the abdomen bends, while in severe cases the tail bends beneath the head and thorax, finally resulting in death. The abdomen of the diseased shrimp is slightly white, but not as opaque as in muscle necrosis disease.

Preventive measures: In the hot season, take care to raise the water level; under high temperature and strong light, try not to catch or disturb the shrimp; after the disease occurs, adding an appropriate amount of fresh water can promote recovery.

However, if, as in this region, a sudden change in water quality caused by adding too much water at one time leads to cramp and opaque necrotic muscle, it is recommended to add salt to a concentration of 5 parts per thousand, and the shrimp will recover their health.