Chronic Soft-Shell Syndrome Soft-Shelling
Chronic soft-shell syndrome is associated with exposure of normal hard-shelled shrimps to pesticides and piscicides. Aquatin at 0.0154 - 1.54 ppm, GusathionA at 1.5 - 150 ppb, rotenone at 10-50 ppm, and saponin at 100 ppm for 4 days can induce soft-shelling in initially hard-shelled stocks.
Shell is thin and persistently soft for several weeks, shell surface is often dark rough and wrinkled, and affected shrimps are weak. The disease must not be confused with the condition of newly-molted shrimps, which have clean smooth, and soft shells that harden within 1-2 days.
EFFECTS ON HOST:
Affected shrimps are soft-shelled, grow slowly, and eventually die; histopathol-ogy of shrimps exposed to Gusathion A shows slight hyperplasia of the gill epithelium, delamination of the cells lining the tubules of the hepatopancreas, and general necrosis and degeneration of these tissues.
PREVENTION AND CONTROL:
• During pond preparation, flush ponds thoroughly particularly when pesti-cide contamination is suspected
• Maintain pond water and soil of good quality