, Diagnosis an-&& of Shrimp Diseases - Central Institute of ...

conditions. Hence, a close examination and recording of the various parameters of water andsoil quality should be done periodically.2. Field observation for signs and synlptomsA. Observation of beltaviorar of shrimpCritical observation on the behaviour of shrimp will give an indication of the health ofthe animals. Significant behaviour includes escape reflex, swimming at the surface, moultingbehaviour, feeding behaviour etc.Healthy shrimp will have quick reflexes i.e., shrimp will respond instantaneously toany outside disturbances or artificial stimulation; Shrimp showing poor escape reflex may notbe in a healthy condition.Swimming at the surface is an indication of either inadequate oxygen level, orrespiratory impairment. Disease conditions, such as fouling, white spot disease etc alwaysshow such behavioural changes.Moulting behaviour is another important factor, which has to be observed. Regularand continued moulting indicates continuous growth. Abnormal moulting indicates a diseasedcondition. Chronic condition due to hepatopancreatic infection may cause abnormal moulting.Feeding behaviour is also an important indicator of health of the shrimp. Diseasedshrimp normally will show reduced appetite (e.g. white spot disease, protozoan fouling).However, it has been reported that juveniles and sub-adult affected with yellow head diseaseshow an abrupt abnormal increase in feeding rate for several days.B. Observation of external signs and symptomsTo assess the health status of a shrimp, following gross signs should be examined.i. Colour and nature of exoskeleton: Healthy shrimp will have pale blue coloured,bright, smooth and clear cuticle with proper hardness. Exoskeleton will showbrownish discoloration and occasional mat-like appearance (muddy cuticle) inprotozoan fouling. Moulted shrimp and shrimp with soft shell syndrome will showsoft exoskeleton. However, the shrimp with soft shell syndrome will have a hardrostra1 spine.ii. Apart from these, visible blisters or brown or black eroded areas on the exoskeletonmay indicate possible bacterial infection. Presence of white spots or patches on thecarapace indicates the visual disease, white spot disease.iii. Appendages: Tips of walking legs, swimmerets and uropods may show necrosis andbecome brownish black indicating a possible bacterial infection. Often, physical injury