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

IV. Accum~ilation of unused feedV. Inadequate aerationVI. Sub-optimal or heavy algal blooms in the pondVII. Physical injury andVIII. Presence of virulent pathogens in high count.In these, changes in the physicaI or chernicaI factors will be obvious, but the biological factorswill be subtle and complicated. This can be explained by micro ecology. This refers to theinteraction of biological factors and it explains the interaction between normal microorganismsand its environment.HostLike any other crustaceans, shrimp host's body is covered by exoskeleton, which isregularly replaced by a new one during moulting. The moulting process exerts energyrequirement on the shrimp and renders the shrimp susceptible to disease agents or cannibalism.In addition, the shrimp's nutritional well being, size and immune response determine its degreeof resistance to disease agents. Behavioural characteristic such as burrowing at the pondbottom also exposes the shrimp condition prevailing in the pond.EnvironmentThe term environment in aquaculture comprises the pond soil, rearing water and thevarious living organisms in it. The living organisms include not only shrimp but also otheraquatic fauna and flora including pathogenic organisms. The survival and growth of theorganisms is largely influenced by various physico-chemical parameters such pH, dissolvedoxygen, temperature, light etc. Any abnormal change in these factors will adversely affectshrimp in the culture system. For example, high ammonia level, low dissolved oxygen etc. arestressful and may affect the survival of shrimp.PathogenVarious pathogenic organisms may be present in the aquaculture system. They may bethe part of the natural flora and fauna of the rearing water or pond soil. Various disease causingorganism of shrimp have been reported. Mere presence of these organisms may not cause anydisease condition. However, when present in large numbers these may readily invade theinjured tissues get established and multiply resulting in disease and death. Nevertheless, the