The tissue response of the giant freshwater prawn Macrobrachium rosenbergii de Man, was studied histologically by investigating clinical cases of natural infectious and non-infectious diseases which occurred in cultured prawns and by carrying out the following experimental intramuscular injection of alcian blue dye, intramuscular injection of BCG vaccine (also using TEM), intramuscular injection of complete Freund’s adjuvant, intramuscular and systemic injection of heat-killed Aeromonas hydrophila, intramuscular and systemic injection of heat-killed and live Vibrio parahaemolyticus and Vibrio anguillarum, grafting or insertion of pieces of cuticle into the muscle of the same or different prawns and by cuticular traumatization or wounding of slight, moderate and severe degrees (also using SEM). Results demonstrated histologically the presence of a unified system of haemocytic cells participating in a range of defensive activities in varying degrees of intensity; viz. infiltration, aggregation, coagulation, melanization, phagocytosis, encapsulation, nodule formation and fibroplasia. More pronounced haemocytic activity occurred in the gills, hepatopancreas, heart and antennal gland, in addition to locally at the site of injection, wounding or grafting.
Electron microscopy revealed that the haemocytes which participate in the tissue inflammatory response consist of cell types belonging to all three main classes, namely agranular, semi-granular and granular haemocytes, although semi-granular and granular haemocytes appeared to predominate.
Findings of the experimentally induced tissue response were comparable to observations in the natural infectious and non-infectious disease conditions in Macrobrachium and in general, similar to those reported in natural infections and experimental challenges of other important wild and cultured crustaceans including penaeid shrimps, crabs and crayfish.
A routine study of the haemocytic tissue response
in cultured prawns can be recommended as a useful means of monitoring their health status and identifying the early stages of a disease process. This can prove of assistance in developing disease control strategies.