Fish Diseases and Management

5.2.6. Filamentous bacterial infection and Mycobacterial infections

Filamentous bacterial infection

Growth stages affected by these bacteria are larvae, postlarvae, juveniles and adults. Signs are the presence of fine, colourless, thread- like growth on the body surface and gills. It can interfere with locomotary process and moulting.  It can cause mortalities of PL in heavy infestations. In larger shrimps, it can even result in respiratory distress. The bacteria involved in this infection are Leucothrix species. Other types of filamentous and chain forming bacteria such as Thiothrix, Flexibacter, Cytophaga, and possibly Flavobacterium, alone or together with Leucothrix are also important agents of filamentous bacterial disease. The infection is treated by KMnO₄ at 5-10 pm for 1hr in static treatment for 5-10 days.

Mycobacterial infections

The causative agent of the infection is Mycobacterium marinum. Symptoms include abnormally dark pigmentation in areas of the body that hard multicolour melanized haemocytic nodules or larger prominent melanized granulomatous lesions composed of multiple nodules. Lesions due to this bacterium were observed in the lymphoid organ, heart, cuticle and systemically in the loose connective tissue of muscle, hepatopancreas, antennal gland, ovary and gills. No control measures or therapy for mycobacterium infection in penaeid shrimp have been reported so far.