The study was carried out to understand current status of use of chemicals and antibiotics in fish health management in freshwater aquaculture activities. Data were collected through questionnaire interview, personal contact, market survey and participatory rural appraisal like focus group discussion with fish and prawn farmers, retailers of animal medicine and representatives of pharmaceutical companies. A range of chemicals including antibiotics were found available in market. Fish health management and disease treatment were the major areas where majority of such chemicals have been used. Other uses included pond preparation and management, growth promotion and improvement of water quality to enhance pond productivity. Commonly found traditional chemicals in health management included Lime, Salt, Potassium permanganate, Sumithion, Melathion, Formalin, Bleaching powder and Malachite green. Of the new products JVzeolite, Geotox, Green zeolite, Orgavit aqua, Fish vitaplus, AQ grow-G, Oxy flow, Oxy max and O 2 -marine were most widely used compounds. Fourteen branded antibiotics were found in market of which Oxysentin, Renamox, Renamycin and Orgamycine were being widely used. Thirty three pharmaceutical companies were producing and marketing these products. The study also identified the problems associated with the use of chemicals which included lack of knowledge regarding use of chemicals, appropriate dose, method of application and indiscriminate use of chemicals.

Tilapia (Oreochromis niloticus) and pangasius (Pangasianodon hypophthalmus) are currently very important and popular species for aquaculture in Bangladesh. They are cultured commercially in high stocking densities which are accompanied by several risk factors leading to disease outbreaks. The present study was carried out to investigate diseases of these two species under farming condition with special emphasis on risk factors analysis and their health management strategies. Data were collected through questionnaire interview and focus group discussion with farmers. Altogether 50 farmers were interviewed of which 25 were tilapia farmers and 25 were pangus farmers in Trishal upazila of Mymensingh district. Possible risks were assessed using certain parameters like season of disease occurrence, presence of predators in farms, contact with livestock, maintenance of farm hygiene, sharing of farming tools, feeding of fish and pond management measures. It was found that presence of predatory birds, maintenance of good farm hygiene, sharing of tools, increased stocking densities and improper pond management were the major risks of disease outbreak. The most prevalent clinical signs of diseased fish included anal protrusion and red spot on body surface in case of pangus while pop and red eye and gas problems were common in both pangasius and tilapia. Generally, pangus were found more susceptible to disease than tilapia. Predatory birds were a big problem in the study area. They act as a potential carrier of infectious organisms among farms from farm to farm.

A study was conducted to know the health and disease problems of three important air-breathing fishes viz. Shing (Heteropneustes fossilis), Magur (Clarias batrachus) and Thai Koi (Anabas testudineus) through clinical and histopathological technique from June 2007 to March 2008 collected from selected farms and from local markets. Generally, during December and January, acute pathologies were recorded. Clinical signs of Shing included haemorrhage, extended belly and ulceration. Histopathologically, partly missing and splitted epidermis and dermis, necrotic, vacuoled and ruptured myotomes of muscle with fungal granuloma were observed. Major gill pathologies included partly missing and highly hypertrophied, haemorrhagic gill lamellae, presence of monogenetic trematode and pyknotic cells. In liver, haemorrhagic areas, necrotic, vacuoled, hyperplasid hepatocytes, cell debris, pyknotic nuclei and plenty of inflammatory cells were evident. Haemorrhages, vacuolation, necrosis, missing and ruptured kidney tubules and pyknotic nuclei were the major pathologies of kidney. Clinically, dark red lesion, haemorrhage, necrosis and ulcer in body surface were seen in Magur. Histopathologically observed pathologies in Magur were almost similar to that of Shing. Clinical signs of Thai Koi included discoloration, loss of scales and fins, abnormal caudal fin, haemorrhage in gill and ulcer. Marked histopathology in the skin and muscle were observed such as totally lost epidermis, dermis separated from muscle, severely ruptured, degenerated and missing of myotomes in many places. In gills, hypertrophy, hyperplasia, telangiectasis, clubbing, haemorrhage and massive necrosis in both primary and secondary gill lamellae were found. Pathologies observed in liver and kidney were most alike to that of Shing. In the months of February and March, all the investigated organs of the three fish species were at a healing stage.

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