Diseases of Pangasius and catfish
Diseases of Pangasius and catfish deteriorate production and benefit. Diseases of Pangasius and catfish are main obstacle of culture. Pangasius culture has become main fish culture in Bangladesh mainly northern part. Diseases of pangasius and catfish caused by viruses, bacteria, fungi, parasites, and other pathogens. The cost of disease prevention and treatment is 5 to 5.5% of total production cost (Dung et al., 2008; Hung and Huy, 2005; Khoi et al., 2008). Farmer use
antibiotic for treatment of fish diseases.
The results of the multiple-case study show that most farmers do not know exactly what kind of antibiotics they should use during disease outbreak (Khoi et al., 2008). Small farmer know about fish diseases from friend and different drug dealer. In many cases, local veterinary drug suppliers have no knowledge in either aquatic organisms or veterinary drugs (Khoi et al., 2008).
Most farmer has no basic knowledge on monitoring, selection, and application of chemicals/veterinary drugs. Farmer use for diseases high dosage of drugs and chemicals and sometimes with non-prescribed drugs. As a result the number of antibiotic products commercially available is larger than the number of permitted products for aquaculture (Dung et al., 2008), which leads to more fish diseases or antibiotic resistances.
Common diseases of pangasisus and catfish fish farming:
- BNP (Bacillary Necrotic in Pangasius
- Red spot
- Swollen kidney
- Intestine damage
BNP (Bacillary Necrotic in Pangasius:
BNP show in fish white spot internal organ. BNP disease of pangasius caused by Edwardsiella ictaluri. Edwardsiella ictaluri can survive in pond water for one to two weeks, but up to three to four months in pond mud (Dung et al., 2008). Edwardsiella ictaluri grow in cooler season because its optimum temperature is about 28ºC.
BNP affected of all ages but fingerlings seem to be more affected. Conditions that favor BNP disease are high stocking densities, environmental pollutants, concurrent health problems, weather changes, moderate water temperatures (22°C-28°C) (Crumlish et al., 2002).
Clinical symptoms of BNP:
The farmers described the clinical signs as follows: immediately before death, fish swim slowly at the surface of water, the fish colour is pale, there are internal white spots on the liver, kidney, and spleen (Khoi et al., 2008).
Time and condition for diseases outbreak of BNP:
- Weather change
- Rainy season
- Water pollution
- Fingerling quality
- Feed quality
Treatment and Prevention: Most important to control water quality and diet feed or proper nutrition. Florfenicol, Antibiotics, Prebiotics and Probiotics are the main treatment for BNP disease of Pangasius and catfish. Florfenicol should not be fed to Pangasius for more than 10 days. Florfenicol must be withdrawn from the feed two weeks prior to harvest (Dung et al., 2008).
Parasites of pangasius and catfish: Parasite diseases for Pangasius are caused by Trichodina spp and Epistylis spp (Dung et al., 2008). Dung (2008) notes a seasonal incidence of heavy infestations on Pangasius pond farms during the rainy season or in cooler weather
Cause of infection: ichthyophthirius multifiliis and myxosporidia
Clinical symptoms of Parasites:
According to farmer description clinical signs of parasite diseases are slow-swimming fish at the water surface; swirling and disoriented fish; lesions, fin rot, hemorrhages, and white spots on fish body. Parasites diseased fishes have reduced appetite and become very weak. Sporadic outbreaks may occur with a low mortality rate.
Time and conditions for disease outbreak:
- Weather change
- Sometime rain and sometime sunsine
- High stocking density
Treatment and prevention: Van de Braak (2008) explains that in the pond aquaculture, diseases are rarely the result of contact between the fish and a potential pathogen alone. They only invade the fish and cause a disease outbreak when one or more stressors like poor water quality, reduced oxygen level, high stocking density, low quality fingerlings, inadequate feed, etc., are present (Snieszko, 1974). PAD (2008) suggests that chemicals/antibiotics should be used for Pangasius disease prevention/treatment. Formalin, liming copper and sulphate are main treatment for parasites.
Red spot disease of pangasius and catfish: Red spot disease is caused by a group of motile aeromonas septicaemia including aeromonas hydrophila, aeromonas sobria, and aeromonas caviae (Liem et al., 2009). This disease occurs in fingerlings and during the grow-out phase of Pangasius production.
Cause of infection: Aeromonas hydro-phila, Aeromonas sobria and Aeromonas caviae.
Clinical sign and symptoms: This disease often occurs during the change from the dry to rainy season and during the flood season in MRD (Khoi et al., 2008). Conditions that favor red spot disease are also high stocking densities, environmental pollutants, a large amount of organic mud in the pond (PAD, 2008).
- Haemorrahages on head, mouth, fins
- Red and swollen vent
- Yellow ascites
- Gas in gut
Time and condition for disease outbreak:
- Liming in the pond
- Salting as per area
- Formalin dipping
- Water changes
Prevention and Treatment: Pond location according to zoning regulation and authority, Water supply with quality and quantity, Fingerling quality, Use of high balance quality feed and tested protein are the main prevention. Proper diagnose fish disease and water quality in the laboratory before treatment. Treatment uses Salinity for parasites, bacteria, Antibiotics for bacteria, Formalin for parasite, Medication can only be obtained through veterinarian. Fish diseases related to four main issue, Pond location, water supply, fingerling quality and feed quality. The most serious threat to Pangasius is poor water quality (PAD, 2008).
The farming disease can control by prevention and treatment at the farm level. There are three main diseases found in the local farm are BNP, parasites, and red spot diseases. Farmer can consult with farmer friend, local laboratory staff, veterinary drug agent authority, Fisheries expert and researcher.