Bacterial haemorraghic septicemia

BHS is also known as dropsy and is a fish bacterial disease in which farmers facing a serious problem to eradicate

1. BACTERIAL HAEMORRAGHIC SEPTICEMIA(BHS) Presented by- Bijayananda Seth Course no.- AAH-501 Subject- Bacterial & Viral Diseases of Finfish & Shellfish

2. INTRODUCTION:- Aeromonas hydrophila causes disease in fish known as “Motile Aeromonas Septicemia” (MAS), “Hemorrhagic Septicemia,” “Ulcer Disease,” or “Red-Sore Disease.” The many synonyms of this disease relate to the lesions caused by this bacterium which include septicemia where the bacteria or bacterial toxins are present within numerous organs of the fish, and ulcers of the fish’s skin. CAUSATIVE AGENT:- Aeromonas hydrophila A. sobria

3. Aeromonas hydrophila is a gram-negative rod-shaped bacterium which is commonly isolated from fresh water ponds and which is a normal inhabitant of the gastrointestinal tract. The disease caused by this bacterium primarily affects freshwater fish such as cattfish , several species of bass, and many species of tropical or ornamental fish. From descriptions of fish diseases in the early scientific literature, Otte (1963) speculated that septicemic infections in fish caused by motile aeromonads were common throughout Europe during the Middle Ages. the pathology was similar to that observed with red leg disease in frogs, in which A. hydrophila was identified as the causal organism.

4. AETIOLOGY: Aeromonas hydrophila  is a nonspore -forming, facultative anaerobic gram-negative, pleomorphic bacillus with a monotrichous flagellum. It is a fermentative, oxidase -positive, facultative anaerobe frequently found in freshwater. Aeromonas hydrophila , present in fresh and brackish waterswater and sewage. It is an opportunistic infections, as well as occasional cases of food- and water-borne illness. Biofilms were produced by  Aeromonas hydrophila  on stainless steel coupons (Lynch  et al ., 2002) and on polystyrene microtiter plates (Canals  et al ., 2006a).

5. Aeromonads could be broken down roughly into two major groupings, based upon growth characteristics and other biochemical features. The mesophilic group, typified by  A. hydrophila , consisted of motile isolates that grew well at 35 to 37°C and were associated with a variety of human infections. The second group, referred to as psychrophilic strains, caused diseases in fish, were nonmotile , and had optimal growth temperatures of 22 to 25°C. This group contained isolates that currently reside within the species  A. salmonicida .

6. EPIDEMIOLOGY :- It causes distinct pathological conditions, including tail / fin rot and haemorrhagic septicemias. This organism is also found to be associated with other pathogens. Haemorrhagic septicemia (motile aeromonas septicemia) is characterized by small surface lesions, local haemorrhage s particularly in the gills and vent, ulcers, abscess es, exophthalmia and abdominal distension. Internally, there may be accumulation of ascitic fluid , anemia and damage to the organs, notably kidney and liver.

7. It transmitted horizontally through discharge from the intestinal tract and external lesions on the skin as well as through parasitic damage and fungal infection. This disease can reach epizootic proportions, and is characterized by erosion of the scales and pin-prick haemorrhages which may cover up to 75% of the body surface with a high mortality rate.

8. In most cases, a stress mediated disease condition has been observed. Seasonal outbreaks of diseases due to this are usually associated with primary viral or parasitic infection. Such secondary invasions with motile aeromonads also characterize a wide range of other diseases such as epizootic ulcerative syndrome (EUS), furunculosis of salmonids , red-sore disease of large mouth bass and many parasite condition of tropical farmed fishes

9. PATHOGENESIS :- Motile aeromonads differ interspecifically and intraspecifically in their relative pathogenicity or their ability to cause disease. Under controlled laboratory conditions, De Figueredo and Plumb (1977) found that strains of motile aeromonads isolated from diseased fish were more virulent to channel catfish than were those isolated from pond water. In the acute form of disease, a fatal septicemia may occur so rapidly that fish die before they have time to develop anything but a few gross signs of disease.

10. Systemic infections were characterized by diffuse necrosis in several internal organs and the presence of melanin-containing macrophages in the blood. Chronic motile aeromonad infections manifest themselves primarily as ulcerous forms of disease, in which dermal lesions with focal hemorrhage and inflammation are apparent

11. SIGN & SYMPTOMS:- Signs of disease associated with aeromonas infection are non-specific and may be easily confused with other diseases. Infections vary greatly in appearance and may be seen in the skin only. When clinical signs of infection are present, affected fish may show exophthalmia, reddening of the skin, and an accumulation of fluid in the scale pockets. In unscaled fish (e.g., catfish), there is often fraying and reddening of fins accompanied by irregular, variably sized areas of depigmentation (paleness) that can develop anywhere on the body surface.

12. DIAGNOSIS:- Presumptive diagnosis of A. hydrophila may be based on the species of fish affected, the past disease status of those fish, and the presence of clinical signs of disease. However, bacteria must be isolated and identified biochemically to provide a definitive diagnosis. Either tryptic soy agar (TSA) or brain-heart infusion agar (BRIA) is a suitable medium for the primary isolation of motile aeromonads from diseased fish.

13. Calabrez and Lintermans (1993) have also developed a polymerase chain reaction (PCR) technique which has been used to detect strains of A. sobria in water, sediments, and fish. Genetic analysis suggests that there are presently 14 genomospecies recognized within the aeromonads (Joseph and Carnahan 1994) and, consequently a number of species-specific PCR tests would need to be developed and run on individual clinical samples in order to achieve accurate diagnosis.

14. TREATMENT:- Obviously the best prevention against Aeromonas hydrophila infection is to never have this disease. By minimizing the stress factors of fish through proper handling, stocking levels, nutrition, transportation, and water quality, fish are much less susceptible to this disease. Excellent sanitation and filtration procedures are an absolute must in order to minimize the chance of this disease ever occuring .

15. Treatment is currently limited to two antibiotics, Terramycin ®, an oxytetracycline , and Remet-30®, a potentiated sulfonamide. The current recommended treament of these two drugs is given in Table 1 below.

16. Table 1. Registered therapeutants for aquatic or fishery use.* Product S p o n s o r D o s a g e Terramycin ® Pfizer , Inc. 2.5-3.75 g/100lb of fish per day for 10 days in feed Remet-30® Hoffman-La 50 mg/kg of fish per day Roche,Inc . For 5 days

17. Another method for antibiotic use is a dip or bath although this is a rather controversial method and the efficiency or successfulness of this method is unknown. Problems associated with this method include the potential devastation to the biofilter of indoor tank systems and the possible lack of antibiotic entry into the fish. Potential problems associated with any antibiotic therapy include inadequate dosage levels, overdosing, drug resistance by the bacteria and the chelating of calcium to hard water in the case of Terramycin ® used in a dip or bath. Also remember that many of the fish which are not actually having symptoms of this disease may be stressed and increased handling associated with therapy may be fatal to these fish.