Quaglio - Bacterial Diseases Flashcards
What are the common bacterial diseases affecting fish?
Motile Aeromonas Septicemia (Aeromonas hydrophila)
Edwardsiellosis (Edwardsiella tarda, Edwardsiella ictaluri)
Flavobacteriosis (Flavobacterium spp.)
Columnaris disease (Flavobacterium columnare)
Nocardiosis (Nocardia spp.)
Common bacterial diseases can vary by species and environmental conditions.
What are the clinical signs of Motile Aeromonas Septicemia (MAS)?
Skin ulcers and hemorrhages
Lethargy and loss of appetite
Exophthalmos (protruding eyes)
Systemic septicemia and organ damage
Clinical signs can vary based on the severity of the infection.
What is the causative agent of Motile Aeromonas Septicemia (MAS)?
Aeromonas hydrophila: a Gram-negative, motile bacterium found in freshwater environments.
This bacterium can thrive in various aquatic conditions.
How is Motile Aeromonas Septicemia (MAS) diagnosed?
Clinical signs and gross lesions
Bacteriological culture on TSA, BHI, or Blood Agar
Identification using biochemical tests
Diagnosis often requires multiple methods for accuracy.
What is Edwardsiella ictaluri and the disease it causes?
Edwardsiella ictaluri causes Enteric Septicemia of Catfish (ESC).
Common in channel catfish farms in the southeastern USA.
ESC is a significant issue in aquaculture, particularly in warm climates.
What are the symptoms of Edwardsiella ictaluri infection?
Petechial hemorrhages
‘Hole in the head’ lesions
Pale internal organs with necrotic abscesses
These symptoms indicate severe systemic infection.
What are the key features of Edwardsiella tarda infection?
Causes Edwardsiellosis or hemorrhagic septicemia
Symptoms: abscesses in liver, bloody ascitic fluid, and ulcers
Affects eels, salmon, flounder, carp, and tilapia
This infection can lead to high mortality rates in affected species.
What is Flavobacteriosis and its common forms?
Cold-water disease (Flavobacterium psychrophilum): Affects salmonids in winter
Columnaris disease (Flavobacterium columnare): Affects warm-water species like channel catfish
Both diseases have significant economic impacts on aquaculture.
What are the symptoms of Cold-water disease caused by Flavobacterium psychrophilum?
Hemorrhages at the base of fins
Tail fraying and skin lesions
High mortality in fry during cold months
Fry are particularly vulnerable due to their size and immune status.
How is Flavobacterium psychrophilum transmitted?
Horizontal transmission via water
Stress and poor water quality increase susceptibility
Vertical transmission is possible
Management practices can significantly influence transmission rates.
What is the main symptom of Columnaris disease caused by Flavobacterium columnare?
Saddleback lesions: erosive skin lesions with cotton-like appearance
Gill necrosis and fin rot
These lesions can severely affect fish health and survival.
What environmental factors favor Flavobacterium columnare outbreaks?
Warm water temperatures (>20°C)
High organic loads and poor water quality
Environmental management is crucial in preventing outbreaks.
How is Columnaris disease diagnosed?
Gross lesions (skin and gill necrosis)
Culture on Cytophaga agar
Microscopic examination with methylene blue stain
Accurate diagnosis is essential for effective treatment.
What is Nocardiosis and its causative agent?
A chronic systemic disease caused by Nocardia spp. (Gram-positive, branching rods)
Nocardiosis can affect various fish species and lead to significant health issues.
What are the symptoms of Nocardiosis?
Granulomas in internal organs (liver, spleen, kidney)
Skin ulcers and muscle nodules
Chronic inflammation leading to systemic infection
The presence of granulomas suggests a chronic infection.
How is Nocardiosis diagnosed?
Observation of granulomas in tissues
Gram staining to identify branching Gram-positive rods
Histopathology and bacterial culture
Diagnosis often requires multiple methods to confirm the presence of the pathogen.
What is the significance of granulomas in bacterial infections?
Granulomas indicate a chronic immune response to infection
Common in Nocardiosis and mycobacterial diseases
The formation of granulomas is a key feature in chronic infections.
What are the primary culture media used for bacterial diagnosis in fish?
TSA (Tryptic Soy Agar)
Marine Agar
Blood Agar
Selective media for Vibrio or Edwardsiella
The choice of media can influence the recovery of specific pathogens.
How does water temperature influence bacterial disease outbreaks?
Higher temperatures favor Flavobacterium columnare and Aeromonas hydrophila
Cold temperatures favor Flavobacterium psychrophilum
Temperature management is crucial in aquaculture to minimize disease risks.
What biosecurity measures help prevent bacterial diseases?
Quarantine new fish
Regular tank sanitation and water quality monitoring
Avoid overcrowding and stress
These measures are essential for maintaining fish health in aquaculture.
What is the role of antibiotic sensitivity testing in fish bacterial infections?
Determines effective antibiotics for treatment
Reduces the risk of resistance development
Antibiotic testing is critical for effective management of bacterial infections.
How is hemorrhagic septicemia associated with bacterial infections?
Caused by pathogens like Aeromonas hydrophila and Edwardsiella tarda
Symptoms: widespread hemorrhages, organ necrosis, and septicemia
Hemorrhagic septicemia can lead to high mortality in affected populations.
What is the impact of Aeromonas hydrophila on aquaculture?
Major cause of fish mortality in overcrowded or poorly managed farms
Can infect multiple freshwater species, including trout, carp, and sturgeon
Effective management strategies are essential to mitigate its impact.
What are the signs of Edwardsiella tarda infection in catfish?
Small cutaneous lesions that develop into abscesses
Bloody ascitic fluid and liver necrosis
High mortality in warm-water conditions
These signs indicate severe infection and require prompt intervention.
What is the geographic distribution of Flavobacterium psychrophilum?
Found in Europe, Japan, North America, and South America
Affects salmonids in cold-water aquaculture
Awareness of its distribution is important for disease management.
How is Edwardsiella ictaluri transmitted among catfish?
Horizontal transmission via water and direct fish contact
Vertical transmission through eggs is possible
Understanding transmission routes is crucial for effective control measures.
What is the significance of ‘saddleback lesions’ in fish pathology?
Characteristic of Columnaris disease caused by Flavobacterium columnare
Indicates skin and muscle necrosis
Saddleback lesions are a key diagnostic feature of this disease.
What treatments are effective for bacterial fish diseases?
Antibiotics (based on sensitivity testing)
Improving water quality and reducing stress
Quarantine and biosecurity measures
A multifaceted approach is often necessary for successful treatment.
What is the importance of histopathology in bacterial disease diagnosis?
Confirms bacterial presence in tissues
Identifies granulomas and necrotic areas
Histopathology provides critical information for diagnosing chronic infections.
What factors increase the risk of bacterial outbreaks in aquaculture?
High stocking density
Poor water quality (low oxygen, high ammonia)
Stress from handling or transportation
Managing these factors is essential for preventing outbreaks.
