Quaglio - Bacterial Diseases

Question 1

What are the common bacterial diseases affecting fish?

Answer 1

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.

Question 2

What are the clinical signs of Motile Aeromonas Septicemia (MAS)?

Answer 2

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.

Question 3

What is the causative agent of Motile Aeromonas Septicemia (MAS)?

Answer 3

Aeromonas hydrophila: a Gram-negative, motile bacterium found in freshwater environments.

This bacterium can thrive in various aquatic conditions.

Question 4

How is Motile Aeromonas Septicemia (MAS) diagnosed?

Answer 4

Clinical signs and gross lesions
Bacteriological culture on TSA, BHI, or Blood Agar
Identification using biochemical tests

Diagnosis often requires multiple methods for accuracy.

Question 5

What is Edwardsiella ictaluri and the disease it causes?

Answer 5

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.

Question 6

What are the symptoms of Edwardsiella ictaluri infection?

Answer 6

Petechial hemorrhages
‘Hole in the head’ lesions
Pale internal organs with necrotic abscesses

These symptoms indicate severe systemic infection.

Question 7

What are the key features of Edwardsiella tarda infection?

Answer 7

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.

Question 8

What is Flavobacteriosis and its common forms?

Answer 8

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.

Question 9

What are the symptoms of Cold-water disease caused by Flavobacterium psychrophilum?

Answer 9

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.

Question 10

How is Flavobacterium psychrophilum transmitted?

Answer 10

Horizontal transmission via water
Stress and poor water quality increase susceptibility
Vertical transmission is possible

Management practices can significantly influence transmission rates.

Question 11

What is the main symptom of Columnaris disease caused by Flavobacterium columnare?

Answer 11

Saddleback lesions: erosive skin lesions with cotton-like appearance
Gill necrosis and fin rot

These lesions can severely affect fish health and survival.

Question 12

What environmental factors favor Flavobacterium columnare outbreaks?

Answer 12

Warm water temperatures (>20°C)
High organic loads and poor water quality

Environmental management is crucial in preventing outbreaks.

Question 13

How is Columnaris disease diagnosed?

Answer 13

Gross lesions (skin and gill necrosis)
Culture on Cytophaga agar
Microscopic examination with methylene blue stain

Accurate diagnosis is essential for effective treatment.

Question 14

What is Nocardiosis and its causative agent?

Answer 14

A chronic systemic disease caused by Nocardia spp. (Gram-positive, branching rods)

Nocardiosis can affect various fish species and lead to significant health issues.

Question 15

What are the symptoms of Nocardiosis?

Answer 15

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.

Question 16

How is Nocardiosis diagnosed?

Answer 16

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.

Question 17

What is the significance of granulomas in bacterial infections?

Answer 17

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.

Question 18

What are the primary culture media used for bacterial diagnosis in fish?

Answer 18

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.

Question 19

How does water temperature influence bacterial disease outbreaks?

Answer 19

Higher temperatures favor Flavobacterium columnare and Aeromonas hydrophila
Cold temperatures favor Flavobacterium psychrophilum

Temperature management is crucial in aquaculture to minimize disease risks.

Question 20

What biosecurity measures help prevent bacterial diseases?

Answer 20

Quarantine new fish
Regular tank sanitation and water quality monitoring
Avoid overcrowding and stress

These measures are essential for maintaining fish health in aquaculture.

Question 21

What is the role of antibiotic sensitivity testing in fish bacterial infections?

Answer 21

Determines effective antibiotics for treatment
Reduces the risk of resistance development

Antibiotic testing is critical for effective management of bacterial infections.

Question 22

How is hemorrhagic septicemia associated with bacterial infections?

Answer 22

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.

Question 23

What is the impact of Aeromonas hydrophila on aquaculture?

Answer 23

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.

Question 24

What are the signs of Edwardsiella tarda infection in catfish?

Answer 24

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.

Question 25

What is the geographic distribution of Flavobacterium psychrophilum?

Answer 25

Found in Europe, Japan, North America, and South America
Affects salmonids in cold-water aquaculture

Awareness of its distribution is important for disease management.

Question 26

How is Edwardsiella ictaluri transmitted among catfish?

Answer 26

Horizontal transmission via water and direct fish contact
Vertical transmission through eggs is possible

Understanding transmission routes is crucial for effective control measures.

Question 27

What is the significance of ‘saddleback lesions’ in fish pathology?

Answer 27

Characteristic of Columnaris disease caused by Flavobacterium columnare
Indicates skin and muscle necrosis

Saddleback lesions are a key diagnostic feature of this disease.

Question 28

What treatments are effective for bacterial fish diseases?

Answer 28

Antibiotics (based on sensitivity testing)
Improving water quality and reducing stress
Quarantine and biosecurity measures

A multifaceted approach is often necessary for successful treatment.

Question 29

What is the importance of histopathology in bacterial disease diagnosis?

Answer 29

Confirms bacterial presence in tissues
Identifies granulomas and necrotic areas

Histopathology provides critical information for diagnosing chronic infections.

Question 30

What factors increase the risk of bacterial outbreaks in aquaculture?

Answer 30

High stocking density
Poor water quality (low oxygen, high ammonia)
Stress from handling or transportation

Managing these factors is essential for preventing outbreaks.