Caseous Lymphadenitis

Question 1

What is caseous lymphadenitis described as?

Answer 1

Infectious, contagious, and chronic.
*Goats and sheep, but can infect people.

Question 2

What tissues does caseous lymphadenitis generally affect?

Answer 2

Lymph nodes and lymphatic tissue(ex: spleen).
*Can affect internal organs.

Question 3

What are the two presentations of caseous lymphadenitis?

Answer 3

1. External (most common).
2. Internal.

Question 4

What economic impact does caseous lymphadenitis have on goat and sheep operations?

Answer 4

Causes severe economic losses due to resulting in culling animals, condemning the carcasses (cannot butcher the animal), and loss of wool and hide (cannot sell for fiber).

Question 5

What is the causative agent of caseous lymphadenitis?

Answer 5

Corynebacterium pseudotuberculosis.

Question 6

What are the characteristics of Corynebacterium pseudotuberculosis?

Answer 6

1. Facultative (Can exist in multiple environments).
2. Gram positive.
3. Intracellular coccobacillus.
4. Two biotypes: One in sheep and goats, the other in horses.
5. Releases an exotoxin that damages the cell walls of hosts.

Question 7

Why is caseous lymphadenitis difficult to eradicate?

Answer 7

It is very resistant to environmental stresses and can persist for extended lengths of time in an environment.
*2 months on surfaces, 8 months in soil.

Question 8

How does Corynebacterium pseudotuberculosis enter the body?

Answer 8

1. Via mucous membranes (Inhalation or ingestion).
2. Through damaged skin (Trauma, ear tagging, shearing injuries, castration, and tail docking).

Question 9

What is the incubation period for caseous lymphadenitis?

Answer 9

1-3 months.

Question 10

What are the symptoms of external caseous lymphadenitis?

Answer 10

1. Draining lymph nodes (Prefemoral, prescapular, parotid, and submandibular).
2. Draining abscesses.

Question 11

What are the symptoms of internal caseous lymphadenitis?

Answer 11

1. Failure to thrive.
2. Chronic weight loss.
3. Symptoms vary based on what organ(s) is/are involved (ex: Pneumonia if in/on the lungs).

Question 12

How is caseous lymphadenitis diagnosed?

Answer 12

1. Culture and sensitivity of purulent material from abscesses. Isolate animal(s) while waiting for results.
2. Bloodwork, radiographs, and ultrasound if suspected to be internal caseous lymphadenitis.
   *Clinical signs are highly suggestive.

Question 13

What are the treatments for caseous lymphadenitis?

Answer 13

1. Aiming to eliminate and limit transmission to other animals in the herd.
2. Surgical excision.
3. Draining/lancing abscesses.
4. Antibiotic therapy can be attempted when culling is not an option.
5. Isolation and environmental decontamination.
   *Challenging to eliminate from an individual patient and recurrence is common.

Question 14

What are the control measures for caseous lymphadenitis?

Answer 14

1. STRICT biosecurity measures: Isolation of infected animals, disinfection of fomites, disinfection of the environment.
2. Ideal to cull any infected animals, after drained abscesses have healed.
3. Vx: Species-specific.

Question 15

What are some methods for controlling the spread of caseous lymphadenitis?

Answer 15

1. Disinfect shears and other mechanical instruments between animals.
2. Feed pasteurized milk to kids/lambs from infected dams.
3. Separate “clean” v. “affected” animals if culling is not an option.
4. Long isolation period for newly introduced stock.
5. Remove environmental hazards, such as nails and barbed wire.