Canine Distemper (Polysystemic Infectious Diseases)

Question 1

What causes canine distemper?

Answer 1

RNA paramyxovirus

Question 2

Who is susceptible to distemper?

Answer 2

Dogs and many other carnivores (LARGE cats)

Question 3

In what part of the world does distemper occur?

Answer 3

Enzootic worldwide

Question 4

Who is the poster child for canine distemper?

Answer 4

Young, non vaccinated dogs (although ALL ages are affected)

Question 5

How is distemper transmitted?

Answer 5

Through ALL body secretions (especially in groups of dogs)

• Shedding is transient after recovery
• Does not survive long in environment (1-2 weeks)

Question 6

What are the two ways that the host can respond to distemper?

Answer 6

1. Low virus-neutralizing antibody production
2. High virus-neutralizing antibody production (most dogs)

Question 7

What are the signs in a host with a low virus-neutralizing antibody response?

Answer 7

• Systemic signs
• Acute encephalomyelitis

Question 8

What are the signs in a host with a high virus-neutralizing antibody response?

Answer 8

• Subclinical infection & recovery (75% of dogs)

OR

• Chronic encephalomyelitis only (prognosis poor)

Question 9

What are the first signs 4-6 days post-infection?

Answer 9

• Transient fever
• Lymphopenia

Question 10

What are the epithelial phase signs 6-9 days post-infection (viremia)?

Answer 10

GI, skin, respiratory

• VOMITING and DIARRHEA
• Hyperkeratinization of pads
• Rhinitis, conjunctivitis (serous discharge)
• Pneumonia (interstitial)

Question 11

What are the ocular signs 6-9 days post-infection (viremia)?

Answer 11

See cloudiness of eyes

• KCS
• Chorioretinitis
• Optic neuritis

Question 12

What are the neurologic phase signs 6-9 days post-infection (viremia)?

Answer 12

1. Acute encephalomyelitis

• Almost no inflammation
• Very young dogs (< 2 months)
• Gray matter destruction

2. Subacute or chronic non-suppurative encephalomyelitis

• Inflammation
• Older dogs (> 2 months)
• Demyelination

3. Old dog encephalitits

• Lymphoplasmacytic encephalitis
• Well vaccinated adult dogs

4. Central vestibular signs (head tilt, nystagmus)

5. Cerebellar signs (ataxia, tremors, hypermetria)

6. Myoclonus

7. Cerebral signs (behavioral, delirium, chewing-gum seizures)

Question 13

What lab work changes do you see in a patient with distemper?

Answer 13

• Lymphopenia initially
• Neutrophilic leukocytosis later
• 4-fold increase in IgG over 2-3 weeks (recent infection or recent vaccination)
• Presence of IgM
• CSF titers with CNS signs (produced locally)

However, presumptive diagnosis based on clinical signs

Question 14

How do you definitively diagnose distemper?

Answer 14

• Viral inclusions
• RT-PCR (urine, serum, CSF)
• qPCR to distinguish vaccine vs. disease

Question 15

How do you treat a patient with distemper?

Answer 15

NOTHING REALLY WORKS!

• Non-specific and supportive
• Treat secondary infections (pneumonia)
• Dexamethasone
  
  • May improve CNS signs, but does not improve survival
  • Makes them feel better
  • Contraindicated in cases with acute encephalomyelitis

Question 16

How can canine distemper be prevented?

Answer 16

• Isolate sick dogs
• Vaccination (core vaccine, modified vaccine)