21. Malignant catarrhal fever.

Question 1

History and Virus?

Answer 1

Malignant catarrhal fever

• Acute, usually lethal, febrile illness with general signs, keratoconjunctivitis, hemorrhagic pneumonia and
• enteritis, encephalitis, mainly in cattle

History:

• 18th century, first isolation from wildebeest,
• worldwide, sporadic

Virus:

• Ovine herpesvirus 2 (OHV-2),
• Alcelaphine herpesvirus 1 (AIHV-1) (Gammaherpesvirinae)
• AIHV-1 can be propagated in cell cultures, not OHV-2
• Other ruminants are also susceptible
• Experimental infection of rabbits - fever, respiratory disease, enteritis, encephalitis
• Sporadically swine can also get sick

Question 2

Epizootiology?

Answer 2

Epizootiology:

• In Africa: wildebeest associated malignant catarrhal fever
• Mostly over 1 year of age are carriers
• Shedding with virus with amniotic fluid with secrets
• Direct infection of cattle
• Outside Africa: sheep associated malignant catarrhal fever
• Sheep (& other Ru) are asymptomatic carriers
• Direct infection of cattle from sheep ʹ after long term (a few months) contact
• The cattle does not transmit further the virus
• Sporadic, sometimes endemic
• Elderly animals are more sensitive (young ones may recover)

Question 3

Pathogenesis?

Answer 3

Pathogenesis:

• In many points unclear, airborne infection, cell-associated viremia, no particular direct
• cytopathogenic effect of virus, immunopathological processes, contribution to another (latent
• bovine) herpesvirus?

Question 4

Clinical signs?

Answer 4

Clinical signs:

• 2 weeks to many months after sheep contact incubation period
• Catarrhal: produced by goblet cells in mucus membrane - all mucous membranes will show signs
• Peracute: high fever (!!!), unappetite, depression, salivation, hemorrhagic enteritis,
• tremor, convulsions, death

Subacute:

• fever, depression, rumen paralysis, agalactia, peripheral keratitis, purulent conjuncitivitis,
• nasal discharge (serous > purulent with necrotized tissue), nasal mucosa suffusion,
• epithelial necrosis, crouposal membranes (labored breathing), laminitis (loose of hoofs, horns),
• swollen LN, edema under skin (mainly on head), abdominal pain, obstipation (severe, hemorrhagic
• enteritis), hemorrhages and necrosis in genital mucosa and skin, meningitis, encephalitis
• (excitement, convulsions, restlessness, paralysis > death), abortive or mild form may occur in
• young, but they can get sick again in a few months

Question 5

Pathology?

Answer 5

Pathology:

• Peracute: inflamed mucosae, hemorrhages, no erosions, liver and kidneys are enlarged and pale,
• urinary bladder wall edema, suffusion, hemorrhage
• Subacute: eye lesions, hemorrhagic pneumonia and enteritis, fibrinaceous membranes,
• hemorrhages, necrosis, swollen LN and follicles, arteritis, capillary and vein fibrinoid necrosis,
• infarcts, lymphocytic polio- and leucoencephalomyelitis (mainly cortical)

Question 6

Diagnosis, DD and treatment?

Answer 6

Diagnosis:

• history (sheep!),
• signs, histopath,
• PCR (tissue, blood),
• serology (IF, ELISA)

Differential diagnosis:

1. Rinderpest,
2. IBR,
3. BVD-MD,
4. BTV,
5. RVF

Treatment: no cure, no vaccine, isolation from carriers (sheep, wildebeest)