41. Encephalomyocarditis.

Question 1

Occurrence?

Answer 1

Encephalomyocarditis ʹ Zoonotic!

Occurrence:

• agent is widespread,
• Europe, N. America, Australia,
• In Hungary it was not identified
• Clinical form of the disease is not widespread

Question 2

Aetiology?

Answer 2

Aetiology

• Picornaviridae, Cardiovirus genus
• Virus of rodents, wide host range
• Good resistance: survives in the environment for several weeks

Question 3

Epidemiology?

Answer 3

Epidemiology

• Wide host range (30 species!) ʹ rodents (mice, rats), swine, elephant, chimpanzee, hippo, lions,
• other mammals, birds, humans (zoonotic!)
• In rodents asymptomatic ʹ maintaining host
• Shed by rodents in faeces & urine or if carnivore eats infected rodent
• Infection is with contaminated feed & water
• Mortality: newborn animals 25-50%, growers/fattening: 5-25%
• Some strains can cause both (A and B), spreads SLOWLY in pigs
• EMCV 1
• Widespread Type A strain
• reproductive problems
• EMCV 2
• Myocarditis

Question 4

Pathogenesis?

Answer 4

• *Pathogenesis**
  1. Per os or aerosol infection

2. Tonsils ➝ replication
3. Viraemia
   - Heart ➝ myocarditis, necrosis in heart muscle
   - Small intestine ➝ shedding
   - Liver, kidney, spleen, lungs ➝ lung oedema
   - Central nervous system (CNS) ➝ encephalomyelitis
   - Foetus ➝ abortion, weak piglets
4. Immune response ➝ maternal immunity 4-6 weeks

Question 5

Clinical signs?

Answer 5

Clinical sign
• Pigs

• Occurs in any age group

• Most frequently in piglets below 4-5 weeks of age

‣ Heart failure

‣ Fever 41℃, anorexia, spasm, forced movement

‣ Dyspnea

• Growers, fattening pigs ➝ dyspnea, sudden death
• Sows ➝ reproduction problems, abortion, stillbirth

• Other animal species ➝ dyspnea, sudden death
s

Question 6

Pathology?

Answer 6

Pathology

• Death of acute myocarditis: some epicardial haemorrhage
• Heart: enlarged (compensating), soft, pale, necrotic foci, hydropericardium, hydrothorax, pulm. oedema
• Foetus: no gross lesions, sometimes oedema, haemorrhages
• Histology: IHC - positive myocardial cells, non-purulent encephalitis
• Myocarditis: interstitial infiltration of lymphocytes & neutrophil granulocytes

Question 7

Diagnosis?

Answer 7

Diagnosis

• Epidemiology ʹ clinical signs ʹ pathology, histopathology
• Detection of the virus: PCR, IF, isolation of the virus (cell culture, embryonatedegg)
• Detection of Abs (foetuses): HAI, ELISA, VN (presence of Abs alone is not enough!)

Question 8

Prevention, control and public health aspects?

Answer 8

Prevention, control:

• rodent control,
• seroconversion,
• some inactivated vaccines

Public health aspects - zoonosis

• Source of infection: rodents & swine
• Clinical signs: rare, seroconversion, myocardial necrosis, damage of the coronaria
• Prevention: rodent control