49. Equine infectious arteritis.

Question 1

Virus details?

Answer 1

• 45-60nm diameter
• Isometric nucleocapsid; enveloped (low resistance in environment)
• +ss RNA genome (12-16kb)
• 7 structural proteins (E, N, M, Gp2, 3, 4, 5)
• Difficult to isolate; can survive in winter
• Affects Eq, Su and Monkeys

Question 2

Equine viral arteritis OIE listed disease?

Answer 2

Equine viral arteritis ʹ OIE listed disease

Ethiology

• Acute, contagious viral in equids ʹ fever, depression, anorexia, decreased WBC, edema, conjunctivitis, nasal discharge,
• skin rash, temporary subfertility in stallions, abortion infrequent ʹ ill and foals die.
• Variable % of post puberty colts and
• stallions carry and shed through semen
• Equidae: horses, ponies, donkeys and zebras (South American Camelids)
• Present everywhere, but different distribution

Question 3

Epizootiology?

Answer 3

Epizootiology

• 2 genotypes
• 1 serotype ➝ difference in virulence, genetically (antigenic) more divergent strain in donkeys
• Shedding

‣ Respiratory secretions

‣ Stallions: longterm carriers (10-70%), semen (for years), persistent infection in mature animals

‣ Mares: vaginal and uterine secretions

‣ Urine and faeces

• Incubation period: 2-14 days
• Sexual transmission: 1 week
• Endothelia damage after 6-8 days

Question 4

Pathogenesis?

Answer 4

Pathogenesis:

• Incubation period 2 ʹ 14 days
• Viral intake: venereal, nasal (per os)
• Primary replication: local lymphoid tissues (macrophage)
• Viraemia:
• Replicate in macrophages, endothelial cells, smooth muscle vascular cells
• Damage of blood vessel walls (inflammation in the endothel and media)
• 1) Solid haemorrhages, oedemas
• 2) Placenta abruption, foetus is infected with virus
• o Sexual transmission: 1 week, Endothel damages: after 6-8 days
• Persistent infection

Question 5

Clinical signs?

Answer 5

Clinical signs

• Mostly asymptomatic
• Old or very young animals
• Fever, depression, loss of appetite, somnolence, nasal discharge
• Severe interstitial pneumonia / enteritis (very young may die)
• Adult horses
• Fever, depression, anorexia, somnolence, nasal discharge
• Oedema: limbs, prepuce, scrotum, mammary gland, ventral abdominal wall, third palpebra -> hot painful
• Urticaria: mainly on neck, head
• Less frequently: conjunctivitis, photophobia, periorbital or supraorbital oedema, rhinitis
• Gastrointestinal problems: Colic, obstipation -> diarrhoea
• Mare: placenta lesions, abortion or stillbirth (10-60%)
• Stallion
• Temporary decrease of fertility, reduced sperm quality (increased scrotal temperature and
• oedema), decreased libido, can persist for up to 4months
• Quality of semen is not decreased in carrier stallions!

Question 6

Pathology?

Answer 6

Pathology

• Oedema, congestion and haemorrhages
• In subcutaneous tissues, visceral organs, lymph nodes,
• Clear, yellowish fluid in body cavities
• Pulmonary oedema, interstitial pneumonia, emphysema
• Spleen infarcts, enteritis
• Aborted foetuses
• Partial autolysis
• Excess fluid in the body cavities
• Fibrinoid degeneration, inflammation and thrombus formation in small blood vessels
• Interlobular interstitial pneumonia
• Fibrinoid-necrotic enteritis

Question 7

Diagnosis?

Answer 7

Diagnosis

• Clinical signs, pathology
• Samples: nasal fluid, WBC, semen, caul
• Isolation(CPE), IF, IHC, RT-PCR(semen)
• Serology: VN (1:4), ELISA (gp5)

Question 8

Differential diagnosis

Answer 8

Differential diagnosis:

1. equine influenza,
2. equine infectious anaemia,
3. African horse sickness,
4. Getah virus,
5. Hendra virus,
6. equine rhinitis A and B,
7. equine adenovirus,
8. equine herpesvirus 1 and 4,
9. leptospirosis

Question 9

Prevention?

Answer 9

Prevention

• Control
• Isolation of freshly infected animals
• Symptomatic treatment (rest, NSAID)
• Isolation & testing of new horses for 3-4 weeks(Serology)
• Control of carrier stallions (test seropositive stallions with PCR)
• Vaccination:
• inactivated (in EU) 2X, eradication
• attenuated USA