Equine - EAV

Question 1

What is the structure of arteritis viruses?

Answer 1

• (+)ssRNA
• Enveloped

Question 2

What is Equine viral arteritis?

Answer 2

• caused by Equine arteritis virus
• Acute, contagious disease of equids
• Viral respiratory pathogen
  
  • less common thatn EIV and EHV
• can cause abortion and neonatal death
• Persistently infected carrier stallions = reservoir

Question 3

Who are the most susceptible to EAV?

Answer 3

• Very young
• stressed, debilitated
• very aged

Question 4

How is EAV transmitted?>

Answer 4

• In utero
• Aerosolized respiratory tract secretions
  
  • primary route of dissemination during acute infection
• Venereal
  
  • primarily in sperm-rich fraction of semen
• Indirect contact (infrequent)

Question 5

What is the pathogenesis of EAV?

Answer 5

1. Inhalation - infects and replicates in Nasopharyngeal epithelium, tonsils, bronchial and alveolar macrophages (24hrs)
2. virus spreads to regional lymphatics by monocytes and lymphocytes (48 hrs)
3. Disseminates throughout body - cause panvasculitis that gives rise to edema an hemorrhage (72 hrs)

Question 6

What are the clinical signs of EVA?

Answer 6

• Most subclinical
• Fever
• Depression
• Inappetence
• dependent edema (lower hind limbs, scrotum, prepuce, ventrum
• Conjunctivitis and lacrimation
• supraorbital or periorbital edema
• Nasal discharge
• Respiratory Distress or dyspnea
• Diarrhea
• Urticarial-type skin reaction
• Decreased fertility
• leukopenia
• potential for abortion

Question 7

When do abortions occur with EAV?

Answer 7

• Between 1-4 weeks after EAV exposure
• anytime between 2-10 months gestation
• rates vary from 10-70% - strain dependent
• May not abort - give birth to a congenitally infected foal
  
  • neonatal foals may develop fulminating interstitial pneumonia
  • foals 1-3 months old may develop progressive pneumoenteric disease

Question 8

What lesions are seen on foals from EVA?

Answer 8

• Pulmonary edema
• emphysema
• interstitial pneumonia
• enteritis
• splenic infarcts
• Interlobular edema, congestion, and mononuclear cell infiltration in lungs
• lymphoid depletion and hemorrhage in lymphoreticular tissue
• Focal hemorrhage and necrosis of intestinal mucosa

Question 9

What are the gross lesions associated with EVA (adults)?

Answer 9

• characterized by vascular damage
• Edema, congestion and hemorrhage
  
  • Subcutis of limbs and abdomen
  • Excess peritoneal, pleural and pericardial fluid
  • Edema and hemorrhage of the intra-abdominal and thoracic lymph nodes, small and large intestine

Question 10

What are the microscopic lesions associated with EVA (adults)?

Answer 10

• characterized by vasculitis
• range between:
  
  • vascular and perivascular edema with occasional lymphocytic infiltration and endothelial cell hypertrophy
  • fibrinoid necrosis of the tunica media, extensive lymphocytic infiltration, necrosis of endothelium and thrombus formation

Question 11

Wen is infectious EAV no longer detectable in most tissues and body fluids?

Answer 11

28 dpi

Question 12

How many males become persistent EAV carriers?

Answer 12

• 10-70%
• EAV persistently infects the repro epithelium
  
  • Ampulla of the vas deferens, epididymis, testes, seminiferous tubules, accessory sex glands

Question 13

How is EAV diagnosed?

Answer 13

• Virus isolation
• PCR
• IHC
• Paired Ab titers (3-4 weeks apart)

Question 14

How are EAV carrier stallions diagnosed?

Answer 14

PCR/Virus isolation of sperm-rich fraction of ejaculate

Question 15

How is EAV diagnosed as the cause of an abortion?

Answer 15

• Virus isolation, IHC, or PCR
  
  • Placental tissues or fetal tissues (lung, liver, lymphoreticular tissues, peritoneal or pleural fluid)

Question 16

What is the Treatment for EVA?

Answer 16

• No specific antiviral treatment
  
  • supportive care (anti-inflammatories, diuretics
• Consider early euthanasia of congenitally infected foals
  
  • low chance of survival
  • Chronic carrier

Question 17

How can EAV be controlled?

Answer 17

• Castration of carrier stallions or only bread to seropositive mares
• Isolate new arrival horses for 3-4 wks prior to co-mingling
• segregate pregnant mares from other horses

Question 18

Is there a vaccine for EAV?

Answer 18

• Modified Live virus vaccine
  
  • protects against development of EVA, abortion, and carrier state in stallions
  • Not recommended for pregnant mares or foals < 6wks
  • Consult with State/federal Animal health officials
  • Only for seronegative animals - testing/records required