Equine Viral Arteritis

Front 1

Equine viral arteritis: Etiology

Back 1

1) Enveloped + strand RNA virus
2) Super family nidovirales, family arteriviridae, genus arterivirus
3) Occurs worldwide
4) genetic diversity
5) breed predisposition: a) standardbreds (70-90% sero+), b) low incidence (2-3%) in Thoroughbreds

Front 2

EVA: Transmission

Back 2

1) Respiratory and venereal during acute phase
2) Venereal only during carrier state

Front 3

EVA: Clinical signs

Back 3

1) subclinical/clinical depends on dose and virulence of strain
2) more severe in young, old, and debilitated animals
3) incubation: 3-14 days (aerosol), 6-8 days (venereal)
4) fever, leukopenia, anorexia, depression, edema, rhinitis and conjunctivitis (serous--> mucopurulent), skin rash
5) abortions-- occur almost immediately after onset of respiratory signs
6) low mortality
7) acute infection--> PI in 30-60% of Standardbred stallions (not mares)

Front 4

EVA: Pathogenesis of EVA

Back 4

EVA infection--> 24hrs-- EAV in macrophages--> 48 hrs-- EAV in satellite lymph nodes--> 3 days-- EAV in endothelium and circulating monocytes--> Systemic distribution of EAV (male carrier state)--> 6-8 days-- EAV in blood vessel endothelium and medial myocytes--> 10 days-- severe damage to blood vessels (abortion infected newborn)--> 10-21 days-- EVA in renal tubular epithelium. Shedding of virus in urine

Front 5

EVA: pathogenesis of EAV Abortion

Back 5

Leukocyte associated viremia. EAV infectes urterine blood vessels and myometrium--> 1) vasculitis and myometritis w/ ischemia followed by precocious chorionic detachment--> Uninfected aborted fetus. 2) EAV infects arcolar trophoblast chorionic mesencyme and sporadically, the fetus--> Infected aborted fetus or infected newborn foal

Front 6

EAV: Gross Lesions

Back 6

1) Edema
2) congestion and hemorrhages in subcu tissues, lymph nodes, and viscera
3) Yellowish clear exudate in body cavities
4) affected neonates have hemorrhages and lung congestion

Front 7

Histologic lesions

Back 7

1) blood vessels: vasculitis w/ fibrinoid necrosis of the tunica media, perivascular infiltration and endothelium loss
2) Lungs: mild to severe interstitial pneumonia; pulmonary arteritis and phlebitis; hypertrophy and hyperplasia of pneymocytes
3) Lymphoid tissue: lymphoid follicle necrosis, edema
4) Kidnay: Interstitial nephritis, possible tubular necrosis
5) Skin: Evidence of vasculitis. Skin biopsy for histopath and or IHC

Front 8

EAV: Diagnosis

Back 8

1) clinical signs
2) Abortions seen shortly after respiratory phase
3) no gross lesions in aborted fetuses
4) should be differentiated from infection w/: a) EHV1,4, b) equine influenza virus, c) equine adenovirus, d) equine rhinovirus
5) Virus isolation (cumbersome): nasopharyngeal and conjunctival swabs; citrated blood
6) PCR or VI: semen, refrigerate citrated blood; send others on dry ice
7) Histopath or IHC
8) VN or paired sera

Front 9

EAV: Prevention and control

Back 9

1) MLV: a) safe for stallions and non-preg mares, b) don't give to mares in last 2 mos. of gestation or to foals < 6 wks
2) Segregation of pregnant mares from other horses
3) Isolation (3-4 wks): a) horses from other farms, b) horses bought at sales, c) horses returning from racetracks