Lecture 4: Rhinopneumonitis (EHV)

What are the most common strains of EHV

1 and 4

Common symptoms of EHV 2 and 5

Respiratory

Common symptoms of EHV 3

Venereal ulcers and pustules

Characteristics of EHV 4

* Respiratory (70% is EHV, 95% of that is type 4)
* rarely neuro
* rarely abortion
* precipitated by stress

Characteristics of EHV 1

* Respiratory
* late term abortion
* neonatal and neuro syndromes
* very contagious
* primarily young horses

Pathophysiology of EHV

Resp epithelium → local lymph nodes → lymphocytes → uterus, causing abortion, or CNS, causing myeloencephalopathy

Where is the dormant virus stored in carriers

Trigeminal ganglion and lymphoid tissue

By what age have most horses been exposed, making them potential carriers

1 yr old

EHV 1 and 4 incubation time

2-10 days

EHV shedding period

7-14 days

Describe EHV resp syndrome

* 102-107 fever
* congestion, nasal discharge
* minimal cough
* anorexia and lethargy
* secondary pneumonia is common

Describe EHV 1 abortion syndrome

* contagious
* 3-12 weeks post clinical/asymptomatic infection
* abortion typically after 6 months gestation
* preceded by resp or neuro signs

Describe EHV 1 neuro syndrome

* equine herpes myeloencephalitis
* acute onset, stabilizes in 24-48 hours
* preceded by fever and resp signs
* prolonged, incomplete recovery
* general neuro signs: incoordination, poor mentation
* mild to severe CNS following fever by 2 days
* symmetric hind limb ataxia
* urinary incontinence
* lack of brain signs

Questions to ask in a neuro exam

1. Neuro or lameness- is the gait abnormality variable or consistent?
2. Location of neuro/lameness?
3. Cause?

How to diagnose EHV

* clinical signs and history
* PCR: blood, nasal swab, placenta
* paired serum titers
* spinal tap
* necropsy

Prevention of EHV

* humoral: antibodies neutralize virus, peaks 3 weeks post exposure
* cell mediated immunity: lymphocytes
* biosecurity: airborne
* vaccine: not always effective

Which type of EHV prevention provides protection against neuro signs?

Cell mediated immunity

EHV tx

* supportive care
* IV DMSO and steroids
* anti inflammatory
* antivirals
* antibiotics for secondary bacterial complications
* isolation

EHV prognosis

Compete recovery not always possible, commonly left with residual deficits.

* if horses go down for 1-2 days, even worse prognosis

If you encounter a resp/neuro case, what is step 1?

Assume it is infectious and isolate. Try to make a diagnosis, rule out EHV