Page 4 - Equine influenza e-Book

Specific

• Lack of effective vaccination against infective strain.

Pathophysiology

• Aerosol spread of the organism → tropism for ciliated respiratory epithelium → tracheobronchitis or
primary viral pneumonia.
• Aerosol infection → droplets penetrate into respiratory tract according to their size → tropism of virus
for ciliated respiratory epithelium → epithelium sloughs → edema and lymphoid and impaired mucous
clearance, infiltration of mucosa → tracheobronchitis in adults or primary viral pneumonia in foals.
• Incomplete separation of lobes of equine lung → spread of infection by direct extension.
• May be complicated by secondary infection, eg streptococci Streptococcus spp.
• Some cases → virus penetrates respiratory tract basement membrane → viremia → myocarditis or
hepatic damage → limb edema.

Timecourse

• Incubation period: 1-3 days.
• Virus shed in nasal discharge and droplets for 7-10 days.
• Seroconversion by 8 days following infection.
• Cough lasts 1-3 weeks.
• Recovery of uncomplicated infection in 1-2 weeks following onset of clinical signs.

Epidemiology

• Virus cannot survive outside host.
• Replicates in respiratory epithelium of horses, donkeys and hybrids.
• Transmitted via nasal discharges and droplets.

Diagnosis

Presenting problems

• Coughing Coughing.
• Pyrexia.
• Inappetence.
• Dyspnea.
• Submandibular lymphadenopathy.
• Nasal discharge Nose: nasal discharge.
• Photophobia.
• Ocular discharge Eye: ocular discharge.
• Exercise intolerance.
• Limb edema.
• Sporadic cases of neurological disease.

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