70. Equine influenza.

Question 1

Occurence?

Answer 1

Equine influenza

• Bird original host
• horse adapted host
• now horse is the permanent host!
• Acute disease of horses with fever & respiratory signs
• Occurrence: worldwide, frequent (except: NZ, Iceland etc.)

Question 2

Epizootiology?

Answer 2

Epizootiology

• H7N7 ʹ Prague ʹ extinct?, H3N8 ʹ Miami ʹ frequent
• Shed through excretes, airborne, oral infections
• Introduction into a stud by infected animals (no signs yet)
• Very contagious, quick spread (shows, race ʹ many meet: impt to have vax updated!)
• Long-term persistence is not known/not significant ʹ Acute until Immune response neutralises

Question 3

Pathogenesis?

Answer 3

Pathogenesis

• Infection of respiratory epithelia
• tracheal & bronchial mucosa damage,
• denudation
• Viremia
• Strong interferon response : general signs:
• All signs are due to high interferon level production, not
• due to the destruction by the virus
• Clinical signs/outcome depends on the immune status

Question 4

Clinical signs?

Answer 4

Clinical signs

• 1-3 days incubation
• High fever (>41oC), depression, anorexia, weakness
• Serous nasal discharge, dry, unproductive cough
• Bacterial complications: purulent nasal discharge, pneumonia, pleuropneumonia, chronic bronchitis,
• atelectasia
• Without complications (from bacterial infections) improvement within a few days & complete
• recovery w/in 2-3 weeks (10 days)
• In complicated cases coughing for months, permanent damages

Question 5

Pathology?

Answer 5

Pathology

• Hyperaemia, erosions, haemorrhage in the upper resp tract mucosa
• Bronchointerstitial pneumonia: oedema, bronchiolar epithel necrosis, secondary bacterial
• pneumonia
• Donkey: croupous and interstitial pneumonia

Question 6

Diagnosis?

Answer 6

Diagnosis

• Virus isolation ʹ embryonated eggs, cell cultures
• HA, IF, Ag capture, ELISA
• RT-PCR

Question 7

Differential diagnosis?

Answer 7

Differential diagnosis

• Herpesviruses: lower morbidity, abortions
• Adeno, Aphto, Erbo, Reoviruses: lower morbidity, age
• Infectious arteritis: abortions, haemorrhages, oedemas
• Bacteria: Glanders (pustules, abscesses),
• Rhodococcus equi (lung abscesses)

Question 8

Treatment?

Answer 8

Treatment

• Rest, dust-free environment
• Supportive therapy ʹ non-steroid anti-inflammatory drugs, AB (efficacy is dubious)
• Amantanine? Oseltamivir? Zanamivir?

Question 9

Control and prevention?

Answer 9

Control & prevention

• Epizootiology measures: quarantine: min 21 days, 32m; outbreak ʹ movement restrictions,
• vaccination of healthy horses
• Immunisations
• Approx. 1 year protection to the homologous strain after recovery from wild type virus infection
• IgA in nasal mucosa, IgG in serum
• Several vaccines on the market
• Attenuated, intranasal: IgA secretion
• Inactivated, canarypox-vector, ISCOM-subunit etc.
• Foals: primary immunisation from 6 month of age ʹ
• Attenuated intranasal 1x OR
• Inactivated 3x (3-6 weeks apart & at 10-12 months of age)
• Repetitions in 6 months
• Mares: immunisation 4-6 weeks before parturition
• Race horses: immunisation before the racing season
• Subtype-specific protection
• Antigenic drift! ʹ virus continuously changing ʹ vaccinate YEARLY