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Year 2 Equine ID > Equine Viral Respiratory infections > Flashcards

Equine Viral Respiratory infections Flashcards

1
Q

Which infectious viral respiratory diseases are endemic or v common in UK?

A
  1. Adenovirus
  2. Influenza
  3. Equine herpes viruses 1&4
  4. Rhinovirus
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2
Q

Which infectious viral respiratory diseases are exotic adn notifiable?

A
  • Equine viral arteritis – has been in UK and we get sporadic reports
  • African Horse sickness – vector borne disease, some incursions into southern Europe – non into UK but with changing climate and populations of vectors, it could potentially come to UK.
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3
Q

Adenovirus

Biggest issue in what?

A

Infectious viral resp disease
• Generally a self limiting transient upper respiratory infection
1. Most cases don’t cause severe clinical signs
2. Only issue in “Severe Combined Immunodeficiency” (SCID) in arab foals which is an genetic immunodeficiency issue, making adenovirus much more severe

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4
Q

Adenovirus clinical signs

A
  • Mild / subclinical disease /carrier state in normal animals and adults
  • One possible cause of outbreaks of mild respiratory disease in yards of young racehorses
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5
Q

Influenza
type of virus?
Subtypes?

A

Infectious viral resp disease
HUGE PUBLIC HEALTH CONCERN
Orthomyxovirus
Subtypes are based on on haemagglutinin (H) and neuraminidase (N) glycoprotein surface antigens.
Means will always be classified with a H or N

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6
Q

Which subtype is responsible for all recent outbreaks of equine influenza virus?

A

• H3N8 subtype

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7
Q

Which subtype displays strong antigenic drift, changing surface antigens regularly and was in Newmarket 1998?

A

• H3N8

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8
Q

Morbidity/ mortality?

A

• High morbidity low mortality – very few actually die, most show clinical signs and infection in nieve (young horses in big group)

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9
Q

Epidemiology of equine influenza virus

  • what countries?
  • highest risk?
  • what inc risk?
A

• All countries except NZ and Iceland
- Highest risk groups: • Young horses in big groups
• Subclinical carriers shed and infect naïve populations
o Not all horses show same degree of clinical signs
• Poor ventilation and high humidity enhance transmission
• Adults can be infected esp. in crowded and stressful conditions
• Morbidity High, Mortality Low (except foals)

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10
Q

Talk about the host pathogen interaction of equine influenza virus

A
  1. Spreads along whole respiratory tract, damage to epithelium and cilia means other pathogens get access to resp system - secondary bacterial infections
  2. Inhaled virus attaches to respiratory mucosal cells
  3. Haemagglutinin (H) attaches to Sialic acid on host cells
  4. Neuraminidase (N) facilitates entry to cell and inhibits mucociliary clearance
  5. Virus spreads along whole respiratory tract in 1-3days
  6. Damage to the epithelium and cilia = Secondary bacterial infections
  7. Can take up to 32 days for mucociliary transport to return to normal
  8. Horses may be unfit for competition up to 50-100 days /1 week off work for each day of fever
  9. Rule of thumb: horse has 1 week off work for every day it was pyrexia
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11
Q

What are the clinical signs for equine influenza virus?

A

Note: normal for infectious viral respiratory disease
1. Pyrexia up to 41.1˚C (106 ˚ F).
2. Nasal discharge – spread by droplets
• initially watery then mucopurulent (snotty) Likely true positive less likely to be positive (false negative)
3. Coughing, tachypnea, inappetance,retropharyngeal lymphadenopathy + weight loss
4. Clinical signs normally last 7-14 days

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12
Q

Incubation period for equine influenza

A

24 -48 hours – slightly easier to control in populations

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13
Q

Equine Influenza Virus: Diagnosis

A

To prove a pathogen is involved:
• Nasal swab for PCR +/- on whole to detect pathogens
o Can also do culture for bacteria or viral isolation
• Look for evidence of immune response:
o 4 fold rise in tire in serum antibody titre over 14 days

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14
Q

What to remember about diagnosis and nasopharyngeal swabbing with equine influenza virus

A

Diagnosis – need to understand when virus first lands, depending on infectious dose, often initial load of viruses move intracellularly and shedding is only 1-5 days! 1 week, shedding very little! No point nasopharyngeal swab day 0 and after 5. Ab titre at day 3 is useless. Paired Ab titre 2 weeks apart

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15
Q

Clinical pathology signs for equine influenza

A

• Characteristic changes in WBC pattern:
o Initial leukopenia (decrease in neutrophils), (inc in lymphocytes)
• Initial leukopenia and lymphopenia
• Later monocytosis, neutrophilia and increased fibrinogen
• IF RETURNED TO EXERCISE TOO EARLY, THE LUNGS HAVENT HAD TIME TO RECOVER  WORSENED DISEASE.

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16
Q

Treatment of equine influenza virus

A
  1. Largely symptomatic:
    a) Non-steroidal anti-inflammatory drugs (NSAIDs)
    b) Air hygiene
    c) Antimicrobials in case of secondary infections
  2. Antiviral drugs
    a) Available but not regularly used – mixed evidence/resistance concerns / cost
17
Q

Equine infleunza virus, how to stop spread

A

PREVENTION main thing.
• Most common visit as a vet is to do vaccination
• Targets the Haemaglutinin Surface Antigens
• Usually inactivated whole or part virus preparations / recombinant canary pox
• Common to get fever for 1-4 days
• Vaccination in the face of outbreak can be useful – herd health more than individual benefit
• Antigenic drift means that vaccines are not equally effective against all H3N8 strains

18
Q

Equine influenza vaccine regulations

A
  1. British Horseracing Authority:
    o 1st vaccine
    o 2nd vaccine 21-92 days after 1st
    o 3rd vaccine 150-215 days after 2nd
    o Boosters within 365 days
  2. FEI (eventing, dressage, jumping, endurance)
    o Same as above except 3rd within 7 months of 2nd
    o To compete horse the last booster must have been within the last 6 months and 21 days
    o No competing for 7 days after a vaccination
    o Worth paying particular attention too because competitions can stop them competing if given too late
19
Q

Quarantine for equine influenza virus

A

ALL new arrivals and ALL horses returning from high risk areas
• Extremely strict Ireland and NZ
• Vaccinated
• Ideally quarantined for 2 weeks
• Separate stables (20-40 feet)
• Separate water source, tack, cleaning equipment etc
• Cleaned and fed last
• Protective clothing
• Wash hands
• Ideally nasal swab and serology on entyr which is to be repeated at the end of the 2 weeks

20
Q

Equine Herpes Virus… which are we interested in

A
  • EHV 1, present in 3 forms: Respiratory (mildist), Abortion, Neurological most devastating
  • EHV 4 – Respiratory only, no abortion or neurological disease
21
Q

Host-pathogen and environment interactions

A
  • EHV 1&4 – 1-3 year olds most affected – young horses
  • Inhaled and attaches and replicates in mucosal epithelial cells of nasal passage, pharynx and tonsillar tissues
  • EHV1 can lie latent infection in lymphocytes and trigeminal ganglia (same as for most people with herpes) – immune suppressor drugs such as corticosteroids
  • Upper respiratory tract inflammation (rhinitis, pharyngitis and tracheitis)
  • Allows secondary invasion of mucosa by bacteria
  • Transported by T-lymphocytes to other tissues
  • Latent infection in CD8+ T-lymphocytes and trigeminal neural ganglion
22
Q

What are the most devastating effects of EHV1?

A

it is a vasculitis (inflammation of blood vessels). Brain  9 days after experimental infection of 1 year old – pronounced inflammatory response (horizontal inflammatory infiltrate around BV). Immune response then damage to neurones
Endometrium – abortion as lose placental supply of nutrients to fetus
Choroid (vascular area of eye that sits between retina and sclera. Strong inflammatory infiltrate around blood vessel

23
Q

How long is equine herpes virus 1& 4 shed adn where from?

A
  • Latent infection and intermittent shedding (sits on trigeminal ganglion)
  • Shed for 2 to 3 weeks
24
Q

Clinical signs equine herpes virus 1 and 4

A
  • 3-7 day incubation (up to 21days)
  • Relatively slow spread through population
  • Biphasic fever (40-41°C), lethargy and inappetence
  • Oedema and hyperaemia of mucosa
  • Serous nasal discharge, becoming mucopurulent if secondary infection
  • (Streptococcus equi zooepidemicus)
  • Coughing in some cases
25
Q

Equine herpes virus adn foals

A
  • Almost always fatal in neonatal foals.
  • Producing icterus, leukopaenia, neutropaenia, petechial haemorrhages, and severe pneumonia.
  • If inutero, mare infected, fetus is aborted in last trimester. Some situations foal survives but is extremely weak and dies within a day or 2
26
Q

What about equine herpes virus and older foals?

A

• Most survive but suffer severe disease similar to influenza virus infection.

27
Q

What about equine herpes virus and yearlings/ adults

A
  • Recrudescence of latent infection

* Much less severe disease producing upper respiratory tract inflammation and tracheitis

28
Q

Diagnosis of equine herpes virus 1 and 4

A
  • History and clinical signs
  • Virus Isolation
  • PCR
  • Serology
  • Blood sample - take WBC and look for virus being present within WBC
29
Q

Talk in detail about virus isolation in equine herpes virus 1 &4

A

o Nasal swab or Tracheal wash

o Citrated whole blood early on when viraemic

30
Q

Talk in detail about PCR and serology in equine herpes virus 1 &4

A

• PCR – evidence of virus itself
o Nasopharyngeal swab
o Some consider too sensitive
• Serology
o 4 fold rise in serum titre, or single titre of >1:80  riding titre
o Be careful of vaccination and maternal antibodies

31
Q

Prevention and control equine herpes virus

A
  • Difficult as 90% horses carry it, just latent in trigeminal ganglia. No external tests to detect virus to detect which are latently carrying Herpes
  • Isolation and barrier nursing as for Equine Influenza
  • Reducing the infectious load
  • Improving air quality
32
Q

Equine Herpes Virus – 1&4 Vaccination

A
  • Not too effective
  • Pneumabort, Duvaxyn EHV 1&4, Rhinomune
  • Both modified live and killed vaccines available
  • Primary injection - 5 months of age
  • Secondary injection - 4-6 weeks later
  • Booster every 6 months
  • Used mostly Pregnant mares at 5, 7 & 9 months
33
Q

Equine Rhinovirus

A
  • Similar to adenovirus
  • Picornavirus
  • Mild transient upper respiratory disease of 3-5 days duration
  • Spreads rapidly
  • Fever, anorexia, Serous nasal discharge, PLH
  • No Vaccine
  • Common: 60-80%seroconverted by 5 years old
  • May be clinically confused for mild Influenza or EHV
  • older horses become immune
  • More severe in young and immunocompromised horses

Year 2 Equine ID (7 decks)

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