Viral diseases Flashcards
(31 cards)
Equine Picornaviruses
- structure?
- important types?
▪ Single-stranded, positive-sense RNA
▪ Non-enveloped
▪ Aphthovirus
> Equine rhinitis virus A
▪ Erbovirus
> Equine rhinitis virus B 1
> Equine rhinitis virus B 2
> Equine rhinitis virus B 3
Equine rhinitis virus A & B - typical disease, geography
- typically cause very mild resp disease
- most horses infected before 6 months of age
- usually we don’t care about this, often no clinical signs
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▪ ERAV
> Endemic worldwide
▪ ERBV
> 1 & 2- endemic worldwide
> 3- Australia, UK, & Japan
Equine rhinitis virus A & B spread
Viral shedding
▪ ERAV
> Respiratory secretions
> Urine
▪ ERBVs
> Respiratory secretions only
Equine rhinitis virus A & B - clinical signs
- may not have any, and if they do, generally mild
▪ Fever
▪ Serous-mucous nasal discharge
▪ Coughing
▪ Anorexia
▪ Pharyngitis
▪ Submandibular lymphadenopathy
Co-infections with ERBV
- common to have multiple infections at the same time
- EIV
- EHV-1 or 4
- ERAV
- S. equi xx equi
Equine rhinitis virus A & B diagnosis, treatment, prevention
Diagnosis
▪ Nasopharyngeal swab
▪ Serology (paired)
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Treatment
▪ Supportive care
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Prevention (not easy)
▪ Isolation of new, young horses (but more for other diseases, eg. herpes, S. equi ss equi)
▪ Vaccination? does exist, but conditional license (not available in all circumstances): probably not necessary anyways
Equine Influenza
- type of virus, classifications?
- subtypes of importance?
▪ Orthomyxovirus > Single-stranded RNA
▪ Classifications > A, B, C & D
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Subtypes IAV
▪ 1= H7N7
▪ 2= H3N8
> American: Florida
> Clade 1
> Clade 2
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- types important for vaccination considerations
Equine
Influenza
▪ Transmission
▪ Aerosol → 1-2 km
▪ Droplets
▪ Fomites → 3 days
▪ Incubation period 1-3 days
▪ Viral shedding 10 days
what age groups get equine influenza? what about seasonality?
- more positives in young adults (1-9 age) than in very young, or adults
- more disease in spring, then winter, less in fall and summer
Equine Influenza clinical signs
Clinical signs
▪ Inappetance
▪ Fever
▪ Nasal discharge
▪ Cough
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Uncommon signs
▪ Tachypnea
▪ Limb edema
▪ General weakness
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- can have severe clinical signs, usually in naive populations or donkeys, mules…
Equine Influenza
▪ Diagnosis, treatment
▪ Nasopharyngeal wash
> Ideal sample
▪ Nasopharyngeal swab
▪ Nasal swab
▪ Paired serum titers
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▪ Treatment
▪ Supportive care
Equine
Influenza
▪ Prevention
▪ Isolation of new horses
> 21 days
▪ Maintain good biosecurity
> Minimize shared items
> Decrease human and horse traffic
> Promote hand hygiene
▪ Vaccination
Is equine Influenza a zoonotic disease?
yes, but very uncommon - usually immunocompromised
Office of International
des Epizooties (OIE) tell us what about equine influenza
- what strains should be contained in our vaccines, and what vaccines that are available meet this standard
Equine Herpesviruses
- what are the strains, and who do they affect?
▪ EHV 1-5= horse
▪ EHV 6-8= donkey
▪ EHV 9= zebra
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▪ Typically species specific
▪ Exceptions EHV-1 & 9
Equine Herpes Virus-1 & 4
- epidemiology: reservoirs, transmission, incubation
Reservoir
▪ Latently infected horses
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Transmission
▪ Aerosol, droplets, and fomites
▪ Shed in nasal secretions
> 1-21 days post-infection
▪ Fetal and placental tissues
> High viral load
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▪ Incubation period= 2-10 days
EHV-1 and 4 pathogenesis
EHV-1:
▪ Enters respiratory epithelial cells
> Nasal and nasopharynx mucosa
▪ Within 24-48 hours
> Spreads to regional lymph nodes
> Mononuclear cells infected > this is how it moves through the body
▪ Within 4-10 days
> Cell-associated viremia (may or may not see fver at this point)
> Infection of endothelial cells
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EHV-4 tends not to have cell-associated viremia, otherwise very similar
EHV-1 & 4 viral latency frequency, locations
▪ >50% of cases post-infection
▪ Persists for life of host
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Locations
▪ Trigeminal nerve
▪ Lymphoid cells
EHV-1 & 4 clinical signs
▪ Fever
▪ Lethargy
▪ Anorexia
▪ Serous→ mucopurulent nasal discharge
▪ Serous ocular discharge
▪ Conjunctivitis
▪ Submandibular lymphadenopathy
EHV-1 sequelae
- this is what we are really worried about
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Abortions
▪ 2-12 weeks after infection
▪ Final months of gestation
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▪ Fetal infection
▪ Chorioretinitis (can lead to blindness)
▪ Myeloencephalopathy: <10% of horses (ascending paresis)
EHV-1 & 4 Dx
▪ Virus isolation (gold standard) > but typically to lengthy in time so we rely on PCR
> Nasopharyngeal lavage
> Leucocyte buffy coat isolation
▪ PCR/ qPCR (often what we use)
> Nasal swab
> Whole blood buffy coat
▪ Serology > also quite a wait between samples
> Paired titers
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- need to interpret in context of clinical signs
EHV-1 & 4 treatment and prevention
Treatment
▪ Supportive care
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Prevention
▪ Elimination is not possible
▪ Isolation of new horses
> 21 days
▪ Maintain good biosecurity
> Minimize shared items
> Decrease human and horse traffic
> Promote hand hygiene
▪ Vaccination
EHV-2 & 5 - what are these? when do they cause issues? latency and transmission?
▪ Gammaherpesviruses
▪ Infected at < 1 year of age
▪ Latency established
> EHV-2 = B-cells, macrophages, and Langerhans cells
> EHV-5 – B-cells, T-cells, and alveolar macrophages
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▪ Transmission
> Viral shedding in nasal secretions
EHV-2 & 5 - what symptoms does it cause?
Upper respiratory disease
▪ Nasal & ocular discharge
▪ Tachypnea
▪ Coughing
▪ Fever
▪ Submandibular lymphadenopathy
▪ Keratoconjunctivitis
