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Equine II > Upper respiratory tract diseases > Flashcards

Upper respiratory tract diseases Flashcards

1
Q

Respiratory clinical exam to include:

A

Respiratory rate and effort

Nasal discharge

Lymph nodes

Lung auscultation

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2
Q

What resp disease panels will commercial labs sponsor?

A

Strep equi subsp equi

Influenza

EHV1 and 4

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3
Q

Most likely causative agents of equine respiratory disease in the UK

A

Rhinitis virus/adenovirus

Strep equi subsp equi

Equine alphaherpes EHV-1,-4

Equine gammaherpes EHV-2, -5

Equine influenza

EVA?

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4
Q

Equine influeza

A

Orthomyxovirus, ssRNA

Type A (H3N8)

Inhaled -> URT respiratory epithelium

Highly contagious

Rarely fatal

Most overt illness in unvaccinated horses

If vaccinated - reduction in severity (and shedding) not for prevention of infection

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5
Q

Clinical signs of equine influenza

A

Pyrexia

Inappetence

Lethargy

Nasal discharge - serous to mucopurulent

Hacking, persistent, dry cough - less likely to be seen in other diseases like strangles

Vaccinated horses often more subtle

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6
Q

Diagnosis of equine influenza

A

Historical/local disease status

NP swabs whilst sick

Try to use viral transport media - survives longer

Consider in-contacts

Collect paired samples 0 +14 days (looking for a rising titre)

Free testing for disease surveillance

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7
Q

Treatment of equine influenza

A

Isolate for 14 days
§ Remember airborne and direct contamination

Rest/recovery prolonged (tracheitis can cause residual cough for a while after infection cleared)

NSAIDs

Antibiotics only if opportunistic secondary infection

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8
Q

Streptococcus equi subsp equi

A

Strangles - global distribution (except Iceland)

G+ cocci

Big concern for owners and the equine industry

Less likely to be aerosolised

Can be fatal - either directly (asphyxia), or costs -> PTS

Certain strains likely more severe?

Perhaps younger more severe signs too?

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9
Q

Pathogenesis of Strep equi subsp equi

A

Oro-nasal infection

Crypt cells of lingual and palatine tonsillar tissue -> regional LN

At this super early stage, may have false negatives from nasal swabs

3-5 days - lymphoid hyperplasia/abscessation

Loads of neutrophils = pus

Rupture of LN 7 days… > +++ after initial infection

Usually pyrexia precedes the purulent nasal discharge

Shedding 1-2 days after pyrexia

The greater the infective load, the faster and more severe the signs

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10
Q

Common clinical signs of Strep equi subsp equi

A

Pyrexia

Lethargy and depression - not just from the pyrexia

Mucopurulent nasal discharge - bilateral but could be unilateral

Submand and retropharyngeal lymphadenopthy - cause a physical obstruction making it painful and difficult to eat

Inappetence/dysphagia (secondary to neuropraxia, physical obstruction, pyrexia?)

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11
Q

Less common clinical signs of Strep equi subsp equi

A

Increased respiratory rate and effort

Pharyngeal swelling

Inspiratory noise - stridor

Mimic of choke (oesophageal obstruction) with bilateral food/water down nose

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12
Q

What is special about strangles?

A

Evolved as a host-restricted pathogen from Strep equi zooepidemicus

Strep zoo is a regular commensal of the URT

Persistent infection in a small % of infected patients
§ Opportunity for endemicity

Will survive for a while in the environment

Guttural pouches are immune privaleged except for the LNs on the floor

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13
Q

States of persistent infection in strangles

A

Lymphadenopathy (tunnocks teacake)

Empyaema (Mustard)

Pus persists in guttural pouch (feta)

Chondroids (babybels)

Chronic persistent infection

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14
Q

What happens during persistent/chronic Strep equi subsp equi infection?

A

Dynamic genome
§ Survival in a low-nutrient state
§ Intermittent shedding
§ Potential infection to other animals

But
§ Does the genomic decay lessen ability to cause disease to the extent that no longer contagious risk?
§ PCR on chondroids is often negative
§ Cannot culture organism from a chondroid
§ You have to remove all the material from the guttural pouch to say that it is free from contagion

Antibody responses can be really variable

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15
Q

How can you test for carriers of Strep equi subsp equi

A

Blood testing
- ELISA

PCR testing of aspirates from other pouches?

Screening

Endoscopy of the guttural pouch

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16
Q

Mild version of strangles

A

In reality you may see
§ Unexplained pyrexia
§ Mild, cloudy nasal discharge
§ No cough
§ Slightly off colour - could easily be missed

May have been given NSAIDs etc, and not responding

All unexplained pyrexia - consider strangles - check the guttural pouches

Why?
§ Attenuated strain, residual immunity, low infective dose?
§ Could still cause significant disease in others…

17
Q

Complications of strangles

A

Can spread via haematogenous or lymphatic system

Aspiration of infective material - rare

Bastard strangles

Purpura haemorrhagica

Myopathies

18
Q

Bastard stangles

A

Meningitis

Skin swellings

Large mesenteric abscessation - tiger-striped basketball sized abdominal abscesses (FNA to see if G+ (likely strangles) or mixed population (likely not strangles)

Often inoperable

19
Q

Most common cause of purpura haemorrhagica

A

Strep equi infection

20
Q

Purpura haemorrhagica

A

Severe vasculitis requiring high doses of steroids

pH also triggered by other bacteria and viruses, and neoplasia

Although derived from the greek for purple - they don’t always have petechiae or echy patches

Should have a massively elevated SEM ELISA titre

21
Q

Strep equi induced myopathies

A

Infarctions

Acute severe myonecrosis - similar in people with beta-haem strep

Possibly also chronic immune-mediated myopathy - atrophy

Cross-reactivity with the M protein and myoglobin

22
Q

Treatment of Strangles

A

Start with NSAIDs +/- paracetamol

Possibly penicillin

Antimicrobials may reduce overall seroconversion and abscess might flare back up after therapy, but these are not reasons to avoid antibiotics where the animal is struggling with strangles.

23
Q

When is penicilling indicated in strangles?

A

Persistently pyrexic

Dull and inappetant/miserable/struggling

Dysphagic or has stridor

24
Q

Treatment of carrier strangles

A

Dilution

Flush the guttural pouches with saline or povidine iodine via scope or folaey catheter

Systemic antimicrobials if signs indicate

Can wash/instil penicillin into the guttural pouches

25
Q

Why can’t you give horses oral penicillin?

A

Causes colitis!

26
Q

EHV-1, -4

A

Alphaherpesviruses

Common respiratory pathogens
○ Approx. 80% infected as youngsters
○ Pyrexia, nasal discharge, cough, lethargy

Appears similar to other respiratory infections
○ May not be noticed by owner/reported as respiratory disease
○ Abortion or EHM might be the first you learn about it!

27
Q

Pathogenesis of EHV-1,-4

A

Respiratory epithelial cells -> mono/lymphocytes -> blood vessels/lymph nodes

Cell associated viraemia -> sites of replication (vessel endothelium)
§ Biphasic pyrexia

Latent infections are common

Recrudescence -> infection considered relatively rare

28
Q

Diagnosis of EHV-1,-4

A

Nasopharyngeal swabs
§ qPCR (fast)
§ Virus isolation (slow)
□ ‘gold standard’
§ Don’t submit dry

Serology
§ Paired titres - rise in antibody using complement fixation
§ Single high CF sample if unvaccinated useful preliminary test

29
Q

Vaccination for EHV-1,-4

A

Should be more routinely vaccinated for, especially around competition?

Shedule 1st vacc from 5mo
§ 2nd vacc 4-6 weeks later
§ Boost every 6 mo

Pregnant mares 5, 7, 9 mo

30
Q

EHV-2

A

Gammaherpesvirus

We don’t fully understand significance yet
○ Pharyngitis
○ Keratoconjunctivitis
○ Pyrexia
○ Inappetence
○ Pulmonary inflammation

Synergistic with EHV-5?

Recrudescence of EHV-1?

31
Q

Equine rhinitis virus

A

A and B

ERAV and ERBV

32
Q

Adenovirus (EAdV1)

A

Severe combined immunodeficiency foals

Also EAdV2 isolated from foals with diarrhoea

33
Q

Equine viral arteritis

A

Notifiable

Equine arteritis virus
○ Alphaarteritisvirus, RNA virus

Maintained in carrier stallions

Important cause of abortion

Venereal or aerosol spread

34
Q

Signs of equine viral arteritis

A

Pyrexia

Inappetence

Serous nasal discharge

Submandibular lymphadenopathy

Conjunctivitis

Vasculitis -> oedema
§ Often hindlimb/ventral

Abortion

Equine II (28 decks)

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