Coughing in horses Flashcards
DDx fore coughing - foals and weanlings
URT disease: EHV1 and 4, EIV, Strep. equi equi
LRT disease: EHV 1&4, EIV, undifferentiated respiratory tract infection, Strep. zooepidemicus, Rhodococcus equi, Strep equi equi, Parascaris Equorum
What is the most common cause of pneumonia in foals and weanlings?
BACTERIA - Strep zooepidemics (UK) and Rhodococcus equi (USA) most commonly. Also Actinobacillus, Klebsiella, Staph aureus, Bordatella, Mycoplasma
CS - infectious pneumonia - weanling - 3
+/- auscultable changes
Mild pyrexia
Cough
How to make a diagnosis - weanling bacterial pneumonia
History, CS, further diagnostic tests:
- ) Endoscopy - mucopurulent exudate in trachea
- ) Radiography - bronchointerstitial pattern
- ) Cytology (BAL or tracheal aspirate) - increased degenerate neutrophils and intracellular bacteria
How is inflammatory non-infectious disease different to inflammatory infectious disease?
INFLAMMATORY NON-INFECTIOUS: non-degenerate neutrophils, no bacteria
INFLAMMATORY INFECTIOUS: degenerate neutrophils, intranuclear bacteria
DDx- coughing - adult horses
INFECTIOUS versus NON-INFECTIOUS
List infectious causes of adult horse coughing
URT disease: EIV, EHV1&4, EVA, ERV, Strep equi equi
LRT disease: EIV, EHV1&4, ERV, Strep zooepidemicus, Strep pneumonia, Pasteurella/actinobacillus, Strep equi equi
Epidemiology - URT versus LRT disease as coughing in adult horses
- +URT: less common that LRT, mainly young horses (1-2 years)
- LRT: common in all racing age groups (esp 2yo flat yards and 4yo in NH yards)
- Bacterial > viral (both can occur in combination
CS - infectious cause of coughing - adult horses
- URT: fever, nasal discharge, coughing, enlarged submandibular LNs
- LRT: fever, nasal discharge, coughing, mucoid tracheal secretion, +/- haemorrhage, poor performance
- May be subclinical
Site of latency for EHV1&4? 3
Bronchial LNs
Submandibular LNs
Trigeminal ganglia (i.e. CNS)
What causes ENH reactivation?
Stress
EHV2 possibly
Sequence of events to be determined
When are horses exposed to EHV1&4?
Foals and weanlings
Source = lactating mares or foal to foal
Immunity to EHV?
Short lived (3-5 months) so become reinfected (breeding or racing career) via respiratory secretions, fomites or aborted material. Vaccine can’t improve immunity rate. Re-exposure usually causes mild or inapparent infection (except broodmare where it causes abortion in the last trimester).
Pathogenesis - EHV1&4
EHV1&4 inhalation. Incubation 3-7 days. Replicates in URT epithelium. EHV-1 only then disseminates to LRT. Transported to other organs in T lymphocytes. Viraemic for up to 3 weeks. Vasculitis – neurological disease, abortion, chorioretinopathy. May be accompanied by secondary bacterial infection. May be subclinical.
What age of horses does EIV usually affect?
most commonly racehorses 2-3yo. worldwide occurence (except Australia and NZ)
Spread - EIV
Highly infectious, spreads by aerosol for distances of >30m. Spreads rapidly through susceptible populations. Spread by inhalation.
Vaccine - EIV
Vaccinated animals are susceptible to infection within 2-3 months. Partial immunity may suppress CS but allow virus shedding.
What does EIV infect? What does this lead to?
epithelial cells or URT and LRT –> laryngitis, tracheitis, bronchitis and bronchiolitis –> loss of ciliated epithelium, compromised mucocillary mechanism. May be associated with secondary bacterial infection.
T/F: EIV has no viraemia.
True - there are no CS reflecting other organs. Diagnosis is ONLY possible via respiratory secretions.
Outline bacteria that cause LRT infection in adult horses
Strep. zooepidemicus
Strep pneumoniae
Pasteurella/actinobacillus
Inhaled and overcome defence mechanisms –> LRT signs only. May occur secondary to viral infection OR non-infectious airway disease.