Equine respiratory Flashcards
A horse presents for respiratory evaluation and chronic weight loss. The animal shares pasture with a mini donkey (Panchito), and the owner does not do any primary health care on Panchito since it is a donkey, and donkeys are tough. How would you diagnose the horses condition?
- Presence of D. arnfieldi larvae in BAL or TTW
- Increase eosinophils in TTW or BAL
Baerman usually false
Peripheral eosinophilia does not correlate.
According to the 2016 Consensus Statement, define the IAD phenotype based on clinical presentation and dx tests.
Clinical presentation:
- any age but more common in young horses
- clinical signs include poor performance (non-respiratory causes should be ruled out if this is only clinical sign) and chronic (>3 weeks), occasional coughing.
Diagnostic confirmation:
- endoscopy revealing excess tracheol-bronchial mucus (>2/5 for racehorses; >3/5 for sports/pleasure horses).
Rule out other causes of poor perfromance OR
- BAL cytology characterised by mild increases in neutrophils, eosinophils and/or metachromatic cells
- further confirmed for research purposes by documenting pulmonary dysfunction based on evidence of lower airway obstruction, airway hyperresponsiveness or impaired blood gas exchange
Exclusion criteria:
- evidenced of systemic signs of infection (anorexia, lethargy, haematologic abnormalities compatible with infection)
- increased respiratory effort at rest (heaves)
Action of macrophages in R. equi ©
Activation of IFNg by CD4+
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) comprise a syndrome of severe pulmonary dysfunction and respiratory failure that affects foals. Which of the following statements is correct?
a) The fraction Pa02/Fi02 is >300mm Hg in cases of ALI (which is the less severe form) and >200mm Hg for ARDS.
b) It is related to pulmonary surfactant deficiency in neonatal foals
c) The pathophysiology includes dysregulation of pulmonary inflammation and coagulation
d) It is not related to an infectious etiology
c) The pathophysiology includes dysregulation of pulmonary inflammation and coagulation
ALI or ARDS arises as a complication after major infectious or noninfectious bodily injury. When this occurs, a protective response starts that involves controlled activation of the inflammatory and coagulation system. In ALIARDS an imbalance of pro inflammatory and anti-inflammatory factors produce an uncontrolled pulmonary inflammatory response and pro coagulation environment in alveoli and the pulmonary microcirculation.
Advantages of ultrasound for R. equi
Evaluation of severity of pneumonia and response to therapy
Best measure for eradication of EAV from herd ©
- Manage carrier stallions
- Vaccinate mares that are bred to the carrier stallion
What is the most effective treatment for M. capillaris?
A regimen of fenbendazole (1.25 to 5 mg/kg) 1 week on/ 1 week off/ 1 week on appeared to provide the most effective treatment.
*Resistant to levamisole
Muellerius Capillaris is probably the most common of the lungworms of sheep and goats. Infection is more pathogenic in goats than in sheep.
Several anthelmintics have been used in the treatment. Moxidectin (0.2 mg/kg oral or injectable) is effective in sheep and may be equally effective in goats. Although larvae may initially disappear in the feces after treatment, they often reappear in fecal samples again after 1 to 2 months, either because anthelmintics are ineffective against immature worms and/or because of resumption of development by inhibited larvae. Treatments that appear to eliminate adult parasites in goats include fenbendazole (15 to 30 mg/kg), albendazole (10 mg/kg), oxfendazole (7.5 to 10 mg/kg), and ivermectin (0.3 mg/kg). Better control of immature or inhibited larvae with fenbendazole was achieved by administering the drug (1.25 to 5 mg/kg) for 7 to 14 days.
Smith, Bradford P.. Large Animal Internal Medicine, Elsevier, 2014, page 628.
Mention some primary pathogenic fungi.
Primary pathogenic fungi such as Blastomyces dermatitidis, Histoplasma capsulatum, Coccidioides immitis, Cryptococcus neoformans, and Conidiobolus coronatus usually infect immunologically normal horses.
Smith, Bradford P.. Large Animal Internal Medicine, Elsevier, 2014, page 495.
Best way to determine the carrier status in strangles
- Endoscopic examination of the GP
- Culture + PCR of GP lavage
Best way to increase detection of R. equi
Culture + PCR (90% detection)
Characteristic pulmonary lesion of EIPH
Bilateral and caudo-dorsally
Cytology of a normal BAL, in horses and llamas?
- Neutrophils: < 5%
- Mast cells: < 2%
- Eosinophils: <1%
Describe gross findings in the lungs of horses with EMPF on post mortem exams.
- Lungs do not collapse on opening thorax. - All lung regions affected. - Multiple firm pale tan-white nodules with a discrete borders. Nodules are uniformly coloured and foci of fibrosis bulge from surrounding tissue. - Bronchial LNs enlarged in 50% of cases. - Two forms described: i) Coalescing: multiple coalescing nodules, 1-5cm diameter, little unaffected lung; more common form. ii) Multiple discrete nodules: larger nodules (up to 10cm diameter), same appearance as coalescing form, larger areas of normal lung tissue in between nodules.
Describe herpesviruses.
- Family: Herpesviridae. - Double-stranded DNA viruses. - Two subfamilies: alpha and gamma.
Describe histopathologic findings in the lungs of horses with EMPF.
- Marked interstitial expansion by well-organised mature collagen, infiltration of the interstium by inflammatory cells (lymphocytes > macrophages and neutrophils > eosinophils) and preservation of ‘alveolar-like’ architecture. - Alveolar luminal infiltrates may be present, predominately neutrophils and macrophages. - Alveoli are lined by hyperplastic cuboidal epithelial cells (type II pneumocytes). - Large macrophages with abundant eosinophilic cytoplasm and intranuclear viral inclusion bodies occasionally observed in the alveolar lumen.
Describe the clinical signs and necropsy findings of EAdV infections in immunocompetent yearlings and foals.
- Yearlings: nasal discharge (4-12d), serum ABs peak at 13d and decrease by 2mo. - Foals (10-35do): incubation period 3-5d, pyrexia, nasal and ocular discharge, tachypnoea, cough, dxa (25%) –> recover by day 10. - PM: atelectasis, suppurative bronchopneumonia, swelling and hyperplasia resp epi, intranuclear inclusion bodies.
Describe the clinical signs and necropsy findings of EAdV infections in immunocompetent foals with SCID.
- Rapid clinical decline and death. - PM: conjunctivitis, rhinitis, tracheitis, bronchopneumonia, pancreatitis, sialodenitis; intranuclear inclusion bodies in resp epi and pancreatic acinar and ductal cells.
Describe the clinical signs of EHV-1/EHV-4 respiratory infection in horses.
- Bi-phasic fever (24-48h then 4-8d if viraemic). - Lethargy. - Anorexia. - Nasal discharge (serous to mucopurulent d5-7). - +/- conjunctivitis, lymphadenitis, oedema/vasculitis in distal limbs.
Describe the epidemiology and pathophysiology of Hendra virus infection.
- Bats –> horses –> humans (+ dogs?) - Horse-to-horse transmission very rare but has occurred. - Majority of cases June-Aug (fruit bat birthing season) in QLD and northern NSW. - Incubation period 5-16d, CSx ~2d pre-death, 25% horses may survive if they weren’t all euthanised. - HeV uses cell surface membrane bound ephrin-B2 (wide dist inc vascular endothelial cells) and ephrin-B3 (CNS) as receptors.
Describe the epidemiology of EAdV infection.
- Worldwide distribution - Unknown if clinical signs in adults; causes dz in foals. - Transmission via direct contact or fomites. - Virus persists in URT of adults (reservoir) and enviro (1yr at 4 C).
Describe the epidemiology of EAV infection.
- Spread by respiratory and venereal routes. - 30-70% infected stallions become carriers; virus persists in ampulla of vas deferens (testosterone dependent). - 85-100% mares bred by stallions/fomites become infected –> spread via resp route to others on farm. - Infection –> immunity for several years. - Colostral ABs last until 2-6mo. - Seroprevalence varies b/w breeds: SB>TB. - Variation in host’s genome (CD3+T) and outcome.
Describe the epidemiology of EHV-1 and EHV-4 infections.
- Ubiquitous; most horses are infected in the first weeks/months of life –> latent infections –> shedding with stress –> dz in host and infection of other horses. - EHV-1: outbreaks of resp dz, abortions, myeloencephalopathy, neonatal death, chorioretinopathy. - EHV-4: outbreaks of resp dz; indv abortions, EHM, neonatal death. - Resp dz particularly of importance in young performance horses.
Describe the epidemiology of equine rhinitis virus.
- Worldwide distribution. - Horses usually infected at 1-2yo. - Survives well in the environment. - ERAV: increased risk with co-mingling, stress, concurrent dz, Winter/Spring. - ERBV: clinical significance unclear.
Describe the equine adenovirus (EAdV).
- Family: Adenoviridae. - Non-enveloped, icosahedral DNA virus. - Two serotypes: EAdV-1 (resp) and EAdV-2 (enteric, foals).
Describe the equine arteritis virus (EAV).
- Family: Arteriviridae (same family as PRRSV). - Order: Nidovirales. - Enveloped, positive-stranded RNA virus. - Major viral envelope proteins: M and GPS. - One serotype, two clades. - Extensive variation in virulence of different isolates. - Readily inactivated by sunlight, high temps, lipid solvents, disinfectants; survives -0 C temperatures.
Describe the equine influenza virus (EIV).
- Family: Orthomyxoviridae. - Genera: Influenza A virus. - Segmented, single-stranded RNA virus.
Describe the equine rhinitis virus.
- Family: Picornaviridae (same as FMDV!) - Non-enveloped RNA viruses. - 4 serotypes: ERAV, ERBV1, ERBV2, ERBV3.
Describe the features of Acute respiratory distress syndrome (ARDS)
A syndrome of lung injury characterised by:
- alveolar damage
- high-permeability pulmonary oedema
- respiratory failure
Describe the findings on BAL fluid cytology on horses with IAD
- mild to moderate increase in neutrophil, eosinophil and /or mast cell percentages
- > 10% neutrophils, > 5% mast cells, > 5% eosinophils
- importance of BAL cytology should be interpreted in light of history, clinical exam and endoscopic findings
- NB. TW cytology not considered an appropriate alternative to BAL cytology for diagnostic confirmation or characterisation of IAD
Describe the Hendra virus.
- Family: paramyxoviridae. - Genus: henipavirus. - Enveloped RNA virus.
Describe the immune response in horses infected with EIV and defences of the virus to the immune response.
- Humoral IR targets HA and NA therefore changes in surface antigens can block host immune response. - Local IgA (nasal secretions) blocks viral penetration, systemic IgGa, IgGb (serum) enhance phagocytosis. - Natural exposure induces protective immunity against homologous strain for 8mo, partial immunity for 12+mo. - Virus defences: antigenic drift, anti-interferon activity of NS1 protein, alveolar macrophages are destroyed by PB1-F2 protein.
Describe the immune response to EHV-1 and EHV-4 infection in horses.
- Protective IR is short-lived post-infection; high titres of VN AB dec shedding but do not prevent infection/CSx –> rapid intracellular translocation of the virus? - Intracellular virus is susceptable to cytotoxic C-lymphocytes (lyse infected cell) –> CD8+ lymphocytes very imp in preventing/minimising infection. - Immunoevasion strategies of EHV-1 modulation of cytokine responses and T/B cell responses, interference with antigen presentation by down regulation of MHC-1 expression, alteration of NK-cell lysis, dec efficient chemoattraction of antigen presenting cells.
Describe the mucus scoring system used to quantify mucus accumulation in the trachea
Grade 0 - no visible mucus
Grade 1 - single to multiple small blobs of mucus
Grade 2 - larger but nonconfluent blobs
Grade 3 - confluent or stream forming mucus
Grade 4 - pool forming mucus
Grade 5 - profuse amounts of mucus
Describe the pathophysiological mechanisms leading to increased pleural fluid production.
Fluid production in the pleural space increases if any of the following occurs:
1) elevation of the hydrostatic pressure gradient (CHF, portal hypertension)
2) a decrease in the colloid osmotic pressures (hypoproteinaemia)
3) an increased permeability of the capillary vessels (infection, malignancy, inflammation)
4) decreased removal of fluid because of impaired lymphatic drainage or obstruction (neoplasia) or infiltration of the pleura or parenchyma (neoplasia).
Also, excessive amounts of peritoneal fluid may accumulate in the pleural cavity as the fluid moves through diaphragmatic defects or through diaphragmatic lymphatics.
Describe the pathophysiology of EAV infection.
- Invades resp epi cells then bronchial and alveolar macrophages –> bronchial and other regional LNs (2-3d) –> viraemia –> replication in adrenals, thyroid, liver, testes. - Virus remains in buffy coat 2-21d, plasma 7-9d, elim 28d. - Virus replicated in endothelial cells –> damage to endo cells and adj muscularis media –> vascularis charac by fibrinoid necrosis of small muscular aa, leukocyte infiltrations, perivascular haemorrhage and oedema.
Describe the pathophysiology of EHV-1 and EHV-4 respiratory disease in horses.
- Infection via inhalation –> EHV-4 mainly stays in resp tract; –> resp LNs –> lymphocyte-associated viraemia (EHV-1) –> delivery of virus to other tissues e.g. uterus. - Viraemia persists up to 21d, nasal shedding 4-7d. - At secondary sites virus spreads to endothelial cells –> vasculitis +/- haemorrhage, thrombosis, ischaemia, necrosis.
Describe the pathophysiology of EIV infection.
- NA alters efficiency of mucociliary apparatus. - HA attaches to sialic-acid containing cell surface receptors on epithelial cells in the nasal mucosa, trachea and bronchi. - Epi cells internalise virus and surround it with an endosome. - Viral replication –> host cell death –> loss of ciliated resp epi and exposure of irritant receptors –> hypersecretion of submucosal serous glands, damage to MCA, inflammation, lymphocytic infiltration, oedema; predisposes to secondary bacterial infection. - Foals can get fatal bronchointerstitial pneumonia. - Recovery of epi damage begins in 3-5d; takes 3-6wk.
Describe the pathophysiology of Multinodular Pulmonary Fibrosis caused by EHV-5 infection and other interstitial lung diseases in horses.
- Inciting agent damages pulmonary epithelial or endothelial cells –> alveolar necrosis. - Acute/exudative stage: pulmonary congestion, interstitial oedema, erythrocyte extravasation, alveolar flooding. Fibrin, protein rich fluid, cellular debris and inflammatory cells form hyaline membranes. - Proliferative stage: type II pneumocytes replace damaged type I pneumocytes. Interlobar septae widen due to proliferation of fibroblast and inflammatory cell infiltration. - Chronic disease: fibrosis of alveolar walls and accumulation of mononuclear cells in the interstitium. Granulomas and smooth muscle hyperplasia may form. - EHV-5 has tropism for lungs and skin and potential sites of latency in lymphocytes, mononuclear cells, macrophages, dendritic cells, conjunctiva. - EHV-2 and EHV-5 share a common isotope, therefore must dx via PCR/virus isolation not serology.
Diagnosis of Chronic carrier state for S. equi
Guttural pouch fluid/swab PCR
Diagnosis of P. carinii pneumonia
- Trophozoites in histology
- Interstitial, miliary pattern
Diagnosis of R. equi pneumonia
Bacterial culture and PCR for VapA gene from TBA
Diseases cause by EHV-1
- Respiratory
- Abortion/Neonatal death
- EHVM
- Chorioretinopathy –> shotgun lesions
Does furosemide affect performance in cases of EIPH?
Administration 4 hrs before is associated with improved racing outcomes
Drug of choice of Pneumocystis carinii
TMS
EIPH, what is associated with?
Histology changes
Elimination of EIV Australia
canary pox 14 days
Equine multinodular pulmonary fibrosis is thought to be caused by which infectious agent? How would you diagnose?
EHV-5
PCR or IHC in lung biopsy or BALF
Is this a definitive diagnosis?
For glanders (farcy), why would you do a IDT?
To certify negative horses
Is zoonotic and cases have to be reported to OIE
Fungi that most commonly causes pneumonia in horses
Coccidiomicosis
Fungi that most commonly causes pneumonia in horses
Coccidiomicosis
Gene associated with virulence in R. equi, and where is it located?
Vap A gene, located in the pathogenicity island (PAI)
Gene implicated in heritability of RAO
IL-4 receptor gene
Gold standard for diagnosis of strangles
Culture
- Nasopharynx, GP wash*
- Preferred method on aspirate of masses
Horse with a nasal granuloma (mass), histopathology revealed large amounts of eosinophils around the lesions.
Condidiobolus coronatus
Condidiobolus is a saprophytic fungus that causes granulomatous lessions in the upper respiratory tract in horses. Single to multiple granulomatous lesions in the nasal passages, trachea, or soft palate can be observed endoscopically. Histologic appearance is similar to that of pythiosis and of basidiobolomycosis. Hyphae are thin-walled, highly septate, and irregularly branched. The lesions typically have large numbers of eosinophils and fewer macrophages, neutrophils, plasma cells, and lymphocytes surrounding hyphae. Definitive diagnosis is based on microbiological culture, immunodiffusion, or PCR.
Smith, Bradford P.. Large Animal Internal Medicine, Elsevier, 2014, page 498
How can EHV respiratory disease be prevented?
- EHV-1 vaccines protect against EHV-4; none against EHM. - Inactivated vacc (low and high antigen load) can limit resp signs, nasal shedding and incidence of abortion storms. - MLV –> limited EHV-specific cellular immunity. - Vacc q6mo; preg mares 5th, 7th, 9th mo gestation.
How can you differentiate between mild and severe equine asthma?
- Poor performance –> mild
- H2 challenge test –> mild
- Bronchoconstriction at rest –> severe
- Hay challenge test –> severe
- BALF cytology
How could you differentiate between some of the causes of pleural effusion?
Cytologic and microbiological evaluation of pleural fluid - identify neoplastic cells or fungal elements - transudate (protein <25g/L; few cells):
CHF, liver fibrosis, hypoalbuminaemia, early neoplastic processes - modified transudate (low NCC; moderate to high protein >25g/L):
neoplasia + many other disorders - exudate (high NCC; protein > 30g/L):
infectious and intraabdominal diseases - can distinguish septic effusions from nonseptic effusions by biochemical analysis of pleural fluid –
septic: pH <7.2, glucose < 40mg/dL, lactate dehydrogenase > 1000IU/L – chylous: milky white-pale pink, TG > simultaneously measured serum
How does EHV-1 evade the immune system?
- Downregulationof MHC-1
- Alteration of NK cells
- Modulation of cytokine response
How does furosemide help RAO affected horses, and which drug blocks this effect?
a. Removes pulmonary edema from negative-pressure pulmonary edema, blocked by diphenhydramine
b. Causes a prostaglandin E2 mediated bronchodilation, blocked by diphenhydramine
c. Removes pulmonary edema from negative-pressure pulmonary edema, blocked by flunixin
d. Causes a prostaglandin E2 mediated bronchodilation, blocked by flunixin
How is EAV infection diagnosed in horses?
- Paired serologic titres 3-4 wks apart; complement-enhanced virus neutralization test most reliable. - In the absence of a certified vacc hx, stallions with a serum neutralizing antibody titer ≥1:4 should be considered potential carriers until proven otherwise, based on an absence of detectable EAV in their semen. - PCR/virus isolation: nasopharyngeal swabs, conjunctival swabs, whole blood, placenta, semen.
How is equine adenovirus infection diagnosed?
- Virus isolation from nasopharyngeal and conjunctival swabs during the acute phase of infection is possible but not frequently reported or from lung at necropsy. - Adenovirus can also be detected in fecal samples by electron microscopy. - Seroconversion can be detected by serum neutralisation of haemagglutination inhibition (HI) of paired samples collected 10-14 days apart.
How is equine adenovirus infection prevented?
No vaccine available.
How is equine rhinitis virus infection diagnosed?
- Serology: 4 fold increase 2 wks apart. - RT-PCR/virus isolation: nasal or nasopharyngeal swab.
How is equine rhinitis virus infection prevented?
No vaccine available.
How is Hendra virus diagnosed?
- PCR: early clinical course of dz, turnaround is 24-48hrs. - ELISA: indirectly detects the presence of HeV antibodies in a sample; screening test – negaive sample is a reliable indicator a horse has not been infected but positive is not always a reliable indicator that a horse has been infected. Therefore ELISA positive require additional testing. - Virus neutralisation test: detects the presence of HeV antibodies in a sample; must be conducted under high-level biocontainment as involves mixing the blood sample with live virus; takes up to 2weeks.
How is Hendra virus prevented/controlled?
- Vaccine. - Strict biosecurity.
How is IAD diagnosed?
The diagnosis of IAD (mild-moderate equine asthma) is based on: 1) presence of clinical signs of lower airway disease (poor performance, cough)
2) documentation of lower airway inflammation based on excess mucus on endoscopy, BAL cytology or abnormal lung function
3) exclusion of severe equine asthma (RAO/heaves) as well as infectious and other respiratory diseases
How is pleural fluid formed?
Pleural fluid is the interstitial fluid of the parietal pleura.
A pressure gradient driving its formation exists because the parietal pleura is supplied by the systemic circulation and because the pressure of the pleural space is more negative than that of the subpleural interstitium.
How long is the isolation for cases of EHV-1?
28 days!
How long is the nasal shedding in strangles
2-3 weeks
How long is the quarantine for strangles?
2-3 weeks
How long is the shedding for EIV?
~ 7 days
How long is the shedding of EHV-1?
4-7 days
How to determine strangles titer?
SeM protein
If you want to diagnose pneumocystosis, what sample would you submit?
BAL for cytology
- Can NOT be cultured