Difference between revisions of "Respiratory Viral Infections"

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#REDIRECT[[:Category:Respiratory Viral Infections]]
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{{toplink
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|backcolour = D1EEEE
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|linkpage =Cardiorespiratory System - Pathology
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|linktext =Cardiorespiratory System
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|maplink = Cardiorespiratory System (Content Map) - Pathology
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|pagetype =Pathology
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|sublink1=Respiratory System Inflammation - Pathology
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|subtext1=RESPIRATORY SYSTEM INFLAMMATION
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}}
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<br>
 +
==In general==
 +
 
 +
*Some viruses are thought to induce modifications of the pulmonary defences by:
 +
**Damaging the upper respiratory tract, thereby facilitating bacterial attachment and colonisation, with reduced [[Respiratory System General Introduction - Pathology#Mucociliary escalator|mucociliary clearance]]
 +
**Decreasing surfactant levels by destroying Type 2 pneu[[Monocytes - WikiBlood]]
 +
**Impairing the phagocytic ability of alveolar macrophages
 +
 
 +
 
 +
==In Dogs==
 +
 
 +
===Canine distemper===
 +
 
 +
*Caused by a [[Paramyxoviridae#Canine Distemper Virus (CDV)|morbillivirus]]
 +
*[[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|Rhinitis]]
 +
*Although many organs can be affected by CDV, a relatively constant feature is the respiratory signs which occur in varying severity
 +
*A syndrome of catharral oculonasal discharge, [[Nasopharynx Inflammatory - Pathology#Infectious causes of pharyngitis|pharyngitis]] and [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis]] is relatively common in the initial stages
 +
*Since one of the primary sites of action of this virus is lymphoid tissue, the resultant immunosuppression -> predisposition to secondary bacterial infection
 +
*May cause [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]] where [[Degenerations and Infiltrations - Pathology#Cellular Inclusions|inclusions]] are found within alveolar macrophages
 +
*Gross pathology:
 +
**Oedematous lungs, diffuse interstitial pneumonia
 +
*Micro pathology:
 +
**Necrosis of pneumocytes, necrotising bronchiolitis, alveolar oedema, thickening of alveolar walls and type II pneumocyte hyperplasia
 +
 
 +
 
 +
===Parainfluenza- 2===
 +
 
 +
*Caused by an [[Paramyxoviridae|parainfluenza- 2 virus]]
 +
*[[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|Rhinitis]], [[Trachea Inflammatory - Pathology|tracheo]][[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis]]
 +
 
 +
 
 +
===[[Infectious Canine Tracheitis|Infectious canine tracheitis]]===
 +
 
 +
===Canine adenovirus===
 +
[[Image:Adenovirus pneumonia.jpg|right|thumb|100px|<small><center>Adenovirus pneumonia (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
 
 +
*[[Adenoviridae|Adenoviridae]]
 +
*Usually mild [[Lungs Inflammatory - Pathology#Bronchointerstitial pneumonia|bronchointerstitial pneumonia]], necrosis of bronchiolar and alveolar epithelium, oedema, type II pneumocyte hyperplasia
 +
*May cause necrotising [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchiolitis]] in immune-deficient dogs ([[Paramyxoviridae#Canine Distemper Virus (CDV)|distemper]])
 +
*Can be associated with [[Respiratory Viral Infections - Pathology#Infectious canine tracheitis|kennel cough]] described above
 +
 
 +
===Canine herpes virus===
 +
 
 +
*Caused by [[Herpesviridae|canine herpes virus 1]]
 +
*Part of '''fading puppy syndrome'''
 +
*Presents with necrotising [[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|rhino]][[Trachea Inflammatory - Pathology#Infectious causes of tracheitis|tracheitis]] and secondary [[Lungs Inflammatory - Pathology#Bronchopneumonia|bronchopneumonia]] in older dogs
 +
*Seems to be common subclinically
 +
 
 +
 
 +
===Canine respiratory coronavirus===
 +
 
 +
*(CRCV)
 +
*Shown to be involved in an outbreak of disease in large kennels with rapidly changing population and high incidence of respiratory disease
 +
*Erles, K., Toomey, C. ''et al.''(2003) "Detection of a group 2 coronavirus in dogs with canine infectious respiratory disease." Virology '''310'''(2):216-223
 +
 
 +
 
 +
 
 +
==In Cats==
 +
 
 +
===Feline viral rhinotracheitis===
 +
 
 +
*Caused by a [[Herpesviridae|herpesvirus]]
 +
*Tends to be more [[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|rhinitis]] than [[Trachea Inflammatory - Pathology#Infectious causes of tracheitis|tracheitis]], may extend to [[Paranasal Sinuses Inflammatory - Pathology#Infectious causes of sinusitis|sinusitis]]
 +
*Feline herpesvirus -1
 +
**One of the causes of Feline viral rhinotracheitis
 +
***Viruses and bacteria are involved in the complex. The most frequent aetiologic agent is [[Herpesviridae|FHV-1]], and less frequently [[Caliciviridae|feline calicivirus]] and/or ''[[Chlamydophila psittaci]]'' (NB: previously called ''Chlamydia psittaci'' var felis)
 +
*All three agents infect URT respiratory epithelium, although FHV-1 has the highest affinity for this epithelium
 +
*Feline calicivirus more frequently infects the oral mucosa -> ulcerative stomatitis
 +
*''C.psittaci'' more frequently infects the conjunctival epithelium -> chronic conjunctivitis
 +
*Infection of the respiratory epithelium by FHV-1 results in a typical neutrophilic rhinitis with intraepitheial intranuclear eosinophilic [[Degenerations and Infiltrations - Pathology#Cellular Inclusions|inclusion bodies]]
 +
*Uncomplicated cases resolve in 2-3 weeks
 +
*FHV-1 remains latent in the trigeminal ganglion, and can reactivate at times of stress
 +
*Can infect the cornea -> ulcerative keratitis
 +
*Mortality may be high in young kittens, debilitated and immune-suppressed animals, usually associated with secondary bacterial infection.
 +
 
 +
 
 +
===Feline calicivirus===
 +
 
 +
*Causative agent: [[Caliciviridae|feline calicivirus]]
 +
*[[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|Rhinitis]],
 +
*Suggested in the presence of ulceration of the dorsal and lateral edges of the [[Oral Cavity - Tongue - Anatomy & Physiology|tongue]], hard palate and external nares
 +
*Lesions present may include [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]] with necrotising [[Bronchi and Bronchioles - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchiolitis]]
 +
*Also see Feline viral rhinotracheitis above
 +
 
 +
==In Horses==
 +
[[Image:Equine respiratory viruses concept map.jpg|right|thumb|100px|<small><center>Equine respiratory viruses Concept Map (Courtesy of B. Stanikova)</center></small>]]
 +
 
 +
===Equine rhinovirus===
 +
*Causative agent: [[Picornaviridae|equine rhinovirus]]
 +
*[[Nasal Cavity Inflammatory - Pathology|Rhinitis]]
 +
*Most common in young horses
 +
*May cause acute upper respiratory disease
 +
 
 +
 
 +
===[[Equine Influenza|Equine influenza]]===
 +
 
 +
===Equine rhinopneumonitis ===
 +
*Causative agent: [[Herpesviridae|equine herpesvirus type 1 and type 4]]
 +
*Primary viral lesions in [[Nasal Cavity Inflammatory - Pathology|nasal mucosa]] and [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|lungs]]
 +
*Mild, transient [[Lungs Inflammatory - Pathology#Bronchointerstitial pneumonia|bronchointerstitial pneumonia]]
 +
*Latent infection acting as a reservoir
 +
*Sites of latency: bronchial lymph nodes and trigeminal ganglia
 +
*Replicates in upper respiratory tract epithelium
 +
*Disseminated to lower respiratory tract
 +
*Transported to other organs in T-lymphocytes - viraemia up to 3 weeks
 +
*Vasculitis, abortion
 +
*May be accompanied by secondary bacterial infection
 +
 
 +
 
 +
===Equine viral arteritis (EVA)===
 +
*Causative agent: [[Arteriviridae|equine arterivirus]]
 +
*[[Nasal Cavity Inflammatory - Pathology|Rhinitis]], peripheral oedema, [[Bronchi and Bronchioles Inflammatory - Pathology|bronchitis/bronchiolitis]], conjunctivitis, periorbital oedema
 +
*Replicates in macrophages and endothelial cells
 +
*Disseminates via the circulatory system causing necrotising arteritis
 +
*[[Lungs Inflammatory - Pathology#Interstitial pneumonia|Interstitial pneumonia]]
 +
*Transmitted by respiratory and venereal routes through direct contact with infected horse or its secretions
 +
*Stallion are a reservoir of infection as they are chronic shedders
 +
 
 +
 
 +
===Equine adenovirus===
 +
[[Image:Adenovirus in equine lung.jpg|right|thumb|100px|<small><center>Adenovirus in equine lung (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
 
 +
*[[Adenoviridae|Adenoviridae]]
 +
*May cause necrotising [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchiolitis]] in immune-deficient foals (Arabian foals)
 +
*Grossly:
 +
**[[Lungs Ventilation - Pathology#Atelectasis (Collapse)|Atelectasis]] and consolidation of lobules in cranioventral region
 +
**Mucopurulent exudate in airways
 +
*Histologically:
 +
**Severe bronchiolitis, necrotising -> proliferative
 +
**Bronchiolar obstruction by sloughed debri and [[Neutrophils - WikiBlood|neutrophils]] -> alveolar atelectasis
 +
*May lead to secondary bacterial infections
 +
 
 +
 
 +
===African horse sickness===
 +
[[Image:Lung oedema in African horse sickness.jpg|right|thumb|100px|<small><center>Lung oedema in African horse sickness (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
 
 +
*Caused by [[Reoviridae|orbivirus]], family reoviridae
 +
*Respiratory distress or cardiovascular failure
 +
*Rapid death due to massive [[Lungs Circulatory - Pathology#Pulmonary oedema|pulmonary oedema]]
 +
*[[Pleural Cavity & Membranes Degenerative - Pathology#Hydrothorax|Hydrothorax]] may also develop
 +
*Large amounts of froth present in airways
 +
 
 +
===[[Hendra Virus]]===
 +
 
 +
==In Cattle==
 +
 
 +
===[[Infectious Bovine Rhinotracheitis|Infectious bovine rhinotracheitis (IBR)]]===
 +
 
 +
 
 +
===Parainfluenza- 3===
 +
 
 +
*Causative agent: [[Paramyxoviridae#Bovine Parainfluenza - 3 (PI-3)|parainfluenza- 3 virus]] (PI3)
 +
*On its own causes [[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|rhinitis]]
 +
*Often part of multi-aetiology disease complex (e.g. [[Respiratory Bacterial Infections - Pathology#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]), often followed by [[:Category:Pasteurella and Mannheimia species|''Pasteurella sp.'']] obscuring viral origin
 +
*Replicates in airway epithelial cells and results in an initial [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis -> bronchiolitis]] -> extension into [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|alveoli]], causing [[Lungs Inflammatory - Pathology#Bronchointerstitial pneumonia|bronchointerstitial pneumonia]]
 +
*Early stages may show [[Degenerations and Infiltrations - Pathology#Cellular Inclusions|intracytoplasmic inclusions]]
 +
*The resulting exudate is predominantly neutrophilic
 +
*Positive confirmation lies in a Fluorescent Antibody Test (FAT) to the specific virus on frozen sections of tissue
 +
 
 +
 
 +
===[[Bovine adenovirus]]===
 +
 
 +
===Respiratory syncytial virus===
 +
 
 +
*Causative agent [[Paramyxoviridae|Respiratory syncytial virus (RSV)]], synonym: bovine RSV (BRSV)
 +
*Outbreaks of RSV associated disease usually occur associated with winter housing
 +
*Gross pathology in severe cases
 +
**Cranioventral [[Lungs Ventilation - Pathology#Atelectasis (Collapse)|atelectasis]] and consolidation
 +
**[[Lungs Ventilation - Pathology#Emphysema|Interstitial emphysema]]
 +
***More prominent in the caudal lung lobes
 +
***Results from bronchoconstriction which results in airway obstruction - this constriction is thought to arise from [[Mast Cells - WikiBlood|mast cell]] degranulation and histamine release
 +
*Histologically
 +
**[[Bronchi and Bronchioles Inflammatory - Pathology#Acute bronchitis/bronchiolitis|Acute bronchiolitis]], characteristic of the bronchiolar response is the formation of syncytial giant cells  (formed by proliferating bronchiolar epithelial cells which may contain [[Degenerations and Infiltrations - Pathology#Cellular Inclusions|intracytoplasmic inclusion bodies]]), alveolar epithelium sometimes affected
 +
**Obstruction of bronchioles by exudate - these may later become obliterated by the fibrous tissue of organisation
 +
*May contribute to [[Respiratory Bacterial Infections - Pathology#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]
 +
 
 +
===Bovine rhinovirus===
 +
 
 +
*Causative agent: [[Picornaviridae|bovine rhinovirus]]
 +
*May cause mild respiratory disease
 +
 
 +
==In Sheep==
 +
 
 +
===Maedi Visna===
 +
 
 +
*Caused by a [[Retroviridae|retrovirus]]
 +
*The respiratory from of the disease caused by maedi-visna virus (Maedi) is also called '''lymphoid interstitial pneumonia'''
 +
*Transmitted by close contact and via milk
 +
*The pulmonary lesions develop very slowly hence this disease is uncommon in sheep < 2 years old
 +
*Increased respiratory rate upon exertion, loss of weight
 +
*Remains in [[Monocytes - WikiBlood]] and macrophages
 +
*Gross findings
 +
**Severe [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]]
 +
**Lungs fail to collapse properly on opening the chest and can weigh more than twice the normal weight
 +
**Impressions of the ribs remain on the visceral pleura
 +
**Lungs are a mottled grey/ tan colour - the lesions can vary from irregular grey speckling to homogeneous grey consolidation
 +
**Rubbery in consistence
 +
**Diaphragmatic lobes most affected
 +
**Associated bronchial and mediastinal lymph nodes are often enlarged
 +
*Histologically
 +
**Major features are extensive lymphoid proliferation around perivascular, peribronchial and peribronchiolar sheaths associated with pulmonary lymphatics
 +
**Many of these areas contain germinal centres and smooth muscle hyperplasia (in walls of terminal bronchioles and alveoli)
 +
 
 +
 
 +
===Parainfluenza -3===
 +
 
 +
*As in [[Respiratory Viral Infections - Pathology#Parainfluenza- 3|cattle]]
 +
 
 +
 
 +
===Pulmonary adenomatosis===
 +
 
 +
*See [[Lungs Hyperplastic and Neoplastic - Pathology#Sheep pulmonary adenomatosis (SPA/ Jaagsiekte)|neoplasia]]
 +
 
 +
 
 +
==In Goats==
 +
 
 +
===Caprine Arthritis-Encephalitis (CAE)===
 +
 
 +
*Caused by [[Retroviridae|retrovirus (lentivirus)]] similar to [[Respiratory Viral Infections - Pathology#Maedi Visna|Maedi Visna]] in sheep described above
 +
*Two forms:
 +
**Non-suppurative leukoencephalomyelitis in young goats and kids
 +
**Chronic, non-suppurative arthritis-synovitis in adult goats
 +
*Also causes [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]] which tends to be obscured by other clinical signs
 +
*Gross pathology:
 +
**Mainly caudal lobes
 +
**Lungs are firm, grey-pink with grey-white focal lesions on cut surface
 +
*Micro pathology:
 +
**Thickened alveolar wall
 +
**Lymphocyte infiltration and type II pneumocyte hyperplasia
 +
*Can be confused with or coexisting with [[Lungs Inflammatory - Pathology#Verminous pneumonia|Parasitic pneumonia]]
 +
 
 +
 
 +
==In Pigs==
 +
 
 +
===Inclusion body rhinitis===
 +
[[Image:Inclusion body rhinitis.jpg|right|thumb|100px|<small><center>Inclusion body rhinitis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 +
 
 +
*[[Herpesviridae|'''Herpesviridae, porcine cytomegalovirus''']]
 +
*Disease of suckling piglets 1-5 wks of age
 +
*Clinical signs: those associated with acute/subacute [[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|rhinitis]] (ie: serous nasal discharge, progressing to catarrhal or purulent discharge with time and secondary bacterial infections; sneezing; pyrexia), fever in young piglets (3-8wks old)
 +
*May progress to [[Paranasal Sinuses Inflammatory - Pathology#Sinusitis|sinusitis]], otitis media or [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|pneumonia]]
 +
*Morbitity high, mortality low
 +
*Gross pathology - catarrhal discharge becoming purulent (secondary infection)
 +
*Histology:
 +
**Large basophilic [[Degenerations and Infiltrations - Pathology#Cellular Inclusions|intranuclear inclusion bodies]] in the surface and subepithelium of nasal and sinus glandular epithelium with lymphocytic infiltration of the mucosa
 +
**Bursting of nucleus with cell necrosis and sloughing of necrotic epithelium
 +
*Can develop viraemic stage, with inclusions and focal necrotising lesions in other organs eg: renal tubular epithelium
 +
**Usually younger piglets, can die during this phase
 +
*Usually resolves if uncomplicated but rhinitis may persist if secondary infection is present
 +
*May persist in pulmonary macrophages
 +
 
 +
 
 +
===[[Swine Influenza|Swine influenza]]===
 +
 
 +
===Porcine reproductive and respiratory syndrome===
 +
 
 +
*The syndrome is caused by a small enveloped RNA virus which belongs to the new [[Arteriviridae|Arteriviridae]] group
 +
*Replicates in and destroys macrophages and endothelial cells causing vasculitis -> viraemia -> virus shedding (nasal secretions, faeces)
 +
*Clinical signs: respiratory and reproductive failure, weaned pigs, tachypnoea, eyelid oedema, conjunctivitis
 +
*Moderate to severe interstitial [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|pneumonia]] in the cranial lobe
 +
*Superimposed bacterial infections are common
 +
*Infectious disease in swine that emerged 10 years ago
 +
*Today, PRRS is endemic in many if not all the pig-producing countries
 +
 
 +
 
 +
===Postweaning multisystemic wasting syndrome (PMWS)===
 +
 
 +
*Caused by a [[Circoviridae|porcine circovirus]] alone or in combination with [[Parvoviridae|porcine parvovirus]]
 +
*May cause mild [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]], failure of lungs to collpse on opening the thoracic cavity
 +
*Microscopically: thickening of alveolar wall due to type 2 pneumocyte hyperplasia
 +
 
 +
 
 +
===Porcine respiratory coronavirus (PRCV)===
 +
 
 +
*Caused by a [[Coronaviridae|coronavirus]]
 +
*Usually mild [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|pneumonia]] unless complicated by other agents
 +
*Virus replicates in epithelial lining of airways

Revision as of 11:25, 22 May 2010


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()Map CARDIORESPIRATORY SYSTEM (Map)
RESPIRATORY SYSTEM INFLAMMATION



In general

  • Some viruses are thought to induce modifications of the pulmonary defences by:
    • Damaging the upper respiratory tract, thereby facilitating bacterial attachment and colonisation, with reduced mucociliary clearance
    • Decreasing surfactant levels by destroying Type 2 pneuMonocytes - WikiBlood
    • Impairing the phagocytic ability of alveolar macrophages


In Dogs

Canine distemper

  • Caused by a morbillivirus
  • Rhinitis
  • Although many organs can be affected by CDV, a relatively constant feature is the respiratory signs which occur in varying severity
  • A syndrome of catharral oculonasal discharge, pharyngitis and bronchitis is relatively common in the initial stages
  • Since one of the primary sites of action of this virus is lymphoid tissue, the resultant immunosuppression -> predisposition to secondary bacterial infection
  • May cause interstitial pneumonia where inclusions are found within alveolar macrophages
  • Gross pathology:
    • Oedematous lungs, diffuse interstitial pneumonia
  • Micro pathology:
    • Necrosis of pneumocytes, necrotising bronchiolitis, alveolar oedema, thickening of alveolar walls and type II pneumocyte hyperplasia


Parainfluenza- 2


Infectious canine tracheitis

Canine adenovirus

Adenovirus pneumonia (Image sourced from Bristol Biomed Image Archive with permission)

Canine herpes virus


Canine respiratory coronavirus

  • (CRCV)
  • Shown to be involved in an outbreak of disease in large kennels with rapidly changing population and high incidence of respiratory disease
  • Erles, K., Toomey, C. et al.(2003) "Detection of a group 2 coronavirus in dogs with canine infectious respiratory disease." Virology 310(2):216-223


In Cats

Feline viral rhinotracheitis

  • Caused by a herpesvirus
  • Tends to be more rhinitis than tracheitis, may extend to sinusitis
  • Feline herpesvirus -1
    • One of the causes of Feline viral rhinotracheitis
  • All three agents infect URT respiratory epithelium, although FHV-1 has the highest affinity for this epithelium
  • Feline calicivirus more frequently infects the oral mucosa -> ulcerative stomatitis
  • C.psittaci more frequently infects the conjunctival epithelium -> chronic conjunctivitis
  • Infection of the respiratory epithelium by FHV-1 results in a typical neutrophilic rhinitis with intraepitheial intranuclear eosinophilic inclusion bodies
  • Uncomplicated cases resolve in 2-3 weeks
  • FHV-1 remains latent in the trigeminal ganglion, and can reactivate at times of stress
  • Can infect the cornea -> ulcerative keratitis
  • Mortality may be high in young kittens, debilitated and immune-suppressed animals, usually associated with secondary bacterial infection.


Feline calicivirus

In Horses

Equine respiratory viruses Concept Map (Courtesy of B. Stanikova)

Equine rhinovirus


Equine influenza

Equine rhinopneumonitis

  • Causative agent: equine herpesvirus type 1 and type 4
  • Primary viral lesions in nasal mucosa and lungs
  • Mild, transient bronchointerstitial pneumonia
  • Latent infection acting as a reservoir
  • Sites of latency: bronchial lymph nodes and trigeminal ganglia
  • Replicates in upper respiratory tract epithelium
  • Disseminated to lower respiratory tract
  • Transported to other organs in T-lymphocytes - viraemia up to 3 weeks
  • Vasculitis, abortion
  • May be accompanied by secondary bacterial infection


Equine viral arteritis (EVA)

  • Causative agent: equine arterivirus
  • Rhinitis, peripheral oedema, bronchitis/bronchiolitis, conjunctivitis, periorbital oedema
  • Replicates in macrophages and endothelial cells
  • Disseminates via the circulatory system causing necrotising arteritis
  • Interstitial pneumonia
  • Transmitted by respiratory and venereal routes through direct contact with infected horse or its secretions
  • Stallion are a reservoir of infection as they are chronic shedders


Equine adenovirus

Adenovirus in equine lung (Image sourced from Bristol Biomed Image Archive with permission)
  • Adenoviridae
  • May cause necrotising bronchiolitis in immune-deficient foals (Arabian foals)
  • Grossly:
    • Atelectasis and consolidation of lobules in cranioventral region
    • Mucopurulent exudate in airways
  • Histologically:
    • Severe bronchiolitis, necrotising -> proliferative
    • Bronchiolar obstruction by sloughed debri and neutrophils -> alveolar atelectasis
  • May lead to secondary bacterial infections


African horse sickness

Lung oedema in African horse sickness (Image sourced from Bristol Biomed Image Archive with permission)
  • Caused by orbivirus, family reoviridae
  • Respiratory distress or cardiovascular failure
  • Rapid death due to massive pulmonary oedema
  • Hydrothorax may also develop
  • Large amounts of froth present in airways

Hendra Virus

In Cattle

Infectious bovine rhinotracheitis (IBR)

Parainfluenza- 3


Bovine adenovirus

Respiratory syncytial virus

  • Causative agent Respiratory syncytial virus (RSV), synonym: bovine RSV (BRSV)
  • Outbreaks of RSV associated disease usually occur associated with winter housing
  • Gross pathology in severe cases
    • Cranioventral atelectasis and consolidation
    • Interstitial emphysema
      • More prominent in the caudal lung lobes
      • Results from bronchoconstriction which results in airway obstruction - this constriction is thought to arise from mast cell degranulation and histamine release
  • Histologically
    • Acute bronchiolitis, characteristic of the bronchiolar response is the formation of syncytial giant cells (formed by proliferating bronchiolar epithelial cells which may contain intracytoplasmic inclusion bodies), alveolar epithelium sometimes affected
    • Obstruction of bronchioles by exudate - these may later become obliterated by the fibrous tissue of organisation
  • May contribute to Enzootic pneumonia of calves

Bovine rhinovirus

In Sheep

Maedi Visna

  • Caused by a retrovirus
  • The respiratory from of the disease caused by maedi-visna virus (Maedi) is also called lymphoid interstitial pneumonia
  • Transmitted by close contact and via milk
  • The pulmonary lesions develop very slowly hence this disease is uncommon in sheep < 2 years old
  • Increased respiratory rate upon exertion, loss of weight
  • Remains in Monocytes - WikiBlood and macrophages
  • Gross findings
    • Severe interstitial pneumonia
    • Lungs fail to collapse properly on opening the chest and can weigh more than twice the normal weight
    • Impressions of the ribs remain on the visceral pleura
    • Lungs are a mottled grey/ tan colour - the lesions can vary from irregular grey speckling to homogeneous grey consolidation
    • Rubbery in consistence
    • Diaphragmatic lobes most affected
    • Associated bronchial and mediastinal lymph nodes are often enlarged
  • Histologically
    • Major features are extensive lymphoid proliferation around perivascular, peribronchial and peribronchiolar sheaths associated with pulmonary lymphatics
    • Many of these areas contain germinal centres and smooth muscle hyperplasia (in walls of terminal bronchioles and alveoli)


Parainfluenza -3


Pulmonary adenomatosis


In Goats

Caprine Arthritis-Encephalitis (CAE)

  • Caused by retrovirus (lentivirus) similar to Maedi Visna in sheep described above
  • Two forms:
    • Non-suppurative leukoencephalomyelitis in young goats and kids
    • Chronic, non-suppurative arthritis-synovitis in adult goats
  • Also causes interstitial pneumonia which tends to be obscured by other clinical signs
  • Gross pathology:
    • Mainly caudal lobes
    • Lungs are firm, grey-pink with grey-white focal lesions on cut surface
  • Micro pathology:
    • Thickened alveolar wall
    • Lymphocyte infiltration and type II pneumocyte hyperplasia
  • Can be confused with or coexisting with Parasitic pneumonia


In Pigs

Inclusion body rhinitis

Inclusion body rhinitis (Image sourced from Bristol Biomed Image Archive with permission)
  • Herpesviridae, porcine cytomegalovirus
  • Disease of suckling piglets 1-5 wks of age
  • Clinical signs: those associated with acute/subacute rhinitis (ie: serous nasal discharge, progressing to catarrhal or purulent discharge with time and secondary bacterial infections; sneezing; pyrexia), fever in young piglets (3-8wks old)
  • May progress to sinusitis, otitis media or pneumonia
  • Morbitity high, mortality low
  • Gross pathology - catarrhal discharge becoming purulent (secondary infection)
  • Histology:
    • Large basophilic intranuclear inclusion bodies in the surface and subepithelium of nasal and sinus glandular epithelium with lymphocytic infiltration of the mucosa
    • Bursting of nucleus with cell necrosis and sloughing of necrotic epithelium
  • Can develop viraemic stage, with inclusions and focal necrotising lesions in other organs eg: renal tubular epithelium
    • Usually younger piglets, can die during this phase
  • Usually resolves if uncomplicated but rhinitis may persist if secondary infection is present
  • May persist in pulmonary macrophages


Swine influenza

Porcine reproductive and respiratory syndrome

  • The syndrome is caused by a small enveloped RNA virus which belongs to the new Arteriviridae group
  • Replicates in and destroys macrophages and endothelial cells causing vasculitis -> viraemia -> virus shedding (nasal secretions, faeces)
  • Clinical signs: respiratory and reproductive failure, weaned pigs, tachypnoea, eyelid oedema, conjunctivitis
  • Moderate to severe interstitial pneumonia in the cranial lobe
  • Superimposed bacterial infections are common
  • Infectious disease in swine that emerged 10 years ago
  • Today, PRRS is endemic in many if not all the pig-producing countries


Postweaning multisystemic wasting syndrome (PMWS)


Porcine respiratory coronavirus (PRCV)

  • Caused by a coronavirus
  • Usually mild pneumonia unless complicated by other agents
  • Virus replicates in epithelial lining of airways