Difference between revisions of "Respiratory Viral Infections"
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+ | {{review}} | ||
− | # | + | {{toplink |
+ | |backcolour = D1EEEE | ||
+ | |linkpage =Cardiorespiratory System - Pathology | ||
+ | |linktext =Cardiorespiratory System | ||
+ | |maplink = Cardiorespiratory System (Content Map) - Pathology | ||
+ | |pagetype =Pathology | ||
+ | |sublink1=Respiratory System Inflammation - Pathology | ||
+ | |subtext1=RESPIRATORY SYSTEM INFLAMMATION | ||
+ | }} | ||
+ | <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]] | ||
+ | **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]]=== | ||
+ | |||
+ | ===[[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|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|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]]=== | ||
+ | |||
+ | ==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]] 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]]=== |
Revision as of 12:48, 12 June 2010
This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing. |
|
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
- 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
- Caused by an parainfluenza- 2 virus
- Rhinitis, tracheobronchitis
Infectious canine tracheitis
Canine adenovirus
- Adenoviridae
- Usually mild bronchointerstitial pneumonia, necrosis of bronchiolar and alveolar epithelium, oedema, type II pneumocyte hyperplasia
- May cause necrotising bronchiolitis in immune-deficient dogs (distemper)
- Can be associated with kennel cough described above
Canine herpes virus
- Caused by canine herpes virus 1
- Part of fading puppy syndrome
- Presents with necrotising rhinotracheitis and secondary bronchopneumonia in older dogs
- Seems to be common subclinically
- (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
- Viruses and bacteria are involved in the complex. The most frequent aetiologic agent is FHV-1, and less frequently feline calicivirus and/or Chlamydophila psittaci (NB: previously called Chlamydia psittaci var felis)
- 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
- Causative agent: feline calicivirus
- Rhinitis,
- Suggested in the presence of ulceration of the dorsal and lateral edges of the tongue, hard palate and external nares
- Lesions present may include interstitial pneumonia with necrotising bronchiolitis
- Also see Feline viral rhinotracheitis above
In Horses
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
- 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
- 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
- Causative agent: parainfluenza- 3 virus (PI3)
- On its own causes rhinitis
- Often part of multi-aetiology disease complex (e.g. Enzootic pneumonia of calves), often followed by Pasteurella sp. obscuring viral origin
- Replicates in airway epithelial cells and results in an initial bronchitis -> bronchiolitis -> extension into alveoli, causing bronchointerstitial pneumonia
- Early stages may show 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 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 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
- As in cattle
Pulmonary adenomatosis
- See neoplasia
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
- 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)
- Caused by a porcine circovirus alone or in combination with porcine parvovirus
- May cause mild interstitial pneumonia, failure of lungs to collpse on opening the thoracic cavity
- Microscopically: thickening of alveolar wall due to type 2 pneumocyte hyperplasia