Difference between revisions of "Respiratory Viral Infections"

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|linkpage =Cardiorespiratory System - Pathology
 
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<br>
 
==In general==
 
  
*Some viruses are thought to induce modifications of the pulmonary defences by:
+
#REDIRECT[[:Category:Respiratory Viral Infections]]
**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 pneumonocytes
 
**Impairing the phagocytic ability of alveolar macrophages
 
 
 
 
 
==In Dogs==
 
 
 
===Canine distemper===
 
 
 
*Caused by a [[Paramyxoviridae#Canine Distemper Virus (CDV)|morbillivirus]]
 
*[[Nasal cavity - inflammatory#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#Infectious causes of pharyngitis|pharyngitis]] and [[Bronchi and bronchioles - inflammatory#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#Interstitial pneumonia|interstitial pneumonia]] where [[General Pathology - Degenerations and Infiltrations#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#Infectious causes of rhinitis|Rhinitis]], [[Trachea - inflammatory|tracheo]][[Bronchi and bronchioles - inflammatory#Infectious causes of bronchitis or bronchiolitis|bronchitis]]
 
 
 
 
 
===Infectious canine tracheitis===
 
*Synonyms: '''Kennel cough''', '''Infectious tracheobronchitis'''
 
*[[Trachea - inflammatory#Infectious causes of tracheitis|tracheitis]], [[Bronchi and bronchioles - inflammatory#Infectious causes of bronchitis or bronchiolitis|bronchitis]]
 
*Multiple agents implicated:
 
**[[Adenoviridae|Canine adenovirus-2]]
 
**[[Paramyxoviridae|Canine parainfluenza-2 virus]]
 
**[[Paramyxoviridae#Canine Distemper Virus (CDV)|Canine distemper virus]]
 
**[[Bordetella bronchiseptica and Bordetella avium|''Bordetella bronchoseptica'']]
 
*Symptoms are of a persistent, non-productive cough
 
*Persistent tracheobronchial inflammation
 
*The outcomes is generally recovery (may persist >3 weeks), but extension to [[Bronchi and bronchioles - inflammatory|chronic bronchitis]] or cranioventral [[Lungs - inflammatory#Infectious causes of pneumonia|bronchopneumonia]] may occur
 
*In severe cases can extend to serous/mucopurulent [[Nasal cavity - inflammatory#Rhinitis|rhinitis]]
 
*Lesions are neither specific nor always significant (catarrhal / mucopurulent tracheobronchitis)
 
*Enlarged tonsils and retropharyngeal lymph nodes
 
 
 
===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#Bronchointerstitial pneumonia|bronchointerstitial pneumonia]], necrosis of bronchiolar and alveolar epithelium, oedema, type II pneumocyte hyperplasia
 
*May cause necrotising [[Bronchi and bronchioles - inflammatory#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#Infectious causes of rhinitis|rhino]][[Trachea - inflammatory#Infectious causes of tracheitis|tracheitis]] and secondary [[Lungs - inflammatory#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#Infectious causes of rhinitis|rhinitis]] than [[Trachea - inflammatory#Infectious causes of tracheitis|tracheitis]], may extend to [[Paranasal sinuses - inflammatory#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 [[Chlamydia and Chlamydophila species|''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 [[General Pathology - Degenerations and Infiltrations#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#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#Interstitial pneumonia|interstitial pneumonia]] with necrotising [[Bronchi and bronchioles#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|Rhinitis]]
 
*Most common in young horses
 
*May cause acute upper respiratory disease
 
 
 
 
 
===Equine influenza===
 
*Causative agent: [[Orthomyxoviridae|equine influenza virus (Orthomyxovirus)]]
 
*[[Nasal cavity - inflammatory#Infectious causes of rhinitis|Rhinitis]],
 
*Pathogenesis:
 
**Inhalation -> replication in epithelial cells of upper and lower airways (attaches  via haemaglutinin spike and gains entry into cell) -> neuramidase alters efficiency of [[Respiratory System General Introduction - Pathology#Mucociliary escalator|mucociliary apparatus]]
 
*Sloughing of the affected area
 
*Severity of signs will depend on dose of virus
 
*Acute [[Trachea - inflammatory#Infectious causes of tracheitis|tracheo]][[Bronchi and bronchioles - inflammatory#Infectious causes of bronchitis or bronchiolitis|bronchitis]] with coughing, and fever
 
*May be accompanied by secondary bacterial infections
 
*No viraemia
 
*In severe cases may cause [[Lungs - inflammatory#Bronchointerstitial pneumonia|bronchointerstitial pneumonia]]
 
*Secondary invaders are usually [[Streptococci|''Streptococci'']]
 
 
 
 
 
===Equine rhinopneumonitis ===
 
*Causative agent: [[Herpesviridae|equine herpesvirus type 1 and type 4]]
 
*Primary viral lesions in [[Nasal cavity - inflammatory|nasal mucosa]] and [[Lungs - inflammatory#Infectious causes of pneumonia|lungs]]
 
*Mild, transient [[Lungs - inflammatory#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|Rhinitis]], peripheral oedema, [[Bronchi and bronchioles - inflammatory|bronchitis/bronchiolitis]], conjunctivitis, periorbital oedema
 
*Replicates in macrophages and endothelial cells
 
*Disseminates via the circulatory system causing necrotising arteritis
 
*[[Lungs - inflammatory#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#Infectious causes of bronchitis or bronchiolitis|bronchiolitis]] in immune-deficient foals (Arabian foals)
 
*Grossly:
 
**[[Lungs - ventilation#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 -> 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#Pulmonary oedema|pulmonary oedema]]
 
*[[Pleural cavity and membranes - degenerative#Hydrothorax|Hydrothorax]] may also develop
 
*Large amounts of froth present in airways
 
 
 
===Hendra virus===
 
 
 
*Causative agent [[Paramyxoviridae|equine morbillivirus]]
 
*Oedematous lungs with distention of [[Pleural cavity and membranes - inflammatory|pleura]]
 
*Micro: diffuse [[Lungs - circulatory#Pulmonary oedema|alveolar oedema]], syncytial cells
 
 
 
 
 
==In Cattle==
 
 
 
===Infectious bovine rhinotracheitis (IBR)===
 
[[Image:IBR nasal cavity.jpg|right|thumb|100px|<small><center>IBR in nasal cavity (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 
[[Image:IBR trachea.jpg|right|thumb|100px|<small><center>IBR in trachea (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 
 
 
*Causative agent is [[Herpesviridae|'''bovine herpesvirus, type 1''']]
 
*URT infection with serous nasal discharge, increases respiratory rate, coughing and moderate fever,from nasal mucosa down to bronchioles
 
*[[Nasal cavity - inflammatory|Rhinitis]], [[Nasopharynx - inflammatory#Infectious causes of pharyngitis|pharyngitis]], [[Larynx - inflammatory|laryngitis]], [[Trachea - inflammatory|tracheitis]], [[Bronchi and bronchioles - inflammatory|bronchiolitis]]
 
*Morbidity is high, mortality is low
 
*Highly infectious URT disease of cattle
 
*Spread by movement of animals, aerosol transmission - requires close contact between animals
 
*Early stages (only first few days) may show [[General Pathology - Degenerations and Infiltrations#Cellular Inclusions|intracellular inclusions]] in the respiratory mucosal epithelial cells
 
*Leading to neutrophilic inflammation of varying severity.... serous -> catarrhal -> purulent
 
*With secondary bacterial infection (eg: [[Pasteurella species and Mannheimia haemolytica|Pasturella spp.]], [[Mycoplasmas|Mycoplasma spp.]], [[Fusobacterium|Fusobacterium necrophorum]]) can lead to fibrinous to necrotizing inflammation; mucosal sloughing, ulceration... pyrexia, dyspnoea ... [[Lungs - inflammatory#Aspiration pneumonia|inhalation pneumonia]]... death
 
*Underlying hyperaemic inflammatory response
 
*Can become latent following primary infection
 
*Clinical signs:nasal discharge, sneezing, coughing, lacrimation, and increased respiratory rate
 
*Clinical disease most severe in young calves - can develop mucosal ulcerative lesions in the [[Oesophagus#Erosive & Ulcerative Pathology|oesophagus]] and forestomachs and viraemia with multiorgan infection
 
*Cause of abortion >5 months of gestation
 
*May contribute to [[Bacterial infections#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]
 
 
 
 
 
===Parainfluenza- 3===
 
 
 
*Causative agent: [[Paramyxoviridae#Bovine Parainfluenza - 3 (PI-3)|parainfluenza- 3 virus]] (PI3)
 
*On its own causes [[Nasal cavity - inflammatory#Infectious causes of rhinitis|rhinitis]]
 
*Often part of multi-aetiology disease complex (e.g. [[Bacterial infections#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]), often followed by [[Pasteurella species and Mannheimia haemolytica|''Pasteurella sp.'']] obscuring viral origin
 
*Replicates in airway epithelial cells and results in an initial [[Bronchi and bronchioles - inflammatory#Infectious causes of bronchitis or bronchiolitis|bronchitis -> bronchiolitis]] -> extension into [[Lungs - inflammatory#Infectious causes of pneumonia|alveoli]], causing [[Lungs - inflammatory#Bronchointerstitial pneumonia|bronchointerstitial pneumonia]]
 
*Early stages may show [[General Pathology - Degenerations and Infiltrations#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===
 
 
 
*Causative agent: [[Adenoviridae|bovine adenovirus]]
 
*[[Nasal cavity - inflammatory#Infectious causes of rhinitis|Rhinitis]]
 
*May contribute to [[Bacterial infections#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]
 
 
 
 
 
===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#Atelectasis (Collapse)|atelectasis]] and consolidation
 
**[[Lungs - ventilation#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 - Anatomy & Physiology|mast cell]] degranulation and histamine release
 
*Histologically
 
**[[Bronchi and bronchioles - inflammatory#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 [[General Pathology - Degenerations and Infiltrations#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 [[Bacterial infections#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 and macrophages
 
*Gross findings
 
**Severe [[Lungs - inflammatory#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#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#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#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#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#Sinusitis|sinusitis]], otitis media or [[Lungs - inflammatory#Infectious causes of pneumonia|pneumonia]]
 
*Morbitity high, mortality low
 
*Gross pathology - catarrhal discharge becoming purulent (secondary infection)
 
*Histology:
 
**Large basophilic [[General Pathology - Degenerations and Infiltrations#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===
 
 
 
*Caused by [[Orthomyxoviridae|Swine influenza virus]]
 
*[[Nasal cavity - inflammatory|Rhinitis]], may progress to [[Lungs - inflammatory#Infectious causes of pneumonia|pneumonia]]
 
*Clinical signs: pyrexia, lethargy, skin erythema, anorexia, severe cough and sneezing, dyspnoea, conjunctivitis, pregnant sows may abort
 
*Grossly:
 
**[[Trachea - inflammatory|Tracheo]][[Bronchi and bronchioles - inflammatory#Infectious causes of bronchitis or bronchiolitis|bronchitis]], airway obstruction -> [[Lungs - ventilation#Atelectasis (Collapse)|atelectasis]]
 
**[[Pleural cavity and membranes - inflammatory|Pleura]] normal or covered with serous or serofibrinous exudate
 
**[[Pleural cavity and membranes - inflammatory|Pleural cavity]] filled with excess fluid
 
**Lung lesions
 
***Clear demarcation of lesions in cranial and middle lobes
 
***[[Lungs - inflammatory#Interstitial pneumonia|Interstitial pneumonia]]
 
*Histologically:
 
**Acute inflammation of mucosa of trachea and bronchi
 
*Zoonotic
 
*Circumstantial evidence of mutation from human strain
 
*Migrating [[Parasitic infections#Ascaris suum|ascarids]] thought to precipitate the disease, reservoir of infection in earthworms containing infected lungworm larvae
 
 
 
 
 
===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#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#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#Infectious causes of pneumonia|pneumonia]] unless complicated by other agents
 
*Virus replicates in epithelial lining of airways
 

Latest revision as of 11:22, 20 July 2010