Difference between revisions of "Swine Influenza"

Latest revision as of 18:07, 30 July 2012

Introduction

Swine influenza is caused by Orthomyxoviridae virus family. There is circumstantial evidence of mutation from the human strain of influenza and hence the disease is zoonotic. The pig is susceptible to human and avian strains of the disease. Because of this, if infection with both strains occurs at the same time, the virus can mutate in the environment of the pig and become avian in pathogenicity with human attachment proteins. Hence it is thought that avian influenza can infect humans. Avian-like H1 and human-like H3 strains vary in virulence.

The disease in swine is thought to be predisposed to by migrating ascarids or by lung worms. The reservoir is the earthworm as this is the intermediate host for the porcine lungworm.

The virus will tend to recycle on farms as litters outgrow maternal antibody at around 12 weeks of age.

Signalment

Pigs of any age, but particularly weanlings and growers. It is also transmissible to humans.

Clinical Signs

Initially upper respiratory signs such as rhinitis, a sneezing, serous nasal discharge and conjunctivitis are seen. This is soon followed by pyrexia, lethargy, skin erythema, anorexia, severe barking coughing, dyspnoea and pneumonia. Tracheobronchitis may cause airway obstruction which may lead to atelectasis. Pregnant sows may abort. The virus is often associated with bacteria such as mycoplasma or immunosuppressive viruses such as PRRS.

Diagnosis

If the animal has clinical pneumonia, influenza is always a suspected cause.

Post mortem examination can be diagnostic and will often show the pleura normal or covered with serous or serofibrinous exudate and the pleural cavity filled with excess fluid. Lung lesions will include clear demarcation of lesions in cranial and middle lobes, interstitial pneumonia causing consolidation of the lungs and giving a 'meaty' appearance. There may be necrotising bronchiolitis with catarrhal pus. Histologically, there will be acute inflammation of the mucosa of trachea and bronchi.

Serology should be performed and this will provide a retrospective diagnosis by haemaglutination inhibition (HI).

Control

In an outbreak of influenza there should be an immediate isolation of premises. No stock should be moved from group to group during this time and strict hygiene measures should be put into place as well as sanitisation of hands prior to entering a farrowing house. Secondary bacterial infections should be treated with antibiotics.

Control measures should include 'all in/ all out' systems being put into place.

Vaccination is not licensed in the UK.

References

Blood, D.C. and Studdert, V. P. (1999) Saunders Comprehensive Veterinary Dictionary (2nd Edition) Elsevier Science

Cowart, R.P. and Casteel, S.W. (2001) An Outline of Swine diseases: a handbook Wiley-Blackwell

Jackson, G.G. and Cockcroft, P.D. (2007) Handbook of Pig Medicine Saunders Elsevier

Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial

Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences

Straw, B.E. and Taylor, D.J. (2006) Disease of Swine Wiley-Blackwell

Taylor, D.J. (2006) Pig Diseases (Eighth edition) St Edmunsdbury Press ltd

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-{{unfinished}}
+{{OpenPagesTop}}
+== Introduction  ==
-===Subtypes===
+Swine influenza is caused by [[:Category:Orthomyxoviridae|Orthomyxoviridae]] virus family. There is circumstantial evidence of mutation from the human strain of influenza and hence the disease is zoonotic. The pig is susceptible to human and avian strains of the disease. Because of this, if infection with both strains occurs at the same time, the virus can mutate in the environment of the pig and become avian in pathogenicity with human attachment proteins. Hence it is thought that [[Avian Influenza|avian influenza]] can infect humans. Avian-like H1 and human-like H3 strains vary in virulence.
-*Avian-like H1 and human-like H3 strains vary in virulence
-===Pathogenesis===
-*Necrotising bronchiolitis with catarrhal pus
-*Barking cough
-*Interstitial pneumonia giving consolidation of the lungs and a 'meaty' appearance
-*Often associated with bacteria, mycoplasma or immunosuppressive viruses (such as PRRS)
-*The virus recycles on farms as litters outgrow maternal antibody at 12 weeks of age
-===Diagnosis===
+The disease in swine is thought to be predisposed to by migrating [[Ascaris suum|ascarids]] or by [[Metastrongylus|lung worms]]. The reservoir is the earthworm as this is the intermediate host for the porcine lungworm.
-*Clinical pneumonia is always suspect
-*Serology: retrospective diagnosis by HI
-===Control===
-*Isolation of premises
-*All-in/all-out systems
-*Vaccination is not licensed in the UK
+The virus will tend to recycle on farms as litters outgrow maternal antibody at around 12 weeks of age.
-*Caused by [[Orthomyxoviridae]]
+== Signalment ==
-*[[Nasal Cavity Inflammatory - Pathology|Rhinitis]], may progress to [[Lungs Inflammatory - Pathology#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 - Pathology|Tracheo]][[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis]], airway obstruction -> [[Lungs Ventilation - Pathology#Atelectasis (Collapse)|atelectasis]]
-**[[Pleural Cavity & Membranes Inflammatory - Pathology|Pleura]] normal or covered with serous or serofibrinous exudate
-**[[Pleural Cavity & Membranes Inflammatory - Pathology|Pleural cavity]] filled with excess fluid
-**Lung lesions
-***Clear demarcation of lesions in cranial and middle lobes
-***[[Lungs Inflammatory - Pathology#Interstitial pneumonia|Interstitial pneumonia]]
-*Histologically:
-**Acute inflammation of mucosa of trachea and bronchi
-*Zoonotic
-*Circumstantial evidence of mutation from human strain
-*Migrating [[Respiratory Parasitic Infections - Pathology#Ascaris suum|ascarids]] thought to precipitate the disease, reservoir of infection in earthworms containing infected lungworm larvae
+Pigs of any age, but particularly weanlings and growers. It is also transmissible to humans.
-[[Category:Orthomyxoviridae]][[Category:Pig]]
+== Clinical Signs ==
+Initially upper respiratory signs such as [[rhinitis]], a sneezing, serous nasal discharge and conjunctivitis are seen. This is soon followed by pyrexia, lethargy, skin erythema, anorexia, severe barking coughing, dyspnoea and [[:Category:Pneumonia|pneumonia]]. Tracheobronchitis may cause airway obstruction which may lead to [[atelectasis]]. Pregnant sows may abort. The virus is often associated with bacteria such as [[:Category:Mycoplasmas|mycoplasma]] or immunosuppressive viruses such as [[PRRS]].
+== Diagnosis ==
+If the animal has clinical pneumonia, influenza is always a suspected cause.
+Post mortem examination can be diagnostic and will often show the pleura normal or covered with serous or serofibrinous exudate and the pleural cavity filled with excess fluid. Lung lesions will include clear demarcation of lesions in cranial and middle lobes, interstitial pneumonia causing consolidation of the lungs and giving a 'meaty' appearance. There may be necrotising bronchiolitis with catarrhal pus. Histologically, there will be acute inflammation of the mucosa of trachea and bronchi.
+Serology should be performed and this will provide a retrospective diagnosis by haemaglutination inhibition (HI).
+== Control ==
+In an outbreak of influenza there should be an immediate isolation of premises. No stock should be moved from group to group during this time and strict hygiene measures should be put into place as well as sanitisation of hands prior to entering a farrowing house. Secondary bacterial infections should be treated with antibiotics.
+Control measures should include 'all in/ all out' systems being put into place.
+Vaccination is not licensed in the UK.
+== References ==
+Blood, D.C. and Studdert, V. P. (1999) '''Saunders Comprehensive Veterinary Dictionary''' (2nd Edition) ''Elsevier Science''
+Cowart, R.P. and Casteel, S.W. (2001) '''An Outline of Swine diseases: a handbook''' ''Wiley-Blackwell''
+Jackson, G.G. and Cockcroft, P.D. (2007) '''Handbook of Pig Medicine''''' Saunders Elsevier''
+Merck & Co (2008) '''The Merck Veterinary Manual''' (Eighth Edition) ''Merial''
+Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) '''Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses''''' Elsevier Health Sciences
+Straw, B.E. and Taylor, D.J. (2006)''' Disease of Swine '''''Wiley-Blackwell
+Taylor, D.J. (2006) '''Pig Diseases '''(Eighth edition) ''St Edmunsdbury Press ltd''
+{{review}}
+{{OpenPages}}
+[[Category:Orthomyxoviridae]] [[Category:Pig_Viruses]] [[Category:Respiratory_Diseases_-_Pig]] [[Category:Expert_Review - Farm Animal]] [[Category:Respiratory_Viral_Infections]]
+[[Category:Zoonoses]]