Difference between revisions of "Picornaviridae"

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==Introduction==
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#REDIRECT[[:Category:Picornaviridae]]
==Aphthoviruses==
 
===Foot and Mouth Disease Virus===
 
====Introduction====
 
*Affects all cloven hoofed animals, cattle, sheep and pigs and others.
 
*1967 + 2001  major outbreaks in UK.
 
*Controlled by slaughter policy in UK.
 
*Still widespread in many parts of world especially S. America, far East.
 
*Very infectious virus.
 
====Clinical====
 
*Foot and Mouth disease is not a high fatal disease - approximately 5% mortality, usually young animals, older animals recover but stop giving milk yield - i.e. production losses are important factor.
 
*It is very debilitating and animals take weeks or months to recover.
 
*Economic impact as stops export of cattle and cattle products.
 
*Fairly easy to diagnose in classical form - difficult in sheep.
 
*Animals froth at mouth, usually in more than one animal (one animal may be just sore mouth from another cause).
 
*Lameness in a number of animals.
 
*Characteristic lesions in mouth that are short lived.
 
*Incubation from two days up to 3 weeks in sheep.
 
====Pathology====
 
=====Gross=====
 
#Initially - hyperaemia of mucosa (e.g. catarrhal inflammation) then within 12 hours produces fluid filled vesicles on dorsum of tongue, may be other places.
 
#Small vesicle coalesce to produce big ones -i.e. Bullae.
 
#Very quickly rupture; epithelium appears dirty grey in colour because of necrosis - sloughed skin, very good for diagnosis.
 
#Leave painful, hyperaemic epithelium.
 
#Looks like "ulcer "with ragged edge but not a true ulcer as stratum germinativum retained and will rapidly heal completely in about 2 weeks unless becomes secondarily infected.
 
 
 
*Also produces sores in interdigital cleft, at coronet and bulbs of heals.
 
**These feet lesions often take a long time to heal as secondary infections may ensue and produce true deep ulceration.
 
*Teats on animals that are suckling may also develop vesicles.
 
 
 
*Sheep develop very few vesicles in mouth but foot lesions can be dramatic - like a whole flock with foot rot.  N.B. Can also be very mild!
 
*Coronets are very red with vesicles and sores.
 
 
 
*Pigs have vesicles on snout, which are quickly eroded - hard to look at pig’s tongue. 
 
*Hoof lesions like other species; hoof may come off, known as "thimbling".
 
*Lesions will heal eventually but is very painful (Often need euthanasia)
 
 
 
=====Microscopic lesions=====
 
*Degeneration of prickle cells. 
 
*Cells "balloon" as fill with fluid and then die to produce vesicle containing straw coloured or clear fluid.
 
 
 
====Diagnosis====
 
Definitive diagnosis.
 
 
 
N.B.  Notifiable Disease.
 
 
 
*Inform MAFF (and police) as soon as suspect clinical diagnosis.
 
*MAFF will take specimens of fluid from vesicle. Suck out fluid with syringe.
 
*Skin that has sloughed off vesicle also good for diagnosis.
 
*If the above two are not available can use scraping of base of erosion.
 
 
 
*May see animals that have discoloration of tongue due to having had FMD.  In these cases take scraping of retropharyngeal region, put scrapings in transport medium.
 
 
 
#Atigen capture ELISA
 
#PCR
 
#Culture (need ph7 buffered transport media)
 
#Antibody capture ELISA
 
 
*In foot and mouth disease usually use ELISA to provide quick diagnosis - especially if have vesicular fluid.
 
 
 
==Enteroviruses==
 
===Swine Vesicular Disease Virus===
 
Caused by an enterovirus. (picorna virus)
 
 
 
May produce vesicles in mouth that are indistinguishable from foot and mouth disease.
 
 
 
Swine vesicular disease produces sporadic large outbreaks; approximately 5% have lesions in mouth, foot lesions much more common.
 
 
 
==Rhinoviruses==
 
==Cardioviruses==
 
==Hepatoviruses==
 
==Parechoviruses==
 
==Erboviruses==
 
==Koboviruses==
 
==Teschoviruses==
 

Latest revision as of 11:22, 23 May 2010