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| | ==Aphthoviruses== | | ==Aphthoviruses== |
| | ===Foot and Mouth Disease Virus=== | | ===Foot and Mouth Disease Virus=== |
| − | ====Introduction====
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| − | *Affects all cloven hoofed animals, cattle, sheep and pigs and others.
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| − | *1967 + 2001 major outbreaks in UK.
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| − | *Controlled by slaughter policy in UK.
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| − | *Still widespread in many parts of world especially S. America, far East.
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| − | *Very infectious virus.
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| − | ====Clinical====
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| − | *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.
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| − | *It is very debilitating and animals take weeks or months to recover.
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| − | *Economic impact as stops export of cattle and cattle products.
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| − | *Fairly easy to diagnose in classical form - difficult in sheep.
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| − | *Animals froth at mouth, usually in more than one animal (one animal may be just sore mouth from another cause).
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| − | *Lameness in a number of animals.
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| − | *Characteristic lesions in mouth that are short lived.
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| − | *Incubation from two days up to 3 weeks in sheep.
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| − | ====Pathology====
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| − | =====Gross=====
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| − | #Initially - hyperaemia of mucosa (e.g. catarrhal inflammation) then within 12 hours produces fluid filled vesicles on dorsum of tongue, may be other places.
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| − | #Small vesicle coalesce to produce big ones -i.e. Bullae.
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| − | #Very quickly rupture; epithelium appears dirty grey in colour because of necrosis - sloughed skin, very good for diagnosis.
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| − | #Leave painful, hyperaemic epithelium.
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| − | #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.
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| − | *Also produces sores in interdigital cleft, at coronet and bulbs of heals.
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| − | **These feet lesions often take a long time to heal as secondary infections may ensue and produce true deep ulceration.
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| − | *Teats on animals that are suckling may also develop vesicles.
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| − | *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!
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| − | *Coronets are very red with vesicles and sores.
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| − | *Pigs have vesicles on snout, which are quickly eroded - hard to look at pig’s tongue.
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| − | *Hoof lesions like other species; hoof may come off, known as "thimbling".
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| − | *Lesions will heal eventually but is very painful (Often need euthanasia)
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| − |
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| − | =====Microscopic lesions=====
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| − | *Degeneration of prickle cells.
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| − | *Cells "balloon" as fill with fluid and then die to produce vesicle containing straw coloured or clear fluid.
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| − |
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| − | ====Diagnosis====
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| − | Definitive diagnosis.
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| − |
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| − | N.B. Notifiable Disease.
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| − |
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| − | *Inform MAFF (and police) as soon as suspect clinical diagnosis.
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| − | *MAFF will take specimens of fluid from vesicle. Suck out fluid with syringe.
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| − | *Skin that has sloughed off vesicle also good for diagnosis.
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| − | *If the above two are not available can use scraping of base of erosion.
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| − |
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| − | *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.
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| − |
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| − | #Atigen capture ELISA
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| − | #PCR
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| − | #Culture (need ph7 buffered transport media)
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| − | #Antibody capture ELISA
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| − |
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| − | *In foot and mouth disease usually use ELISA to provide quick diagnosis - especially if have vesicular fluid.
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| | ==Enteroviruses== | | ==Enteroviruses== |