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| | ====[[Bacillary Necrosis]]==== | | ====[[Bacillary Necrosis]]==== |
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| − | | + | [[Infectious Necrotic Hepatitis]] |
| − | ====Infectious Necrotic Hepatitis (Black Disease)====
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| − | *''Clostridium novyi'' type B
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| − | *grazing animals
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| − | **mainly sheep, also cattle (and reported sometimes in horses and goats)
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| − | *organism is widely distributed within the soil and normally present in GIT and [[Liver - Anatomy & Physiology|liver]] of grazing animals on infected pastures
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| − | **worldwide
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| − | *it is ingested by the animal and spores are absorbed via the gut and travel to the [[Liver - Anatomy & Physiology|liver]] , where they lie dormant in [[Macrophages - WikiBlood|macrophages (Kupffer cells)]] - also found in [[Bone Marrow - Anatomy & Physiology|bone marrow]] and [[Spleen - Anatomy & Physiology|spleen]]
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| − | *seasonal disease associated with Fasciola [[Liver - Anatomy & Physiology|liver]] flukes
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| − | **migrating immature [[Liver - Anatomy & Physiology|liver]] flukes precipitate the disease
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| − | **causes [[Liver - Anatomy & Physiology|liver]] damage which provides ideal anaerobic conditions for the activation and germination of spores
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| − | *''C. novyi'' produces three exotoxins
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| − | **alpha - a lethal toxin
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| − | **beta - a lecithinase which is both haemolytic and necrotising
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| − | **zeta - a haemolytic toxin
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| − | *acute toxaemia produced by organism
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| − | **affected animals are usually found dead because death is sudden due to the action of the powerful bacterial endotoxins
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| − | **not all animals will become sick - only when organism starts producing toxin
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| − | *post mortem changes occur rapidly
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| − | =====Clinical=====
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| − | *found dead/sudden death
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| − | **well conditioned sheep 2-4 years old
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| − | **lateral recumbency, few signs of struggle
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| − | **vaccination history (against Clostridium)
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| − | **no red urine or other bleeding
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| − | *IF seen alive
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| − | **severe depression
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| − | **not eating
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| − | **pyrexia
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| − | **hypothermia
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| − | **respiratory distress
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| − | **muffled heart sounds
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| − | | |
| − | =====Gross=====
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| − | *rapid decomposition of carcass
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| − | *extensive subcutaneous vessels engorged and haemorrhage causing dark colouration of the skin - hence the name ''''Black Disease'''' - and oedema
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| − | *blood stained fibrinous fluid in abdomen, thorax, and pericardium which clots on exposure to air
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| − | *tissues are autolysed
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| − | *[[Liver - Anatomy & Physiology|liver]] swollen and congested
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| − | *characteristic pale (greyish-yellow) foci (3cm diameter) of necrosis surrounded by a rim of haemorrhage where the bacteria have multiplied upon incision
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| − | *evidence of [[Liver - Anatomy & Physiology|liver]] fluke
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| − | *other organs show general signs of toxaemia
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| − | NB: Distinguish Black Disease from Red Water! The former will have several small areas of necrosis while the latter has one big lump
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| − | | |
| − | =====Microscopically=====
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| − | *coagulative necrosis
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| − | *possible evidence of migrating flukes
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| − | *demonstration of bacteria
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| − | **in the necrotic tissue
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| − | **especially near its junction with viable tissue
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| − | **rim of neutrophilic cells
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| − | =====Treatment=====
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| − | *rarely possible
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| − | *Penicillin or Oxytetracycline at very high doses
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| − | =====Prevention=====
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| − | *vaccination
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| − | **normally lasts up to 6 months
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| − | *[[Liver - Anatomy & Physiology|liver]] fluke control
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| − | *remove dead carcasses from pasture
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| | ====Bacillary Haemoglobinuria (Red Water)==== | | ====Bacillary Haemoglobinuria (Red Water)==== |