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