Black Disease in Sheep

Black Disease
It is also called Infectious Necrotic Hepatitis. It is an acute toxiema&infection disease of sheep. Sometime in Cattle but rare in horse and pig.
Epidemiology:
World wide in distribution where sheep and liver flukes are found.it effect the 1-4 year old sheep with well-nourished or having well planned nutrition. In summer and early fall this is common.
Etiology:

·         Causative Agent Clostridum novii bacteria type B

·         It is soil born bacteria which are found in Intestine and liver of herbivores. It may also be present on Skin of animal. Carrier animal shed it by feces.

·         Potentional source of this disease is wound infection. Feco-oral route.by wound.

Pathogenesis:
Entry by wound and mouth then entered into blood, from there go into liver and bacteria multiply in liver and produce lethal toxin which are necrotizing in nature and cause necrosis of liver. That toxin damages the hepatic parenchyma. Alpha toxin are necrotizing and lethal in nature clostridium novii suspect but not yet conform to cause sudden death in cattle which are feed on high level of grains with no lesion on liver.
In Sheep
Entry of bacteria by wound or feco-oral route >intestine >blood (Toxemia, Toxin lethal and necrotizing) >liver which is already damage with liver fluke>bacteria penetrate at that site and cause necrosis of live >C.novii multiply in liver and produce lethal toxin
Clinical finding:

·         Usually sudden death of animal with no well-defined signs

·         Sternal recombancy death within few hours in 1-4 year old sheep

·         Animal tend to leg behind&it is limited to animal which are infected with liver fluke.

·         Animal die with out struggling

Gross lession:

·         Extensive rupture of sub-cut capillaries which cause adjacent skin to turn black. That’s why its name Black disease.

·         Postmortem examination on liver greyish yellow necrotic focci on liver.

·         Enlarge pericardial sac filled with straw colour fluid.

·         Fluid accumulation in peritoneal/thoracic cavity

Histopathology:

·         Liver show scare due to immature flukes

·         Pyloric region of the stomach show congested mucous and clear gelatinous oedema in sub mucosa.

Diagnosis;

·         On postmortem lesion

·         Also see season

Treatment and Control;

·         Snail-Lymnea spp present in water muluskicidal agent

·         No effect of Antibiotics

·         Clostridium novii toxicide effective in this

·         Burn the pasture which contaminated

·         Vaccine-long term immunity at early summer done

·         Also vaccine new coming sheep in flock.

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