L19 - Liver Infections II

What organism is associated with infectious necrotic hepatitis (black disease)?

Clostridium novyi type B

What species does Clostridium novyi target?

Sheep and cattle

Sometimes pigs and horses

Is Clostridium novyi always fatal?

Almost always in sheep and cattle

What age groups are typically affected by Clostridium novyi?

Sheep 2-4 years old, lambs rarely

There is an epidemiological associate between Clostridium novyi and what? Why?

Liver flukes → both in soil where black disease is found

What type of pastures predispose sheep to Clostridium novyi?

• Marshy/heavily watered ground → increases development of flukes

Where are Clostridium novyi spores typically found?

Soil and liver

What causes the clinical disease associated with Clostridium novyi?

Necrotic process in liver (caused by liver flukes) → creates anaerobic conditions → triggers Clostridium novyi to proliferate → produces lethal amounts of toxins

How is Clostridium novyi transmitted?

• Fecal-oral

• Cadavers

• Movement of contaminated sheep between farms

• Flooding of contaminated soil → more liver flukes

Pathogenesis of Clostridium novyi

• Spores are ingested and carried to liver

• Migrating liver fluke causes tissue destruction → anaerobic conditions → pathogen proliferates

• Produces alpha-toxin → local liver necrosis and damage to vascular system

Symptoms of Clostridium novyi

• Sheep → rapid decline (die overnight with no signs)

• Cattle → slow decline (1-2 days)

• Sheep isolate themselves/lag behind

• Shallow and rapid respiration

• Sternal recumbency

• Fever then subnormal temperature

How do Clostridium novyi lesions appear?

• Liver is swollen, gray-brown, yellow areas of necrosis surrounded by bright red hyperemia

• Engorgement of SC vessels and edema

• Dark appears of inside the skin → “black disease”

How is Clostridium novyi treated?

No effective treatment in sheep

Horses and Cattle: Penicillin, but case fatality is high

How is Clostridium novyi controlled?

1. Vaccination → highly effective

2. Control of liver fluke

3. Burn carcasses

What pathogen causes Bacillary Hemoglobinuria (Red Water Dz)?

Clostridium haemolyticum

Where is Clostridium haemolyticum found?

Soil and Liver

What species does Clostridium haemolyticum typically target?

Cattle, sometimes sheep and pigs

What type of pastures does Clostridium haemolyticum typically found in?

Poorly drained pastures/wet

How is Clostridium haemolyticum spread?

• Flooding, natural drainage or carrier animals

• Ingestion

Pathogenesis of Clostridium haemolyticum

• Spores of Clostridium haemolyticum ingested and carried to liver

• Migrating liver fluke causes tissue destruction → anaerobic conditions made → causes pathogen to proliferate

• C. haemolyticum produces beta-toxin → hemolysis, necrosis of hepatocytes and damage to capillary endothelium

• Focal heaptic necrosis, hemoglobinuria, loss of vascular fluid

Symptoms of Clostridium haemolyticum

• Acute → cattle can be found dead overnight with no signs

• Complete cessation of rumination, feeding, lactation and defecation → GIT stops doing everythinggg

• Abdominal pain, grunting

• Edema of brisket → common

• Urine is dark red

• SC edema and SC hemorrhages

Is Clostridium haemolyticum always fatal?

Up to 95% mortality in untreated animals

What characterizes Clostridium haemolyticum lesions?

• Focal necrosis of liver

• Lesion is pale, surrounded by zone of hyperemia

What kind of pathogen is Clostridium haemolyticum?

• Gram +

• Large rods

• Anaerobic

How is Clostridium haemolyticum treated?

• HIGH dose of ABX: Penicillin and tetracyclines

• Antitoxin serum

• Supportive Tx (blood transfusions, fluids, electrolytes)

• Guarded prognosis

How is Clostridium haemolyticum controlled?

• Vaccine

• Destroy carcasses