North American Veterinary Licensing Examination (NAVLE) Practice Test

What is the most effective control measure for infectious necrotic hepatitis in sheep secondary to fluke infestation?

1. Vaccinate with Clostridium novyi toxoid

2. High-dose penicillin

3. Clostridium hemolyticum bacterin

4. Treat ponds with copper sulfate

The correct answer is: Vaccinate with Clostridium novyi toxoid

Vaccination with Clostridium novyi toxoid is the most effective control measure for infectious necrotic hepatitis (also known as Black Disease) in sheep that arises secondary to liver fluke infestation. The disease is caused by the bacterium Clostridium novyi, which can proliferate in the liver when liver tissue is damaged due to fluke migration. The use of a toxoid vaccine helps stimulate the immune system of the sheep to produce antibodies against the toxins produced by the bacteria, thereby preventing the disease from developing. Vaccination is particularly crucial in herds where fluke infestations are common, as these infestations create an environment conducive to the disease's onset when liver damage occurs. By providing immunity through vaccination, producers can significantly reduce the incidence of infectious necrotic hepatitis in their flocks. While other options like high-dose penicillin or Clostridium hemolyticum bacterin may provide some benefits in treating existing infections or specific bacterial challenges, they do not prevent the disease effectively as vaccination does. Additionally, treating ponds with copper sulfate addresses fluke control indirectly but does not specifically target the prevention of Clostridium novyi-related diseases. Overall, vaccination represents a proactive approach to controlling infectious necrotic hepatitis in sheep.