Veterinary Preventive Medicine-II

CLINICAL MANIFESTATIONS

• The incubation period is 2 to 10 days
• Calves are least affected, those less than 6 months of age showing no clinical signs.
• After an incubation period of 2-10 days, there is sudden onset of fever. A biphasic or triphasic fever and sharp fall in milk yield are commonly observed.
• There is severe ruminal stasis followed by constipation.
• Muscular signs become more evident on the second day with severe stiffness.
• Swellings in shoulders neck and back may be seen. A posture similar to that of acute laminitis, with all four feet bunched under the body is characteristic.
• On the third day the animal begins eating and ruminating and the febrile reaction disappears
• Some animals remains standing in acute stage and exhibit sternal recumbency associated with hypocalcaemia (Milk fever posture). Most recovered animals develop a solid immunity.
• The morbidity rate may reach 100% and the fatality rate is 1%. Milk yield returns to normal within 2 to 3 weeks.