Systematic Veterinary Virology

SYMPTOMS

• The clinical signs are very characteristic and can be very severe. Fever is most important symptom. The fever of ephemeral fever is generally biphasic, sometimes triphasic, with peaks of 40-41.5°C (104-107°F) spaced 12-18 hours apart.
• The physical signs during the first febrile phase tend to be mild except for the dramatic fall in milk production of lactating cows. The characteristic signs associated with BEF are those of the second febrile phase. These signs include accelerated heart and respiratory rates, anorexia, ruminal atony, depression, serous or mucoid nasal and ocular discharges, salivation, muscle twitching or waves of shivering, a generalized stiffness or a shifting lameness.
• There may be submandibular edema or patchy edema on the head. Nasal and ocular discharges, drooling of saliva and periorbital swelling and increased excitability and agitation are other signs. With the onset of fever, there is a rapid fall in circulating lymphocytes with eosinopenia.
• Many animals become recumbent for 12-24 hours. Animals may be unable to rise and remain in sternal recumbency for hours or days with the head turned to the flank, or in lateral recumbency with or without loss of most reflexes.
• Recovery begins 1-2 days after the clinical signs are first noticed and is usually complete and without sequelae in a further 1- 2 days after the overt clinical signs are first noticed. By day three the affected animal is usually standing again and will begin to eat.
• However, lameness and weakness may last for another two or three day. Milk yield will return to normal after three weeks. Death can occur suddenly in the febrile or in the recovery phase.