It is also known as three days sickness and affected animals suffer from pyrexia, muscular stiffness and lameness.
Etiology: The disease is caused by ephemeral fever virus that belongs to rhabdoviridae family. Most of the cases occur in hot and humid environmental conditions and when the mosquito population is high.
Pathogenesis: After entering into circulation, virus multiplies and localizes in the mesodermal tissue such as muscles and joints. There is inflammation of the tissue causing pain and muscle stiffness.
Clinical signs: The infected animals show sudden high rise of body temperature, anorexia and reduction in milk yield. There is increase in the heart and respiration rate, and nasal and ocular discharge. Swelling over muscle area of shoulder, back and neck, shivering, stiffness and clonic muscular movements are noticed. The lameness is also very prominent and animal adopt typical posture of laminitis. Occasionally, animal shows lateral recumbency. Abortions occur in pregnant animals. After 3 days, the body temperature becomes almost normal and they start eating and ruminating.
Hematological analysis reveals leukocytosis, neutrophilia with shift to the left, lymphopenia and increased fibrinogen levels are noticed along with hypocalcemia. Postmortem examination shows accumulation of serofibrinous exudate in synovial, pericardial, pleural and peritoneal cavities. The lymph nodes are enlarged and swollen.
Diagnosis: The disease is diagnosed by clinical signs and examination of blood, and confirmed by serological tests like agar gel precipitation, fluorescent antibody, ELISA and complement fixation tests. It should be differentiated from laminitis, parturient paresis and traumatic reticulitis. In laminitis, there is local pain in feet and this may occur due to excess carbohydrate feeding while parturient paresis usually occurs after parturition and cases respond well to calcium therapy. Traumatic reticulitis can be detected by metal detector if caused by metallic object and its course is quite long. If it is not caused by metallic object, its diagnosis is possible by cardinal signs, X-ray examination and rumenotomy.
Treatment: As the symptoms disappear in 3 days, so usually supportive treatment is recommended. The affected animals are given drugs to relieve the temperature and muscle stiffness. So, paracetamol and phenylbutazone are given by parenteral route. Top recent secondary bacterial infection, broad spectrum antibiotics like streptopenicillin or tetracycline are given.
Control: There is no vaccine available against the disease. The only way to reduce its occurrence is by adopting hygienic measures and reducing the vector population.