Atypical interstitial pneumonia or fog fever.

摘要

Atypical intestinal pneumonia ('fog fever') is a metabolic disorder of cattle that is attributed to the consumption of feed with a high L-tryptophan content. This amino acid is degraded and converted in the rumen to 3-methylindole (3MI) which then causes pulmonary oedema and emphysema. Hyperacute, acute and chronic cases have been described according to the concentrations of tryptophan in the diet. The disease can affect >50% of the herd, but the incidence is mostly low. The epidemiology, aetiology, pathogenesis, clinical aspects, diagnosis, differential diagnosis, treatment, prevention and control of this disease are reviewed and discussed. There is no effective cure owing to the acute course and irreversible character of the pulmonary lesions, and the symptoms are treated with atropine, dexamethasone, antihistamines and broad spectrum antibiotics. Prevention strategies include pasture management, modification of ruminal fermentation by the use of antibiotics, and blockage of the effects of 3MI in the lungs.