Atypical interstitial pneumonia (Fog Fever)

Introduction:Atypical interstitial pneumonia, also commonly known as fog fever, is a syndrome farmers see in their cattle after placing the animals on lush green grazing. Animals that are fed a dry ration prior to grazing lush pastures are more likely to be affected by this syndrome. Fog fever is also known as acute bovine pulmonary oedema and emphysema (ABPEE).ย Disease progression:Cattle affected by this syndrome have been on dry feed for extended periods of time and the rumen fermentation pattern has adapted to this situation. With the change to lush green pasture the dietary protein concentration increases dramatically. One of the amino acids in this plant protein, tryptophan, is the culprit. The tryptophan in the feed is converted by rumen bacteria to a substance called 3-methylindole (3-MI) at a very high rate.This 3-MI is absorbed through the rumen wall and circulated around the body. The 3-MI is toxic to the primary cells (Type 2 pneumocytes) that line the interior surface of the lungs at the alveolar-blood barrier. Thus, as the high levels of 3-MI move from the rumen to the lungs, more and more lung tissue is destroyed.ย Clinical Signs:Difficulty breathingCoughingFrothing at mouthCattle do not normally run a fever- This is an extremely important point as the clinical signs seen with fog fever are very similar to those seen with Bovine respiratory disease.Anxiety (separation from group)CollapseDeathย Treatment:Unfortunately, there is no specific treatment for fog fever. Mild cases may recover without treatment, should they be caught early enough. Most severely affected cattle will not […]