The effect that is seen depends on the mechanism of disease involved. This factsheet describes some conditions that may result when cattle eat moldy feeds. Infection usually occurs after an episode of grain overload or fungal pneumonia. One consequence of these diseases is that particles of fungus enter the blood stream and settle in the pregnant uterus. If the infection passes through the placenta to the fetus, plagues or crusts of fungus will develop on the skin of the fetus.
Diagnosis is made by culturing the organism from aborted tissues.
To prevent mycotic abortions, do not abruptly change the diet of pregnant cattle from all forage to one that includes a large amount of grain, and avoid moldy feeds when possible. The bacterium, Listeria monocytogenes , is widespread in nature. It is often associated with a dirty environment because it is found in animal, bird and human stool. Infection occurs primarily by eating or inhaling the organism. The infected cow may have a brief fever and depression but abortion will only follow after a stressful event, so a long time may pass before an abortion occurs.