But moose do have their problems. Signs of moose sickness include aimless walking in circles, holding head and ears in abnormal positions, frequent stumbling, poor coordination or balance, and apparent weakness or paralysis of a leg. Once I tried to shoot a videotape of a moose charging someone, but the moose kept coming after me even though the other person was closer. Animals showing such severe signs of disease will eventually die. Conservation officers and wildlife managers are often called on to end the animal's suffering.
Sick moose can be a safety hazard along roadways.
People sometimes see a sick moose but do not report the sighting because they do not realize the animal is sick. Some sick moose have been photographed by people who have assumed the animal was especially tolerant of people. People have reported leg or hip injuries in moose that, in fact, were suffering leg paralysis from the disease. The cause of this disease eluded detection until 1964, when Canadian biologist Roy Anderson discovered it was caused by Parelaphostrongylus tenuis, a parasitic nematode, or roundworm, commonly referred to as brainworm. The white-tailed deer is the normal host and is unaffected by the parasite.