Why is My Animal Lethargic?

Causes for Lethargy in Dogs, Cats and Other Animals

May 11, 2008 Mia Carter

Infections, injuries and illness can all cause lethargy and off-color behavior in your pet or livestock. Learn why lethargy occurs and when to contact the vet.

Lethargy is often one of the first symptoms of illness, infection or injury in an animal, so knowing the potential causes for this condition and taking action can often mean the difference between a quick recovery or a serious bout of illness.

Lethargy can be described as a sudden decrease in activity level. The animal may be inactive and hesitant to take part in normal activities, like walking, eating and even going to the bathroom. Therefore, lethargy is often associated with a lack of activity, increased periods of sleep, an unwillingness to eat and drink, and bathroom accidents indoors or in odd locations, like the pet’s bed.

Lethargy is considered a generalized, non-specific symptom, meaning that a vast array of ailments and conditions can be associated with lethargy and when considered alone, lethargy does not point to one particular illness or ailment.

So the key to diagnosis in a lethargic cat, dog or other animal involves an examination and testing, like basic blood work. Other symptoms must also be taken into consideration.

Lethargy can be associated with any number of illnesses and conditions.

In the case of a bacterial or viral infection, the body’s immune system and resources are focused on fighting the virus or bacteria, and therefore, there’s less energy available to take part in normal activities.

“The body’s resources are limited, so when a significant portion of those resources are utilized to fight an infection, the animal goes into a period of rest so that vital resources are directed to where they’re most needed,” Dr. Levine explained.

Many illnesses and diseases can also lead to lethargy, as many of these ailments result in impaired function in one or more body system. When one body system is not working normally, the body’s natural balance is upset. Illnesses affecting the digestive system are notorious for causing lethargy, as nutrients, fluids and sugars are not absorbed in a normal manner, resulting in fewer vital resources and less-than-optimal performance among the animal’s other body systems.

Injuries, particularly those involving the skeletal structure and connective tissues (like ligaments and muscles), are another common cause of lethargy. In many cases, there is a great deal of pain and discomfort associated with these sorts of injuries, so the animal naturally tries to limit movement to avoid further injury and to limit the distress associated with pain. Also in the case of an injury, many of the body’s resources are redirected to the injury site to promote healing, resulting in fewer resources to fuel other activities.

“Lethargy is one of those symptoms that should not be ignored. It’s an early warning sign that says something is not right with your pet,” Dr. Levine explained, concluding, “The sooner you begin treatment, the less taxing the ailment will be on the body’s resources and on the owner’s financial resources. In short, it’s easier to fight a small fire; wait until the fire is larger, and the fight will be more difficult and taxing.”

The copyright of the article Why is My Animal Lethargic? in Pet Care is owned by Mia Carter. Permission to republish Why is My Animal Lethargic? in print or online must be granted by the author in writing.

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