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The Ferret Circulatory System

What happens when a ferret's heart, blood and blood vessels work well, and what happens when they don't.

By Jerry Murray, DVM
Posted: May 1, 2009, 5 a.m. EDT

ferret portrait
© Isabelle Francais/I-5 Publishing
The heart, blood and blood vessels all work together in the ferret's circulatory system.

The ferret’s circulatory system has three main parts: the heart, the blood vessels and the blood. Its major role is to get oxygenated blood distributed to all of the organs in the ferret’s little body, and to remove carbon dioxide and other waste products from the organs. In general, the ferret circulatory system is similar to other animals and humans, but there are a few little things that are unique to ferrets.

The Ferret’s Heart
The heart of the ferret is a cone-shaped, muscular organ that is divided into four separate chambers. It lies in the chest cavity in the middle of the two lungs and between the sixth and eighth rib. This is farther back in the chest cavity than most animals.

The average heart of a 1 kilogram, male ferret weighs less than 1 ounce. The heart rate depends a lot on the activity level of the ferret, but a rate of 200 to 300 beats per minute is considered normal. The normal heart rate for a person is between 60 and 80 beats per minute.

The blood enters into the heart through the right atrium, which is the upper right part of the heart. From the right atrium the blood goes down into the right ventricle. The right ventricle pumps the blood to the lungs. In the lungs, the blood releases carbon dioxide and picks up oxygen. The oxygen-rich blood then goes back to the heart and enters the left atrium, which lies in the upper left part of the heart. Next the blood travels down to the left ventricle. The left ventricle pumps the oxygenated blood out to the body.

The heart is basically a specialized muscle for pumping the blood throughout the body. Unfortunately, as the ferret ages heart disease becomes more common. Ferrets are generally prone to three types of heart disease.

Dilated cardiomyopathy is the most common heart problem in ferrets. In this disease the heart muscles stretch and cause the heart to enlarge. As the cardiac muscles stretch, the heart becomes weaker. With time, the heart gets so weak that it can no longer pump the blood effectively, and congestive heart failure develops. There is no cure for dilated cardiomyopathy, but it can be treated with medications. Your veterinarian can recommend what ACE inhibitors, diuretics or muscle-contraction strengthener medications are needed.

Hypertrophic cardiomyopathy is a disease where the heart enlarges as a result of the cardiac muscle becoming thicker and bigger. This makes the space inside the heart chambers smaller, so the heart can no longer fill up with the correct amount of blood. After a time, the heart no longer pumps the blood effectively.

The third problem is heart valve disease. This disease can allow the blood "to flow backward,” and the heart becomes ineffective at pumping the blood out of the heart.

Another concern regarding ferret hearts is heartworm disease. Ferrets are very susceptible to heartworm disease, even more so than dogs are. The ferret’s heart is very small, so only one to two worms can cause a fatal problem. Heartworm disease can be easily prevented by using one of the many heartworm preventives. Talk to your veterinarian about which is best for your ferret.

The Ferret’s Blood Vessels
There are a few different kinds of blood vessels. The large blood vessels that carry oxygenated blood are called arteries. The largest artery is the aorta. It is the vessel that carries blood out of the left ventricle of the heart. As the arteries travel through the body, they divide and become smaller. The smaller vessels are called arterioles. Arterioles also become smaller until they become capillaries. Oxygen is released from the capillaries and carbon dioxide enters the capillaries.

As the blood starts its journey back to the heart, the capillaries develop into the larger venules. The venules develop into the larger veins. The veins finally dump the unoxygenated blood into the right atrium. The veins commonly used to give intravenous (IV) fluids and medications in ferrets include the cephalic vein in the forearm and the lateral saphenous vein in the lower leg, just above the ankle. The veins commonly used to collect blood samples are the cranial vena cava inside the top of the sternum and the jugular vein in the neck.

Fortunately ferrets do not develop hardening of the arteries (atherosclerosis) like people do, but they can develop blood clots and vasculitis. Ferrets with heart disease are prone to having a blood clot develop at the distal end of the aorta near the rear legs. This is commonly called a saddle thrombus. Vasculitis is inflammation of the blood vessel wall and is common in Aleutian disease, Ferret Infectious Peritonitis, and in some immune-mediated diseases.

The Ferret’s Blood
The last part of the circulatory system is the blood itself. The average male ferret has about 2 ounces (60 milliliters) of blood in his body, and the average female ferret has less than 1.5 ounces (40 milliliters) of blood in her body. Blood is made up of four things: red blood cells, white blood cells, platelets and plasma. Red blood cells have the main function of carrying oxygen to the organs and bringing carbon dioxide back to the heart. White blood cells have many functions but are mostly involved in the immune system. Platelets are sticky, and plug leaks and holes in the blood vessel walls. They are also involved in forming blood clots. The plasma is the watery part of the blood. It is about 90 percent water and carries nutrients, such as proteins and electrolytes, to the organs.

Part of the routine blood work is the complete blood count (CBC). The CBC includes information on the number of red blood cells, white blood cells and platelets. The CBC can determine if the ferret has anemia and help determine the type of anemia.

The main problem with the blood involving the circulatory system is anemia. Anemia is basically a deficiency in red blood cells. A deficiency in red blood cells means a decrease in the amount of oxygen the blood can carry to the organs and a decrease in the amount of carbon dioxide the blood can carry away from the organs, which results in a ferret that does not feel good.

Many medical problems can cause anemia in ferrets. High estrogen levels in an intact female that stays in heat or in a ferret with adrenal gland disease can cause the bone marrow to stop producing red blood cells and cause a moderate to severe anemia. Kidney disease can also cause the bone marrow to decrease the production of red blood cells and cause a mild to severe anemia. Chronic diseases like insulinomaadrenal gland disease and heart disease can cause a mild to moderate anemia. Stomach ulcers and inflammatory bowel disease can cause blood loss and a mild to moderate anemia. Cancer such as lymphoma can cause a mild to severe anemia. Infectious diseases such as Aleutian disease and Ferret Infectious Peritonitis can cause a mild to severe anemia.

The ideal treatment of anemia is to correct the underlying problem that is causing the anemia; however, some cases also require blood transfusions to correct the anemia. Fortunately, ferrets do not have blood types like people do, so any healthy ferret can be used as a blood donor.

The ferret circulatory system is complex. Many diseases can affect the ferret’s circulatory system, but many of these diseases can be managed with the proper medications.

Posted: May 1, 2009, 5 a.m. EDT


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