AN OVERVIEW OF BILIARY IN DOGS:
Biliary is a very common cause of deaths in dogs in South Africa. It is more commonly know as Tick Bite Fever by most pet owners. The parasites that cause the disease are carried and spread by a tick which is why it is most prevalent in the summer months, but it is important to keep in mind that it is not limited to the summer months. Because this is a common disease it is important to understand as much as possible about the transmission, disease processes as well as treatment to identify infections as early as possible to response to treatment.
The disease is transmitted by ticks once they attach and bite a host animal. The parasites are carried in the saliva and mouths of infected ticks and get into the blood stream when an animal is bitten. The ticks pick up the parasites from feeding on an infected dog, but it can also be transmitted to the next generation of ticks via the eggs of an infected female tick. Once the parasites are in the blood stream, they multiply in the red blood cells causing these cells to be destroyed. As red blood cells are the oxygen carriers of the body, the clinical symptoms are associated with lack of oxygen. Some animals die before any symptoms are seen, but most dogs will show symptoms of the disease. The most common signs seen are fever, pale or yellow gums, listlessness and decreased appetite, vomiting and a red discoloration of the urine. In severe cases seizures can also be observed.
Diagnosis in the consult room is done via a simple test. A small drop of blood is collected and a smear made. Once stained, the parasites can be seen in the red blood cells under microscopic evaluation. When evaluating the blood smear it is also important to check the white blood cells as there is another tick born parasite (Ehrlichia) that often occurs together with the biliary parasites. They often occur together as they are transmitted by the same ticks. This infection has similar symptoms to biliary and can also be found as an infection on its own.
In cases that do not have a large parasite load present on a blood smear and do not show any signs of immune mediated destruction of red blood cell, outpatient treatment is a viable option. Daily re-evaluation is needed to monitor for any signs of complications. Most cases would however benefit from hospitalization and intensive treatment and monitoring. Some of the complications associated with a biliary infection can necessitate treatment in hospital. If the red blood cell numbers have decreased below 20% of the blood volume, a blood transfusion will be needed as part of the treatment to supplement oxygen carriers while the body increases its own production of new red blood cells. The body may also develop antigens against its own red blood cells due to over stimulation of the immune system causing the body to attack and destroy its own red blood cells. For this a course of cortisone would be needed to suppress the immune system for a week or two.
Another important fact to consider is that, although biliary is not contagious, dogs that are exposed to the same tick population may be infected at the same time. It is then possible for more than one dog in a household to be affected. The incubation period after the initial bite is about 10 -14 days. If you are at all concerned that your dog may have been exposed to ticks or they are showing any of the mentioned symptoms, take them to your vet for a check and blood smear sooner rather than later.