Dr W J Grobler BVSc
Several similarities exist between biliary fever and an African disease of humans — malaria. Both diseases are caused by protozoa — single-celled organisms that invade the host's red blood corpuscles and upon destructing the same lead to anaemia. Death may ensue in both cases if correct and timely treatment is not carried out.
The name Biliary indicates that jaundice develops in a percentage of cases due to damage to the liver and an inability to secrete bile into the intestinal tract. The single-celled organism causing the disease (Fig. 1) is transmitted in South Africa by the yellow dog tick (Fig. 2) to a susceptible dog. The organisms invade the animal's red blood corpuscles, divide by binary fission and thus lead to bursting of the corpuscles or their removal from the blood stream by the spleen.
Fig. 1: Several Biliary fever organisms in the red corpuscles of a dog. (magnified c. 2000 times)
If a large percentage of red blood cells burst in a short time, their contents (hemoglobin) escape into the blood stream and may be seen in the urine (Biliary of dogs and redwater in cattle are caused by similar organisms). The hemoglobin is converted to bile salts that are excreted into the intestines with the liver still functioning properly. This explains the yellow, soft stool often seen with biliary. If the liver is damaged by the anaemia, it is no longer able to excrete the bile salts which accumulate in the body thus causing jaundice.
Anaemia is the direct result of the loss of red blood cells due to breakage and removal from the blood stream by the spleen. This anaemia explains most of the symptoms seen in uncomplicated cases:
Fig. 2: A drawing of the yellow dog tick Haemaphysalis elliptica (leachi) — the vector of biliary in South Africa
A vet will make a blood smear from a small drop of blood, usually taken from the animal's ear. The organisms are very small (about 300 will fit into a single millimetre!), but they can easily be seen if magnified a thousand times under a microscope. The vet may also deduce from the blood smear whether new red cells are being formed, whether the body is fighting the infection adequately and if there are signs of concomitant infections like Tick Bite fever. If no parasites are found, other reasons for the anaemia must be sought.
Various drugs may be used to kill the biliary organisms. These drugs are all in injectable form and are all toxic if not used correctly. Side effects include inter alia:
From the above it is understandable that all these remedies are used under supervision of a veterinarian.
Cortisone is often administered, especially in cases where a complication of biliary where the body attacks its own red cells occur. Iron and vitamins are given to boost appetite and stimulate red cell formation, allthough some deem it unnecessary. Jaundiced animals are treated with liver supportive therapy.
In severe cases the number of red blood cells may decrease to dangerous levels, necessitating a blood transfusion. There are eight different blood groups in dogs, but fortunately most are compatible, so transfusion reactions occur infrequently. It is however safer if cross-matching is done beforehand. Blood transfusions are quite expensive, but have saved many a sick dog that would not have pulled through otherwise.
As from September 2008 a vaccine is available in South Africa to prevent biliary. It is still of the utmost importance to keep dogs free from ticks as far as possible. This means dipping weekly in summer, or making use of the long-acting sprays or tick collars available. It is also important to keep the animal's environment free from ticks by regular washing of bedding and application of dips to the kennels. In the summer rainfall areas it is however very difficult to keep dogs completely free from ticks, so it is important to have a sick dog seen to early in the disease. The good news is that most dogs do develop a good immunity to the disease at some stage or other.
Biliary fever is a deadly disease, but timely treatment is effective in a large proportion of cases. Good rains in spring and summer mean an abundance of ticks in the following season resulting in large numbers of sick animals. Dog owners are cautioned not to take any chances with a sick animal, but to take it to a veterinarian as soon as possible. Mention must be made here of Tick Bite fever, a completely different disease that may occur together with Biliary. This disease will be discussed in a separate article.
Fig 2: Scientific pamphlet No. 393, Dept. Agricultural Technical Services 1983