Dog's Diseases

Tick Fever

Tick fever is a relatively common disease found in dogs in Hong Kong. The three common parasites which cause the disease here are Babesia canis, Babesia gibsoni and Ehrlichia canis. These parasites infect the common dog tick and should an infected tick bite a dog it can release the parasites into the dog's bloodstream. Ticks need to feed for two to three days in order to cause an infection. The parasites enter the dog's red blood cells and the dogs immune system then destroys the infected red cells hence killing the parasites but also destroying the red cells. The dog's immune system may become so sensitive that it will start to destroy perfectly normal red cells and this condition is called Immune-Mediated Haemolytic Anaemia.

Signs of Tick Fever
The signs of tick fever result from the loss of the dog's red blood cells. The membranes appear pale owing to the anaemia, the urine becomes dark in colour because of the excretion of destroyed red cells by the kidney, the platelet count often drops resulting in animals bruising easily, animals become weak, most develop a fever and some may have vague signs such as vomiting and diarrhoea. A few animals show only mild signs such as slowly loosing weight over a long time or simply not 'being themselves.'

Diagnosis
The diagnosis of Tick Fever is made based upon a number of factors. The clinical signs are often suggestive and would encourage the veterinarian to carry out further blood tests. It is sometimes possible to see the micro-organisms on a blood smear but at present the most sensitive test is PCR which can detect minute numbers of the organism.

Treatment and Prognosis
Severely effected animals may require blood transfusions. Treatment of tick fever varies depending upon the particular parasite involved but involves antibiotics, injections (Imizol, Berenil), corticosteroids and atovaquone, a new oral treatment which is safer than the injections.

The best treatment is prevention which is achieved by the use of products such as frontline which kill ticks before they can infect your dog and the oncurrent use of tick collars if your dog is at high risk.

Tick fever is a serious disease and relapses may occur after treatment has finished. As stated above it can develop into autoimmune haemolytic anaemia which is very difficult to treat and can be fatal.