Tick fever is a term used to describe a type of blood disorder in dogs caused by blood parasites. It is a common and serious disease in Hong Kong and often fatal if left untreated.

Signs of tick fever

Some of the signs of tick fever are paleness, poor appetite, nose-bleed, weakness, jaundice, skin or eye bruising; fever, vomiting and diarrhoea may be seen also. However, at times, the signs could be vague. In certain types of tick fever, the signs could be very little, and the dogs may just show chronic weight loss, or just being "not so lively".

What are these blood parasites? Where do they come from?

There are several different blood parasites that can cause tick fever. These blood parasites are microscopic organisms and live in the blood cells of the dogs. The most commonly seen types of parasites are called Babesia canis, Babesia gibsoni and Erhlichia canis.

The parasites are transmitted to dogs from tick bites, hence the name ‘tick fever'. Unborn puppies could be infected through the womb of their mother.

How does my dog fall sick with tick fever?

It has been shown that there are some dogs which carry these blood parasites but they do not show any clinical signs. Thus, sometimes finding these blood parasites in the blood of your dog may not mean that your dog has tick fever.

It is thought that there are other factors involved which cause your dog to fall sick from these parasites, which include immune status, stress factors, genetics or breed. For example, German Shepherds are known to be very vulnerable to these parasites and they easily fall ill to tick fever.

Dogs fall ill due to infection with Babesia canis or Babesia gibsoni have low red blood cell count. These parasites live in the red blood cells, causing them to be abnormal, and the dog's body responds by destroying these red blood cells. In some cases, the parasites can also cause a drop in platelets number, causing bleeding problems.

Dogs fall ill due to infection with Erhlichia canis most frequently has low platelets, but their red blood cell and white blood cell numbers may also drop. It is thought that Erhlichia canis causes bone marrow dysfunction - bone marrow is important in the production of red blood cells, white blood cells and platelets. However, dogs with Erhlichia canis could have many different signs and these are not easily picked up. Sometimes, some dogs may just present with blindness or recurrent fever.

Loss of red blood cells cause the dog to be tired, pale, weak and can lead to organ failure; loss of platelets increases the tendency to bleed, leading to bruises, blood loss; lowered white blood cells can lead to poor immune system, leading to ease of getting secondary infections. All can lead to death!

Diagnosis

This is done from the clinical signs and blood tests. Diagnosis may not be always very easy in some cases as there are other diseases which have similar signs and blood tests results. These others disease include heartworm disease and autoimmune haemolytic anaemia (self-destruction of body's own red blood cells due to disorder in the immune system).

Treatment

Depending on the type of tick fever and the severity, this may include hospitalisation, certain injections (imizol or berenil), oral antibiotics (doxycycline, metronidazole), corticosteroids , or in severe cases blood transfusion. The treatment is aimed at lowering the number of parasites in the blood circulation, providing supportive care, preventing further destruction of the blood cells and platelets.

Prognosis

This depends on how early the treatment is given, the type of tick fever and the resistance of the dog. In most cases, relapse is common, as there is no effective drug in the world to completely kill off all the blood parasites once they get into the dog's body. The drugs we use will lower the parasite number but not eliminate them all. In cases of chronic Erhlichia infection, the prognosis is extremely poor - the dogs often eventually die from secondary infection or blood lost from low platelet counts.

Prevention

Once your dog has been infected with the blood parasites, there is always a chance of your dog falling ill due to tick fever or even when treated, relapses may occur. To prevent infection with these parasites, it is very important that your dog not have the chance to get infected --- they should be prevented against ticks, which transmit the parasite. The regular proper use of frontline spray or spot-on frontline should be effective against prevention of ticks.