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Tick Fever Ehrlichia

Ehrlichia canis is a blood-borne disease of dogs spread by ticks. The tick transmits the disease to the dog during feeding and previously clear ticks will pick up Ehrlichia from an infected dog.

Many dogs are bitten by more than one tick, and some ticks may also carry other diseases, mainly Babesia, so it is possible for a dog to have more than one disease at a time!

Clinical Signs

Dogs may develop acute (recent) infection or chronic disease months or even years later. The parasite infects and destroys platelets, small cells within the blood vital in the process of clotting.

As a result fever and clotting abnormalities are predominant.

Clinical signs vary widely and can include

-       fever, anorexia and dullness

-       enlarged spleen (splenomegaly) and lymph nodes (lymphomegaly)

-       areas of bruising under the skin or in the mouth and spontaneous nosebleeds

-       inflammation within the eyes

-       Joint and muscle pain and resultant lameness (rare)

-       Central nervous signs such as seizures (rare)


Comprehensive laboratory tests are required

-       A complete blood count (CBC) is required to determine platelet levels and also white and red blood cells

-       Biochemistry to determine general organ function

-       Blood testing for antibodies to Ehrlichia. This is easily done on site at Acorn with a simple kit. Because it measures antibodies to the disease, rather than the disease itself, it may not reliably differentiate between active infection and a dog previously exposed. By taking samples 2 weeks apart, a rise in antibodies indicating active infection can be seen but this is often not practical in critically ill patients

-       A PCR test measuring Ehrlichia DNA (ie the parasite itself) can routinely be performed now.


Doxycycline is given for a minimum of 4 weeks, usually with food as it can cause stomach upsets in some dogs.

This is usually effective, but if not , a course of imidocarb (“Immizol”) can be given by injection.

In extremely severe cases a blood transfusion may be needed to provide fresh platelets but this is rarely required.

Follow Up and Prognosis

Normally clinical signs improve within several days of starting medication, and follow-up bloods are usually advised to monitor platelet levels.

Tick prevention is VITAL to reduce the risk of infection/ re-infection and we recommend monthly Frontline and an effective tick collar in dogs potentially exposed to ticks.

Prognosis is usually good, but more guarded in seriously ill dogs with central nervous signs

There is some evidence to suggest E canis occurs in people but is not thought to be direct infection from dogs. Tick exposure is thought to be necessary.