Tick Bite Fever (Ehrlichiosis) in Dogs

Tick Bite Fever (Ehrlichiosis) in Dogs

Tick Bite Fever in dogs is caused mainly by Ehrlichia Canis, a blood parasite of the rickettsia group. The parasites are microorganisms that infect the blood of various animals. They are transferred to dogs by the brown dog tick. When a dog is bitten by a tick, the parasite is injected into the blood system. Today it is assumed that in order to transfer the bacteria, the tick must stick to the dog’s flesh for at least 24 hours (if the tick sticks for a shorter period of time, the bacteria will not be transferred, and tick bite fever will not occur).
The disease-bearing parasite is not carried by every tick; however, one infected tick is enough to infect the dog.

Is tick bite fever contagious to humans?
The blood parasite which infects dogs is not contagious or dangerous to human beings. However, it should be remembered that the ticks transferring the disease to the dog may be carriers of other diseases which are threatening to humans.


Disease stages in dogs
Incubation period – the incubation period lasts from the moment of infection until the outbreak of the clinical disease, and ranges anywhere from 7 to 21 days. During this period there are no visible signs of the disease.
Acute stage - the first symptoms of the disease are apparent.
Subclinical stage – the dog is a carrier of the bacteria, but no signs of the disease are visible.
Chronic stage – the stage which is hardest to treat; the dog is very ill by this stage.
It should be noted that not all dogs reach the chronic stage; some manage to get over the disease at an earlier stage  (either independently or aided by medication).

The acute stage
This stage lasts between 14 and 30 days, during which the bacteria are distributed throughout the organs. In Israel, this stage of the disease is usually diagnosed during the summer, when ticks are most prevalent.

Symptoms of tick bite fever during the acute stage
Fever, enlarged lymph nodes, minor dermal bleeding, nose bleeding (very common), red-eye / enlarged blood vessels in the eye, weakness and lack of appetite.
Some dogs exhibit relatively minor symptoms, and their owners may not realize that they are sick. Blood tests at this stage will mainly show low levels of blood platelets.
It should be remembered that correct and swift treatment at this stage will lead to a quick recovery; dogs that are not adequately treated will continue to carry the parasite and will progress to the subclinical stage or even the chronic stage.

The subclinical stage
During this stage the dog carries the bacteria that cause tick bite fever, but does not exhibit any symptoms of the disease! The dog may appear perfectly healthy, but the disease continues to develop.
This stage may continue for months or even years. The dog may even recover spontaneously and never reach the chronic stage, in which symptoms are once again visible.

The chronic stage
This stage is characterized by significant weight loss, weakness, depression, pale mucous membranes, acute anemia, fever, peripheral edema, diarrhea, bloody urine, bleeding in the skin, mucous membranes and nose (due to bone marrow damage) and damage to the eye – infections and even blindness (due to bleeding behind the retina). By this stage, unfortunately, treatment does not always prove useful and the dog may not always be saved.

Diagnosis of tick bite fever
Diagnosis is based on a combination of clinical signs and findings from blood tests: a PCR scan to test for presence of the bacteria's genetic data in the blood (a very reliable test), and blood counts indicating lowered levels of platelets / white blood cells / red blood cells.

Treating tick bite fever
The most effective and preferred treatment is an antibiotic called Doxycycline (Doxylin). In severe or chronic cases steroids may be administered in order to restrain a possible overreaction of the immune system, which may cause the destruction of blood cells and platelets.
In case of severe anemia, there may be a need to administer blood transfusions or hormones (such as Erythropoietin), which encourage the production of red blood cells. If a severely low level of white blood cells is detected, hormones may be administered to rectify this as well.
Some cases call for hospitalization, subcutaneous or intravenous fluids, medication to lower fever, or iron and vitamin supplements. Treatment during the chronic stage is lengthy, complicated and very costly due to the high costs of substances and hospitalization. Therefore, preventive care against ticks has been proven as the most efficient way to combat the disease, and should not be underestimated.

Chances of recovery
If tick bite fever is diagnosed in its early stages and treated with antibiotics, the prognosis is good. Unfortunately, if the disease is only diagnosed in the chronic stage, chances of recovery are slim.

How can one prevent the infection of dogs with tick bite fever?
Regrettably, there is currently no vaccine against tick bite fever, and even a dog that has had the disease before is not immune to contracting it again. The most effective way to combat infection is to prevent the dog from being exposed to ticks. This must be done by regular use of anti-tick substances – collars, sprays or drops – as recommended by a veterinarian. Bear in mind that although ticks and the disease are more prevalent in the summer, infection during the winter is possible, if the weather is warm enough. Therefore, preventive care against ticks is recommended year round. In cases of severe tick infestations in your area, an exterminator should be consulted, to rid your dog’s environment of ticks as much as possible.

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