What is ehrlichiosis?
Ehrlichiosis (also named canine rickettsiosis, canine hemorrhagic fever, and canine typhus) is a tick-borne infectious disease of dogs, usually carried by the brown dog tick. It first gained attention as a significant disease when military dogs returning from Vietnam during the 1970s were found to be infected. Because of its origin in military dogs in Vietnam, it has also been called tracker dog disease and tropical canine pancytopenia. The disease seems to be particularly severe in German Shepherd Dogs and Siberian Huskies due to a reduced cell-mediated immune response.
The organism responsible for this disease is a rickettsial organism. Rickettsiae are similar to bacteria. Ehrlichia canis is the most common rickettsial species involved in ehrlichiosis in dogs, but occasionally other strains of the organism will be found. We noticed that we see this disease more and more often in our UAE Pet Population and therefore in our Al Barsha Veterinary Clinic.
The disease develops in dogs after they got bitten by an infected tick. The brown dog tick is the main carrier in nature. Other tick species have also been shown to transmit Ehrlichiosis in dogs and may carry other subspecies of Ehrlichia.
The signs of the disease can be divided into three stages:
- Acute stage (early disease)
- Subclinical stage (no clear signs of the disease)
- Chronic or clinical stage (long-standing infection)
In the United Arab Emirates, where ehrlichiosis is common, many dogs are seen during the acute phase. In this stage, infected dogs may have a fever, swollen lymph nodes, respiratory distress, weight loss, bleeding disorders (spontaneous hemorrhage or bleeding),
and occasionally, neurological disturbances (they may seem unsteady or develop meningitis). This stage may last two to four weeks and some dogs may eliminate the infection or head into the sub-clinical phase.
The sub-clinical phase represents the stage of infection in which the organism is present, but not causing any outward signs of disease. Sometimes a dog will pass through the acute phase without its owner being aware of the infection. These dogs may become sub-clinical and develop changes observed at the laboratory level, yet have no apparent signs of illness. The sub-clinical phase is often considered the worst phase because there are no clinical signs and therefore the disease goes undetected. The only hint that a dog may be infected during this phase may be after a blood sample is drawn when the dog shows prolonged bleeding from the puncture site. Dogs that are infected sub-clinically may eliminate the organisms or may progress to the next stage, clinical ehrlichiosis.
Clinical ehrlichiosis occurs because the immune system is not able to eliminate the organism. Dogs are likely to develop a host of problems: anemia, bleeding episodes, lameness, eye problems (including hemorrhage into the eyes or blindness), neurological problems, and swollen limbs. If the bone marrow (site of blood cell production) fails, the dog becomes unable to manufacture any of the blood cells necessary to sustain life (red blood cells, white blood cells, and platelets).
It may be difficult to diagnose infected dogs during the very early stages of infection. The immune system usually takes two to three weeks to respond to the presence of the organism and develop antibodies. Since the presence of antibodies to E. canis is the basis of the most common diagnostic testing, the early stages of disease dogs may be infected, yet test negative. Testing performed a few weeks later will reveal the presence of antibodies and make confirmation of the diagnosis possible. At the clinic, we can perform an in-house screening test using a special test kit to see if you dog was exposed and seropositive. Additionally, we may use PCR (polymerase chain reaction) or IFA (indirect fluorescent antibody) tests to determine the severity or species of Ehrlichia that is infecting your dog. These tests are sent to more advanced laboratories for analysis.
Detection of antibodies with the special test kit, coupled with appropriate clinical signs, is the primary diagnostic criteria. Baseline blood tests including a complete blood cell count and chemistry should also be done. A low platelet count (called thrombocytopenia), anemia (low red blood cell counts), and/or high levels of the protein globulin in the blood may be found.
Dogs experiencing severe anemia or bleeding problems may require a blood transfusion. However, this does nothing to treat the underlying disease.
Certain antibiotics, such as doxycycline, are quite effective. A long course of treatment, generally three-four weeks, is needed. This is the treatment of choice as it is easily accessible and generally well tolerated. Our veterinarians will discuss treatment options with you as some supportive medications such as steroids may be needed depending on the clinical state of the patient and blood parameters.
Tick preventives are the most effective means of prevention. Topical options include Advantix (Bayer). Oral chewable options include Bravecto (Merck Animal Health). There are also collars available. Our veterinarians are more than happy to discuss with you the best option for your dog.
Although humans cannot get Ehrlichiosis from their dogs, humans can get canine ehrlichiosis from tick bites.
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