Ehrlichiosis (canine)
Ehrlichiosis in dogs is a tick-borne disease caused by bacteria of the genus Ehrlichia. The most common causative agent is Ehrlichia canis, but other species, such as Ehrlichia ewingii and Ehrlichia chaffeensis, can also cause infection.
Transmission:
The primary mode of transmission is through the bite of infected ticks. The brown dog tick (Rhipicephalus sanguineus) is the most important vector for Ehrlichia canis. When a tick feeds on an infected dog, it ingests the bacteria. The bacteria then replicate within the tick and can be transmitted to another dog during a subsequent feeding.
Pathophysiology:
Once transmitted, Ehrlichia organisms infect white blood cells, specifically monocytes and macrophages. The bacteria multiply within these cells, eventually causing them to rupture and release more bacteria into the bloodstream. This infection triggers an immune response, leading to inflammation and damage to various organs.
Clinical Signs:
The clinical signs of canine ehrlichiosis can vary depending on the stage of infection (acute, subclinical, or chronic) and the individual dog's immune response. Common signs include:
- Fever
- Lethargy
- Anorexia
- Weight loss
- Enlarged lymph nodes
- Bleeding disorders (e.g., nosebleeds, bruising)
- Lameness or stiffness
- Neurological signs (e.g., seizures, incoordination)
- Eye problems (e.g., uveitis)
Diagnosis:
Diagnosis of canine ehrlichiosis typically involves a combination of clinical signs, blood tests, and serological tests.
- Blood tests: Complete blood counts (CBC) may reveal anemia, thrombocytopenia (low platelet count), and leukopenia (low white blood cell count) or leukocytosis (high white blood cell count).
- Serological tests: These tests detect antibodies against Ehrlichia organisms in the dog's blood. Common tests include indirect fluorescent antibody (IFA) assays and enzyme-linked immunosorbent assays (ELISA). Polymerase chain reaction (PCR) testing can also be used to detect Ehrlichia DNA in blood or tissue samples.
Treatment:
The primary treatment for canine ehrlichiosis is antibiotics. Doxycycline is the most commonly used antibiotic and is typically administered for several weeks. In some cases, supportive care, such as blood transfusions or intravenous fluids, may be necessary.
Prevention:
Preventing tick bites is the most effective way to prevent canine ehrlichiosis. This can be achieved through:
- Using tick preventative medications (e.g., topical spot-ons, oral medications, tick collars)
- Regularly checking dogs for ticks and removing them promptly
- Avoiding tick-infested areas
Prognosis:
The prognosis for canine ehrlichiosis is generally good if diagnosed and treated early. However, chronic infections can be more difficult to treat and may result in long-term complications.