CONDITION
Ehrlichiosis
Ehrlichiosis is an infection caused by bacteria carried by ticks. These bacteria live inside certain white blood cells and can affect how the immune system functions, sometimes leading to problems with blood cells, clotting, or the body's ability to fight other infections. The condition is seen primarily in dogs that have travelled to or live in regions where specific tick species are found, particularly parts of continental Europe, Africa, Asia, and the Americas. Owners may notice signs that develop weeks to months after a tick bite, though the range is broad. These can include lethargy, reduced appetite, fever, unexplained bruising or nosebleeds, swollen lymph nodes, or joint discomfort. In some cases, signs are subtle or intermittent, and the infection may only be discovered during investigations for other concerns. Some dogs develop long-term effects if the infection persists. This page explores the signs that may prompt consideration of ehrlichiosis, what happens inside the body during infection, how the condition is investigated through blood tests and other means, and the approaches used to address it. The focus is on helping owners understand the shape of the condition and the thinking that guides decisions around it.
Why this matters now
Ehrlichiosis can affect dogs of any age, though it is often identified in adults that have travelled to or lived in regions where the brown dog tick or other carrier species are established. Young dogs and certain breeds, particularly German Shepherd Dogs and Belgian Malinois, may be more susceptible to developing clinical signs after infection. The condition is linked to tick exposure, so risk tends to be higher during warmer months when ticks are active, or following travel to endemic areas in continental Europe, the Mediterranean basin, Africa, parts of Asia, and the Americas.
The infection typically moves through phases, though not every dog shows signs at each stage. An acute phase may appear one to three weeks after the tick bite, with fever, lethargy, and mild bleeding tendencies. This can resolve on its own or progress to a subclinical phase where the dog appears well but the bacteria persist. In some cases, particularly if untreated, a chronic phase develops weeks to months later, with more persistent or severe problems affecting blood cells, the immune system, or multiple organs. The trajectory varies widely between individuals, and some dogs remain in the subclinical phase without further progression.
Signals & patterns
Early signals
Lethargy and reduced activity
The dog may seem less interested in walks, play, or usual routines, often appearing quieter or more reluctant to move. This can develop gradually over days to weeks and may be subtle enough to be attributed to other causes initially.
Reduced appetite or weight loss
A mild drop in interest in food, or a slower pace of eating, may be noticed. Some dogs lose weight over time, particularly if the infection persists or other signs develop.
Intermittent fever
Body temperature may rise and fall, though owners typically notice this as warmth to the touch, shivering, or general discomfort rather than measuring temperature directly. Fever may come and go, making it difficult to detect without observation over several days.
Swollen lymph nodes
Lymph nodes under the jaw, in front of the shoulders, or behind the knees may feel larger or firmer than usual. This reflects the immune system's response to the infection and is sometimes found during routine handling or grooming.
Mild bruising or small bleeds
Small purple or red spots may appear on the gums, belly, or inner ear flaps, or the dog may have brief nosebleeds or blood in the urine. These reflect early effects on platelets or clotting and can be easy to miss.
Later signals
Persistent or worsening bleeding
Nosebleeds, blood in the urine or stool, or larger areas of bruising may become more frequent or pronounced. This signals more significant disruption to platelet numbers or function.
Lameness or joint swelling
Stiffness, reluctance to bear weight, or visible swelling in one or more joints can develop as the infection affects joint linings or causes immune-mediated inflammation. This may shift between legs or persist in one area.
Neurological or eye changes
Some dogs develop signs such as head tilt, loss of balance, seizures, or changes in the appearance of the eyes, including cloudiness or bleeding inside the eye. These patterns suggest more widespread or severe involvement.
Marked pale gums or weakness
Gums may appear white or very pale pink, and the dog may tire quickly, breathe more rapidly, or collapse after mild exertion. This can reflect severe anaemia or low platelet counts affecting oxygen delivery and clotting.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
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