Ehrlichiosis is a tick-borne disease caused by one of several organisms. It is most often transmitted through the bite of the brown dog tick. Although seen more often in the southeastern part of the United States, it has been reported throughout the country. It can occur in any age or breed of dog, and is most common in the German shepherd dog. Rocky Mountain spotted fever (RMSF) is another tick-borne rickettsial disease that can present with similar signs, especially in the early stages.
Different phases of the disease are associated with different clinical signs. The acute (immediate) phase develops within 8 to 20 days after the parasite enters the body. This delay between infection and manifestation of clinical signs is called the incubation period. The acute phase often lasts for two to four weeks. In some dogs, the acute phase resolves spontaneously without the dog showing any clinical signs.
Some dogs go on to develop a subclinical infection that persists for months. The parasite remains in these dogs, but no clinical signs are produced. The disease may also enter a chronic phase, which generally occurs two to three months after infection and can last for months to years. Dogs with chronic disease may show a variety of clinical signs. Ehrlichiosis may be associated with subtle nonspecific signs like lethargy, depression, anorexia and fever, or it can have a major impact on certain blood components, such as the platelets, red blood cells, and white blood cells. Decreased numbers of platelets (thrombocytopenia) are common and may be associated with life-threatening bleeding.
There are several diseases or disorders that appear clinically similar to ehrlichiosis. These include:
Immune-mediated thrombocytopenia is a disorder in which the body's immune system destroys it's own platelets. Thrombocytopenia is often seen in ehrlichiosis.
Systemic lupus erythematosus (SLE) is a disorder in which the body's immune system breaks down and affects many different systems in the body, such as the joints and kidneys.
Multiple myeloma is a malignant cancer of the white blood cell called the plasma cell. It may induce a high protein level in the blood, similar to ehrlichiosis.
Chronic lymphocytic leukemia, a type of cancer of white blood cells, may be confused with ehrlichiosis in cases that have certain changes in the bone marrow.
There are many other diseases that can cause bleeding problems, enlargement of the liver and spleen, and vague signs of fever and weight loss that must also be ruled out.