Anaplasmosis / Anaplasma phagocytophilum (dog)

Pathogen / Biology

The causative agent of canine granulocytic anaplasmosis is Anaplasma phagocytophilum, a Gram-negative, obligately intracellular bacterium of the family Anaplasmataceae. Unlike Ehrlichia canis, it infects neutrophils, where it multiplies in morula-like inclusions. A related species, Anaplasma platys, infects platelets and causes infectious cyclic thrombocytopenia in dogs.

Transmission / Epidemiology

Anaplasma phagocytophilum is transmitted by hard ticks of the genus Ixodes; in Europe, this is primarily the common wood tick (Ixodes ricinus). Since the same vector also transmits Borrelia burgdorferi, co-infections occur. The pathogen has a broad host range and is of zoonotic significance as the causative agent of human granulocytic anaplasmosis; its distribution follows that of Ixodes ticks and increases with longer tick seasons.

Course & Symptoms

Many infected dogs show no obvious symptoms. If clinical signs do appear, they usually occur during the acute phase one to two weeks after transmission: fever, lethargy, loss of appetite, and often lameness due to painful joints. Less commonly, vomiting, diarrhea, coughing, or respiratory distress may also occur. A decrease in blood platelets (thrombocytopenia) is a common laboratory finding. The prognosis is generally favorable.

Diagnostic Relevance

The clinical presentation resembles that of other tick-borne diseases, particularly Lyme disease and granulocytic ehrlichiosis, and cannot be definitively diagnosed based on clinical findings alone. The detection of antibodies indicates an immune response to the pathogen; however, antibodies may not yet be present in the very early phase of infection. Due to the shared Ixodes vectors and the possibility of co-infections, it is advisable to test for Borrelia and Ehrlichia simultaneously.

Rapid Test Component

The Fassisi® combination tests CanVecto 3 and CanVecto 4 detect antibodies against Anaplasma phagocytophilum in serum, plasma, or whole blood, in each case alongside other vector-borne pathogens. CanVecto 3 additionally detects antibodies against Borrelia and Ehrlichia canis, while CanVecto 4 additionally detects Dirofilaria immitis antigen as well as antibodies against Leishmania and Ehrlichia canis. This facilitates the identification of multiple pathogens from a single sample in cases of tick-borne diseases.

The technical details are documented on the sources page.