The clinical spectrum of H. canis infection ranges from subclinical to severe life-threatening disease. An asymptomatic to mild disease is the most common presentation of the infection and is usually associated with a low level of H. canis parasitemia (1-5%), while a severe illness is found in dogs with a high parasitemia often approaching 100% of the peripheral blood neutrophils. High parasitemia rates are frequently accompanied by extreme neutrophilia. H. canis is commonly associated with co-infection of other diseases, in particular ehrlichiosis, leishmaniosis and babesiosis in endemic areas, and clinical presentations are variable: fever, emaciation, lethargy, anorexia, lymphadenopathy, pale mucus membranes associated with anemia, and muscle pain.

H. americanum infection is almost always a severe disease that leads to debilitation and death. Most dogs show fever, gait abnormalities (stiffness, hind limb paresis, ataxia and inability to rise) and muscular pain induced by myositis, generalized muscular atrophy and mucopurulent ocular discharge. The pain can be generalized or localized in the lumbar and cervical spine, or joints. A marked neutrophilia is one of the consistent haematological findings. Serum biochemical abnormalities include increased alkaline phosphatase acitivity and hypoalbuminemia.

Further information

• Shaw, S.E. et al.: Tick-borne infectious diseases of dogs. Trends Parasitol., 17, 2001, 74-80 (Download)
• Baneth, G.: Hepatozoonosis. In: Arthropod-borne Diseases. BSAVA Congress, Birmingham, Scientific Proceedings, 2002 (Download)