Blood Parasites of Dogs (Haemobartonellosis)

Haemobartonellosis is a medical term for a parasitic blood infection transmitted to our dogs by ticks and fleas. Haemobartonellosis is the result of infection of the red blood cells by the mycoplasma parasite M. haemocanis.

Mycoplasma haemocanis is a parasite that lives on the red blood cells of affected dogs. Infections do not usually cause signs, but red blood cell destruction (hemolysis) can be seen in dogs that have had their spleens removed.

The mycoplasma is a class of bacterial parasites belonging to the order of Mollicutes. They are able to survive without oxygen, and lack true cell walls, making them resistant to antibiotics and therefore a greater challenge to detect and treat. They are the most common cause of urinary tract infections and pneumonia.

The parasites are transmitted through the transfer of infected blood (for example, blood transfusions or contaminated needles) or through the bites of lice, flies, ticks, and mosquitoes.

Causes of Haemobartonellosis in Dogs

Most cases of Haemobartonellosis are caused by M. haemocanis in dogs. M. haemocanis is transmitted to dogs by the brown dog tick, Rhipicephalus sanguineus, or by contact with infected blood such as receiving a blood transfusion with infected blood. The mycoplasmas attach to the surface membrane of the red blood cells causing the blood cells to become fragile and damaged. This decreases the lifespan of the red blood cells and can lead to hemolysis and anemia.

Symptoms of Haemobartonellosis in Dogs

Parasitic blood infections in dogs are quite noticeable and need medical treatment as soon as possible. Symptoms of Haemobartonellosis include:

• Loss of appetite
• Tiredness
• Listlessness and weakness
• White to purple colored gums
• Depression
• Weight loss
• Fever

Diagnosing Haemobartonellosis in Dogs

Haemobartonellosis is diagnosed on complete blood count (CBC) or with polymerase chain reaction (PCR). There may be frank blood loss, although commonly the anaemia may be normocytic normochromic. The PCV may decline to 15% or lower. Clinical signs occur once the PCV falls below about 20% by which time about 50% cats have large numbers of parasitised erythrocytes in circulation.

Several different Haemobartonella-specific PCR tests are available, targeting the 16S rRNA subunit gene for the different species. PCR for FIA is generally more sensitive than other methods of diagnosis, e.g., haematology.

Treatment and Prognosis

Treatment with doxycycline, tetracycline or oxytetracycline is usually effective. Supportive treatment of blood transfusions may be needed in severe cases. Glucocorticoids can also be administered. The PCV should be monitored until it has returned to a normal level and clinical signs have resolved.

Infection with Haemobartonellosis is usually non-pathogenic unless the dog have had a previous splenectomy or chemotherapy, in these cases the prognosis depends on the severity of clinical signs and level of concurrent disease but treatment is usually successful.