Babesiosis in Dogs
Dr. Arnold Plotnick
Canine babesiosis is a tick-borne disease caused by the protozoan blood parasite Babesia. Although primarily a red blood cell parasite, Babesia can affect multiple organs. Hemolytic anemia, whereby the red blood cells are destroyed, is the hallmark of Babesia infection, many variations and complications can occur. Acute kidney failure
The organism that causes babesiosis is either Babesia canis or Babesia gibsoni. There are three subspecies of Babesia canis. One subspecies is found in Europe, another in northern Africa and North America, and the third in southern Africa. Babesia canis is pear-shaped and is usually infects red blood cells in pairs. Babesia gibsoni is round or oval, and is smaller than Babesia canis. It is found in Asia, North America, and eastern Africa.
Babesiosis is transmitted by ticks. A tick will feed on a dog that is sick or incubating the disease, and then feed on a susceptible dog. The incubation period following the tick bite is 10 to 21 days. Dogs of all ages can be infected, although it tends to be seen in dogs younger than three years of age. Other canids, such as wild dogs, jackals, and wolves are also susceptible. A seasonal variation in the number of cases diagnosed has been described in North America, with most cases occurring between March and October. In the southeastern United States, greyhounds have a higher prevalence than that of the general pet population.
The Babesia organism infects red blood cells. This causes hemolysis, which is destruction of the red blood cell. Fever and enlargement of the spleen may occur. Although the parasite infected red blood cells, it triggers an excessive inflammatory response that may cause widespread inflammation and multi-organ damage. The kidneys may be affected, and acute kidney failure may occur. The parasitized red blood cells may cause sludging in the small vessels in the brain, resulting in neurologic signs such as seizures, semi-coma, or coma. The excessive, unchecked inflammatory response that occurs throughout the body may affect the lungs, causing a serious condition called acute respiratory distress syndrome in which dogs show severe life-threatening respiratory compromise.
Canine babesiosis is often classified as uncomplicated or complicated. Uncomplicated babesiosis tends to have signs relating to anemia only, such as fever, anorexia, depression, pale gums, enlarged spleen, and bounding pulses. Uncomplicated babesiosis is further subdivided into mild, moderate, or severe, depending on the severity of the anemia. Mild uncomplicated cases may progress to severe uncomplicated disease, whereby the anemia becomes life threatening. Complicated babesiosis involves clinical manifestations that are unrelated to anemia.
Cerebral babesiosis (neurologic signs are the most evident)
Coagulopathy (blood clotting disorders)
Jaundice (yellow discoloration of the mucous membranes)
Acute respiratory distress syndrome
Acute kidney failure is an uncommon complication. Dogs with babesiosis and acute kidney failure will have abnormally elevated kidney values on their serum chemistry panels, and will have many abnormalities on their urinalysis. Most dogs will produce less urine than normal, and some will have total kidney shutdown and will not produce any urine at all.
Cerebral babesiosis involves the brain and is characterized by neurologic signs such as incoordination, partial paralysis of the hind legs, muscle tremors, different sized pupils, intermittent loss of consciousness, seizures, stupor, or coma. Fortunately, survivors of cerebral babesiosis often have no long-term neurologic deficits.
The most consistent abnormality on a complete blood count is a low platelet count, however, clinically apparent hemorrhage is rare.
In advanced cases of babesiosis, jaundice can occur. Jaundice is often seen in dogs that have anemia caused by destruction of their red blood cells, however, jaundice may also be due to liver damage, and this should always be considered and investigated in cases of babesiosis.
Acute respiratory distress syndrome is a severe, usually catastrophic complication of babesiosis. Dogs will experience a sudden increase in their respiratory rate, develop severely labored breathing, and may cough up frothy blood-tinged foam. This frothy discharge may come from the nose as well. A blood test that measures how well the lungs are oxygenating the blood confirms severe lung impairment. Radiographs also help confirm the diagnosis. This is a grave complication of the disorder, and most dogs succumb.
Dogs with babesiosis will occasionally present in shock. They will often be collapsed, and have either weak or bounding pulses, and pale or jaundiced gums. This is a life-threatening complication of babesiosis and requires immediate emergency care.