Ron Hines DVM PhD 4/21/06

Babesias are microscopic blood parasites that cause disease in many animals. This group of protozoal organisms are spread from dog to dog by ticks. In the United States, babesiosis of dogs are spread by the brown dog tick (Rhipicephalus sanguineous). It can also be spread through infected blood transfusions. Two of them, B. canis (“large” babesia) and B. gibsoni (“small” babesia) cause the sudden destruction of blood known as acute hemolytic anemia in dogs. These parasites live within the cytoplasm of the red blood cells. In the past, B. gibsoni was associated with Asia, Africa and the Middle East. But from 1979 on it has been found in several locations in the United States. The most commonly affected dogs are pit bull terriers and greyhounds. Subclinical and carrier dogs are common. There are three subtypes of B. canis that differ in strength (virulence), geographic location and the tick that carries them. In the United States the most common strain is B. canis vogeli which is the weakest of the strains. Most dogs infected with this babesia show no symptoms. However, occasionally young dogs will become severely ill. These ill dogs are very anemic and their blood fails to clot. This organism is now found throughout the Southeastern United States where it is especially common in greyhounds. Thirteen percent of shelter dogs in California were also positive for Babesia canis.

Diagnosis:
There are three forms of the disease, peracute, acute, and chronic. In the fulminating or peracute form, young dogs arrive at the animal hospital not eating, depressed and weak. Their gums are very pale and they are generally running a fever. Often these dogs recently weathered a stressful situation such as another illness, hard work or surgery. Dogs that have this disease usually arrive with substantial anemia. They are often jaundiced (yellow) due to large amounts of blood pigments present in their skin. This occurs when destroyed red blood cells overwhelm the liver’s ability to process them. The color change is particularly apparent in the whites of their eyes. When I see a jaundiced anemic animal several diseases come to mind. The one I see the most is acute autoimmune anemia, the second is zinc toxicity and the third is babesiosis. I usually stain a thin film of blood taken from the earflap or toenail of these animals in my office. It is common to see “bullseye” appearing red blood cells that lack the proper amount of hemoglobin. When I am fortunate I will see the parasites. Babesia gibsoni organisms can easily be overlooked in a blood smear because they are small, usually single and variable in shape (pleomorphic). If I do not find any parasites but still suspect that they are there I send blood off for an indirect fluorescent antibody test. Dogs with the peracute form of the illness can die before treatment has a chance to take effect.

In the acute form of the disease the same symptoms are present but they are less severe. In the chronic form of the disease the dogs just don’t have much energy. They are anemic but not severely so. Examination of the blood from these dogs may not detect the parasite. One does find a large number of immature red blood cells (regenerative anemia) because the body sends them into circulation prematurely to make up for those that are lost to the disease. These dogs also have a very enlarged spleen. They are rarely jaundiced. Most owners complain that their dog just doesn’t have the pep it once did. These dogs are usually thin and if they run a fever it is low and intermittent. Kidney and liver function in these dogs is often poor. Laboratory tests on the blood of these patients show, besides regenerative anemia, increased red cell pigments free in the blood and urine. Sometimes, enzymes that measure liver function (AP, ALT and LDH) as well as tests that measure kidney function (BUN, Creatinine) are elevated, indicating damage to these organs. Unfortunately this disease is often misdiagnosed as autoimmune hemolytic anemia because tests for autoimmunity become positive in babesiosis.babesia dog babesiosis

In dogs that succumb to the disease pathological examination of the liver often shows severe hepatitis (centrilobular hepatitis), inflammation of the arteries (multifocal necrotizing arteritis) and kidney inflammation (membranoproliferative glomerulonephritis) as well as inflammation of the lymph nodes (lymphadenopathy)

Treatment:
We treat this disease with anti-babesiosis drugs, intravenous fluids, blood building tonics and good nursing care. Imidocarb dipropionate (Imizol, Burroughs Wellcome, Schering-Plough) is the drug of choice. It is given at 2.5 mg/pound body weight by deep muscular injection every two weeks for two treatments. Sometimes dogs are simultaneously infected with a second parasite, Ehrlichia canis. When this is the case imidocarb destroys them both. Some dogs treated by this method recover very rapidly but others do not. Many cases relapse and those that do recover may become chronic carriers that transmit the disease to other dogs.

In dogs that are not treated, the chronic antigenic stimulation associated with persistent infection can result in chronic kidney inflammation (glomerulonephritis), liver failure and inflammation of the blood vesicles (vasculitis).

Prevention:
The secret of keeping the dog free of babesia is good tick control.
Check your pet and yourself daily for ticks and remove them. Be particularly thorough in brushing and combing if your pet has been in high weeds or brush. In removing the ticks try not to crush them. The best way I have found to remove them is to grasp the ticks mouth parts as close to the skin as possible with a pair of small tweezers and pull the tick away removing all of the head a small tag of skin. Ticks secrete a liquefying enzyme into the skin surrounding their mouth parts. Removing a small tag of skin with the tick allows for quicker healing in the long run.

Treat your yard with insecticides approved for controlling ticks or hire a professional to do so.

Uses shampoos and dip products that kill and repel ticks.

Keep your yard closely mowed. Clear brushy areas that harbor ticks and trim your trees so that sunshine reaches the ground.

For dogs, collars that contain amitraz (Preventic Collars) combined with monthly fipronil spray (Frontline Plus) are quite effective in repelling ticks. Frontline spray is more effective than the dropper form.

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