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Babesia And Other Tick - carried Infections In Your Dog

Babesiosis

 

Ron Hines DVM PhD

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What Are Babesia?

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 kinds of babesia, 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 red blood cells of your pet. 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. I associate this with the unsanitary lifestyle many of these breeds endure rather than any increased sensitivity of these breeds. Sub clinical (silently infected) and carrier dogs are common. There are three subtypes of B. canis that differ in strength (virulence), where they are found and which tick species is likely to carry 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 quite ill. These ill dogs are very pale and 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. Dogs that have improved on their own may relapse with stress and exertion.

When your pet encounters a tick that has fed on an infected dog, the disease is transmitted. There have been a few instances where pregnant dogs spread the parasite to their unborn puppies and a few where the disease was spread through a dog bite.

How is Babesiosis Diagnosed In Your Pet?


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, heavy exertion 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 their liver’s ability to process them. The color change is particularly apparent in the whites of the eyes of these pets. 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 “bulls eye” 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 somewhere,

I send blood off a blood sample for an indirect fluorescent antibody test. Dogs with the peracute form of the illness can die before their treatment has a chance to take effect and dogs that have recovered may still have positive antibody tests. The best test currently available is the PCR-test (polymerase chain reaction test).

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 pets 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. If the dog is not overweight or anxious, this can be readily felt by the veterinarian. The pets 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.

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

What Treatments Do We Have?

If your pet is severely anemic, it may require a blood transfusion.

In dogs that are not treated, the chronic stimulation of the immune system, associated with persistent infection can result in chronic kidney inflammation (glomerulonephritis), liver failure and inflammation of the blood vesicles (vasculitis). Each of these problems require treatment of their own.

We treat this disease with anti-babesiosis drugs, intravenous fluids, blood building tonics and good nursing care. Unfortunately, all medications that kill this parasite are harsh on your pet's body. Treatment with these drugs should not be undertaken solely on the basis of parasites having been seen in your pet's blood or a positive antibody test in the absence of marked anemia. We also know that these medications may not kill all the parasites.

Imidocarb dipropionate (Imizol, Burroughs Wellcome, Schering-Plough) is the only approved drug for this disease in the USA. It is given by deep muscular injection because it causes severe inflammation. A single dose is usually sufficient for Babesia canis but two doses, given two weeks apart are needed for Babesia gibsoni other smaller Babesias. 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.

Diminazene Aceturate (Berenil)

This drug is not available in the U.S. It has worked well in other countries where it is sold for human trypanosomiasis. A single injection is effective against Babesia canis but more must be used for other babesia. It has a lot of serious side effects that include pain at the site of injection, drop in blood pressure seizures and other reactions that have been fatal.

Pentamidine isethionate (NebuPent), an antipro-tozoal agent is a medication sold in the US primarily to treat Pneumocystis pneumonia in HIV patients. It seems to have potential in treating babesia as well.

Trypan Blue This old-fasioned medication may help pets, but it will not eliminate the parasite entirely.

Other medications that have been tried are quinuronium sulfate and combinations of quinine and azithromycin in combination with atovaquone or clindamycin. Because Babesiosis can get better spontaneously, it is difficult to decide how effective these medications really are until we have tried it in more infected dogs.

How Can We Prevent This Disease?

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) or Revolution (Selamectin) drops are quite effective in repelling ticks. Frontline spray is more effective than the dropper form. I have noticed that in Florida and South Texas, ticks and fleas are becoming resistant to Frontline and Advantage. Oral spinosad containing products such as Comfortis are being used more in these areas to eliminate fleas - but they do not kill ticks. Livestock producers have found that spinosad topical sprays do eliminate ticks. I have not encountered problems using these sprays where dogs reside.with monthly fipronil spray (Frontline Plus) or Revolution (Selamectin) drops are quite effective in repelling ticks. Frontline spray is more effective than the dropper form. I have noticed that in Florida and South Texas, ticks and fleas are becoming resistant to Frontline and Advantage. Oral spinosad containing products such as Comfortis are being used more in these areas to eliminate fleas - but they do not kill ticks. Livestock producers have found that spinosad topical sprays do eliminate ticks. I have not encountered problems using these sprays where dogs reside.