Heartworm Treatment For Boxer Dogs

Heartworm disease is caused by the parasitic roundworm Dirofilaria immitis that live in the arteries of the lungs and right side of the heart of dogs, which are considered the definitive host for heartworms. Heartworms can also affect cats, other mammal species and to a rare extent, humans. Dogs and cats of any age regardless of the breed are highly susceptible to Heartworm infection.

Heartworm infections have received in-depth studies on canines since this is a very important disease condition in dogs. Many cats may have died due to heartworm disease, but because of the absence of clinical signs and definitive diagnostic tests to confirm the presence of the heartworm in cats.

Transmission of Heartworm infection occurs when infective larvae of Dirofilaria immitis is carried by a mosquito which passes on the infection each time that it bites a dog. The infective larvae then grow and migrate in the body over a period of several months and until they develop to become sexually mature male and female worms. These adult heartworms are usually found lodged in the right side of the heart and the arteries of the lungs. Mating gives rise to offspring which are released into the bloodstream.

Unlike dogs, the adult heartworms do not give birth to microfilaria in cats. Thus cats are infected from a mosquito which has fed from an infected dog. Since the body of the cat treats the presence of heartworm as foreign, the body may form cysts in the brain, liver, kidneys and other vital organs to stop the invasion of the heartworm. This is the reason why cats with Heartworms do not show definitive signs indicative of the disease condition. Cats may exhibit certain signs associated with a defect in the nervous system such as circling and seizures. They may also have liver and kidney failures, or sudden explained death. But in dogs, the main sign associated with Heartworm disease is a slow progressing heart failure.

Tests to Detect Heartworms:

Diagnostic tests for Heartworms are made by extracting and examining blood of the patient.

Occult Heartworm Test. This is a serological test where blood is processed with a Heartworm detection kit to detect antibodies to the adult heartworms. This is the latest test used for Heartworm diagnosis since it is more sensitive for detecting the presence of adult worms in the heart. Microfilaria Test. An old method of Heartworm diagnosis and it is used to detect microfilaria present in the blood. The problem with this method is the possibility of yielding false negative results in situations where the adults are not producing microfilaria especially with an all male or all female heartworm infections. The time of blood extraction is also a contributing factor in the outcome of the test because microfilaria do not circulate in the bloodstream during the day hours. Aside from the above tests, x-rays, angiography and echocardiography (ultrasound) can also help detect the presence of Heartworm infection in both dogs and cats.

Modes of Treatment of Heartworm Infection

Veterinarians often give a poor prognosis for cats found to be positive for Heartworms. Treatment in cats has been observed to reach a 70% treatment fatality rate. This adverse outcome is due to the apparent sensitivity of cats to the drugs that are used to treat Heartworm. The line of treatment which has been successful in dogs cannot be used in cats for the reason that cats tend to form blood clots that can plug blood vessels thereby killing the patient. Approximately 70% of cats have been found to die during the treatment process.

At present, there are no Heartworm medications in the United States approved for the treatment of Heartworm infections in cats.

In cats, the best line of treatment would be to go for symptomatic and supportive treatment—such as intravenous fluids, oxygen therapy, cage confinement, bronchodilators, cardiovascular drugs, antibiotics and proper nursing care—the adult heartworm will die in two or three years time within the cat’s body, thus losing the foreign body. When x-rays reveal lung disease, small tapering doses of prednisone is often prescribed. This favorable development will only occur if there is no further infection from infected mosquitoes.

Surgical removal of Heartworms can also be done with the visualization provided by ultrasound of the tricuspid valve or in the right atrium.

Heartworm treatment in dogs is often very risky and expensive. Although the serological test can tell us whether there is the presence or absence of Heartworm, it does not give the amount or quantity of adult heartworms present.

When a dog suspected to be harboring Heartworms is brought to the veterinarian, there will be many tests to be performed before a line of treatment can be formulated. Blood tests and x-rays have to be performed. If the tests come out positive, then a drug is given through the intravenous or intramuscular route for two days to slowly but surely kill the adult heartworms. Slowly, because sudden killing of all adult heartworms at a single time can result in these dead worm blocking smaller blood vessels causing the death of the patient.

But if the worms will be slowly killed, then the body’s macrophages, the body’s defensive cells, will have time to reduce and engulf the remains of the adult worms.

This treatment procedure is done when the dog is still confined in the hospital so that the veterinarian can keep an eye on him and can readily detect any adverse reaction to the treatment.

After two days, the dog is ready to go home, but with orders to keep him calm for the next six weeks or so. Exciting him would increase the heart rate sending worm debris into small blood vessels which can still result in the death of your dog. At this time, the owner should be vigilant in observing signs of pneumonia brought about by the death of worms in the lungs. They should readily report any signs of pneumonia so that the dog can be given antibiotics and supportive care.

After six weeks, you bring back your dog to the veterinarian for microfilaria treatment. This is an oral medication and you can bring your dog back to your home.

After two weeks, a microfilaria check will have to be conducted again. The presence of microfilaria will reveal the presence of adult Heartworms and the long process must start all over again. Bit these situations happen only once in a while.


Prevention is still the best course of action to consider. If you live in an area infested by mosquitoes, then your dogs and cats should be taking heartworm preventative.

You can choose from two types of heartworm preventative medications—daily or monthly. The purpose of these heartworm preventative medications is to kill any migrating larvae in the body which is heading towards the heart. There has been no heartworm preventative which has been made to kill adult worms in the heart.

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