Beef flavored chunks are available in addition to the beef flavored tablets or solutions that can be given orally to the dogs as a measure against the incidence of heartworms.  Avoid mosquito bites by providing proper mosquito-proof shelter facilities to the dogs.

Just plan whether there is any need to go for the heartworm prevention though out the year or only in some months of the year. For example, in the case of some countries, the mosquitoes may be dormant in most of the colder months.

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However, in some countries, this is not a position. Many times, medications are available for oral administration to prevent heartworms along with hookworms etc.  Such oral medications need to be taken as per the instructions. However, be cautious about the occurrence of any adverse drug reactions in the dog given with such prophylactic therapy.

Adverse event reports need to be sent if you come across any sorts of adverse drug reactions in your dog during the preventive treatment.

Soft beef flavored tablets are highly preferred by the pet animals as the preventive measure against heartworms.  The pet owner needs to consult a veterinarian if the dose for the prophylaxis of heartworm is missed for few months.  In such occasions, the pet animal needs to undergo the heartworm test.

Heartgard, Sentinel, interceptor, revolution, etc. are available in the commercial fields as drugs for the preventive measure.  Avoid water stagnation around the dog shelter and the bushes around the area that facilitate mosquito breeding.  This test needs to be carried out in consultation with a veterinarian who is specialized in the pet animal health care and medicine.

As a preventive measure for the heartworms, the dogs need to be tested for the evidence of these worms at an age of six months.  Real beef chewable tablets are available containing medical agent like ivermectin.

Dirofilariasis in Dogs (Heartworms in Dogs)

Dogs suffering from heartworm disease are parasitized by the organism Dirofilaria immitis, a nematode (roundworm) commonly referred to as the heartworm. The severity of heartworm disease in dogs is directly dependent upon the number of worms present in the body, how long they’ve been there, and the response of the host (dog).

In regions where Dirofilaria immitis is endemic, dogs without proper heartworm protection are very likely to develop heartworm disease. The heartworm is mainly endemic in geographic areas with tropical and subtropical climates. It is commonly found along the Atlantic and Gulf Coasts, and the Ohio and Mississippi river basins. The presence of Dirofilaria immitis is not limited to these areas, however. It is found worldwide. Dogs have been diagnosed with heartworm disease in all 50 U.S. states.

Heartworm disease is preventable with the administration of heartworm prophylaxis (preventative medication), as recommended by a veterinarian. For dogs who do contract heartworm disease, the prognosis is good for mild to moderate cases with appropriate and timely treatment. Dogs with more severe cases may suffer from serious short- and long-term complications associated with the disease and its treatment. Treating heartworms is expensive and always carries some risk to the dog. It is certainly better to prevent the disease than to deal with its consequences. Without treatment, most cases of heartworm disease are eventually fatal.

If you would like to read how heartworms affect cats, please click here and visit an article in the petMD health library.


Common signs of heartworm disease in dogs include coughing, exercise intolerance, and poor body condition, but symptoms can vary depending on the severity of the infection.

Heartworm disease is divided into classes. Dogs with Class I heartworm disease are often asymptomatic, meaning they exhibit no visible symptoms, or may only exhibit minimal signs such as an occasional cough. Signs of heartworms in Class II patients typically include coughing and intolerance to a moderate level of exercise. Class III cases may show a generalized loss of body condition, more extreme exercise intolerance, labored breathing, and a pot-bellied appearance associated with fluid accumulation in the abdomen as a result of right-sided heart failure. Dogs with Class IV heartworm disease have a condition known as caval syndrome caused by the presence of so many worms that they block the flow of blood into the heart.


Heartworms are spread through the bites of mosquitos that carry the infective heartworm larvae. These larvae then migrate through the dog’s body until they reach the heart and blood vessels within the lungs, a process that takes approximately six months. The larvae continue to mature in the dog’s heart and lungs—an adult heartworm can grow to be about 12 inches long. These adults reproduce and release immature heartworms, known as microfilariae, into the dog’s bloodstream. When a mosquito bites an infected dog, the microfilariae can enter the mosquito’s body, mature, and then be passed on to another dog, thereby continuing the parasite’s life cycle and spreading the disease to the next host.

Risk factors associated with heartworm disease include residence in endemic regions, exposure to mosquitos, and lack of proper preventative medications.


A veterinarian can run a quick blood test to screen a dog for heartworms. These tests are routinely run both on dogs who are suspected of having heartworm disease and to monitor dogs who are on preventative medications. A positive screening test should be confirmed with another type of test before a definitive diagnosis is made.

Additional tests that are routinely run on dogs with heartworm disease include a blood chemistry panel, complete blood cell count, urinalysis, and chest X-rays. These, and possibly other tests, are necessary to plan appropriate treatment and to determine the dog’s prognosis.


Dogs with heartworm disease will initially receive any treatments needed to stabilize their condition. They will then be given medication to kill circulating microfilariae, and most will undergo a series of three injections over a month’s time to kill adult worms in the heart and lungs. Hospitalization when these injections are given, and possibly at other times, is necessary so that your veterinarian can watch closely for side effects. Prednisone and doxycycline are also typically prescribed to reduce the chances that the dog will react badly to the death of the worms. Other treatments may be needed based on an individual dog’s condition.

If a dog has the caval syndrome, a surgical procedure will be necessary to remove adult worms from the right heart and pulmonary artery by way of the jugular vein. Most dogs with caval syndrome die regardless of treatment.


Exercise restriction before, during, and after treatment for heartworm disease is absolutely vital to its success. Severely affected dogs may need to be kept in a cage to limit activity. For dogs recovering from congestive heart failure, a moderately restricted sodium diet may be recommended.

A  test for the presence of adult heartworms should be done approximately six months after treatment is complete to check for the continued presence of Dirofilaria immitis. If the test is positive, the treatment can be repeated.


Heartworm prevention medications should be given to all at-risk dogs, for example, those living in or traveling to endemic regions, as directed by your veterinarian. There are a number of preventatives that are safe, highly effective, and commonly used. Dogs who have been treated for heartworm disease also need to receive preventive medications since they can be reinfested. Heartworm preventatives are not 100 percent effective, particularly if they are not used per label instructions or doses are missed. Therefore, routine heartworm screening is recommended so that the disease can be caught early when treatment is the safest and most effective.

How is Heartworm Disease Treated in Dogs?


If your dog is not protected by monthly heartworm preventive medications, he/she is a definite risk of becoming infected with heartworms. This potentially fatal disease could result in your dog having adult heartworms living in his/her lungs and heart, causing many serious problems.

Dogs infected with heartworms will cough, tire easily, and sometimes cough up blood. The symptoms will vary depending on where the worms lodge in the dog’s body and how many of them are present.

Heartworms are transmitted by the bite of an infected mosquito. They can only be prevented with heartworm medications that kill off the immature larvae. The medication would kill the larvae prior to them becoming an adult while in the dog’s body. Prevention is much easier, safer, and cheaper than treating a case of heartworm disease.


If your dog does contract heartworm disease, your veterinarian will determine the stage of the disease.  This would be before suggesting a course of treatment for heartworms. There are four stages or classes of heartworm disease. Class One is less severe and is the easiest stage to treat. Class Four is the stage that is the most difficult to deal with.  These dogs have the worst chance for recovery. Dogs with Class Four heartworm disease need some care before the drugs and treatment can be used to stabilize them. This may involve a surgery where the largest worms are physically removed from the heart and largest blood vessels.


Before giving any heartworm medication for dogs, your veterinarian will want to look for any underlying conditions in the dog that may cause problems. Chest X-rays will be taken to look for signs of heart disease or lung damage. Blood tests will be run to look for liver or kidney problems. These are problems that could hamper the dog’s ability to clear the drug from the body. Any problems that are discovered will be dealt with before starting drug therapy.

The most common drug used to treat heartworms in dogs is called melarsomine hydrochloride. The drug is given as a series of injections over a 24-hour period. The dog usually needs to be hospitalized for a time during and after the treatment. This is to watch for signs of shock or other adverse reactions that may require further treatment.

After the medication has been given, it will take at least four weeks for the adult heartworms to be eliminated. During this time, the dog will be given monthly heartworm preventive medication. This is to rid the body of the immature worms in the system. Because the worms are dying, they will migrate through the body and be absorbed.

During this time, your dog must be kept from running or playing. This may cause a rapid movement of a large number of dead worms to the lungs. They can actually cause a blockage.  Dying worms could cause that as well. For this reason, the dog will need to be watched closely for signs of coughing, vomiting, depression, or diarrhea. Any abnormal signs should be checked by your veterinarian.


While most dogs (about 98 percent) treated with heartworm disease will clear the infection. Your dog requires additional treatment, there is the chance that the second round of medication is needed. It can take many months for the dog to have a negative follow-up heartworm antigen test. If the dog is still positive at six months following treatment, the second dose of medication may be needed.

Treatment for heartworms will not guarantee immunity from ever getting them again in the future. Your dog will need to stay on heartworm preventive medications for life to prevent future re-infection.

Denisse Donnelly
Denisse Donnelly
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