After treating a dog with melarsomine injections, adult worms may continue to die for more than a month following this treatment. Heartworm antigen testing is the most reliable method of confirming that all of the adult heartworms have been eliminated.
A positive test result confirms the patient has adult heartworms. It is likely these worms survived the adulticidal treatment, but their presence could also signal a new infection if the owner wasn't compliant in administering heartworm preventives during and after adulticide therapy.
early infection and starting life-saving therapy, as heartworms can cause significant damage to your dog's heart and lungs. Even after adulticidal therapy, in rare cases a dog will test positive again, requiring further treatment.
Prognosis: heartworm treatment success rates
With the three-dose adulticide protocol described above, in conjunction with doxycycline and macrocyclic lactones as recommended by the American Heartworm Society, 98% of dogs will be cleared of heartworm infection.
The options for a dog that remains positive after treatment depends on the animal's health status and the stage of disease at the time of diagnosis. According to some veterinary cardiologists the treatment options are either to continue a monthly preventive for six months and retest, or do another round of treatment.
A newer drug is available that does not have as many side effects, allowing successful treatment of more than 95% of dogs with heartworms. "Many dogs have advanced heartworm disease by the time they are diagnosed."
Because heartworms must be eliminated before they reach this adult stage, it is extremely important that heartworm preventives be administered strictly on schedule (monthly for oral and topical products and every 6 months or 12 months for the injectable).
Dogs can live for at least six to seven months after becoming infected with heartworms. This is because it takes that long for adult heartworms to grow.
The life expectancy of a heartworm inside a dog is 5 to 7 years, and an average of 15 worms can be found in an infected dog. Heartworms are a serious problem, but infected dogs may not show symptoms at first, so it's important to test for heartworms annually and administer monthly preventatives.
Adult heartworms have been known to survive inside a dog's heart for 7 years before they die on their own.
Melarsomine dihydrochloride (available under the trade names Immiticide and Diroban) is an arsenic-containing drug that is FDA-approved to kill adult heartworms in dogs. It's given by deep injection into the back muscles to treat dogs with stabilized class 1, 2, and 3 heartworm disease.
Signs of heartworm disease may include a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite, and weight loss. As heartworm disease progresses, pets may develop heart failure and the appearance of a swollen belly due to excess fluid in the abdomen.
Dogs with heartworm disease, for example, require exercise restriction before and heartworm treatment, as well as for a short time after treatment. Physical activity increases the likelihood of adult worms causing a pulmonary thromboembolism, which may be fatal. Limiting a dog's physical activity decreases this risk.
If given to a heartworm positive dog by accident
If the larval worms die too quickly, a shock-like circulatory reaction can occur so for this reason the American Heartworm Society recommends that the first dose of ivermectin be given under veterinary supervision.
“No running, jumping, playing or high-impact exercise as these activities may cause the worms to break loose and cause significant harm to the pet being treated.”
Six months after your dog completes their treatment, you should retest for heartworms. And then be sure to continue with annual testing and a monthly heartworm preventative.
With heartworm disease treatment can be extremely difficult even for the young otherwise healthy dogs but our senior dogs can see more severe side effects and death if progressed disease is present. Know that 1 in 10 dogs will develop some form of heart disease as they age.
After treatment, the adult worms die and are carried by the blood to the lungs where they lodge in small blood vessels. There they decompose and are absorbed by the body over a period of several months.
Even if heartworm infection is treated, we all know it does serious, permanent damage to the body. This in-depth look at that damage will renew your commitment to consistent prevention recommendations for your veterinary patients.
Heartworm disease in dogs is known as a silent killer, because it can take months before your dog shows symptoms. In the early stages of infection, most dogs show little to no symptoms at all, and the more the disease progresses, the more likely apparent symptoms will develop.
Stage 4. There is a large mass of worms which physically blocks the blood flowing back to the heart. This stage is life-threatening and requires quick surgical removal of the heartworms. However, surgery is risky and even with surgery, most dogs in this stage die.
Though the dog's system has not displayed the ability to damage or dislodge adult worms, an otherwise very healthy dog may be able to outlive the worms, which can survive in the heart for five to seven years. The tests that can detect canine heartworm have increased in sophistication.
Although there are fewer mosquitoes in the winter, there is still a risk that your pet could get heartworms if you stop giving heartworm prevention medication during this season. That's one reason veterinarians strongly recommend pets receive heartworm prevention medication year-round.
Myth: Heartworm disease is contagious for pets.
Truth: You should be concerned if we diagnose one of your pets with heartworm disease, but you do not need to quarantine your infected pet. Heartworms must go through a mosquito to develop into adults, so heartworm-positive pets are safe to be around.
As mentioned above, the infected blood is carried by affected mosquitoes from host to host. This means that if your dog is located in close proximity to another heartworm infected dog, the chances could be higher for your dog to be infected. They cannot be spread from one pet to another pet directly.