How To Test Heartworm In Dogs

Blood tests are used by a veterinarian to examine a dog for heartworms. An antigen test looks for particular heartworm proteins, or antigens, that mature female heartworms release into the dog’s circulation. Antigen tests can typically detect infections with one or more adult female heartworms with high accuracy. About 5 months after a dog is bitten by an infected mosquito, the heartworm proteins can first be found in its bloodstream.

Microfilariae are found in a dog’s bloodstream by another test. The presence of microfilariae in the bloodstream reveals that the dog has adult heartworms (because only adult heartworms can mate and produce microfilariae). A dog can have microfilariae found in its bloodstream as early as six months after being bitten by an infected mosquito (because it takes about that long for the heartworms to develop from infective larvae into adults that mate and produce microfilariae).

How much does testing for heartworms in dogs cost?

The majority of heartworm tests can be completed in your veterinarian’s office, and the results may be ready in a matter of minutes. Even if they are on heartworm prevention, it is advised that all dogs undergo annual heartworm testing.

What kind of test is performed to identify a heartworm infection?

The parasite Dirofilaria immitis, also referred to as the heartworm, is what causes heartworm illness. The pulmonary artery, a sizable blood vessel that delivers blood from the heart to the lungs, and the right ventricle of the heart are home to the parasites, which are long, hair-like worms. When a dog is bitten by an infected mosquito carrying immature, contagious heartworm larvae, the mosquito infects the dog.

“Dogs contract heartworm infection when bitten by an infected mosquito carrying immature, contagious heartworm larvae.”

The larvae enter the dog through the bite of the mosquito, pass through the body’s tissues, eventually enter the bloodstream, and then migrate to the right ventricle of the heart. The worms develop into adults inside the heart, reproduce, and give birth to immature worms called microfilariae that move through the bloodstream. The microfilariae are ingested by the mosquito when it bites another dog that is afflicted. The microfilariae grow inside the mosquito to become infectious larvae. These infectious larvae enter the mosquito’s mouth and wait there till the insect bites a dog again. The heartworm life cycle can be completed in 5 to 6 1/2 months.

Where is heartworm infection most common?

Heartworm infection is very frequent throughout the country, but it is more prevalent in the gulf and southern coasts as well as in the Mississippi River valley. Heartworm infection is more uncommon in Canada, where it is mostly found in southern Ontario, southern Manitoba, and southern Quebec, with sporadic cases elsewhere in the nation.

When mosquitoes are actively feeding, there is a higher chance of infection. Usually, this calls for temperatures above 50°F (10C). The risk of contracting heartworm infection is greatest during the warmer months in regions that get frequent deadly frosts (late spring to late fall). Heartworm infection, however, is a year-round risk in a large portion of the United States.

Can infection be spread directly from one dog to another, from dog to cat, or from a dog to a person?

No. Heartworm can only be transmitted to dogs by infected mosquitoes. Dogs do not transmit the heartworm infection to cats, people, or other dogs. However, if bitten by an infected mosquito, both cats and dogs are susceptible to contracting heartworm.

What are the clinical signs of heartworm disease?

Dogs frequently show no clinical symptoms in the early stages of the illness, especially if they are just carrying a few worms.

Clinical indications of the disease, which include resistance to activity, fast exhaustion from exertion, coughing, and even collapse, become more obvious as the condition worsens. Dogs with severe illness might develop congestive heart failure. Congestive heart failure in dogs causes weight loss, poor physical condition, rapid or labored breathing, and an accumulation of fluid in the abdomen.

How is heartworm disease diagnosed in the dog?

A quick blood test is typically used to identify heartworm illness. Heartworm infection can be identified using two major tests; one looks for adult worms and the other for microfilariae.

The American Heartworm Society advises utilizing the Heartworm Antigen Test as the main technique for determining whether a person has adult heartworm infection. This particular test only detects mature female heartworms. Positive results can be obtained with as little as 1 to 3 adult females in the heart, and the antigen is detectable by 61/2 to 7 months following infection.

Tests for antigens will be mistakenly negative if

  • less than five months had passed since the infection started (dog is infected, but it is too soon for adults so there is no antigen present).
  • All of the worms are males or young females (no adult female worms).
  • There are hardly any worms at all (level of antigen is too low to detect).
  • The test itself is experiencing technical issues (test should be repeated).

Testing for Microfilariae: A test for microfilariae should be performed after any antigen test that is positive or “weak positive.” Microfilariae demonstrate the presence of mature adult worms in the heart and point to the necessity for a specific treatment to eradicate them. Concentration tests are the most effective procedures for identifying microfilariae. The modified Knott’s test, which concentrates the microfilariae by rapidly spinning the sample in a small circle in a centrifuge, is the test of choice. The filter test, which includes putting the sample through a very small filter that captures the microfilariae, is another typical test. Microfilariae are found and identified using a microscope in both tests.

Tests for microfilaria may result in false negatives for a number of causes, including:

  • No adult worm is developed enough to mate and give birth to microfilariae.
  • Since all mature worms are of the same sex, mating is not possible.
  • Too few microfilaria are present in the bloodstream for detection (mating is just beginning, or there too few adults to produce large numbers of microfilariae).

What about the DNA-PCR test?

Dogs cannot yet be screened for heartworm infection with this test, which finds the heartworm’s DNA. However, the DNA-PCR is useful to confirm that microfilariae are Dirofilaria immitis and not another type of blood parasite if there is any uncertainty regarding their identity.

What other methods are used to detect heartworm infection?

Blood testing in some affected dogs come back negative even when the heartworms are present.

several blood tests (CBC, blood chemistries, electrolytes). The presence of heartworm illness may be indicated by abnormalities on the complete blood count (CBC) and blood tests for kidney and liver function. Dogs with heartworm infection frequently undergo these tests to evaluate organ health and function before starting treatment.

Radiographs (X-rays). The major artery (pulmonary artery), which connects the heart to the lungs, will typically be swollen on a radiograph of a dog with heartworms. Heartworm infection is presumed to be present based on these symptoms. Radiographs can also show how the heart, lungs, and pulmonary arteries are doing. We can forecast a higher likelihood of treatment-related problems thanks to this knowledge.

Electrocardiogram (EKG or ECG). The electric currents produced by the heart are traced on an ECG. Identifying the presence of aberrant cardiac rhythms is its main purpose. Additionally, this test can identify heart chamber enlargements and assess if a dog can safely get heartworm disease treatment.

Echocardiography (ultrasound of the heart). When the heart chambers are seen using ultrasound, the general health of the heart can be assessed. Heartworms can also be seen in the pulmonary artery and heart.

Do all dogs need to be tested?

No. Puppies that are younger than 6-7 months old do not require testing. Both antigen tests and microfilariae tests will come back negative since adult worms are not present at this stage.

Is there treatment for heartworm disease?

Two types of medications are typically used in treatment: one to kill adult heartworms and the other to kill microfilariae. Although tiny numbers of adult heartworms can occasionally persist following treatment, the majority of the time, treatment is effective.

Due to dead worms being pushed out of the heart and into the lungs, heartworm treatment frequently has negative effects. Although all infected dogs are at risk, side symptoms are more frequent in dogs with a high number of mature heartworms. All dogs receiving treatment must be kept very quiet throughout the course of the procedure and for four weeks following in order to reduce adverse effects, even if they are not exhibiting any symptoms of disease. To lessen adverse effects and enhance treatment response, other medications such anti-inflammatory medicines, antihistamines, and antibiotics (like doxycycline) may be utilized. If significant issues develop, hospitalization for additional care may be required. Please refer to our brochure “Heartworm Disease in Dogs – Therapy” for further details on the course of treatment.

How can I prevent heartworm disease in my dog?

To avoid heartworm disease in your dog, annual heartworm tests and preventative treatment are advised. For the prevention of canine heartworm disease, a number of good preventative medications are available. Your vet can provide you advice on the best product for your pet and whether year-round therapy is required. While dogs in Canada, the northern United States, and Alaska are most at danger during the warmer months, dogs in subtropical United States are susceptible to heartworm all year round (late spring to late fall). Regardless of the season, dogs from lower risk areas who travel to high risk locations need to be on preventive medicine during that time.

Can you test at home for heartworms?

Use a few drops of whole blood or serum. So quick and simple! Furthermore, the shelf life is 12 months without refrigeration. rapid and early outcomes.

How can a veterinarian identify heartworms in a dog?

We will advise a heartworm test at routine vet visits. This test needs a little blood sample and looks for the presence of heartworm proteins. We will advise additional testing to establish the best course of treatment if your dog tests positive for heartworms.

When Should Dogs Be Tested for Heartworms?

When dogs see the vet for preventative care, heartworm testing should be done regularly. A decent rule of thumb for when to have your dog get a heartworm test is provided below:

  • Since it takes 6 months for a dog to test positive for heartworms after being infected, puppies under the age of 6 months can get their first heartworm preventive medicine without first having a heartworm test. To ensure that your puppy continues to test negative for heartworms, you should take them for heartworm testing again six months later and then once a year.
  • Before starting a year-round preventative regimen, adult dogs over the age of 6 months who have not taken prophylactic medication should be tested for heartworms. This should be followed by tests every 6 months and once a year to ensure that the tests will continue to come back negative.
  • Your dog should be tested right away and then tested again six months later if he or she misses one or more doses of heartworm protection.

Even for dogs receiving year-round treatment, routine heartworm testing is necessary to ensure that the medicine is effective. Despite the fact that heartworm medication is typically effective, there is a slight chance that your dog could develop an infection as a result of events like vomiting the pill or rubbing away the topical medication.

Does your dog exhibit heartworm disease symptoms? Keep in mind that our chances of being able to preserve his life increase with the earlier we can identify a heartworm infection. To find out more about heartworm prevention, detection, and treatment, contact our office right now.

Can I treat my dog for heartworms without having them tested?

Many variables affect when and how often heartworm testing should be performed. Among these elements are:

  • the age of the dog when heartworm treatment is initiated;
  • If and for how long the owner neglected to administer heartworm prophylaxis;
  • if the canine is changed from one heartworm prevention method to another;
  • if the dog recently visited a region where heartworm infection is more prevalent; and
  • the duration of the dog’s local area’s heartworm season.

Before beginning heartworm prophylaxis, dogs 7 months of age and older should get a heartworm test. A dog may look healthy on the exterior, yet heartworms may be present and actively reproducing within. A heartworm-positive dog should be diagnosed before beginning a preventive treatment because otherwise, the dog will carry adult heartworms until it becomes unwell enough to exhibit symptoms. Adult heartworms are not killed by heartworm preventives. Additionally, it may be hazardous or fatal to administer a heartworm preventive to a dog that already has adult heartworms. The preventative may cause the microfilariae to abruptly die if they are already present in the dog’s bloodstream, which could result in a shock-like reaction and even death.

All dogs should undergo annual heartworm preventive testing. The ideal timing for your dog’s annual heartworm test should be discussed with your dog’s veterinarian.

How many heartworm-infected dogs survive?

This leaflet offers details on canine heartworm disease therapy. Consult the handouts “Heartworm Disease in Dogs” and “Testing for Heartworm Disease in Dogs” for more detailed information on the causes, transmission, and testing techniques of heartworm disease in dogs.

What causes heartworm disease?

Dirofilariasis, sometimes known as heartworm disease, is a dangerous and possibly fatal condition. It is brought on by the parasite Dirofilaria immitis, which lives on blood.

Infected dogs have adult heartworms in their hearts, pulmonary arteries, and nearby big blood vessels. Worms may occasionally be discovered in other areas of the circulatory system. Female worms are 1/8″ broad and 6-14″ long (15-36cm) in length (3 mm). The size of males is roughly half that of females. When diagnosed, a dog can have 300 worms present.

Infected dogs’ hearts, pulmonary arteries, and nearby big blood vessels all contain adult heartworms.

Heartworm adults can live for up to five years. Millions of microfilaria, the females’ progeny, are produced throughout this period. These microfilariae primarily inhabit the tiny blood arteries.

How is heartworm disease spread?

The disease is not transmitted from dog to dog directly because the mosquito serves as an intermediary host in the transmission process. Therefore, the disease’s spread correlates with mosquito season, which in many regions of the United States can persist all year. The prevalence of heartworm disease in any given area is closely connected with the number of affected dogs and the length of the mosquito season.

My dog has been diagnosed with heartworm disease. What is the treatment?

Although fatalities are uncommon, treating dogs for heartworms carries some risk.

More than 95% of dogs with heartworms can now be successfully treated thanks to a new medication that has fewer adverse effects.

In the past, the medication used to cure heartworms contained significant amounts of arsenic, which usually resulted in toxic side effects. More than 95% of dogs with heartworms can now be successfully treated thanks to a new medication that has fewer adverse effects.

When they are diagnosed, many dogs already have advanced heartworm disease. Consequently, the heart, lungs, blood vessels, kidneys, and liver have sustained significant harm as a result of the heartworms’ protracted presence. Rarely, cases may be so severe that treating organ damage and providing the dog with comfort is preferable than risking the side effects of heartworm treatment. The lifespan of a dog in this condition is most likely limited to a few weeks or months. Your vet will provide you advice on the most effective course of action for treating pets with advanced heartworm illness.

a method to eradicate adult heartworms. To eliminate adult heartworms, melarsomine (marketed under the name Immiticide) is administered via injection. Adult heartworms in the heart and surrounding arteries are killed by melarsomine. A series of injections are used to give this medication. The precise injection schedule will be decided by your vet based on the health of your dog. Most dogs have a first shot, a 30-day rest period after that, and then two further injections spaced 24 hours apart.

In order to prevent infection with the bacteria (Wolbachia) that live inside the heartworm, many dogs will also receive treatment with an antibiotic (doxycycline).

Following treatment, total rest is necessary. Within a few days, the adult worms pass away and begin to rot. In the lungs, where they lodge in the tiny blood vessels after fragmenting, they are finally reabsorbed by the body. The majority of post-treatment difficulties are brought on by these pieces of deceased heartworms, and their resorption can take many weeks to months. The dog must be kept as quiet as possible during this potentially dangerous time and must not be permitted to exercise for one month after receiving the final injection of heartworm medication. Because the worms are dying during the first week following the injections, this period is crucial. Many dogs with severe infections continue to cough for seven to eight weeks following treatment. For treatment alternatives if the cough is severe, contact your veterinarian.

If the dog experiences a major reaction in the weeks after the initial treatment, prompt treatment is crucial, albeit such reactions are uncommon. If your dog exhibits depression, fever, intense coughing, shortness of breath, blood in the cough, or loss of appetite, call your veterinarian right once. Anti-inflammatory medications, antibiotics, cage rest, supportive care, and intravenous fluids are frequently effective treatments in these circumstances.

a method to eradicate microfilaria. Your dog will also receive a medication to kill microfilariae in addition to the medication used to treat adult heartworms (heartworm larvae). On the day that this medication is given, your dog might need to stay in the hospital for observation; this could happen either before or after the injections for adult heartworms. Your dog will begin taking a heartworm preventive after treatment.

“Various medications are used in more recent heartworm treatment protocols to kill the microfilariae.”

Various medications are used in more recent heartworm treatment procedures to kill the microfilariae. Based on your dog’s condition, your veterinarian will decide on the best medication and timing for administration.

Are any other treatments necessary?

Prior to receiving treatment for the heartworms, dogs with severe heartworm disease may need to take antibiotics, painkillers, special diets, diuretics to eliminate fluid buildup in the lungs, and/or medications to improve heart function. Some dogs might need lifelong heart failure medication even after the heartworms have been eradicated. Diuretics, heart drugs like beta-blockers, ACE-inhibitors, or cardiac glycosides, as well as specialized low-salt diets, are all examples of this.

What is the response to treatment and the prognosis post-treatment?

Dog owners are frequently taken aback by their dog’s improvement after heartworm treatment, especially if the dog had been displaying clinical heartworm disease symptoms. Many dogs exhibit increased vitality, better appetites, and weight gain.

How can I prevent my dog from getting heartworms?

Using a heartworm preventive will help you keep your dog’s heartworms at bay. After a dog has undergone a successful heartworm treatment, it is crucial to start a heartworm prevention regimen to avoid recurrence. No pet should ever have to deal with the terrifying disease thanks to the safe and economical heartworm preventives that are currently accessible. To find out which heartworm prevention strategy is best for your dog, speak to your vet.