How to Protect your Dog from Heartworm Disease

What is heartworm disease?

Heartworms disease is caused by a filarial worm called “Dirofilaria immitis”  and are found most often in dogs. However this worm can infect  a wide variety of mammal including Human as well. Human infection of heartworm disease has also been reported from India. They are parasites that spend their adult life in the right side of the heart, lungs and associated blood vessels. Heartworms can be present anywhere. To protect your dog against becoming infected with heartworms, your veterinarian can prescribe medication.

It is a parasitic infection that is transmitted by culicine mosquitoes. Baby heartworms, called microfilaria, are drawn up with blood from an infected dog when a mosquito bites. During the next 10-14 days, these microfilaria grow in the mosquito until they reach the infective larval stage. The next time the mosquito bites another dog; it injects the larvae into the dog's bloodstream.

This larva will remain in the tissue surrounding the bite wound for about two months while it grows into an immature adult worm. From there, these immature worms begin to enter the dog's bloodstream and within three to four months, they reach the heart and surrounding arteries. The adult heartworms reach maturity about six to seven months after the initial bite, and can grow 6- 14 inches in length. They are now mature enough to begin their own reproductive life cycle within the dog and their life span in dog appears to be at least 5 -7 years

Who is susceptible to heartworms?

All dogs, from Chihuahua to St. Bernard, can fall prey to heartworms.

Mosquitoes can easily slip inside through cracks around windows, doors or screens. That means that every dog is at risk, indoors or outdoors That's because most dogs do go outdoors, even if it's only for a short time. However where mosquito populations are more, chance of getting heart worms by dog is more.

What happens if your dog becomes infected?

Heartworm may cause lot of medical problems within the same dog which include damage to the dog’s heart, lungs, liver and kidneys. In light infection there is barely a detectable sign but slowly infection becomes chronic and the host become a potent source for spreading infection .In moderate infection there is cough and exercise intolerance. However, in severe infection the following signs and symptoms are noticed:

·         Cough

·         Reluctance to exercise or walk far

·         Difficulty in breathing

·         Abnormal lung sound

·         Hepatomegaly

·         Loss of appetite

·         Weight loss

·         Ascities

·         Some times loss of consciousness 

How can you tell if your dog has heartworms?

Without testing, you won't know until the disease has progressed far enough to cause serious damage to the dog's heart and lungs. That's because there are no visible symptoms of heartworm infection in the early stages. Consult your veterinarian about suspected case.

How heartworm is detected?

First, the clinical symptoms with accurate patient history and then use of several diagnostic procedure. Most often blood test is recommended for detection of circulating microfilaria. However, that leaves the detection of occult or immature case or where single sex worm is there.  We recommend running two tests: one for the microfilaria, and one for the "occult" or hidden adults. The first blood sample is filtered and stained, and then viewed under a microscope to see if any microfilaria are present. The second test detects antigen produced by adult heartworms. This combination of tests provides the most accurate, safe, and effective way to ensure that your dog is heartworm free. These tests are available in clinic or in veterinary reference laboratory. Other test includes radiology and echocardiography. 

Can heartworm disease be treated or is there any preventive measure?

Yes. Heartworm infection can successfully treated against both adult worm as well as against microfilaria. ,An organic arsenical compound , melarsomine dihydrochloride has a higher level of effectiveness. The first step in treating for heartworms is assessing the dog's medical condition. This includes a thorough physical examination, laboratory tests and chest x-rays. The second step is eliminating the adult heartworms. A series of two or three injections are given over a twenty-four hour period. During hospitalization, the dog is carefully monitored for any adverse reactions.

If the treatment is successful, your dog will be discharged with very explicit instructions: his exercise will be strictly limited for 6-8 weeks (that means staying in a crate and being walked on leash when he needs to eliminate) to minimize the potential for the dead worms to cause severe damage to the lungs, or block blood flow. 

Finally, your dog will be treated with medication to kill the microfilaria in the bloodstream. The most effective drugs for microfilaricide are macrocylic lactone(milbemycin, selamectin ,high dose of ivermectin,etc) Only when subsequent heartworm tests are negative  preventative medication can be recommended.

Is yearly heartworm testing necessary?

If you give prevention year-round, you might wonder why we recommend yearly heartworm testing. The reason is simple: we care about your dog. All the manufacturers of preventative medication recommend testing to prevent serious complications. If, for any reason, your dog contracted heartworm disease, successive doses could cause illness, or even death. Even if you're certain your dog swallowed the pill, he might go outside, eat a little grass, and throw the pill up before it was digested. That leaves him at risk of becoming infected.

Some dog owners give their dogs' heartworm medication only during the hot summer months. In India, however, our changing weather leaves too much to chance. We often see mosquitoes well into October. With weather this unpredictable, we recommend keeping your dog on medication year round. In addition, you're also protecting your dog from intestinal parasites, which can be contracted from contaminated soil or other animal's feces year round.

So at least we recommend you testing your dog with any of the commercial kits( Solo Step CH or Snap test) available for detection of heartworm in your dog which can be performed by all Veterinary practitioner.

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