Heartworm Disease
General Information
The life cycle of the heartworm begins when an infected dog, carrying tiny immature heartworms (microfilariae) circulating in its blood, is bitten by a mosquito. The mosquito takes in microfilariae (larvae) when it
During the next two-three weeks, the larvae develop within the mosquito into the infective stage.
When the mosquito feeds again, it can transmit infective larvae to the healthy dog. The larvae penetrate the dog=s skin through the mosquito's= bite wound and migrate through the tissues and develop over the next few months, eventually reaching the dog=s heart. Heartworms may be present in the heart and lungs approximately four months after initial infection.
Once in the dog's heart, the worms can grow to as long as 14 inches and cause significant damage to the heart, lungs and other vital organs. If left untreated, heartworm disease can result in death. After adult heartworms mate and produce immature heartworms an infected dog which is bitten by an uninfected mosquito will transmit microfilariae to the mosquito beginning the cycle again. The life cycle of the heartworm is approximately 6 months.
Heartworm FAQ=s
What is heartworm ? Heartworms are parasites that infect dogs and other animals. The
How does a dog get heartworm ?
Heartworm is transmitted by mosquitoes. When carrier mosquitoes bite a dog, they inject tiny heartworm larvae into the dog=s bloodstream. These microscopic larvae eventually settle in the dog=s heart, where they can grow to be 30 cm (12 inches) long. When the adult heartworms produce new larvae, the larvae circulate in the dog=s blood and are picked up by biting mosquitoes. The carrier mosquito bites a new victim and the cycle begins again.
Can my dog get heartworm disease ?
Yes. Your dog can get heartworm disease, whether he=s and Aoutside@ dog or even if he stays inside most of the time. Dogs get heartworm disease from mosquitoes. It is the female mosquito that bites and transmits the infection. Female mosquitoes are very tiny and can easily slip through cracks around windows, doors or screens. Every dog can be at risk, indoors or out.
Are some dogs more susceptible than others ?
Unfortunately, no dog, or breed of dog, is immune to heartworm disease. The mosquito that bites your dog could be carrying this deadly parasite. One bite from an infected mosquito is all it takes for your dog to become infected.
What are the symptoms of heartworm disease ?
There is a wide spectrum of symptoms, depending on how many worms are living in the dog=s heart. Dogs with only a few worms may carry them for years without showing any symptoms. Dogs with many worms usually develop serious heart, lung, liver and kidney problems, with symptoms such as weight loss, coughing, fever, poor hair coat, and inability to tolerate exercise. Dogs with heavy infestations will usually die unless the disease is treated.
Is there a test for heartworm ?
If your veterinarian feels your dog is at risk for heartworm, he or she will probably recommend a simple blood test to rule out the disease. If the initial test is positive, further tests may be recommended to confirm that your dog is infested. It is very important to confirm the dog=s heartworm status before starting preventative medication or treatment.
When is the right time to get my dog tested ?
Mosquitoes, the carriers of heartworm disease, can be found at varying times of the year depending on the climate. Ask your veterinarian when the best time is to have your dog tested.
Do we have heartworm in Canada ?
Yes. Heartworm occurs in warmer regions, where summer temperatures are high enough for the worm larvae to survive inside the carrier mosquitoes. The high-risk areas in Canada are southern Ontario, southern Quebec, Manitoba, and the Okanagan in British Columbia. Heartworm is also found in most states in the US.
Although it is not absolutely certain, it appears that heartworms are unable to survive at prevailing temperatures in Alberta and Saskatchewan. A few cases are diagnosed in these provinces every year, but to date they have all been dogs that have visited or lived in heartworm risk areas.
How do I protect my dog from heartworm ?
With heartworm, an ounce of prevention is truly worth a pound of cure. The disease can easily be prevented with inexpensive monthly tablets, a monthly topical application or a Aonce every six month@ injection, prescribe by your veterinarian. Treatment of full-blown heartworm disease, however, is costly, time consuming, hazardous, and not always successful.
If you are travelling outside Alberta with your pet, talk to your veterinarian about heartworm before you leave. Your veterinarian will identify heartworm risk areas and prescribe appropriate preventive medication, if needed.
Can my cat get heartworm ? Although dogs are the natural hosts for heartworm, cats will occasionally become infested as well. Preventative medication is therefore recommended for cats travelling to high-risk areas during mosquito season. Heartworm tests and medications specifically for cats have recently become available - talk to your veterinarian.
Heartworm Disease in Cats
When it comes to heartworm disease, dogs and cats have a lot in common. But new research shows that in cats there is the potential for more severe reactions and even sudden death. Indoor cats are also at risk for heartworm disease.
Cases of heartworm disease in cats have been reported across the US and many other countries. Heartworm disease is common in areas where dogs are also at risk.
What are the signs ? The most common signs of heartworm disease in cats - coughing, vomiting, breathing difficulties, weight loss, and lethargy - are often mistaken for other conditions such as asthma, pneumonia and digestive problems. In fact, most common clinical signs of heartworm disease in cats resembles bronchial asthma.
Once a cat is diagnosed with heartworm disease, managing the disease can be difficult. Treatment, as well as non-treatment, is very risky, because there's currently no approved product for treating adult heartworms, and the onset of clinical signs is impossible to predict in cats that are left untreated. Even if the disease is treated, your cat may experience sever complications or even death when the worms die. Prevention is the best medicine. Ask your veterinarian about heartworm disease prevention for your cat. It will help give your feline friend the best chance for a long healthy life.
Feline Heartworm Disease FAQ's
What is heartworm disease in cats ?
Heartworm disease in cats is a serious and potentially fatal condition caused by Dirofilaria immitis. This is the same parasite that causes heartworm disease in dogs but new research shows a potential for more severe reactions and even sudden death in cats.
How do cats get heartworm disease ?
Cats get heartworm disease the same way dogs get it. Mosquitoes transmit the disease by biting an infected animal, then passing the infection on to other animals they bite.
Where are cats at risk for heartworm infection ?
Cats are at risk wherever dogs are at risk, including cats that live indoors. In fact, some studies estimate that 70 % of cats may be at risk in areas where there are heartworm-infected dogs.
What can I do to prevent heartworm disease in my cat ?
Prevention is your best option. Ask your veterinarian for more information.
Heartworm and Travelling with Your Dog
Dog owners, be aware of the following :
Alex, a Labrador retriever, lives in a heartworm-endemic state. He has Heart worms, but his owners don't know it because the disease is not easily detected until its later stages. Alex travels with his owners on vacation to places where there are fewer incidences of heartworm disease like the Calgary Stampede in Alberta. While in Alberta, Alex is bitten by a mosquito, which picks up the heartworm larvae from his bloodstream. If the weather is warm enough over the next 2 weeks the same mosquitoe, if it bites a healthy local dog, can infect him with heartworm. The cycle continues.
A problem can also result if a dog from low-incidence province like Alberta travels into an area where heartworm disease thrives, is bitten by a mosquito and then brings the disease back home.
What does this mean for all dog owners ?
Now that greater numbers of people are travelling across the country with their dogs, on vacation or visiting friends and relatives, no place is entirely heartworm-free. Heartworm disease continues to pose a threat to dogs across Canada & the US. Because heartworm disease is potentially fatal, owners should visit their family veterinarian to learn how easy and convenient prevention can be.
When travelling, help protect your dog from heartworm disease !
http://www.ovc.uoguelph.ca/PathoBio/Heartworm/HEARTWORM.html
American Heartworm Society www.heartwormsociety.org/heart.htm
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