Parasites

Heartworm

April 15th is the official start date of heartworm testing for dogs in Ontario. Heartworm is a blood parasite that lives in your pet’s heart and not only causes irreparable damage to the heart and can lead to heart failure and death if left undetected. A simple blood test is required to look for the heartworm parasites that may have entered your pet’s bloodstream last summer or fall. Once mosquitoes start biting, the heartworm can be transmitted so monthly prevention is recommended for all dogs in Ontario. Heartworm prevention is started in early June and continued until November. This may be in the form of a topical medication (applied to the skin) or one that is given orally as a treat. Both are highly effective at preventing heartworm infestations and most contain an intestinal dewormer as well. Flea prevention can also be combined with heartworm prevention as fleas and mosquitoes follow the same pesky time table. In 2009, 674 dogs tested for heartworm at IDEXX lab had positive results, 60 of these dogs lived in the Halton region. Heartworm also circulates in the coyote and stray dog population so the number of positive cases is likely much higher than we can know. For more information on heartworm disease, please see our Pet Health section under Parasites.

Heartworm

Heartworm is a blood parasite that poses a serious health threat to dogs in Canada and the United States. Heartworms are large round worms that live in the right side of the heart and the blood vessels that supply the lungs, surviving on nutrients which they steal from the dog's bloodstream. They can grow to a length of 15-30 centimetres, and in severe cases a dog may be infested with hundreds of worms. Damage to the heart, lungs and liver as well as obstruction of blood flow result from this infestation. Eventually, fluid may build up in the lungs and restrict the dog's breathing. When damage to the internal organs is severe enough, death may be the result.

Heartworms are spread from one dog to another by mosquitoes. When a mosquito bites an infected dog, it will ingest the immature worms (microfilariae) produced by the adults in the heart along with the blood from the dog. The immature worms develop in the mosquito over the next few weeks until they reach an infective stage. When the mosquito bites an uninfected dog, it will inject the immature worms into the tissues with it's saliva. From here, the immature worms will eventually mature into adults and begin reproducing. This cycle continues unchecked unless treatment is given. From this it is easy to see how one infected dog can infect a whole neighbourhood. The signs of heartworm disease are usually detectable only after the disease has progressed and much damage has already been done to the internal organs. This damage may be irreversible. An advanced case may develop such signs as general listlessness, a chronic cough, laboured breathing, and weight loss. The animal may also tire easily during exercise and collapse due to heart failure.

Prevention is the Key
Heartworm may be easily prevented in southern Ontario. A simple blood test is all that is needed to detect the presence of heartworm in an infected dog. Once a negative result is obtained, preventative medication can be given. Preventatives should not be started before your dog has been tested for the presence of heartworm disease with a blood test. In Southern Ontario, heartworm prevention begins in June and continues until November of each year (during peak mosquito season). For those of you who vacation in the United States with your dog, continual protection may be required. Even dogs who take medication every year must be re-tested before beginning another season of preventatives. While the preventative drugs are highly effective, sometimes failures do occur. Most failures of protection result from irregular and infrequent administration of the drug, discontinuing medication too early in the fall, vomiting medication after ingestion and the dog not receiving the proper dose due to growth or weight gain.

Most heartworm preventatives are given monthly, either topically (applied to the skin) or as a chewable or flavoured tablet. This medication interrupts the life cycle of the heartworm, preventing mature worms from reaching the heart. Many heartworm preventatives are now coupled with monthly flea and internal parasite protection allowing one easy application. We will never be able to completely eliminate heartworm, as it is now being found in the wild dog (coyote) and stray dog population which we cannot control. This will, unfortunately, act as a source of infection for the pet population.

Heartworm Disease in Cats
Cats are much less susceptible than dogs to developing infection and are much less likely to show outward signs of disease. Unlike dogs, cats will also often clear their own heartworm infection, although not necessarily before it causes a problem. It is interesting and important to note that up to one third of affected cats are kept strictly indoors. Adult heartworms live in the heart and therefore tend to cause problems related to the heart and lungs. Clinical signs may include coughing, trouble breathing, lack of energy, nosebleeds, collapse and sudden death as well as more general signs including vomiting, weight loss, and neurological abnormalities (head tilt, blindness, seizures). Any animals exhibiting one or more of these signs should be examined by a veterinarian.

Because of the range of signs that can be seen with heartworm disease it is a much more difficult disease to diagnose in cats than in dogs whose signs are restricted more or less to the heart and lungs. Heartworm blood testing is available, but is also much more complicated in cats than in dogs and must usually be supported by other evidence of infection. It is important for all owners of cats who die or are humanely euthanized due to signs that could be related to heartworm disease consider a post mortem to help determine how widespread heartworm disease is in cats in Ontario. We know that it is here, we just don't know how many cats it is currently affecting.

PREVENTATIVES ARE AVAILABLE FOR CATS THAT ARE GIVEN DURING PEAK MOSQUITO SEASON (JUNE TO NOVEMBER)

Internal Parasites

The most common internal parasites are tapeworms, hookworms, whipworms, and roundworms. These parasites can affect your pet's ability to absorb nutrients, and without treatment, they can potentially damage the lining of the intestinal tract.

Tapeworms can be contracted if your pet is a hunter or if they have fleas. In most instances they will be seen as rice shaped segments around the pet’s rectum.

Hookworms can lead to bloody diarrhea, weight loss and anemia.Hookworms can be passed from mother to pup, and they can even be fatal to a puppy, if left untreated.

Whipworms can also cause diarrhea, weight loss and anemia. They can also be very difficult to detect.

Roundworms are the most common of all internal parasites. The majority of all puppies and kittens are born with roundworms. One female roundworm can produce over 100,000 eggs in one day, which means that a pet with a roundworm infection can shed over 20 MILLION eggs in one week. These worms may cause vomiting and diarrhea and resemble strands of spaghetti in your pet's stool. They are easily transmitted to humans, especially children, and can cause serious human health problems, including blindness. If your children enjoy playing in the sandbox, remember that the neighborhood cat might, too. If the sandbox has become his litter box, your children run the risk of contracting roundworms through fecal-oral transmission. Gardeners also need to beware that neighborhood cat may be using your garden for his litter box as well. The best preventatives are to cover up the sandbox, wear gloves when gardening, and constantly wash your hands after being outside. Daily removal of pet waste from the yard is also helpful in preventing infection. Do not allow children to go barefoot, sit or lie on playgrounds or in parks where they are exposed to animal feces.

A yearly examination of your pet’s stool (fecal exam) will help detect common parasites. Routine deworming for all pets is also recommended.

External Parasites (ectoparasites)

Fleas, ticks and mites live on or burrow into their hosts' skin. Fleas are particularly pesky, since they not only infest your pet, but also can take over your home.

Fleas are small (a little more than one millimeter), wingless, brown, and fast moving. Some dogs and cats also can be allergic to fleas' saliva, which causes their skin to become inflamed.

For every flea you see on your pet there are 10,000 more in the environment. Severe flea infestation can also cause anemia in your pet.

In addition, if the fleas carry pathogens, cats may easily become infected because they ingest about 50 percent of the fleas on their coats while grooming.

Ticks can be found looking for a free ride almost anywhere in most climates, though they prefer to hang out in wooded, damp, and grassy areas before attaching themselves to your pet. Some of the most common diseases transmitted by tick bites are Ehrlichia, Lyme disease, tick-borne fever, and Rocky Mountain spotted fever. If untreated, these diseases can cause severe health problems and can be fatal. All tick stages feed for several days before dropping to the ground. Disease transfer can occur as early as 36 hours after attaching Female Ticks remain attached until fully engorged whereas, male ticks feed for short periods of time and move around more frequently. Female ticks can lay thousands of eggs on the ground that are seldom seen. With more people heading north to cottages, the risk of coming into contact with infected ticks has increased. Urban sprawl is another reason we are seeing more incidents of Lyme disease and Ehrlichia. As subdivisions move farther and farther north, wildlife that once inhabited the region are forced to share their space with humans. This means ticks are now being found in backyard ravines, parks and walking trails. Some tick bites may be harmless; others can cause anemia, skin damage, irritation, and hypersensitivity.

The best preventative is to apply a preventative topical medication and to check your pet's skin daily. DO NOT USE MATCHES TO REMOVE TICKS FROM YOUR PET. Use tweezers to properly remove a tick. Grip the tick as close to the head as possible, and gently twist. If you are concerned with removing the tick or if you are not sure you removed all of the tick, contact your veterinarian. Once removed, the best way to kill a tick is to place it in a sealed jar with alcohol. If you are at all unsure about how to remove the tick your best bet is to have a veterinarian remove it for you.

Ear mites (otodectes) are a parasite that lives in the ear canals of dogs and cats. If you notice your pet scratching his ear intensely or biting himself, he could have ear mites. These pests also leave a brown or black crust on the outer ear.

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