Feline Heartworm Disease

Cats are very different from dogs when it comes to heartworm disease. Not only do they differ in their susceptibility to the disease, but also in how the disease affects them and how the disease is diagnosed.

There are significant differences between feline heartworm disease and canine heartworm disease. Cats are more resistant to the disease, and typically when they do become infected they have a smaller burden of worms in their bodies. But due to their smaller size, even a few worms can be considered a heavy infection for a cat. Even one worm can cause illness or death in a cat.

Heartworms are caused by a parasite called Dirofilaria immitis. Cats and dogs become infected with this parasite through the bite of an infected mosquito. When an infected mosquito bites the cat, the parasite enters the bloodstream of the cat and grows into an adult worm several centimeters long. These worms tend to accumulate around the vessels of the heart and lungs and cause inflammation of these vessels. In severe cases, they can cause a thromboembolism which results in an acute death.

Since heartworm disease in cats happens less often than in dogs, cats with heartworm disease are often misdiagnosed. Cats with heartworms are often wrongly diagnosed as having asthma or allergic bronchitis. Also, many cats can have heartworms and not appear ill at all.

The true percentage of heartworm positive cats is hard to determine due to diagnostic limitations. In dogs an antigen test is the "gold standard" in diagnosing heartworm disease and it is a very accurate test. Unfortunately in cats these tests are not as accurate. In cats, several tests must be used together to arrive at an accurate diagnosis. These tests can include serology, x-rays and echocardiographs.

Cats that are positive for heartworm disease have many treatment options, but they all have risk associated with them. In mild cases an anti-inflammatory like prednisone may be used. This drug helps support cats by reducing the inflammation of affected vessels. For cats showing severe clinical signs, more extensive treatment and hospitalization are needed. Surgery is also an option to physically remove any worms.

There are many medications on the market to help prevent your cat from getting heartworm disease. Talk to your veterinarian before purchasing heartworm medication as she/he can recommend the most effective one for your area. Monthly preventatives are an option for cats living in areas where heartworm disease is endemic. Even indoor cats may be at risk if windows are left open. Year-round preventatives are increasingly being recommended by more veterinarians. Kittens as young as eight weeks can be started on preventatives.

The most common products used for cats include Interceptor, Heartgard, and Revolution. Interceptor and Heartgard are given orally as chewable medication. Revolution is a topical medication that is applied to the hair over the shoulders. At a minimum, the medication should be started within 30 days of heartworm transmission season and continued until at least 30 days after it ends. In most places this means starting the medication in early Spring and continuing until the end of Fall.

If you live in an endemic area of heartworm disease, be sure to keep your cat on preventatives for the entire year. Talking to your veterinarian is the best source of advice about the prevalence of heartworm in your area.

Until next time,

Teia

Beware of Dog Ticks

People have always known that ticks can carry various forms of disease. But now, due to a number of conditions, tick numbers are increasing across the United States and southern Canadaand their chances to infect your dog with disease are also increasing.

Urbanization of the woods and farmland is probably the most common factor that causes dogs to become exposed to ticks. Another cause cited by experts is a warming climate. In the past, diseases that ticks carried would often show seasonality. But, due to a warming climate, some ticks are active all year long and hence the diseases they carry are seen all year long.

Also the migrating patterns of birds are changing as well due to climate changes. Due to sub-urbanization, more people are enjoying outdoor activities with their dogs leading to increased exposure to ticks.

Ticks have been implicated in carrying dozens of diseases. The most common ones known to dog owners are Lyme's disease, Rocky Mountain Spotted Fever, and Canine Ehrlichiosis.

Ticks start their life cycle as larvae that hatch from eggs. Once the larvae hatch, they immediately start seeking hosts which are often rodents. After the larvae feed off the rodents, they fall off and live on the ground feeding off decaying material. They then molt into nymphs and then seek another blood meal from a small animal. If this nymph fails to find its first blood meal it will die. But if this nymph succeeds in finding its first blood meal, it will fall off the host and live off the soil again, molting into an adult.

For an adult tick the preferred animal to get a blood meal from is a large animal, probably a deer. Deer are one of the main causes of a thriving tick population. If we didn't have deer we wouldn't have as large of a problem with ticks as we do.

Deer were heading toward extinction in the early part of the last century, but due to restrictions on hunting their numbers are increasing, hence we have an increase in the number of ticks. On the Canadian prairies, particularly in the Province of Saskatchewan, the deer population has exploded. It is common to see herds of deer numbering into the hundreds.

Due to this increasing problem with ticks and disease most veterinarians are now recommending year around tick protection for dogs. Most common heartworm medications also prevent fleas and ticks so chances are your dog may already be protected against ticks but you should check with your veterinarian to be sure.

Ticks are continually increasing in numbers so it is important to keep your dog protected. Always be sure to check yourself and your dogs for ticks after going into an area known to be populated by ticks.

Until next time,

Teia