Protecting Your Pet from Pesky Parasites
March 18, 2008
An archive of Pet Columns from the University of Illinois College of Veterinary Medicine is available online at Requests for reprints of this article may be directed to Mandy Barth,

As spring continues to taunt us with its eminent yet seemingly elusive arrival, it is time to once again start thinking about flea, tick, and heartworm prevention measures for your four-legged companions. Since these pesky parasites can afflict anything from the smallest kitten to Great Danes it is important to understand how to safely and effectively protect our pets from these harmful parasites and the diseases they cause.

"Prevention is much easier, safer, and cheaper than treatment," says Dr. Allan Paul, a veterinary parasitologist at the University of Illinois College of Veterinary Medicine in Urbana.

When it comes to fleas and ticks it is a common misconception that only outdoor cats and dogs are at risk for infestation with these bothersome parasites. While the risk for completely outdoor animals is higher, any pet that goes outdoors is at risk of coming in contact with fleas and ticks, even if it is only to frolic through the backyard or sunbathe on the porch. Owners should also be aware that indoor cats are still at risk for flea infestation if there is another animal in the house that is helpful enough to bring them indoors.

To keep your animals flea and tick free it is important that every pet in your household is on a monthly prevention schedule. Unfortunately for pet owners living in Illinois the mild winters that we have had over the past few years have made year-round flea and tick prevention almost a necessity. Fleas and ticks are extremely bothersome to pets and are carriers of other parasites and diseases, like tapeworms and Lyme disease, which can be extremely harmful to your pet. There are a wide variety of preventative medications that are available through your veterinarian.

With spring on its way this is now the perfect time to start thinking about protecting your pet against heartworm disease. The heartworm cycle begins when a mosquito bites an infected animal. As the mosquito feeds on the blood of the infected animal, immature heartworms, known as microfilaria, enter the mosquito. During several weeks of warm weather the microfilaria begin to mature within the mosquito, then are passed to another animal when the mosquito feeds again.

From the time of infection, it takes approximately six months for the microfilaria in the pet's bloodstream to mature to adulthood. The adult worms like to live near and in the heart, as the name heartworm implies. The majority of the adult worms are located in the pulmonary artery, the blood vessel that carries blood from the heart to the lungs.

The heartworms can grow up to 12 to 14 inches in length, causing irreparable damage to the heart. The extreme stress that the adult heartworms place on the animal's heart and other internal organs can cause coughing, difficulty breathing, fainting, fatigue, weight loss, and, if left untreated, eventually causes death from heart failure and other complications.

Though heartworm disease can be deadly, pet owners can easily and safely prevent heartworms in their animals. Among the most common methods of prevention are monthly tablets and chewables that are prescribed by a veterinarian based on the animal's weight. Topical monthly heartworm preventives can also be used. An advantage of many of the oral medications is that they also prevent intestinal parasites such as hookworms, roundworms, and whipworms.

Whenever possible, heartworm prevention should begin at a young age. Puppies and kittens should start receiving heartworm medication at between 4 and 8 weeks of age. In order to ensure the lowest chance of infection, it is also recommended that the pet then stays on this preventative year-round for life.

Dr. Paul explains that although the preventative medications on the market have proven to be extremely effective in the prevention of heartworm disease, they cannot be 100 percent effective. As a result, yearly heartworm tests are recommended for dogs older than 7 months; this simple blood test detects only the adult worms.

While the incidence of heartworm disease in cats is lower than that of dogs, cats are indeed susceptible to the disease. Unfortunately for cat owners, accurate testing and treatment for heartworm disease in cats is not available at this time, which makes year-round prevention key for the health and well-being of both indoor and outdoor cats.

If you have any questions about fleas, ticks, heartworm disease, or how to protect your pet against these problems, contact your local veterinarian.

An archive of Pet Columns from the University of Illinois College of Veterinary Medicine is available online at Requests for reprints of this article may be directed to Mandy Barth,

Veterinary Extension/Office of Public Engagement
University of Illinois College of Veterinary Medicine