Many pet lovers and their animals enjoy spring and summer.

They enjoy more time outdoors with the longer days and warmer temperatures. But the pleasant weather also signals the return of mosquitoes and the diseases they can carry. One of the most deadly diseases your dog can get from a mosquito bite is heartworm. April is National Heartworm Awareness month. Dogs are infected every year even though there are preventatives available that are almost 100% effective.

How is heartworm transmitted?

The baby worms (microfilaria) produced by adult female heartworms live in the host's bloodstream. When a mosquito bites the animal, it ingests some of these microfilaria. They mature into a larvae that are in an infectious stage for 10 to 14 days. When the mosquito bites another host animal, the larvae are deposited onto the surface of the animal's skin, and make their way through the bite into that animal's bloodstream, where they mature.

What are the symptoms of heartworm disease?

Heartworms take about 6 months to mature. During this time, your dog may have an occasional cough or no symptoms at all. Even blood tests and x-rays may not indicate any problem. As the worms reach adulthood, your dog may exhibit more signs including a persistent cough, fatigue, weight loss, lack of desire to exercise, and loss of appetite. In severe cases, dogs can suffer from pale gums, dark or even bloody urine, and very labored breathing.

Can heartworms be treated?

Heartworms can be treated. Generally, treatment starts with killing the adult heartworms. Since the adults continue to reproduce while in the dog, additional treatments to kill the microfilaria are also administered. In severe cases, surgery may be required to remove the worms, which can grow to be a foot long and live for years. Heartworms can infest not only the heart, but also lungs and blood vessels. Most dogs recover following treatment, but the extent of recovery depends on how much damage was done before the heartworms were eradicated.

Are cold climates safe from heartworms?

Heartworms have been reported in every one of the United States, including Alaska and Hawaii. Not only dogs, but foxes, coyotes, wolves, and even sea lions can harbor heartworms. Mosquitoes are developing a higher resistance to cold. Winds can blow mosquitoes into areas they wouldn't naturally inhabit. People also move and take their dogs with them, so an infected dog from the south could bring heartworms to a colder climate. The American Heartworm Society recommends giving your pet a heartworm preventative every month all year long.

How do I start my dog on a heartworm preventative?

Talk with your vet about starting your puppy on a preventative as soon as possible. Puppies under six months old don't need to be tested to start on medication, but should be tested at one year, and annually after that. Your vet will help you monitor the dosage to keep up with your puppy's growth. Adult dogs must be tested before starting the preventative, and should be tested each year even when regularly taking the medication. Your vet can either supply the medication or give you a prescription for it.

What about heartworms and cats?

Although cats can get heartworms, heartworms don't thrive in their systems like they do with dogs. If a cat is infected, the heartworm likely won't grow to adulthood. Even if it does, one or two heartworms aren't likely to affect your cat's health. However, there is no safe treatment for cats if they do get heartworms. Putting your cat on a preventative is the best course of treatment, especially in areas where heartworms are common. There an old saying that goes, "An ounce of prevention is worth a pound of cure." This is so true for heartworms. Put your dog on a preventive when he's young and keep him on it for life. The peace of mind it brings you and elimination of risk for your best furry friend more than outweighs the cost of the medication.