Dog Heartworms: Prevention and Treatment

With summer right around the corner, dog heartworms should be a concern of any dog owner. Canine heartworm disease (CHWD) is a serious, potentially fatal disease that can infect certain animals. A parasitic roundworm, heartworms invade an animal's heart, valves, and arteries. They are anywhere from 6 to 14 inches long. Although it is more commonly found in dogs, it can be found in cats, foxes, wolves, and even humans.

The scientific name for heartworms is called dirofilaria immitis. While heartworms were once more common in the southern United States, it is now found in every state except Alaska. A temperature-dependent disease, below consistent temperatures of 57 degrees Farenheit, the lifecycle of heartworms is not sustainable.

Heartworms are transmitted by mosquitoes. When a mosquito bites an infected animal, the heartworm's young or microfilariae enters the mosquito's system. After 10 to 14 days, the microfilaria develop into an infective larvae, and when an infected mosquito bites another animal, it infects that animal. From the time the animal is bitten until the heartworms mature, it usually takes six to seven months. After an animal is infected, heartworms can live withing the animal for up to seven years.

Heartworms are asymptomatic at first. It takes approximately six months for heartworms to mature and start causing damage. Symptoms may include:

• Coughing with or without blood
• Heavy breathing
• Listlessness or general weakness
• Weight loss
• Dull coat
• Enlarged abdomen
• Fainting
• Pulsating jugular vein while sitting or standing
• Congestive heart failure

By the time symptoms are evident, the animal could have already been infected for years. If your dog has any of these symptoms, you should set up an appointment with a vetenarian. Fortunately, heartworms can be treated in 95% of the cases.

When it comes to heartworms, an ounce of prevention is worth a pound of gold. Preventative dosages of heartworm medication during mosquito months safeguards your dog against heartworms. If you live an area where it's warm year-round, dogs need to be treated throughout the year. However, if you live in an area where it's not warm year-round, treatment should begin a month before mosquito season begins and last until a month after the mosquito season ends. Before beginning a preventative program, dogs should have an atigen test or heartworm serology test for heartworms. If the antigen test is positive, dogs should have a microfilaria concentration test next. While the heartworm serology test looks for protiens in the dog's blood produced by heartworms, the microfilaria screen looks for concentrations of baby worms circulating in the dog's blood.

Before beginning a preventative treatment for heartworms, it is very important you have your dog tested first. Otherwise, if you begin a preventative treatment program and your dog has heartworms, they can get sick. If your dog tests clean for heartworms, I can't stress enough the importance of preventative treatment. Once your dog has heartworms the bills can accumulate quickly. For instance, if the tests are postive for heartworms, the vetenarian may do a complete physical examination followed by various laboratory panels, chest x-rays, and an ultrasound of the heart. It can costs $3,500 or more for the tests, vetenarian care, and medications dependent upon where you live.

To prevent dog heartworms, the medicines usually used are: ivermectin (Ivomec and Heartguard), milbemycin oxime (Interceptor), and selamectin (Revolution). Collies and other herding breeds can have a gene called MDR-1 which causes a senstivity to ivermectin which can be potentially fatal. However, the recommended dosage of Heartguard is usually safe for them. If you have a herding breed and you're still concerned, there is a genetic test available to test for the gene. You might want to consider this test if you have a Collie, Border Collie, Shetland Sheepdog (Sheltie), Australian Shepherd, Old English Sheepdog, or long-haired Whippet.

The tablet forms of preventative heartworm medication are based on the dog's weight and given in a once-a-month dosage. If you miss a dosage, restart the medication and have another heartworm serology test run several months later. Heartguard also contains pyrantel which protects against roundworms and hookworms. Interceptor is also safe for herding breeds and controls hookworms, roundworms, and whipworms. Interceptor is also safer for herding breeds. Whereas Heartguard and Interceptor are oral tablets, selamectin is a liquid applied to the skin of the neck between the shoulder blades. It also controls against earmites and fleas.

If your dog is infested with heartworms, they are treated with melarsomine (Immiticide) or sodium thiacetarsemide (Caparsolate). While melarsomine is given in a two-day series, sodium theacetarsemide is given in two injections either eight hours apart for two consecutive days for a total of four injections. Caparsolate is currently off the market in the United States.

If your dog tested positive for microfilaria too, one month after the injections, the vetenarian will prescribe either milbemycin (Interceptor) or Ivermectin (Ivomec). Both medications are aimed at killing the microfilaria whereas the injections are aimed at killing the adult heartworms.

One of the biggest problems in treating heartworms are the possible complications. While most of the dead worms are destroyed by white blood cells, some dead worms can break apart and block small arteries and restrict blood flow to the lungs. Consequently, it is critical that you restrict your dog's exercise for at least four weeks.

Although it can be expensive to test your dog for heartworm and buy the preventative medicine for dog heartworms, it is far more costly to treat your dog once they're infested. Consequently, by testing your dog and implementing a prevantative program for dog heartworms will ensure dog is healthier and give you the peace of mind and save you costly vetenarian bills later on.