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A rapidly growing population of a rare mosquito that carries heartworm has pet parents in the Los Angeles area concerned. As they should be – if not treated, heartworm can be fatal to dogs. What’s scary is that the symptoms don’t start appearing until several months after the dog becomes infected, and by then it can sometimes be too late to save his life.
The good news is that heartworm is 100-percent preventable.
Heartworm is a parasitic disease that can only be transmitted by mosquitoes. Although it was once confined to southern geographical areas where the insects are plentiful, heartworm has become a global disease. In addition to dogs, heartworm affects cats, wolves, coyotes, foxes and other animals – but dogs are considered the disease’s definitive host.
What are the Symptoms of Heartworm?
According to the American Heartworm Society (AHS), an organization founded in 1974 as a global resource for the prevention, diagnosis and treatment of heartworm disease, dogs do not usually show signs of illness until adult heartworms have developed in their lungs.
The first symptom is mild, persistent coughing. This may be followed by lethargy, loss of appetite and difficulty breathing. Your dog may seem to get worn out after just moderate exercise.
What Causes Heartworm?
The American Veterinary Medical Association (AVMA) notes that heartworms can only be transmitted by mosquitoes. A mosquito picks up tiny larval heartworms by biting an infected animal. Unlike other worm parasites, heartworms do not lay eggs; instead they give birth to these larval heartworms, called microfilariae. If microfilariae don’t pass through a mosquito first, they cannot mature into adult heartworms.
The microfilariae in the mosquito mature to the infective stage within two weeks. When the mosquito bites a dog, the infective larvae enter the dog’s bloodstream through the bite wound.
It takes about six months for the larvae to mature into adult heartworms in an infected dog. During this time they migrate through the dog’s body, eventually reaching the lung’s blood vessels. As they mature into adults, the worms can grow to 14 inches, resembling strands of spaghetti.
If the infection is heavy (for example, there are more than 25 worms in a 40-pound dog), the worms back up from the lungs into the heart’s right ventricle, which pumps blood through the lungs, and take up space that should be occupied by blood.
In an extremely severe infection (called “Caval Syndrome”), more than 100 worms may fill the entire right side of the dog’s heart. This condition is almost always fatal.
Adult heartworms can survive from five to seven years in dogs. They produce microfilariae that are released into the dog’s circulatory system, where they can live for up to two years. If a mosquito does not bite the dog and pick them up, the microfilariae die of “old age.”
A mother dog infected with microfilariae can transfer the larvae via her placenta to her unborn puppies. However, the puppies will not develop heartworms from these microfilariae since the larvae must be transmitted via a mosquito in order to mature into adult worms.
How is Heartworm Diagnosed?
According to the AHS and AVMA, your veterinarian may perform the following tests to detect a heartworm infection and its severity:
Antigen test – This is the most commonly performed blood test to determine if adult female heartworms are present in your dog. However, the test is not consistently positive until about seven months after your dog has been infected.
Chest X-ray and echocardiogram (heart ultrasound) – These tests are sometimes performed on dogs known to be infected in order to confirm the diagnosis, evaluate the severity of the disease and determine the best treatment plan.
How is Heartworm Treated?
The goal of heartworm treatment, reports AVMA, is to kill the microfilariae as well as adult worms in your dog as safely as possible. According to the AHS and the Dog Owner’s Guide website, adult worms are killed with an arsenic compound called an adulticide, which is injected into your dog’s heart through a series of treatments usually performed while your dog is hospitalized.
It is important to understand that during the treatment, heartworms are dying inside your dog’s lungs. For up to two months following the final treatment, you must limit your dog’s exercise to a brief walk. Overexertion can dislodge the dead worms from your dog’s heart; they can travel to his lungs and may cause death.
Various medications may be necessary to help prevent your dog from having inflammatory reactions as the worms die and are broken down in his lungs.
In some cases, heartworms may need to be surgically removed. This high-risk surgery is usually only performed for severe cases.
The AVMA reports that while there is a substantial risk in treating the disease, serious complications are less likely if your dog is otherwise in good health and you carefully follow your vet’s instructions.
How is Heartworm Prevented?
Heartworm is almost 100 percent preventable, and the AVMA says it is easy, safe and inexpensive to protect your dog. Your veterinarian may prescribe daily or monthly tablets, a monthly topical solution or a six-month product that is administered by injection. When given to your dog properly and on schedule, these medications interrupt heartworm development before adult worms can reach his lungs and cause disease.
These preventives do not kill adult heartworms, however, and will not eliminate an existing heartworm infection. Before beginning a prevention program, your vet will likely recommend a blood test to make sure your dog does not have heartworms.
Since the blood test only detects adult worms, your dog should be retested after about six months to make sure he was not infected prior to beginning the treatment. After that, he should be tested annually to ensure he doesn’t subsequently become infected and to make sure the appropriate amount of medication is being administered.
“There have been reports of pets developing heartworm infection despite year-round treatment with a heartworm preventive,” writes the AVMA, “so having your pet tested regularly is the best way to keep them protected.”
A poster by the American Heartworm Society says it best: “Preventing heartworm is easy. Treating it, sadly, is anything but.”
PHOTOS: heartwormsociety.org, standardpoodlesusa.com, carsonvalleyvet.com, brewervet.com
Does your dog have heartworm? How are you treating it? Please tell us about it in the Comments section below.
Category : HOW TO
