At Littleton West Animal Hospital we have a strong support for the American Heartworm Society’s recommendation for all dogs to be on year around preventive against Heartworm Disease. We have seen an increase in incidence not only in dogs coming from other states to our shelters, but also dogs who have never left Colorado. We have treated dogs for this condition, and we have a large majority of our patients on year around prevention. Preventive care is the cornerstone of medicine and this is an easy way to prevent a horrible disease.
Current Recommendations:
- Year Around Preventative medication for all dogs in all 50 states
- Annual Antigen Testing (some states with lower risk only test every other year if dogs are on year around prevention)
What is Heartworm Disease?
Heartworm disease is a serious and potentially fatal condition caused by parasitic worms living in the arteries of the lungs and occasionally in the right side of the heart of dogs, cats and other species of mammals, including wolves, foxes, ferrets, sea lions and (in rare instances) humans. Dogs and cats of any age or breed are susceptible to infection.
Heartworm disease has been reported in all 50 states. Jefferson County CO had 124 reported cases in the past 5 years, and many cases go unreported.
How Heartworm Happens:
First, adult female heartworms release their young, called microfilariae, into an animal’s bloodstream. Then, mosquitoes become infected with microfilariae while taking blood meal from the infected animal. During the next 10 to 14 days, the microfilariae mature to the infective larval stage within the mosquito. After that, the mosquito bites another dog, cat and the infective larvae enter through the bite wound. It then takes a little over 6 months for the infective larvae to mature into adult worms. In dogs, the worms may live for up to 7 years. Microfilariae cannot mature into adult heartworms without first passing through a mosquito.
What Are the Signs of Heartworm Disease?
For both dogs and cats, clinical signs of heartworm disease may not be recognized in the early stages, as the number of heartworms in an animal tends to accumulate gradually over a period of months and sometimes years and after repeated mosquito bites.
Recently infected dogs may exhibit no signs of the disease, while heavily infected dogs may eventually show clinical signs, including a mild, persistent cough, reluctance to move or exercise, fatigue after only moderate exercise, reduced appetite and weight loss.
Cats may exhibit clinical signs that are very non-specific, mimicking many other feline diseases. Chronic clinical signs include vomiting, gagging, difficulty or rapid breathing, lethargy and weight loss. Signs associated with the first stage of heartworm disease, are often mistaken for feline asthma or allergic bronchitis, when in fact they are actually due to a syndrome newly defined as Heartworm Associated Respiratory Disease (HARD).
How Do You Detect Heartworm Disease?
Heartworm infection in apparently healthy animals is usually detected with blood tests for a heartworm substance called an “antigen” or microfilariae, although neither test is consistently positive until about seven months after infection has occurred.
Heartworm infection may also occasionally be detected through ultrasound and/or x-ray images of the heart and lungs, although these tests are usually used in animals already known to be infected.
Prevention: Heartworm prevention is safe, easy and inexpensive. While treatment for heartworm disease in dogs is possible, it is a complicated and expensive process, taking weeks for infected animals to recover. There is no effective treatment for heartworm disease in cats, so it is imperative that disease prevention measures be taken for cats.
There are a variety of options for preventing heartworm infection in both dogs and cats, including monthly tablets and chewables, monthly topicals and a six-month injectable product available only for dogs. All of these methods are extremely effective, and when administered properly on a timely schedule, heartworm infection can be completely prevented. These medications interrupt heartworm development before adult worms reach the lungs and cause disease.
Treatment
 Heartworms in the heart of a dog |
Usually, all but the most advanced cases of heartworm disease can be successfully treated in dogs. Currently, there are no products in the United States approved for the treatment of heartworm infection in cats. Cats have proven to be more resistant hosts to heartworm than dogs, and often appear to be able to rid themselves of infection spontaneously. Unfortunately, many cats tend to react severely to the dead worms as they are being cleared by the body, and this can result in a shock reaction, a life-threatening situation. Veterinarians will often attempt to treat an infected cat with supportive therapy measures to minimize this reaction; however it is always best to prevent the disease.
 Heartworms in the Pulmonary Artery of a dog |
Adult heartworms in dogs are killed using a drug called an adulticide that is injected into the muscle through a series of treatments. Treatment may be administered on an outpatient basis, but hospitalization is usually recommended. When the dog is sent home, exercise should be limited to leash walking for the duration of the recovery period, which can last from one to two months. This decreases the risk of partial or complete blockage of blood flow through the lungs by dead worms.
Re-infection during treatment is prevented by administration of a heartworm preventive. These preventives may also eliminate microfilariae if they are present. Dogs in heart failure and those with caval syndrome require special attention.
Thanks to The American Heartworm Society for this information
Link to American Heartworm Society
