How Heartworm Happens: The Life Cycle
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. The mosquito then bites another dog or cat and the infective larvae enter through the bite wound. It 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, when the
heartworms enter a blood vessel and are carried to the pulmonary arteries, are often mistaken for feline asthma or allergic bronchitis, when in fact they are actually due to the syndrome 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.
Because heartworm disease is preventable, pet owners should talk us about how to best protect their pets from this dangerous disease. 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 we recommend for preventing heartworm infection in both dogs and cats, monthly chewables, monthly topicals and a six-month injectable product available only for dogs. These are extremely effective, and when administered properly on a timely schedule, heartworm infection can be prevented. These medications interrupt heartworm development before adult worms reach the lungs and cause disease.
It is imperative that you faithfully maintain the prevention program you have selected.
Products we Recommend
Monthly heartworm preventives available from Community Veterinary Clinic include Iverhart Plus and TriHeart Plus. These easy to give chewable tablets are to be given by mouth each month on a year around basis.
ProHeart6 is a new injectable heartworm prevenative given in our office by our veterinarians. ProHeart 6 (moxidectin) provides six months of continuous protection against canine heartworm disease with a single dose, which is different from oral preventatives that must be administered every month. ProHeart 6 eliminates the need for dog owners to remember monthly dosing and places control over heartworm disease completely in the hands of the veterinarian.
Safety studies have demonstrated that ProHeart® 6 (moxidectin) is safe for all types of dogs six months of age and older. Even when administered at 5 times the recommended dose, no adverse effects were noted in target animal safety tests. In field clinical studies ProHeart 6 was proven safe when used in conjunction with other medications we commonly administer.
All but the most advanced cases of heartworm can be treated in dogs. Currently there are no approved products in the United States for the treatment of heartworms infection in cats.
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 in the hospital overnight. 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.