Protect your pets from heartworms as mosquito population grows

Charlotte’s high mosquito population puts your pets in danger. Dogs and cats, as well as ferrets and other wildlife animals can be infected by heartworms.

“At The Veterinary Medical Center of Fort Mill we will diagnose a case of heartworm disease at least weekly if not daily. If a pet is not on heartworm prevention, it is really not a matter of if they will get heartworm disease it is a matter of when,” Dr. Julie Reck said.

“Heartworm disease runs rampant in the southeast region of the United States. The hot humid climate is a breeding ground for mosquitoes and the mosquito season is longer than (in) other climates. Heartworm larvae, or microfilaria, are transmitted through mosquito bites just like malaria is for humans,” she added. See for a map of heartworm incidence.

The Centers for Disease Control is also warning humans about the Chikungunya virus, an incurable mosquito-borne illness. Cases have been confirmed in both Carolinas and are tied to traveling to Asia, Africa and the Caribbean. On rare occasions, humans have contracted heartworms.

Mosquitoes transmit heartworms
Although considered an outside disease, infected mosquitoes can come inside, endangering inside pets, as well. So prevention is critical.

Even if pet owners administer heartworm preventatives as prescribed, pets can spit out pills or rub off a topical solution. So the preventative is not 100 percent effective. Pets should be tested annually for heartworms and sometimes more frequently, depending on age or previous infection.

Exposure to mosquitoes can be minimized by avoiding the outdoors at dawn and dusk when the insects are most virulent and by eliminating standing water from the home or property and exercising caution around pools and lakes. Also, wearing light-colored clothing and not wearing sweet perfumes can make humans less of a target. Chemical-free repellants can ward off mosquitoes. Some recommend burning sage or growing mint to fend off the insects.

Heartworms are transmitted by mosquitoes that pick up young, microscopic worms from the bloodstream of an infected dog, cat, coyote, ferret or other carrier. The worms develop within the mosquito in 10 to 14 days. Then the mosquito transfers the infective larvae onto the skin of its victim when the larvae enter through the mosquito bite. Within about six months, the larvae mature into adults. Mature heartworms can live for five to seven years in dogs and two or three years in cats. Therefore, animals can be infected by several different worms.

Heartworms range from six to 12 inches. Male worms are shorter than females shorter. These worms look like clear spaghetti and live in the host’s heart, lungs and blood vessels. The mass of heartworms is called a burden. Burdens typically have 15 worms, but dogs can have from one to 250 worms. The number of worms does not dictate the severity of the disease. Occasionally the burden must be removed with surgery.

Estimates are that up to a million dogs in the United States are infected by heartworms each year. Heartworm disease affects dogs’ heart, lungs and arteries and can diminish the dog’s health and quality of life for their lifetime, even if the parasites are eliminated. In dogs, symptoms of disease can include a mild persistent cough, lethargy, fatigue after moderate activity, decreased appetite, and weight loss. With the progression of the disease, pets can develop heart failure and a belly swollen with excess abdominal fluid.

“Ultimately, heartworm disease causes right sided heart failure. Fluid in the lungs and COPD (chronic obstructive pulmonary disorder) are also common. The lasting health concerns will vary for each pet and are dependent on how long the heartworms were present in the pet’s body,” veterinarian Reck said. “When caught quickly, a dog can be treated early in the diagnosis and be left with no long term damage. Pets that have been heartworm positive for long time periods can experience permanent heart/lung damage. This can be documented with the sound of a heart murmur, as visible evidence on x-ray and as changes in bloodwork.”

The pet’s prognosis depends on the damage the heartworms have already caused to the cardiovascular system and other parts of the body.

Two different treatments are available for dogs that have contracted heartworm disease. The fastest method involves a series of painful injections of an arsenic-based medication called Immiticide. The injections are given into the back muscles and the pet must be kept calm for one month following treatment. Because the medication will kill adult worms in the pet’s bloodstream, if the pet is overly active the bodies of the dying parasites will become free floating in the bloodstream and act like a blood clot. This treatment is for a pet that has been screened with bloodwork and x-rays to ensure that the dog is capable of handling the aggressive treatment, Reck explained.

The slower method of treatment involves giving a heartworm positive dog a specific type of heartworm prevention monthly in combination with an antibiotic. The combination of these two medications reduces the lifespan of adult heartworms from three to five years to one to three years and prevents new heartworms from forming the circulatory system. “With this method you are hoping that the pet will outlive the heartworms. It is a less ideal treatment method but it is sometimes the only option for a pet that has already suffered heart and circulatory symptoms from heartworm disease,” Reck continued.

“Both treatment options are currently described as expensive,” Reck said. The Immiticide medication is an expensive upfront cost, but the antibiotic used in the slow method has risen substantially in cost in recent years, making this option less economical. The cost will ultimately depend on the size of the dog because the medications are dosed based on weight. There are also costs associated with staging the heartworm disease (x-rays, exam, bloodwork). The total cost of treatment typically ranges from $1000-$3000 depending on the size of the dog.

Heartworms infect dogs and cats differently, and although dogs can be cured, cats cannot. The disease can often be fatal in cats.

Cats are atypical hosts to heartworms, and most heartworms don’t survive until adulthood in cats. Often heartworms are not diagnosed in felines. Only one to three worms live in cats, but the immature worms can cause Heart Associated Respiratory Disease (HARD). No treatment is available for cats, and the treatment for dogs is harmful to cats.

Preventative medication options
Heartworm prevention is regulated for efficacy by the FDA in the United States and is only available through prescription by a veterinarian at a place like Easy Vet Clinic who also offer Pet Vaccinations Frisco TX. Reck explained how these heartworm prevention medications work. “These medications are monitored for effectiveness by the requirement of a negative heartworm test every year. This annual testing across the country will allow the veterinary community to immediately be aware if resistance to heartworm prevention develops.” Prevention options include topical drops, monthly pills, or a six-month lasting injection.

“The best choice is found after a discussion with your veterinary professional to find what best suits your and your pet’s lifestyle. Many options now have combined flea preventatives and intestinal parasite prevention,” Reck said. “The cost of basic heartworm prevention pills is around $5 to $10 per month based on a pet’s size, making heartworm prevention an affordable option for pet owners.”

“It is important to purchase heartworm prevention directly from the veterinary clinic and avoid the purchase from online pharmacies for many reasons. First, the pharmaceutical manufacturers only intend to distribute their FDA regulated products directly to veterinary clinics,” she continued, offering this warning. “In many instances these products are diverted and sold indirectly to online retailers. The product loses its guarantee of effectiveness at that point. When purchased directly from veterinary clinics, the manufacturer guarantee will cover the cost of treatment if a dog did come up heartworm positive on their product. “


By: Beth Crosby