Heartworms pose danger to companions

Most pet owners are adamant about making sure their animals receive proper care and nutrition. One important step in your pet's care is to protect your beloved companion from heartworm disease.

According to the College of Veterinary Medicine's Web site, www.cvm.uiuc.edu, "Heartworms are long, slender parasites that can reach up to 12 inches in length. The worms live in the right side of the heart and adjoining vessels of infected cats or dogs and are capable of causing substantial damage to the heart and lungs before the animal shows any signs of the disease."

Dr. Mark Pettit from Animal Medical Clinic in Fremont, said, "Heartworm is spread from animal to animal by having a mosquito bite an infected animal."

Most animals infected by heartworm will have microfilaria (baby heartworms) circulating in their blood, which is picked up by mosquitoes.

"In most cases, this particular larvae (microfilaria) has to go through the mosquito to infect an animal. The mosquito is a necessary vector for heartworm infections in cats and dogs," Dr. Lewis Verner from Verner Veterinary Clinic in Fremont, said.

Local veterinarians note heartworm is found predominantly in domestic dogs and other members of the carnivore family, such as coyotes, foxes or wolves. However, cats (and humans) can also get the disease.

"Humans and cats can get heartworms, but the adult heartworms do not reproduce in cats and humans. Cats and humans are considered a dead-end host for heartworms. If a mosquito bites a cat or human, the disease cannot be transmitted any further," Pettit said.

Pettit notes heartworm is found in the lower 48 states, with minimal numbers in the arid states such as Nevada, New Mexico and Utah.

"It is more of a problem where you have mosquitoes. The further south you live where mosquitoes live longer, the higher the problem," Pettit said.

In the Fremont area, local veterinarians have seen a "fair amount" of heartworm cases.

"Our number of dogs that test heartworm positive goes up every year. The disease is becoming more prominent and widespread," said Dr. Landon Lugar from Animal Clinic Downtown in Fremont.

While outside dogs may be more exposed to heartworm, inside dogs also can be affected.

"We've had a lot of indoor dogs that are heartworm positive. Anywhere a mosquito can fly into, the dog is exposed. It only takes one mosquito to fly into the house," Lugar said.

Symptoms of heartworm disease can vary in pets, including lack of stamina, lethargy, and a mild cough, which progresses to a severe cough. More severe symptoms include weight loss, bloody cough, acute collapse and heart murmurs caused by heartworms blocking the animal's heart valve.

"Some dogs are asymptomatic, where there are not outward clinical signs of heartworm," Pettit said.

If an animal is not treated for heartworm, this disease can be fatal to your pet.

"The dog may have such an overload of heartworms that it causes a blockage in their heart or lung, or a piece of a dead heartworm can cause blockage of major internal organs," Pettit said.

To help prevent your pet from being exposed to heartworm, local veterinarians recommend first having your animal tested for heartworm, followed by putting your pet on a heartworm preventative.

"(To test for heartworm,) we draw a blood sample from the dog. That's the way we diagnose it. It picks up even the lightest heartworm infection, depending on the type of test we are using," Pettit said.

"The biggest thing is getting the dog's blood drawn from the heartworm test to make sure the dog is heartworm negative, and then get the dog on a heartworm preventative."

However, even if your pet's test does come back negative for heartworm, pet owners should still be aware of the possibilities.

"When you do test for heartworms on these dogs, there is nothing certainly 100 percent. Part of that is due to the timing of the infection, if there are low numbers of heartworms, or if the heartworms are not mature. Then, they may possibly not show up on the test," Verner said.

"It generally takes six-seven months from the time an infected mosquito bites a dog, to the time when you see any heartworm positive tests in your dog with the commonly used test."

Most local veterinarians recommend having pets tested for heartworm on a year-round basis.

"We recommend year-round testing because of the spread of heartworm disease, and the irregularity of the mosquito season. It has become a year-round concern," Lugar said.

Most local veterinarians also recommend putting your dog on a heartworm preventative on a year-around basis. However, prior to putting your pet on a heartworm preventative, the animal first needs to be tested for the disease.

"It is hazardous to start a dog on a heartworm preventative when there is the possibility the dog is heartworm positive. You could see some adverse reactions from heartworm preventatives if you put dogs that were heartworm positive with mature infections on a preventative. This should be discussed with your veterinarian," Verner said.

Local veterinarians recommend starting your dog on a heartworm preventative as a puppy, age 12-16 weeks, and continuing with the preventative throughout the dog's lifetime.

There are a variety of heartworm preventatives available through veterinarians including daily chewable tablets, monthly pills or chewable tablets, monthly topical treatments, and a six-month injection.

"The oral heartworm preventatives have the added benefits of preventing other parasites, not just heartworms," Lugar said.

Choosing a heartworm preventative for your pet often depends on what your veterinarian recommends and what the pet owner's compliance might be.

"You need to be very disciplined about giving your dog its heartworm preventative medication, depending on the preventative used," Verner said.

"It only takes a few times if you forget to give your dog its heartworm preventative, or if the dog vomits up the pill, for the dog to become infected with heartworms."

Verner also recommends trying to minimize your pet's exposure to mosquitoes to help prevent infection.

While it may seem expensive to keep your pet on a heartworm preventative, there are other factors to consider.

"Over the course of years here with dogs, heartworm preventatives can add up for expenses. But, it is much more economical and healthy for a dog than to wait for an infection to occur, and then have to treat the dog," Verner said.

Lugar added, "From an expense standpoint, if you have an average-sized housedog, you would literally go through 10-12 years of preventive medicine and testing, compared to the cost of one heartworm treatment."

Pettit notes the blood test to screen for heartworm disease runs between $20-$25, and heartworm preventative medication runs between $20-$80 a year, depending on the size of the dog. However, the cost to treat a dog for heartworm can run between $300-$500.

Verner notes pet owners need to be aware heartworm preventatives and heartworm treatments are not the same thing.

"Heartworm is a preventable disease. If pets are not protected from heartworm, it is an oversight of an educated pet owner. The average pet owner has heard of heartworm disease or knows someone whose dog has had it," Pettit said.