May 8—Heartworm disease in dogs is common, potentially deadly and difficult to treat, but experts say it is easy to avoid with preventive medicine and annual testing.
Veterinarian Dr. Harry Greenbaum, with Bryan Animal Clinic, said parasitic heartworms are transmitted by mosquitoes, which are present in large numbers in the Tennessee Valley.
“It only takes one bite from one infected mosquito to transmit it,” he said.
When heartworm disease progresses, Greenbaum said, the dog ends up with a heart full of worms which can lead to life-threatening congestive heart failure.
Veterinarian Dr. Steve Osborne said heartworm disease can affect dogs of any age. “I think it is the most likely communicable disease that dogs stand the risk of getting.”
Osborne said dogs in this area who are not on preventive medicine have about a 1 in 3 chance of contracting a heartworm infection.
It takes six months for a heartworm to develop into an adult, Osborne said. In most cases, it takes two or three years after an infection begins before a dog shows signs of heartworms.
“Coughing is the first thing you’ll see, weakness, initially pale gums to the extreme,” Greenbaum said.
The cost of treatment can range from $700 to $1,000 or more.
There are three phases of treatment for heartworm disease, Osborne said.
“Phase one is evaluating the dog’s capability of coping with treatment.” This is to see how healthy the dog is and includes bloodwork and checking the other organs, he said.
Phase one also involves the administration of an “arsenic-like drug” which will kill the adult heartworms. The product, Osborne said, is much safer than it used to be. He said it is a pure product, less toxic and “animals do quite well with it.”
“It is arsenic, and arsenic is poisonous to mammals, so it does have some risks of having some reactions. But dogs that are asymptomatic have about a 97% chance of going through the treatment OK,” Osborne said.
To make sure the dog is coping well with the first phase of treatment, Osborne’s clinic requires the dog to remain at the clinic from a Monday through Friday so it can be monitored, especially for bad reactions that require immediate attention.
Osborne said when a dog is treated for round worms or hook worms, the parasites die and exit the animal through the intestines. Heartworms are in the heart and circulatory system and there is no way for the dead worms to leave the body. The dog’s body must break them down and destroy them, which takes 30 days.
“Phase two involves time for the dog’s body to get rid of that now foreign, dead protein within the circulatory system. As that is happening, there is a risk of a worm… escaping the heart and going to the lung,” Osborne said.
This would cause inflammation in the lung and that part of the lung will not function, Osborne said. This can be life-threatening if many worms or large chunks of worms end up in the lungs.
“The worst days are kind of between day 11 and day 21 out of that 30 days, but it can happen at any time,” he said.
Osborne said to reduce this chance, the dog should be 100% confined for 30 days “so they don’t have a high cardiac output.” The dog must not exercise or become excited.
After the 30 days, the dog stays at the veterinarian’s office for one day for phase three and observation. This final phase involves another treatment that kills the immature heartworms.
Ten days later, Osborne said, the heartworms should have all died and the dog can be started on a preventive treatment.
Greenbaum said there is a treatment called a “slow kill,” but he recommends against it. It consists of giving the dog antibiotics for a month to weaken the worms and then the dog stays on a monthly preventive in hopes that the worms will die in two to three years.
“It’s not ideal because there’s some damage going on to the heart and lungs during that time,” Greenbaum said.
This treatment, Osborne said, is dangerous and should never be implemented.
The best approach, Osborne said, is to make sure the dog doesn’t get heartworm.
“The prevention products are thought to be very, very effective when given in compliance,” he said.
Dog owners have several choices for preventives. One is a six-month ProHeart heartworm preventive injection that ranges from $43 to $130 depending on the dog’s weight. A six-month supply of the monthly Interceptor Plus heartworm preventive pill ranges from $45 to $60 depending on the weight of the dog.
While the preventives are effective, there are exceptions.
“As of 2012, the American Heartworm Society identified a certain strain of resistant heartworms … to the current preventive products,” Osborne said.
The resistant heartworms are not found nationwide, but they are prevalent in the Tennessee Valley.
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