21 May 2011 Heartworms increasing in dogs in the 501
Missy was 10, a smart, active, border collie/Australian shepherd mix. When we took her for her yearly checkup in October, we never expected to get this diagnosis:
“This dog has heartworms.”
No symptoms. We’d been Johnny-on-the-spot with the chewable monthly preventative for the five years she’d lived with us.
And yet we faced two months of expensive treatment, including three nights in the hospital, and several weeks of keeping her confined between the treatments to ensure one of the dead or dying worms didn’t cause a blood clot that could kill her.
Just before Christmas, we got the news we’d hoped for:
“All clear.”
Now we want to get the word out about this insidious disease that is increasing in prevalence in the 501.
Dr. Greg Hartman has been in practice at Hartman Animal Hospital in Conway since 2004. He has seen a 20-25 percent increase in the number of heartworm cases in dogs each year of his practice.
Geography is part of the culprit. Heartworms are transmitted to dogs by infected mosquitoes, and the lakes and rivers we enjoy in our area are also breeding grounds for those mosquitoes.
Hartman points out that since Hurricane Katrina, the problem has gotten worse, between the flooding and the transport of Katrina pets to the 501 and other places.
And Hartman said that while 80-87 percent of dog owners use a preventative, it seems that many of these heartworms have become resistant to the drugs. He has seen an increase of 10-15 percent in diagnoses of dogs on the preventative.
That was the situation we found ourselves in with Missy.
Manufacturers of the preventatives are in close contact with local veterinarians to update them on their efforts to constantly try to stay ahead of those pesky worms.
They have to. Their products are guaranteed, so dogs on the preventative who test positive for heartworms have their treatment — several hundred dollars’ worth — paid for by the manufacturer.
We weren’t out a dime for Missy’s treatment.
“The main thing we’ve attributed that to is the heartworm larvae, those guys are just flat-out forming a resistance to the medications,” Hartman said. “They become intolerant to being destroyed. They’re just evolving, mutating.”
It’s the same principle, he said, as antibiotic resistance in humans.
“The thing we have to realize is there is not a 100 percent preventative because of that window of resistance, so they’re doing constant research — tests, lab studies, updating the strength of the product, coming up with new medications,” Hartman said. “We just need to be vigilant.”
He said the FDA had approved three categories of preventatives: oral, topical and injectable drugs. The dosing schedule for almost all of these is every 30 days.
Missy and her partner, Ruby the dachsund, have always gotten their heartworm pill on the 24th of every month.
“If you stick to that schedule, it’s going to be great,” Hartman said.
The choice of which method to use should be made in consultation with your vet. Some pets do better with oral tablets, but if they are prone to tummy trouble, the topical might be preferred. The injection, done at the vet’s office, is good for six months.
And since the manufacturers guarantee their product, they have a vested interest in improving it.
“They’ve got to get it figured out,” Hartman said. “That’s why they want to know about any break. It helps them overall with further research of how efficient one product is, and which one they need to focus on. They are constantly doing that every year to stay a step ahead of it.
“It’s good business for them, but it’s also quality medicine to stay ahead of this larvae.”
Thankfully, as we found out with Missy, all is not lost if a dog tests positive, particularly if she is non-symptomatic, as she was.
“It’s just like with any disease — the sooner we can diagnose it, the sooner it can be treated,” Hartman said. “And we have valid treatments. So the key for these products is a lot of due diligence — give the preventative regularly, get the dog tested once a year.”
The treatment, though not fun for the dog or the owner, is better, safer and more effective now than older ones were. It’s an injectable medication, and there have been changes in protocol as well. Instead of the old two injections, now it’s a series of three.
Hartman said for non-symptomatic dogs, the success rate for treatment is 80-90 percent.
“Those are really good numbers,” he said. “And another thing is the preventatives also cover the intestinal worms as well. And we don’t see much resistance in those worms as we have in the heartworms.”
Without treatment, the dog will, in all likelihood, die from the worms, which ultimately attack its vital organs.
“Some animals can have a really overactive immune system, and their bodies may be able to mount just enough resistance to hang on, but that’s less than a handful of a percent,” Hartman said.
One thing to remember is that a dog that is infected with heartworms won’t test positive for six months. Puppies should be started as soon as possible (by 8 or 9 weeks of age), Hartman said. So he advises owners to bring their dog to see a vet, have a heartworm test and then go on the preventative for six months. Another negative test after the first round of the preventative should ensure that the dog is truly heartworm-negative.
“Once you get that, we know we’re clean,” he said. “Then we stay on the FDA-approved product and go from there. And you have a guarantee the company will back it up.”
Missy and her owners are glad we did. But we’ll keep checking once a year just in case.
