I love everyone, even the Stupid Chinese Crested I live with. But I think I’m noticing some discrimination in my house. Howard, the dog, gets this medicine to keep him from getting heartworms. I don’t. Does that mean that cats have a better design and don’t need it, or that I’m not as loved as Stupid?
Cupid from Tucson
To answer your question: Yes. You are being discriminated against. And yes. You should be on a heartworm preventative just like Stupid. Kitties get heartworms the same way dogs do, by mosquito bites. It’s a totally different disease in cats. Our hearts don’t turn into a spaghetti bowl of worms like those plastic models you see in the vet’s office; in kitties, it’s a lung disease. Vets call what we get Heartworm Associated Respiratory Disease (HARD.)
Dogs are lucky dogs. If they get heartworms, there’s a medicine that can kill them (the heartworm, preferably not the dog.) It’s expensive, but kitties don’t even have that option.
Vets often mistake HARD symptoms for feline asthma or other respiratory ailment. In kitties, symptoms (coughing, wheezing, difficulty breathing, exhaustion, puking and loss of appetite) can start showing up with only one heartworm larva. Numbers vary, but somewhere between 10% and 17% percent of heartworm kitties start pushing up the catnip with no previous symptoms.
Mosquitoes pick up heartworm larvae when they drink blood from an infected animal like a dog. Vets call that poor heartworm pooch a “reservoir.” Later, when the mosquito enjoys a feast of Cabernet Catus, it can infect the new dog or cat. Over the next 90 days, the nasty little larvae travel from the skin to the veins. Once they hit the circulatory superhighway, the larvae get a passport stamp through the cat’s heart and lungs and into the nearby arteries. This is when our antibodies, jump to our defense. Most of those immature heartworms meet their maker at this stage, in the arteries around the lungs. Dead larvae aren’t necessarily something to celebrate cuz the damage is already done.
“We understand the cat’s disease comes from the immune system overreacting to the presence of the larvae,” Dr. Cathy Lund tells me. She knows her parasites. She’s the president of the Companion Animal Parasite Council. “It’s the peripheral reaction that causes the inflammation.”
HARD is almost impossible to diagnose in kitties. None of the methods that would work for your buddy, Stupid, work for us. Viewing microfilariae (larvae) in a dog’s blood under a microscope gives the vet a definitive “yes” cuz once larvae appear in dog’s blood, they stay there. Microfilariae show up in fewer than 20% of kitty blood samples because we don’t have adult heartworms making babies.
Those in-office antigen heartworm tests won’t work on cats cuz they’re sexist. The antigen is a protein secreted by an adult female heartworm. Guy-only infections or immature females test negative. And one lady worm may not release enough antigen to make that little blue dot appear.
“Since the damage occurs in the larval stage, and few worms make it to maturity in cats, negative results may give a false sense of security,” Dr. Lund says. “The cat’s body kills off the larva but the collateral damage is what results in the asthma symptoms. Your cat could test negative despite suffering extensive damage to the blood vessels.”
A positive antigen means you either have an adult female worm taking up residence in your body or one recently croaked.
Vets have to look at the big picture (antigen test, antibody test (which tends to give kitties incorrect results too), X-rays, ultrasound scans, and symptoms) to diagnose HARD. If a kitty has an adult worm, right now Dr. Nelson says vets don’t have a medical therapy that will improve the outcome
And they treat HARD the same way they treat asthma. They use steroids like prednisone to reduce inflammation, and asthma inhalers to make breathing easier. The steroids help control symptoms but it’s not a “cure” for heartworms. So if you had adult heartworms, they’d put you on a preventative (so you don’t get infected with more of them) then allow the heartworms to check out naturally.
Sometimes when the worm dies naturally, the cat might suffer from an anaphylactic reaction to the dead adult worm, or the decomposing worm might cause an embolism. Neither of these events happens in the majority of cats. A cat with adult worms stands a 20 percent chance of dying when the worm dies, Dr. Nelson told me.
As with any illness, prevention is the best treatment. Although 59 percent of dog owners in these United States give their pups heartworm preventives, fewer than 5 percent of cat owners protect their cats. What are we? Chopped liver? Prevention is really the only treatment. Monthly chewables Heartgard® prevents new heartworm infections and kills hookworms. Interceptor® for Cats prevents new heartworms, as well as hookworms and roundworms. Monthly spot-ons Revolution® and Advantage Multi® have the added advantage of being one-stop bug-icides. These topicals get rid of most intestinal worms (except for tapeworms), ear mites and fleas. Nothing will kill adult heartworms or the larvae once they’ve found their way to your bloodstream, so try to talk your people into getting you on a preventative as soon as possible.
You need to get your prevention once a month on the dot. If they’re a little late and that larva develops into a juvenile worm, it’s too late.
In the watery aftermath of Hurricane Katrina, the mosquitoes were fruitful and multiplied and so did the heartworms. Vets working at the scene after the big blow believed that 65% of the dogs evacuated across the country had heartworms.
Before Katrina, heartworms were mainly concentrated in the southern half of the U.S., the Southeast, and along the Mississippi River Valley. Now, heartworm reservoirs (a.k.a Katrina dogs) were shipped all over the U.S.. So, Cupid, if heartworms haven’t been a problem in your area, they will be.
Over the last eight years the number of positive cases has soared. According to a survey released by the American Heartworm Society (AHS), in 2004 over 250,000 American dogs and cats tested positive for heartworms. The latest AHS heartworm incidence survey released in 2010 revealed that heartworm disease has been diagnosed in every state in the U.S.—and almost every county and parish as well. According to AHS, “it is estimated that approximately one million pets in the U.S. are now heartworm-positive.”
In 1998, Tom Nelson, DVM, past president of AHS, did necropsies on 259 healthy cats euthanized by an animal shelter in the Beaumont, Texas-area. Dr. Nelson told this humble correspondent the he found adult heartworms in almost 10% of the cats examined. Holy cat! And just because you live inside doesn’t mean you’re exempt from heartworm heartbreak. The mosquitoes can sneak inside through a hole in the screen, when the kids run in and out or when your human brings the groceries in. In one North Carolina study, 28% of the cats diagnosed with adult heartworms were inside-only.
Dr. Nelson says, “Heartworms in cats are much more common than people realize. We know if you went to shelters and did necropsies on unprotected dogs and cats, for every 10 dogs with an adult heartworm, you’ll find a cat with an adult worm. I’m thinking for every cat with adult worm, there are 10 times more with lung lesions. We believe the infection rate is the same as dogs.”
You may think that doesn’t matter to you, cuz the word “water” isn’t even in the Tucson lexicon. That might have been true 10 years ago, but not today.
Every community has “micro-climates” like golf courses, irrigated fields or lily ponds where mosquitoes have a nice comfy place to pass on their genes. Remember those “reservoir” dogs and cats from Katrina? They’re now in a backyard near you. The mosquitoes will happily spread the plague around. Heartworms have been found in wolves, foxes, sea lions and ferrets (Yes, our little weasel brothers get it too, so ferrets unite. Your humans need to put you on heartworm preventative, too.) Once wild animals like coyotes and wolves become reservoirs, vets won’t be able to stop the spread of heartworms. They will only be able to prevent infection by putting pets on a year round monthly preventative.
Even if a kitty has an adult heartworm, the cat is considered an end host. A mosquito feeding from a cat won’t pick up larvae to transmit to another pet so the heartworm life cycle ends without producing a new generation of heartbreakers. However, if your buddy, Stupid, was infected, your people must protect you. There’s an 80% chance of cats having heartworms if they live in a home with an infected dog! And remember, if pooches in your area get heartworms, the cats get ‘em too.
Remember: Heartworms—they’re not just for dogs anymore. Demand equal time. If you’re humans have their dog on heartworm preventative, you need to be on it, too. You know what they say: “A tube of prevention is worth a pound of something that can’t be cured.”
About the Author (Author Profile)
communications. She also serves as vice president of the Cat Writer’s
Association. With 25 years of animal rescue under her collar, Dusty has
rescued or fostered over 1000 cats. She’s author of Kittens for Dummies
and Cat Wrangling Made Easy.
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