A Heartworm Preventative Misconception and How to Save Your Pet From Tuco the Evil Drug Lord

Sometimes people think things that are incorrect, but they don’t know they are incorrect so they continue to think them.  These are different from opinions.  Someone may decide that your opinion is the wrong one, but that’s your and their prerogative.  There are no wrong or right opinions. But when our thoughts consist of facts are flat-out wrong: well, then that’s a problem. 

God knows extricating the facts from the opinions during this presidential election quagmire is growing exhausting.  Which reminds me I’ve got to go out and vote soon so that my opinion gets counted.  Incidentally, you’ve better get off your keester and vote too, no matter what candidate. This one is too close for you to just sit it out, then whine about who wins later.

Anyhow, couple misconceptions that I run into at the office:

#1:   Oral Heartworm preventative stays in the dogs bloodstream for a whole month, continually protecting him or her from infection.  Not true.  According to Plumb’s Veterinary Drug Handbook, Ivermectin’s (Heartgard, Iverhart) half-life is 2 days.  Milbemycin (Interceptor, Sentinel, Trifexis)  is hours.  Selamectin (Revolution) is a topical product, it sticks around longer.  Half life of Revolution is 11 days. Oh and for those not in the know, the half-life is the time it takes for half of the drug to be gone from the patient’s system. 

The way these products work is sort of nuclear bomb-esque.  But first a word about how heartworms grow up…

Your dog goes about his or her day potentially getting bitten by heartworm infected mosquitoes (or definitely being bitten if you live in the south and the dog ventures outside at all. Even “just to potty”, and lets not forget those stupid mosquitoes that get in the house and buzz around your head all night).  These skeeters inject the pet (cats can get them too, by the way) with baby heartworms which then make their way via multiple life stages (they start as babies, then molt through toddler/adolescent/teen/young adult and adult stages) to the heart to set up housekeeping.  Once a month you give your heartworm preventative and it detonates a little virtual bomb that kills off all baby/adolescent/teen/toddler heartworms in the system from the previous month (It takes the heartworm larvae about a month to go through these stages).  There is a much more technical and detailed account of this using boring L1,L2,L3, etc. terminology but I’m going for simple.  IF you want the dull details goto The American Heartworm Society website (many thanks to Cindy at Weeknite Meals who is also our awesome website designer for teaching me how to insert links into my blog). 

Anyhow, moving on, heartworm prevention does not kill young adult and adult heartworms.  So if you are too late in giving the prevention and the worms mature into young adult stage, those guys are going to get to the heart to grow into adults and set up an actual heartworm infection that can make the dog sick.  At this point, the only way to get rid of them is to use the arsenic derivative Melarsomine to kill them. That is expensive, hard on the dog, hard on the owners and no fun at all. (I might mention at this point that it’s hard on me too because I generally have to give the dog one to three shots IN THE BACK using an INCH AND A HALF LONG NEEDLE!!! I hate doing that. Tiny dogs get 3/4 of an inch, still in the back). 

So bottom line: give your heartworm preventative monthly. There isn’t chemical swimming around your pets bloodstream 365 days a year (unless you use Revolution or Proheart 6, but that’s another blog topic). 

#2 That microchip your pet has implanted under his skin is NOT a GPS device.  We’re not talking lo-jack here.   If your microchipped dog wanders off, nobody is going to be able to zero in on his location and rescue him from the clutches Tuco the evil drug lord (I’ve started watching Breaking Bad. I’m on episode 2, season 3.  It’s heart wrenching, highly stressful, torture to watch, but I can’t stop). 

Anyhow, all the microchip does is transmit a number when scanned with our handy universal scanner thingy.  Sort of like a bar code.  Once we get that number, we call the parent company database (AVID, Home Again, AKC etc.) and see who that number is registered to.  If you didn’t register that chip with anyone well then that number is totally useless.  Registration entails filling out a form or going to the website and giving them all of your contact information. Generally there is some fee involved to register, but you don’t necessarily have to go for the monthly extras. 

A client recently told me that somebody in a pet store told them NOT to register the microchip, that it was a waste of money.  THAT, is ridiculous and subsequently renders the chip 100% useless.  So find out what kind of chip you have and then register it, or your pet will become Tuco’s new friend, and Tuco does not treat his friends well. 

As to the GPS thing.  In order to transmit a GPS signal, you need a battery.  Nobody has made a battery small enough to fit into an injectable pet ID microchip (Yet.  I have on good authority that one is in the pipes).  There are GPS collars which are a great idea, but dogs and cats that get lost and don’t get back home usually aren’t wearing their collars.  Nature of the beast.

OK I’ve rambled long enough. Hope I made some of you a little smarter.  If not and you still have questions…hit me (not literally).

UPDATE: I forgot to mention that Home Again, the microchip company actually tracks which chip numbers they send to which veterinary practice. So if your pet has a Home Again chip, but isn’t registered, the chip number can at least be tracked to a particular vet clinic.  With any luck then the folks at the clinic might be able to subsequently ID the pet.


4 thoughts on “A Heartworm Preventative Misconception and How to Save Your Pet From Tuco the Evil Drug Lord

  1. Thank you for he heads up on the lifespan of the heart drugs. I’m sure I’m not the only owner who occasionally forgets to dose her pet…this is a new incentive for me to put a calendar in my pantry to track doses.

    On another note…why would someone go through the trouble of chipping their pet and not register them?

    1. Sadly, it’s super common. Lots of folks think that the microchip automatically comes loaded with all of their information and the tech/vet/shelter worker doing the scanning will immediately know who the pet belongs to. Probably a communication error by whoever put the chip into the pet (or a listening error on the chip receivers owners part).

  2. Great info Dr. C, I never knew that’s how heartwarm preventative chewable work, just know that Booger loves eating them!

    Thank you for the mention, I feel like a celebrity!

  3. First of all, I will be standing in line at 6 AM when the polls open.

    I’m flabbergasted that some people think that a chip can act as a GPS device. (If it did, there would be an app for that. No doubt it’s coming, though.) There are GPS devices that can be attached to a collar, but they’re totally separate from a chip and don’t carry owner information.

    Thanks for the information on how heartworm preventatives work. I saw a video of a heartworm surgery and, oh boy, it was nasty! They kept pulling out really long, awful-looking worms.. and kept pulling them out and pulling them out. It was hard to believe the dog survived and ended up being fine. No doubt the happy ending doesn’t happen as often as we would like.

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