Raja Has Heartworm - I feel horrible

How's Raja doing?

Here are the detailed stages (L1-L6) of the heartworm life cycle:
(1) blood stream of original infected dog - L1 (microfilaria)
(2) inside the mosquito - L1 develops into L2 and then L3
..... Growth occurs only above 64 degrees Fahrenheit (2 weeks to about a month)
..... Developing heartworm dies if temperature falls below 57 degrees Fahrenheit
..... Developing heartworm dies if mosquito dies (lives about 35 days)
(3) in the skin of the new host dog
..... L3 deposited by mosquito (day 1)
..... L3 develops into L4 and then L5 (young adult)
..... L5 becomes too old for "preventives" to kill it (about day 45)
(4) L5 enters the blood stream of the new host (about 3.5 months)
..... L5 develops into L6 (mature adult)
(5) L6 can mate (approximately 5-7 months after day 1)
 
There are several ways that one can get a negative heartworm test, give preventatives, and then get a positive results:
(1)  Heartworm preventatives are not foolproof.  If a baby gets into an area of low blood flow, it may not get enough of the pesticide to kill it before it gets too big for the pesticide to work.  This is why you need yearly tests.
(2)  The cheaper heartworm test just checks for microfilaria (L1) in the bloodstream.  If the dog is on a preventative, there can be adult female heartworms, but no microfilaria.  The test for adult female heartworms is more reliable, but still not foolproof.  There is no test for stages L3-L5 or for adult male heartworms.
(3)  At the time of the first test, there can be L5's on the skin and/or in the bloodstream which are not subsequently killed by the pesticide. 
 
Puppies under 6 months are not tested for heartworms before they are put on preventative.  This is because there has not been time for adult female heartworms to develop.  A pup could have L5's that the pesticides can't kill, so the pup should be re-tested 6 months later.
 
All dogs and pups over 6 months who are not on preventative and who test negative should be rechecked after 6 months on preventative, because they could have had L5's at the time of the first test.
 
ETA:  If a dog has been on preventative, you should always use the test for adult female heartworms.  In fact, if someone tells you a dog is negative, but has only tested for microfilaria, I would advise an immediate re-test for adult female heartworms.  In my opinion the cheaper test for microfilaria should really only be used by shelters for initial screening (detects a "contagious" dog).

CAUTION:  Putting a dog on preventatives without testing for heartworms can kill the dog.  Dead microfilaria (L1) can congest the heart and lungs.
 
Note:  I think it is hilarious that we "prevent" adult heartworms by killing the babies.

Very informative post! I wish the vet we had first taken Gracie too had told us to re-test her after six months. I'm telling everybody that adopts a dog to do that now, after what's happened to us and Ashley and Raja. Gracie is doing pretty well, very little coughing, although she did vomit today (just yellow bile). We're at day 11 post-injection, so we're heading into the choppy waters over the next week or so! Thanks for all the kind thoughts we've been getting!

Thanks for the information, Janet.  I had no idea.

Janet - this was a GREAT post !  Very informative.   My dog was tested for HW by the Rescue Org.  She's somewhere between 7 - 10 months old, so from your post it seems that HW is really a possibility with her (esp since she was picked up as a stray in Miami - year round mosquito's).   She was tested 2 months ago (when she was between 5 and 8 months old) so your post has me even more concerned now.   I'm definitely going to have her retested but I want to make sure I "time it right".
 
Two questions:
1.  When would be the best timing for retesting (she's been on preventatives for 2 months now) ?
2.   What are the various treatments, depending up stage ?
 
 

Here in Florida -- even in CENTRAL Fl (which isn't as bad as Miami) the statistics are something close to 90% of the dogs that come thru Animal Control ARE *heartworm positive*.  AT this point they are seeing puppies BORN heartworm positive because Mom was positive when she carried them.  It's truly sad.
 
 

Callie - you're scaring me !  I'm taking her back to the vet for another test on Wednesday.   And I'll repeat it every 2 months if I have to !   I'm really scared now.

JoAnneDe, most sites I have read say the antigen can't be detected for about six months after infestation, so if you just had your dog tested two months ago, that would be another four months before anything would show up.

Two questions:
1. When would be the best timing for retesting (she's been on preventatives for 2 months now) ?

 
JoAnnDe, let's look at the timeframe. 
(1)  Day 1 the L3 enters the dog's skin. 
(2)  L5 becomes too old for "preventives" to kill it (about day 45).
(3)  At 5-7 months the L6 adult can breed (3.5-5.5 months after an L5 is old enough to survive a preventive).
 
Assume your pup had heartworms at birth (bitten by a mosquito on day of birth) - that way the age of the pup and of the heartworms is the same.  A test at 5 months might show heartworms, but might not depending on how fast they developed.  A test for adult female heartworms at 7 months should detect all of those initial at-birth heartworms (if any).  Since your test could have been before 6 months, I think it is worth a retest now.
 
Next assume that your pup has heartworms that were just old enough (about 45 days)  for the preventative not to kill them.  These heartworms would now be 3.5 months old (45 days + 2 months).   In about another 3.5 months all of those heartworms would be at a breeding age (7 months).
 
If you retest now and the results are negative, I would relax, but then retest again in 4 months (3.5 months plus a fudge factor).  That should detect the last of any possible adult female heartworms.  Note that this is 6 months after your first test and the start of the preventative.
 

2.   What are the various treatments, depending up stage ?

I am not up on the lastest treatments.  However, since your pup is on preventatives, you would only need to treat to kill the adult heartworms.  Dogs with both microfilaria and adult heartworms need treatments to kill both.  The adult heartworms are killed to prevent injury to the dog.  The microfilaria are killed to prevent the spread of heartworms.

Callie - you're scaring me ! I'm taking her back to the vet for another test on Wednesday. And I'll repeat it every 2 months if I have to ! I'm really scared now.

JoAnnDe, your pup is young and healthy.  Even if heartworms are found, her odds of full recovery are excellent.
 
Consider this - If a dog tests clear of adult female heartworms 6 months after starting a preventative, statistically there could still be a couple of adult male heartworms that we can't detect.  This is not considered a serious problem.  The males will just die of old age.  The odds of there being a lot of adult males without a single female are very, very low.

ORIGINAL: gradyupmybutt

How's Raja doing?

 
Raja is doing really good. As you probabaly know I decided to treat her myself, with the way Callie suggested. And not do it through the vet's.
 
I've been treating her for about 3 weeks and so far everything is going great.
The only think that has been hard is keeping her quiet!
 
But, other then that she has been doing good. She starts dog training next month, I will just have to make sure she does not get too exited and play with other dogs there.
 
But, thanks for asking!

Don't be scared -- it's all SO treatable.  If you DO find it, it's going to be a very light case or it would have shown up before. 
 
Just be sensible and use a good preventive like Interceptor (HeartGuard and REvolution both are getting reputations for failing and Revolution is systemic anyway).  Discuss with your vet the KIND of test given -- Janet's giving you some excellent information above on the type of test.  Vet's often have a 'favorite' test -- whether because of cost or ease in adminstration, etc. -- ASK. 
 
This isn't beyond your control -- there is SO much you can do here.  Don't be terrified -- simply be proactive.  If it turns out positive you get her treated (and there's more than one way to do that as well) -- but yours is a young dog and it's very do-able.  The BIG deal is you have this dog now.  This dog is blessed!! It's with folks who CARE!!  That's the edge that most dogs that go thru animal control don't have. 

I'm so glad Raja is doing well - I know how upset you were when you found out about the HW.
 
And thanks to Callie and Janet for the info and the support.   I'm going to make an appt for Prancer for tomorrow for a retest and then I'll retest again in 3 - 4 months.  Given her history I feel that I can't be too careful about this.

From Calliecritters:
 
Here in Florida -- even in CENTRAL Fl (which isn't as bad as Miami) the statistics are something close to 90% of the dogs that come thru Animal Control ARE *heartworm positive*. AT this point they are seeing puppies BORN heartworm positive because Mom was positive when she carried them.

I believe that this means that the puppies are born with just heartworm microfilaria (stage L1).   They are "contagious" in that mosquitos can pick up the microfilaria when they bite the pup.  An adult heartworm in the bloodstream requires the bite of a mosquito carrying a stage L3 baby heartworm and about a 3.5 month wait for the heartworm to become an young adult (stage L5) who migrates from the skin into the bloodstream.
 
Callie, am I right about this?  I can see the tiny microfilaria making it through the placental barrier, but I sure hope that adult heartworms can't get to the developing pups!!

Thank god he's doing well