Increase in Heartworm Positive Cases

We are seeing a large increase in heartworm positive dogs in the last few months.  Nearly every case that we see is directly related to owners forgetting to give the heartworm preventative they are purchasing or opting out of giving heartworm prevention at all.  Heartworm prevention should be factored into the cost of owning a dog and not giving the prevention is like playing Russian Roulette with your pets health.  In our region, with the high mosquito population, rates of heartworm infection continue to rise.  An important note to make is that when you give the heartworm prevention, you are killing the larval form of the adult heartworm that has already infected your dog in the previous 30 days.  When you miss even a month, the larvae may have developed into late stage L4 larva or juveniles which cannot be killed by heartworm preventatives.  Actually, it’s only after this stage has developed into adults that we can kill them with Immiticide.  When less than 6 months of heartworm prevention has been missed, your pet will not test positive for heartworms.  It takes 6 months from the time of infection for our tests to be able to detect circulating antigen that is derived from the uterus of the female worm.  If you miss the dose, give it as soon as you remember and then give it every 30 days.  Your pet should come in for a heartworm test 6 months after the missed dose to be tested.  Due to the high prevalence in our area, we recommend testing every 6 months.  We don’t want your pet to potentially go an entire year without heartworm disease being detected.

How is heartworm disease treated?

First, the heartworm disease must be staged.  This is done through blood tests, urinalysis and X-rays as well as thorough history taking.  Dogs in late stages of heartworm disease would need to be stabilized before Immiticide treatment.  Obviously the risk of treatment for these dogs is higher than in the dogs that are treated in earlier stages of disease.  In general we recommend treating with Minocycline for 30 days to kill a bacteria that lives on the adult heartworm.  It has been proven that killing this bacteria weakens the heartworm and renders the Immiticide treatment more effective at eliminating the adult worms.  We offer three levels of heartworm treatment depending on what an owner can afford financially.  The gold standard treatment is done by giving 3 total injections of Immiticide.  Following treatment with Minocycline, the dog is given the first injection of Immiticide.  Thirty days later, two more injections are given 24 hours apart.  The three dose protocol has been shown to be the safest method and is the protocol preferred by the American Heartworm Society.  We still offer the two dose protocol because the most expensive part of the heartworm treatment is the Immiticide injections and some owners cannot afford the three dose protocol.  Up until approximately three years ago, most veterinarians were using the two dose protocol on all dogs unless they were severely debilitated.  The injections are given in the lumbar muscles which can be uncomfortable for some animals.  We send home prednisone to be given and in some cases tramadol for the discomfort.  The most difficult part of the treatment for the pet and the owner is the exercise restriction which can last 30-60 days depending on the protocol chosen.  We retest for heartworms 6 months after treatment to make sure the treatment was effective in clearing the heartworms.

What is the cost of heartworm treatment?  $590-1200 depending on protocol and weight of pet

What is the cost of heartworm prevention for 1 year?  $80-120 for pets up to 100#

What can you do to prevent this disease?

First and foremost, give the heartworm pill every 30 days!  Do whatever you need to do to help yourself remember.  Put an alarm on your phone that repeats periodically during the day to remind yourself.  Put a calendar on the fridge.  Schedule it for the 1st of the month to help you remember.  Through Vetsource on our website, you can have the pill delivered monthly on the day it is due if you are one of those people who check your mailbox daily.

Proheart!  For those clients who still can’t seem to remember, we offer an injectable called Proheart that is given every 6 months.  Some of you may remember Proheart from the early 2000’s.  It had a voluntary recall in 2004 due to some safety concerns and was finally brought back to the market in 2008.  From 2008-2011, over 1.3 million doses of Proheart were given with an adverse reaction rate of 0.04%.  Most of these reactions were consistent with what would be seen with a vaccine reaction.  When Proheart 6 first came out in 2001, I gave hundreds and hundreds of these injections with no apparent reaction other than a injection site rection (lump).  I felt it was very safe and effective and was not happy when it was recalled.  Statistically, 1 in 4 dogs were receiving Proheart for their heartworm prevention by 2004.  The reasons for the recall were murky and when it returned to the market, it took me 3 years to decide to use it again.  Part of this reason is that the patent changed hands from Fort Dodge to Pfizer Animal Health which is a great company.  Most dogs are candidates for Proheart except those that have a history of vaccine reactions, severe skin allergies or the very old.

Use topicals!  Vectra doesn’t directly do anything for heartworms but it does repel mosquitoes so you have an added layer of protection.

Make sure you are purchasing your heartworm preventatives directly from a veterinarian.  Products purchased online are not covered by the guarantee provided by the manufacturer. 

What does Dr. Rush use on her dog Hank?

Currently we are using a combo of Trifexis and Vectra since he is still a growing boy (100lbs and 7 months old!).  Once he reaches his adult size, we may switch to Proheart because we aren’t perfect either.  He was 4 days late this month getting his Trifexis which is one of the reasons I decided to write this blog.  I literally woke up at 3:45 AM thinking about it!

What about cats?

Cats get heartworm disease too!  Even one adult heartworm can be fatal to your cat.  In the event your cat contracts heartworm disease, they cannot be given Immiticide as it is toxic to cats. Their symptoms closely resemble asthma and they are generally treated with prednisone.  Other symptoms can range from vomiting, anorexia, neurological symptoms and sudden death.  Some clients are hesitant to purchase heartworm preventatives for their cats since the perception is that since they stay inside, they don’t need it.  Unfortunately, mosquitoes frequently get in our homes and can bite us and our pets.  We recommend Revolution for cats.

I hope everyone found this article informative and not too technical.  As always, we are here to answer any of your questions you have about your sweet babies. 

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