Heartworms are a deadly disease and untreated, will most certainly cause a painful death to dogs and now to cats that are outdoor cats.  We strive to provide the best care for our fosters and all dogs that are negative should NEVER miss a dose of prevention.  It is up to you as a foster to make sure that your foster dog has prevention on a regular basis. HWP can be mailed to you before the due date so make sure to be in touch with your Medical Coordinator to have prevention on a timely basis.

Basic protocols

  • Treatment will vary for each dog depending on the following factors; age of the dog, activity level, severity of the disease, overall health and the attending veterinarian.
  • Each vet has a slightly different protocol, and although we are not vets, we have established some basic protocols for treatment in conjunction with Dr. Collins of Shadow Creek, who is also on our advisory board. Our basic protocol is as follows.
    • All dog should go on prevention upon intake if they are over 3 months of age. If you do not know your foster’s HW status, they should be given ivermectin based HWP, ie. Heartgard, Triheart, etc. as soon as possible.
    • If you know your dog is negative and it has been confirmed by a non shelter vet, you may use Sentinel, Advantage Multi (also contains flea prevention), Revolution or Trifexis.  Please see your MC for dosing as the Advantage multi is the most economical way to treat for HW and flea prevention and we will be moving towards that as a main medication for non HW+ dogs.
    • If you have a puppy and it reaches the age of 3 months, it should go on prevention at that time. Shadow Creek is administering prevention at the time of s/n for foster dogs that are puppies. If you do not get it and your puppy is not already on prevention, please ask for it. If your foster is 3 months it should go on prevention no matter what the vaccine status is or whether it is s/n or not. WE DO NOT TEST FOR HW UNTIL 6 MONTHS, but prevention is needed before this time.
    • If you dog tests positive for HW disease, the dog will go on one month of doxycycline (or an antibiotic prescribed by the vet in the case of dogs too small in weight for doxy). It will also start taking PREVENTION at this time (ivermectin based)

Treatment for heartworm disease

  • Heartworm disease can be treated several different ways. The way we choose to treat will depend on several factors stated above.
  • For dogs that are positive (AND in very good health otherwise), a two injection protocol can be used. With the 2 injection protocol, the dog is given two immiticide injections back to back in a 24-48 hour period. The dog will usually stay overnight to be observed for any signs of distress.  This method is a very quick kill and there is little time for the dog’s body to absorb and pass the dead worms, so it can be very hard on small dogs. (The worms are basically the same size no matter how large the dog is). After the treatment the dog should be on kennel rest until released by the attending vet. This treatment would not be advisable for dogs with heavy HW loads (high or strong positive) or older dogs with compromised lungs or heart function. On a case by case basis, this might also be used for younger, otherwise healthy larger dogs, with no other issues that would preclude the treatment.  This decision would be made in conjunction with SAVE medical coordinators and the attending vet.
  • Dogs with a high or undetermined HW load will be treated with 3 injections. One injection will be given after 30 days of antibiotics (and in some cases, prednisone) are completed. After 30 days of kennel rest, a second set of two injections is scheduled and there is an overnight stay for monitoring for adverse reactions.  This will be followed by 30 more days of kennel rest. Each vet will have a slightly different follow up procedure.
  • VERY RARELY, we will use the “slow kill” method of treatment. This consists of one month of antibiotics and bi monthly heartguard or advantage multi. Then one month of no antibiotics but continue the bi monthly prevention.  This can take MONTHS to show a clear test, but can be used in VERY active dogs that are stressed by crate rest, older dogs with underlying health issues and when advised by a veterinarian.  It is also used when a dog has undergone treatment and still shows positive for HW disease. To better understand the role of Doxycycline in heartworm treatment read this article.

What to expect with heartworm treatment

  • Your dog will be very sore from the injections as they are given very close to the spine. You may be given pain meds for your dog to take for a day or two after the injections. If you do not get meds and your foster is in pain, please advise your MC so that appropriate meds can be obtained for your dog.
  • Some dogs will not eat or will be reluctant to get up. This is a reaction to the pain.  Very rarely a dog will vomit, again usually from pain.
  • Warm compresses on the injection site will help with pain management. Limiting your dog’s jumping up and down on furniture will also help.
  • Pamper him as it is a painful time. Give extra treats and love, but limit activity to leashed potty breaks.
  • Should you see blood in the urine, stool or bloody mucous from the mouth or nose, contact your MC or FC immediately, as this can be a medical emergency.
  • All dogs should have limited activity. Leash walks to go potty and crate rest are mandatory.  Short times of quiet couch or floor cuddling is okay, but nothing that will raise the heart rate.  If you household includes lots of noise, rambunctious dogs, or rowdy kids that are likely to provide too much excitement, move the dog to a quiet bedroom or climate controlled space that will be quiet.

Other issues with heartworm treatment

  • Not all dogs will be free of heartworms even after the most aggressive treatment. There is a fail rate of about 5% so with the numbers of animals that we treat, some will fall in that 5% of failure rate. Each case will be looked at on a case by case basis to determine what further treatment is required.
  • A dog that tests negative, may test positive a few month later as the initial test did not pick up the larvae that could not be detected by testing. Larvae that are not mature, but not microfilaria (immature first stage larvae) are not detectible with any standard tests. This is why it is so important to not miss a single dose of prevention.  We need everything possible in our favor.
  • If this is confusing, don’t feel bad! It is confusing to all of us who have to make decisions about care.  We are doing our best to make the right treatment available for each animal.  Things are constantly changing in medicine so hopefully soon with will have new tools to fight this disease.