The Show Dog Super Site


Mary C. Wakeman, D.V.M.
Ashford Animal Clinic
Canine Fertility Center
Ashford, CT

Let's start this discussion with the big word and get it out of the way. Jarisch-Herxheimer Reaction; Herxheimer or Herks for short.

When the body is harboring a significant amount of foreign protein, for instance, as in the form of migrating heartworm larvae, migrating larvae of intestinal worms, or the very large spirochaete bacteria that cause Lyme disease, it is faced with a set of problems which cause disease (such as Lyme).

When those living organisms die, due to treatment with monthly heartworm medication (any of the monthly meds) or due to treatment of Lyme disease with a good antibiotic, the body reacts differently to the dead protein in its tissues and blood stream. The dead spirochaetes may not be causing symptoms of Lyme any longer, but they now cause an extreme inflammatory response in the individual. The migrating larvae of intestinal parasites usually do no great amount of harm while live, but when dead they, too, cause a massive inflammatory reaction. Killing intestinal parasites as adults does not entail any such risk. Likewise, killing heartworm stages with the daily heartworm medications causes no risk of this nature.

The Herxheimer reaction in those of us who have Lyme disease usually manifests itself as feeling really 'sick' one to five days after starting on antibiotic medication, or after starting a different antibiotic medication, and often periodically while continuing on the same medication. This is taken clinically as proof that the disease is still active, and that the antibiotic is effective as well. So there is something good about feeling bad under these circumstances.

The exact same thing happens in dogs. The manifestations of Lyme disease in dogs are exactly the same as in humans. Anything from headache, feeling 'sick', kidney malfunction, heart arrythmias, stiff neck, headache, muscle and nerve pain, and joint pain can be affecting your dog. How do you know if your dog has a headache?

One day a Dane bitch walked into my office with feet swollen to about 3 times normal size. She had had her monthly heartwormer the day before, and her feet were swollen with edema due to the massive inflammatory reaction she had to the dead protein of intestinal parasites she was host to.

So, the point of all of this is, what happens to the pregnant bitch if she has this kind of reaction. What happens to sperm if the stud dog gets monthly heartworm and also harbors intestinal parasites. These are some of the matters which have led a significant number of veterinarians to say 'no' to monthly heartwormers. 'No' to all of them, since the precise chemical isn't the problem, but the very mechanism of action of this form of heartworm control. All of those 'monthlies' which advertise control of intestinal parasites are actually saying they can cause this kind of problem.

When a new medication comes on the market, we are supposed to ask three questions:

  • 1. Is it more effective?
  • 2. Is it safer?
  • 3. Is it cheaper?
Monthly heartworm medication gets a 'no' response to each of these questions. Is it good for your vet's bottom line? Well, that one gets a 'yes'. The rule for breeding animals, dogs or bitches is no monthly heart worm medication.

What about Lyme disease in pregnant bitches? We are strongly suggesting a Lyme Western Blot test in bitches before they are bred. First, Lyme disease can be transmitted to the baby from the mother. Second, the antibiotic medications we are most likely to prescribe to the pregnant bitch - due to their known safety in pregnancy - are Amoxicillin and Cephalexin (Keflex). These are also effective antibiotics for treating Lyme disease. Use of these good antibiotics can precipitate a Herxheimer reaction in the pregnant bitch with subclinical Lyme, disease which can cause resorption of fetuses. Ask yourself this; how many litters have been lost in the past 15 years in areas with Lyme disease due to Herxheimer reactions in pregnant bitches with Lyme disease? How many stud dogs have wiped out their sperm for a period of 6 weeks following treatment with a monthly heartwormer? How many pregnant bitches are given monthly heartworm medication?

Our recommendations are:
No monthly heartworm medication ever in breeding animals. Lyme Western Blot blood tests should be performed on bitches 4 to 6 weeks before they are due in heat.

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