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  Discussion on Strangles treatment
Author Message
Member:
wgillmor

Posted on Friday, Jun 15, 2007 - 11:02 pm:

DrO,

In the article associated with this topic you write:

"It is a common misconception that Strangles cannot be treated. Strangles being an upper respiratory infection caused by a Streptococcus species is very easily treated if abscesses have not formed yet. Horses with cough, snotty nose, and fever with no to minimal lymph node enlargement will respond to adequate doses of penicillin within 24 to 48 hours."

We have a Strangles outbreak at the barn where we board our horses. The local veterinarians are not recommending the treatment described -- they believe that antibiotics can make it worse. Can you point me to information that I can point them to that might change their minds?

Neither of our horses has Strangles as yet, but I want to be prepared.

For accuracy, I should note that I have not talked directly with any of the vets but am just relaying what other owners have reported. They may have good objections in the particular cases and no objection in principle.

Thanks,
Wiley
Moderator:
DrO

Posted on Monday, Jun 18, 2007 - 10:05 am:

Unfortunately there is very little published about natural outbreaks. The microbiologist knows Streps are sensitive to penicillin, know that it will not penetrate already formed abscesses so don't do much work on it.

I have been called into two very large (more than 50 horses in each case) ongoing outbreaks of Strangles. Using the technique described in the article I have seen many dozens of horses respond to treatment within 24 to 48 hours of beginning penicillin while untreated horses who contracted the infection almost invariable went on to a protracted course with abscessation. I don't remember treatment failures unless the lymph nodes were already questionable abscessed but even they improved though they went ahead and ruptured once removed from antibiotics.

Here is a interesting experimental infection with Strangles, through the non-respiratory route, that also illustrates our principles about the use of TMP-SMZ for strangles:

J Vet Pharmacol Ther. 2003 Aug;26(4):247-52.
Clinical efficacy of trimethoprim/sulfadiazine and procaine penicillin G in a Streptococcus equi subsp. zooepidemicus infection model in ponies.

Ensink JM, Smit JA, van Duijkeren E.
Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands. j.m.ensink@vet.uu.nl

Tissue chambers, implanted subcutaneously on both sides of the neck in eight ponies, were inoculated with Streptococcus equi subsp. zooepidemicus in order to compare the clinical efficacy of trimethoprim/sulfadiazine (TMP/SDZ) and penicillin G treatment in a purulent infection. The TMP/SDZ treatment consisted of one intravenous (i.v.) injection of 5 mg/kg TMP and 25 mg/kg SDZ and the same dose of TMP/SDZ per os (p.o.), both given 20 h after inoculation. The oral dose was then repeated every 12 h for 21 days. The penicillin treatment consisted of one i.v. injection of 20 000 IU/kg sodium penicillin G and intramuscular (i.m.) injection of 20 000 IU/kg procaine penicillin G, both given 20 h after infection. The i.m. dose was then repeated every 24 h for 21 days. Eight ponies, each with two tissue chambers, were used in a cross over design; in the first experiment the left tissue chamber (TC) was infected and in the second experiment the right. TMP/SDZ treatment resulted in a limited reduction of viable bacteria in the TC but did not eliminate the infection, resulting in abscessation in 10-42 days in all eight ponies. However, penicillin treatment eliminated the streptococci in seven of eight ponies, and only one pony suffered abscessation on day 10. This constitutes a significantly better efficacy of the penicillin treatment in this model. The most probable cause of the failure of TMP/SDZ to eliminate the streptococci is inhibition of the action of TMP/SDZ in the purulent TCF. Therefore, TMP/SDZ should not be used to treat purulent infections in secluded sites in horses.
Member:
wgillmor

Posted on Monday, Jun 18, 2007 - 6:42 pm:

Thanks, DrO,

The situation is unfortunate. Two different vets have refused to give penicillin to horses that were only running a fever with some coughing (no detectable abscesses as yet.) The number of cases at the ranch is over ten.

Would it be OK to give the vets a copy of your article and your statement in this thread? Or would you like to vacation in Colorado for a month or so?

Thanks,
Wiley
Moderator:
DrO

Posted on Tuesday, Jun 19, 2007 - 7:29 am:

The vacation sounds promising Wiley but I am tied down right now I am afraid. But you are more than welcome to use the articles and posts in any way that might help you and your friends. Take heart in that with good nursing care and those with full blown cases have a excellent chance of full care.

I have long contemplated why Strangles is in this very odd situation. We have already discussed in detail the abscess problem and treatment. But I also think there is another scenerio that the non-scientist has trouble figuring out that leads to this conclusion. Here is the set up:
1) Many horses with upper respiratory disease get well on commonly recommended dosages of penicillin using commonly available products.
2) Strangles cases do not respond to the same therapy.

But what if you commonly use suboptimal doses of penicillin (25 cc's once daily is often given by members here as the dose recommendation by their vet) and/or suboptimal products like mixtures of benzathine pen and procaine pen are used? And you use them frequently for contagious upper respiratory infections. First you can convince yourself this is effective therapy since most upper respiratory infections are self limiting viral problems where fevers break quickly. But this is not the case with Strangles and what seems to be working for other infectious diseases does not work for Strangles. I have seen this actual scenerio and the all-to-frequent recommendation, even by veterinarians, of suboptimal dosages of penicillin make me wonder if this is not the case.
DrO
New Member:
malone

Posted on Tuesday, Jun 26, 2007 - 5:09 pm:

Dr. what is your recommended dosage of Penicillin in horses that do not have swollen glands and also is SMZ's the same as Penicillin?

thanks
Member:
wgillmor

Posted on Monday, Jul 23, 2007 - 1:04 pm:

DrO,

The following is from "Review of Streptococcus equi infections in Horses: Guidelines for Treatment, Control, and Prevention of Strangles" by Corinne Sweeney, DVM; John F. Timoney, MVB, PhD, DSc, MRCVS; J. Richard Newton, BVSc, MSc, PhD; and Melissa T. Hines, DVM, PhD. Published 2005 by the AAEP.

This largely confirms your treatment recommendations and may be of interest to other Horse Advice members who wish to discuss treatment of a Strangles outbreak with their veterinarians. I recommend members obtain a copy of the entire article from your veterinarian.

6. Treatment
Appropriate treatment of horses with strangles usually depends on the stage and severity of the disease. Veterinary opinion on the use of antibiotic treatment remains markedly divided. However, the majority of strangles cases require no treatment other than proper rest, a dry, warm stall, and soft, moist, and palatable food of good quality for the duration of the disease. Food and water should be easily accessible to the horse.

Horses with Early Clinical Signs
During an outbreak, immediate antibiotic therapy of new cases in the early acute phase with fever and depression may be curative and may prevent focal abscessation. Antibiotics should be given for 3–5 days. However, treated animals are likely to remain susceptible to reinfection. Experimentally infected ponies treated with antibiotics at onset of fever usually do not develop lymph node abscessation if protected from further exposure. Because abscesses have not developed at this early stage, the antibiotics have adequate access to the bacteria.
Unfortunately, antibiotic treatment will also inhibit the synthesis of protective antigens, and the development of protective immunity will not be stimulated from strangles; therefore, if the horse remains exposed to infected horses, it will be highly susceptible to reinfection when treatment is discontinued.
It has been argued on theoretical grounds that treatment of strangles with antibiotics is contraindicated, because killing the organisms is indirectly affecting the development of immunity and thereby increasing the risk of bacteremia, septicemia, and metastatic abscessation. There is no experimental or clinical data to support such a phenomenon.
Immediate treatment of horses that show the earliest clinical sign of fever could be an effective way of controlling strangles outbreaks in racing stables or riding barns; however, the disadvantages of treatment should be weighed.

...

S. equi is consistently sensitive to penicillin; thus, it is considered the antibiotic of choice. Laboratories handling hundreds of S. equi strains have noted no emerging antibiotic resistance to penicillin by S. equi or S. zooepidemicus. The incidence of resistance to most other drugs is low with the exception of aminoglycoside resistance, including gentamicin, which is consistently observed.

Thanks,
Wiley
Member:
wgillmor

Posted on Monday, Jul 23, 2007 - 6:51 pm:

I found an earlier but more comprehensive version of the article I quoted above at:

https://www.acvim.org/uploadedFiles/Consensus_Statements/Strangles.pdf

Wiley
Moderator:
DrO

Posted on Tuesday, Jul 24, 2007 - 7:44 am:

Usually, if I wait long enough Wiley the rest of the world usually catches up.
DrO
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