Could this be related to the Rickettsia instead of a disc injury?

[nortexp]

   My 4+ yo 10# neutered poodle was diagnosed with herniated/ruptured disc 3+ weeks ago. Had CT ran.  Diagnosis was "symptoms suggestive of a herniated/ruptured disc". Placed on 1/2 of 57mg Previcox - Tramadol up to 3/4 50mg tab 2-3 times per day three weeks ago. No known injury,  had arched back and painful spine upon exam.  Had been anorexic, lethargic, vomited bile and depressed for 2-3 weeks prior. Refer to test results and dates.

    After two weeks on meds he still did not seem quite right, but neither the specialist or regular vet thought anything else was wrong. Compared to normal activity levels and littermate something was still wrong. Took back to regular vet. Had BUN, UA and at my request a "Tick Panel" that was sent to NCSU was completed. Both vets thought I was wasting my time and money as my dog has only had one, maybe two ticks in his life. I found one in his ear the afternoon before the appt. with the surgeon/specialist. However, the vet's office lost it before it could be examined/identified.

     Received the test results back and they were positive for Rickettsia. Vet started on Doxycycline 25mg 2X per day for 30 days.  Given these symptoms and inability to locate herniated/ruptured disc on the CT, is it possible the arched back and serology results, along with the vomiting bile, lethargy, depression and failure to eat were all symptoms of the Rickettsia, and not a ruptured disc?   If the disc problem doesn't exist, I would like to slowly return him to normal activities from the 3+ weeks he has now had in his crate with me carrying him outside to relieve himself.    

Also, is it possible that he will be immune to Rickettsia once he has had sufficient time for the meds to work their magic?  Will this flare up at some time in the future?   If it can, is there any way to prevent these recurring episodes now, rather than put my dog through this extreme medical scenario again?

[Arnold L Goldman, D.V.M.]

Dear Nortexp,

Your "could-it-be" question is  a challenging one. The approach to diagnosing disease taught to students of medicine, including veterinary medicine, is one of exclusion, rather than inclusion. In other words, based upon history, clinical signs (not symptoms as symptoms are verbally communicated only) , laboratory findings and imaging studies the doctor compiles in his/her mind or on paper a "differential diagnosis list." From this ideally all inclusive list of possible diseases that could fit all the findings, further tests and deductions are used to eliminate all but one of the possibilities. When it works as designed just one possibility is left and that is the true diagnosis.
Sometimes findings do not agree with published disease characteristics. Sometimes a pet may have a second problem newly occurring simultaneously, though the odds are usually against this. Occasionally findings or second problems are incidental to the main illness causing the clinical signs an owner is concerned about. Sorting all this out is the job of a primary care veterinarian,

The disease Rocky Mountain Spotted Fever (RMSF)  is caused by a rickettsial organism "Rickettsia rickettsii" which is carried by certain ticks. RMSF cases may include a wide variety of symptoms affecting many body systems including the nervous system sometimes. Common signs include fever for a time, and are nonspecific for the illness. Many illnesses may have similar such signs. Another infectious disease Ehrlichiosis is often indistinguishable from RMSF.

Many cases of RMSF (40%) have low blood platelets. Your list of lab results did not mention this so I am assuming the platelet count was normal or unremarkable.

As far as the titer of 1:128, while relatively high, in and of itself it does not confirm a RMSF diagnosis. That would require repeating the titer to show a rising titer. Indeed there is more nuance to this in that there are more than one kind of antibody to evaluate, IgG and IgM. RMSF confirmation requires either an increased IgM titer or a four-fold IgG titer. Unless single titers are markedly increased (1:1064) RMSF cannot be confirmed (Infectious Diseases of the Do & Cat, 3rd Ed., p238).

Your description of the course of your dogs illness does not closely fit what would be expected with a  simple intervertebral disc herniation. Typically pain, motor or sensory dysfunction or all three are found in such cases. Also I'd expect a CT or MRI to at least hint of a localizing lesion, i.e. one or more sites along the spinal cord that are suspicious for disc compression. Your description "anorexic, lethargic, vomited bile and depressed for 2-3 weeks prior"  also does not fit that scenario.

My approach at this point might be to review all minimum database laboratory findings and then repeat those tests (CBC, Chemistry profile, urinalysis) and also the RMSF titers (IgG and IgM) ad see where we are now. Of course response or lack thereof to empirical treatment (doxycycline) may be instructive as well.

To answer your specific questions:

1. “is it possible the arched back and serology results, along with the vomiting bile, lethargy, depression and failure to eat were all symptoms of the Rickettsia, and not a ruptured disc?” YES, but there are other illnesses that could also tie all this together.
If the dog is not responding or new signs are appearring it may be time to retravel the path of minimum database and see what today's physiologic "snapshot" looks like.

2.  "is it possible that he will be immune to Rickettsia once he has had sufficient time for the meds to work their magic? " YES. Naturally infected dogs that recover from RMSF have never been shown to be reinfected (Greene, p240).

3. "Will this flare up at some time in the future? " It is unlikely acute disease will reoccur (see #2 above) however some recovered animals have a degree of permanent organ damage of the "cardiovascular, neurologic and renal" systems in particular (Greene p240).

I wish you luck with solving your dog's problems. In such a complex case it is never wrong to seek second opinions and it is important to retread minimum database testing to attempt to observe changing clinical pathologic (lab test evaluated) findings.
Please let us know how this turns out.

Very best regards

Arnold L. Goldman DVM MS

[Arnold L Goldman, D.V.M.]

Dear nortexp,

You are very welcome. No question your dog has a problem or problems that poses a diagnostic challenge. When that occurs, and after the thorough workup your dog has had, it would not be unreasonable to consult with a Diplomate of the American College of Veterinary Internal Medicine, i.e. a "Board Certified" internist.

This is especially pertinent if your dog is not improving clinically while on doxycycline and the analgesics. I did note no mention that corticosteroid medications were given, which commonly are in acute intervertebral disc disease (IVDD). Was there a reason these were avoided?

As far as the CT study, "reading" them is an art best practiced by those who read them frequently. If the study has not yet been reviewed by a radiologist, I would have that done definitely. Such an individual gas the expertise to interpret the subtle signs that might be missed by someone with limited experience in reviewing such studies.

It would be up to your veterinarian to determine when it would be best, or even useful, to repeat serologic tests but 3 -6 weeks apart is typical for paired serum analysis in such a situation.

In summary, when you are not satisfied with an outcome, the communications about your pet or the general lack of progress of an ongoing case, it is prudent to seek an additional opinion. I would only seek opinions, however, from those with advanced credentials, so that you dont end up with three equally valuable, but conflicting, general practitioner viewpoints. Do seek out an ACVIM Dip to achieve that.

Please do keep me informed. I am very interested to learn what the actual diagnosis will be. Thank you and good luck.

Sincerely,


Arnold L. Goldman DVM, MS

[nortexp]

Thanks for your support in my search for answers.   If going to a third vet (not our regular vet or the surgical specialist) would my dog be better served by going to an Internal Medicine specialist or Oncologist, rather than general practice vet?   We live outside the metroplex and our vet does both large and small animals in a group practice.   This means he must focus on the big picture more often than the details.   He is very interested in getting to the final correct diagnosis, but is more of the "wait and see if this helps" type of vet.

In pursuing a more definite diagnosis would it be helpful to have the CT reviewed by a veterinary radiologist?   There is one in our area who will do an interpretation with a referral.

Also, the initial Tick Panel was done before the doxycycline was administered.   When I originally took him to the vet I had noticed he had an arched back when walking and occasionally cried when I picked him up.  Upon the vet's workup he barely (but did a little) flinched when the T12-13 area was pressed.  No cry of pain, no limping.   Thus, the initial diagnosis of herniated/ruptured disc along with the Previcox and Torbugesic and crate restriction.  His inability to get comfortable after five days made us request a referral to a specialist for CT or MRI.  CT broke, so they had to keep the dog for an extra 24 hours to complete the CT.  No actual location of lesion or rupture specified, either verbally or in the written report.  

10 days later with no improvement return to regular vet.  BUN and UA ran with normal results.   Sent additional serum to NCSU for tick panel.   9 days later positive Rickettsia diagnosis and started doxycycline.  

Should additional titers be done and if so when?   Should we start over with all serology and are there add on tests that would help us close in on a more defined diagnosis?   We are very proactive in his care and would like to get answers and best outcome promptly.

Thanks again for your prompt answer and support.