A herniated disk would be very easy to miss on plain radiographs, though back pain should be very apparent on physical exam, and it seems unlikely that the signs would just come and go (and with a fever, too) like that
Thinking out loud and thumbing through a vet med textbook. Nothing more than a fellow A2Ker being sympathetic and curious and looking a few things up
How old is Zoe? Zoe's a boxer, right?
If you're on or near the Gulf Coast or up around north Texas/Oklahoma, your vet might be thinking in terms of Hepatozoon americanum - though there should be a mild to severe elevation of white blood cells on the CBC. This is most common on the gulf coast but moves up into Oklahoma, as well. (Dunno where you liver, bella
)
Clinical signs of hepatozoonosis as described in Small Animal Internal Medicine (Nelson and Couto, 3rd ed.):
Quote:Clinically affected dogs have been in all age-groups, but disease is most commonly recognized in puppies. Fever, weight loss, and severe hyperesthesia {exaggerated response to sensory stimulation - patiodog's off-the-cuff definition} over the paraspinal regions are common findings. Anorexia, pale mucous membranes from anemia, depression, oculonasal discharge, and bloody diarrhea occur in some dogs. Clinical signs can be intermittent and recurrent. {any typos are patiodog's, too}
More info at
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/10407.htm&word=hepatozoonosis
The episodic nature of the sickness makes me wonder about immune-mediated disease, too. Immune-mediated meningitis, for instance
(from
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/60208.htm)
Quote:The clinical signs in Beagles, Boxers, and German Shorthaired Pointers consist of cyclic bouts of fever, severe neck pain and rigidity, reluctance to move, and depression. Each attack lasts 5-10 days, with intervening periods of complete or partial normalcy lasting ≥1 wk. During attacks, protein and neutrophils in the CSF are increased. The lesion is an arteritis, primarily of the meningeal vessels, but occasionally of other organs as well. The disease is often self-limiting over several months; attacks become milder and less frequent. Glucocorticoid therapy reduces the severity of attacks. In some animals, the disease becomes chronic and only partially amenable to therapy.
Have your vets ever considered an endocrine problem? The signs aren't exactly perfect for hypothyroidism or Addison's disease (hypoadrenocorticism), but that doesn't necessarily mean they might not be involved (slim chance though, I think). Hypothyroidism doesn't seem terribly likely given the fever, but it can be assoicated with nervous system signs (confusion, incoordination, unexpected aggression). Hypothyroid dogs may have low body temperatures and most have high serum cholesterol.
Dogs with Addison's disease may occasionally show intermittent signs (as this book puts it, "Observant owners may occasionally describe an illness with a waxing-waning or episodic course; however, this bit of information is the exception rather than the rule.") Usually signs of Addison's appear to be related to the gastrointestinal tract or, less commonly, the urinary tract, but our clinicians always warn us that Addison's is "the great pretender." By definition, dogs with Addison's should have low sodium and chloride and high potassium in the serum, but this won't be picked up in all cases. Common signs of Addison's disease include lethargy, anorexia, vomiting, and weakness. Less common signs include diarrhea, weight loss, shivering, peeing a lot, and abdominal pain.
Again, just some thoughts, maybe some things to talk about with your vet when you talk to him if he hasn't come up with anything
