Download Disseminated ldiopathic Myositis in Young Marshall Farms Ferrets

DisseminatedldiopathicMyositisin Young
MarshallFarmsFerrets
DVM, PhD andMarkBurgess,DVM
By KatrinaRamsell,
An apparentlynew, seuere,and preai- would produce even with severe
ously unknown illness has recently infections. The white cell counts
beenseenin aariousparts of the United in our patients have varied from
States,fficting young ferrets from around 14,000to nearly 60,000,with
Marshall Farms, usually behueenthe most cells being neutrophils, not
agesof 5 and 10 months.Theillnesscan lymphocytes. Some patients show
occurin isolatedferrets that haaeliaed a mild to moderate anemia, which
alonefor months,or in multipleferret initially may be nonregenerativebut
whereinthe otherferrets in can become strongly regenerative
households,
thehouseseem(sofar) to beunaffected. (many red blood cells being proThe diseasestrikes rapidly, and most duced). The combination of high
casesreportedhaaebeenfatal. This ar- WBC and regenerative anemia can
ticle discussesthe generalappearance superficially resemble autoimmune
of the illnessand possiblecausesand anemia. However, there is usually
no elevated bilirubin in the blood
treatments.
(which would be expected if the
immune
system was destroying red
DEFINITION
cells). Another form of immuneDisseminated Idiopathic Myositis mediated anemia can occur if the
is a descriptive term for what the immune system damages the bone
"disseminated"means
diseasedoes:
"idiopathic" means marrow, but the anemia in those
widespread;
(no new
"of unknown origin or cause"; and cases is nonregenerative
made)
being
red
cells
"myositis" meansmuscle inflammation. This illness causeswidespread The serum chemistry tests are usumuscle inflammation and dam- ally unremarkable, though one of
age, and no known cause has been our four patients had elevated ALT
found. Other tissues can also be af- suggestingliver damage (hepatitis).
fected, but the inflammation seems Surprisingly, although this disease
to focus especially on muscles. In causes extensive muscle inflamour practice/ we have seen four matiorL CK values (which detect
casesof this diseasein the past three muscle damage) are usually fairly
months. Signs typically are lethargy, normal in thesepatients.
fever (often over 104" F), weakness
and reluctance to move, sometimes When an external lymph node is
pain when handled (especiallyover enlarged, biopsy of the node shows
the back or hips). Appetite may be suppurative
granulomatous
to
depressed. Some patients have ex- inflammation, with no inJectious
ternal lymph node swelling, some- organisms seen microscoPicallY.
times in a single node, such as in a Bacterial cultures yield no growth.
leg or in the neck area.
Complete necropsy and microscopic
exam of deceased patients shows
The blood test results in theseferrets widespread suppurative in{lammaare unusual, and provide the stron- tion with the muscles of the bodY
gest initial evidence of this disease. being the most heavily targeted.
The CBC is particularly abnormal, The esophagusand skeletal muscles
with extremely elevated white cell seem particularly hard-hit by this
counts, far above what most ferrets disease,but even the heart and gas-
to
AMERICAN
FERRET
trointestinal muscles are affected.
Some non-muscular organs such as
liver can be affected,as well. Again,
no infectious organisms such as bacteria, rickettsia, etc., have been seen
in any of the affected tissues, even
with special stains applied. Electron
microscopy has also failed to find a
visible infectious agent, including
viruses.
"Suppurative"
inflammation (i.volving neutrophils as the primary
white blood cell in the inflamed tissues) is typical of bacterial disease
rather than viral. The high neutrophil counts in the blood would
also fit severe bacterial disease.
Flowever, one would expect to see
such organisms with microscoPic
exam of the tissues in most cases.
Also, these patients routinely fail to
improve (other than briefly) on any
antibiotic combinations we have
tried, including penicillins, cephalosporins, tetracyclines, quinolones
(such as Baytril@), metronidazole,
or chloramphenicol. Brief improvement on antibiotics might be due to
treating a secondarybacterial infectioru which took advantage of the
already-weakenedpatient.
Ce,usE oF THE DISEASE
We are forced to conclude that a
likely cause of the disease is viral.
An immune mediated disease attacking the muscles isn't out of the
question; however, none of our
cases have improved when given
high dosages of cortisone. An immune deficiency (inherited?) which
shows up in young adults could be
hypothesized, but if a ferret were
overwhelmed by infection due to
immune deficiency, then infectious
(bacterial) organisms should be
REPORT,
VOLUME I 3, NUMBER 3, 2OO3
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