Objective—To characterize clinical features of avian
vacuolar myelinopathy (AVM) in American coots.
Animals—26 AVM-affected American coots and 12
Procedures—Complete physical, neurologic, hematologic,
and plasma biochemical evaluations were
performed. Affected coots received supportive care.
All coots died or were euthanatized, and AVM status
was confirmed via histopathologic findings.
Results—3 severely affected coots were euthanatized
immediately after examination. Seventeen
affected coots were found dead within 7 days of
admission, but 5 affected coots survived > 21 days
and had signs of clinical recovery. Abnormal physical
examination findings appeared to be related to general
debilitation. Ataxia (88%), decreased withdrawal
reflexes (88%), proprioceptive deficits (81%),
decreased vent responses (69%), beak or tongue
weakness (42%), and head tremors (31%), as well as
absent pupillary light responses (46%), anisocoria
(15%), apparent blindness (4%), nystagmus (4%),
and strabismus (4%) were detected. Few gross
abnormalities were detected at necropsy, but histologically,
all AVM-affected coots had severe vacuolation
of white matter of the brain. None of the control
coots had vacuolation.
Conclusions and Clinical Relevance—Although
there was considerable variability in form and severity
of clinical neurologic abnormalities, clinical signs
common in AVM-affected birds were identified.
Clinical recovery of some AVM-affected coots can
occur when supportive care is administered. Until the
etiology is identified, caution should be exercised
when rehabilitating and releasing coots thought to be
affected by AVM. (J Am Vet Med Assoc 2002;221: