“Head-down syndrome” in a rabbit
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Acute onset of “head-down syndrome”, also referred to floppy head syndrome or dropped head syndrome, has been observed in rabbits. The head is tilted forward and rabbits seem unable to lift it. The forward flexion is caused by weakness or contraction of the extensor muscles in the neck, which leads to the inability to hold the head upright and against the force of gravity. There is no tilting to the side. It may be accompanied by reluctance to move, decrease of appetite and pain.
It is important to differentiate between muscle weakness in the neck region, and excessive contraction of the muscles. Typically, necks weakness relates to one of these categories: motor neuron disease, auto-immune muscle disorder (myasthenia gravis-like), inflammatory muscle disease (polymyositis-like) or idiopathic, while contracted neck muscles relate to torticolis or neurotoxins. Since the flexion of the head is forward and not to the side, it is unrelated to an active infection by Encephalitozoon cuniculi or middle/inner ear infection.
In spite of a complete physical examination and diagnostic tests such as blood tests, radiography, and the history of the rabbits, the etiology of this disorder remains uncertain. Veterinarian were puzzled by this health disorder. What could it be ?
A few years ago, rabbit presented the exact same clinical features and blood chemistry results and vets were amazed about his condition too: Twilight.
A closer analysis of the blood chemistry panel of Midnight and Twilight indicates high liver values (AST, ALT, Alk Phosphatase) and a low level phosphorus (hypophosphatemia). Hypophosphatemia has typically been associated with fulminant hepatic failure as well as increased metabolism of phosphorus during hepatic function recovery and hepatocyte regeneration. A working hypothesis is that these rabbit may have suffered hepatic encephalopathy as a consequence of fulminant liver failure and a raised level of blood ammonia.
Affected rabbits were given antibiotics, fenbendazole and metacam. Treatment consists of supportive care, antibiotics, control of pain, force-feeding when necessary. Most animals recover between 7 to 14 days. If needed, subcutaneous fluids and feeding with a syringe should be started. Prognosis is guarded to good. All affected rabbit recovered within a week.
The following table’s list causes related to difficulties to hold the head high as observed in other herbivorous animals, horses, cattle, sheep and goats. Further causes cannot be excluded.
Depending on the cause, the inability to hold the head upright is reversible or irreversible. Recovery may be fast, within a week, or take weeks to months. Prognosis is guarded to good. Treatment consists of supportive care, antibiotics, fluid management, control of pain, force-feeding when necessary.
Many thanks to Kathleen Bourdelais, Suzanne Trayhan and Bonnie Salt for sharing the information about Midnight
and for the permission to use the pictures and videos.