This article is intended only to alert caretakers and vets of a
potential problem that they should be aware of. There is no clinical
proof at this time of a relationship between the rabbit deaths or
illnesses and the drugs mentioned.
the last six months three unrelated spayed female rabbits from different
households have gone into bone marrow failure. Dr. Sari Kanfer,
Zooh Corner’s medical director, believes that all three cases
may have been related to administration
of albendazole, fenbendazole or oxibendazole, the general drugs
of choice used to treat rabbits with positive titres for e. cuniculi.
presenting signs were acute onset of anorexia and GI stasis. Blood
work showed that all three [rabbits] had EXTREMELY low numbers of
white blood cells, red blood cells and platelets
(all cells produced by the bone marrow). Says Dr. Kanfer, “These
rabbits were not just anemic secondary to e. cuniculi-related kidney
problems, note that they also were lacking platelets and white blood
cells.” The additional lack of platelets and white blood cells
is strongly suggestive of bone marrow failure.
A young female rabbit, excellent husbandry and diet, ‘medium’
e. cuniculi positive titre. Near the end of her six week treatment
with albendazole this rabbit went into acute GI stasis, began drinking
large amounts of water and became lethargic. The rabbit was treated
for GI stasis (fluids, motility drugs, other supportive care) at
the emergency clinic, then transferred to Dr. Kanfer, who did x-rays
and a full blood work-up. There was no obstruction and the blood
work showed strong evidence of a rabbit in bone marrow failure (low
red & white blood cells, low platelets and liver enzymes through
the roof). Dr. Kanfer felt there was no other course but a blood
transfusion at this point. It took two whole blood transfusions,
the second one including the administration of Epogen (a drug that
encourages red blood cell production) as well as various antibiotics
and GI supportive care – but this rabbit is alive and well
today (several months later) and her blood work is nearly back to
normal. (More details available, e-mail author.)
Kanfer has no clinical proof that these drugs did
indeed cause the bone marrow failure, she has only strong suspicion,
supported by the fact that higher doses of these drugs have
been known to cause similar problems in a percentage of dogs,
cats, birds and reptiles.
it is true that there are thousands of rabbits currently being treated
with [one of] these drugs, with no apparent side effects,
we still feel that the question needs to be asked: If the ‘bendazoles
could cause bone marrow failure in a [percentage] of various species
of other animals, could it also have adverse effects on a small
percentage of rabbits?
is important to note that while these various treatments for e.
cuniculi are not cures, practical experience has shown them to have
the beneficial effect of decreasing signs or slowing organism spread
in many rabbits. The author herself has used all three of these
drugs at various times in various rabbits and believes she has seen
positive effects; further, she will continue to use them, [now]
with the addition of frequent blood panels to monitor each rabbits’
How Concerned Should You Be and What you Can Do
There is certainly no need to panic. Even if side effects
are being seen, it is most likely only a very small percentage
of rabbits that would be so affected. We simply suggest that you
and your vet monitor your rabbits while they are being treated with
these drugs (a good idea with any drug). We suggest that all rabbits
who are being treated with one of the bendazoles (Albendazole, Oxibendazole,
Fenbendazole) have blood work (a CBC - Complete Blood Chemistry)
done before, during and after treatment.
research and a more official article is pending.
is E. Cuniculi?
Encephalitozoon Cuniculi (e. cuniculi) is an obligate protozoal
parasite. Little is known about its biology, but it is thought to
be transferred from mother to offspring prior to birth, and possibly
shed into the urine of infected rabbits. The organism is thought
to travel through the body in white blood cells, the cells that
normally fight disease, and may infect the tissues of the rabbit’s
brain, kidney, spinal cord, heart, liver and lungs. It has also
been known to cause damage to the eyes (uveitis).
general drugs of choice to used to help control e. cuniculi, Fenbendazole,
Oxibendazole and Albendazole, all benzimidazole derivatives, are
de-wormers that are used on various species of animals (cats, dogs,
horses) to rid them of intestinal parasites. They do their job by
blocking the transport and uptake of glucose. Though e. cuniculi
is a protozoal parasite, the thought is that it will have
a similar effect.
tire for e. cuniculi means only that your rabbit has been exposed
to the parasite at some point. Many rabbits who test positive for
e. cuniculi never show any clinical signs.
If your vet feels that this may be happening with your rabbit and
wishes to consult with Dr. Sari Kanfer, she can be reached at Animal
Medical and Dental Group (310)546-5731.
would like to learn more. We are currently doing further
research on this topic. You can help us out. If your rabbit becomes
suspiciously ill or dies while on one of these medications (or shortly
thereafter) you can help us gather more info by 1) asking your vet
for a necropsy and histopathology and then sending us a copy of
the results; 2) Sending us copies of all related medical records
(blood tests, vet’s diagnosis and logs, and so on) along with
any info you personally wish to add (please be concise).
you wish to do this, please contact me, Alex Logsdon, firstname.lastname@example.org
or at (909)868-BUNI, mailbox *2
you have any general questions about the article or the various
cases, please feel free to contact the author at email@example.com.
Alexandra Logsdon, Zooh Corner Rabbit Rescue 2003, 2004 . All rights