Megacolon in spotted/checkered
rabbits
Esther van Praag Ph.D.
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Warning: this file contains pictures that may
be distressing for people
Greetings,
my name is Zippy,
a small tricolor Charlie rabbit, over two years. I was born with a congenital
disorder that affects approximately 25% of all spotted and checkered rabbits
with a butterfly surrounding the nasal region: megacolon.
We, Charlie's, are bicolored or
tricolored spotted straight-eared or lop rabbits. We are distinguished by our
fur, which is more white over our body than our litter brothers and sisters.
The nasal portion of the colored butterfly is reduced and stops in the middle
of the upper lip, reminiscent of the moustache of Charlie Chaplin.
Our
eyes are surrounded by a ring of colored fur, our nasal region typically has
a partial butterfly or spots, our ears are colored, a colored spot is found
on our cheek, and we have a finer and/or partial dorsal line. The presence of
spots on the hip region is reduced or nonexistent.
The spotted fur is under the
control of the 'En' gene, which is dominant on the 'en'
gene. This gene is responsible for colored fur throughout the body. An
"Enen" rabbit will have colored fur all over its body, while an
"Enen" rabbit will be spotted or checkered, and an "EnEn"
rabbit will be a Charlie with very white fur. The offspring of two spotted
rabbits (e.g., the Swiss Petit Papillon Tricolor rabbit) who each have the
"En" gene will thus be composed of newborns possessing:
·
Heterozygous
'Enen' offspring with a spotted coat,
·
Homozygotes
'enen' offspring with a harlequin coat,
·
Homozygotes
'EnEn' offspring with the characteristic white fur characteristics and few
colored regions only.
Charlie spotted rabbits suffer from the megacolon syndrome
The
harmful effects of the 'En' gene are evident at various levels in homozygous
'EnEn' individuals. A significant number of newborns die at weaning or
shortly thereafter. Those who survive often develop chronic megacolon, a
syndrome that worsens with age. This condition stems from an abnormal
dilation of the colon and the absence of neuroganglionic
cells (aganglionosis), which regulate the muscular
contractions of the digestive system. These contractions enable the contents
of the colon to move toward the anus. The activity of the intestine and the
cecum is affected.
In rabbits with megacolon, the
small intestine is shorter compared to normal rabbits. The pH level of the
intestinal content in the initial portion of the small intestine (the
duodenum) is lower than that of normal rabbits.
Absorption of sodium (Na+)
through the cecum's wall is significantly reduced. Consequently, this organ
contains a lower percentage of dry matter derived from ingested food.
Abnormal liquefaction of the intestinal content has also been observed in the
first half of the colon (proximal colon).
The heart and adrenal glands of
rabbits with megacolon are larger than those of healthy rabbits. It is
conceivable that the observed increase in organ size is associated with
metabolic megacolon disorder.
Effects of
megacolon on health and fecal production
Abnormalities
of the intestine and the cecum result in abdominal distension. Megacolon
rabbits frequently exhibit an enlarged abdomen, resembling a pot belly. These
changes can lead to intestinal food malabsorption and, consequently,
nutritional deficiencies. These rabbits require a diet consisting of a
variety of foods rich in fiber, including good quality pellets containing
minerals and vitamins, fresh hay, and, if tolerated, a variety of fresh
vegetables and aromatic herbs. In some cases of megacolon in rabbits, the
administration of vitamin C or multivitamin supplements has been shown to
promote vitality and facilitate the production of more normal-looking, drier
droppings.
Fecal production is also
affected. The hard droppings are large, oval-shaped, and contain a high-water
content, resembling a sponge. It is impossible to detect the presence of
fibers when fresh. The latter will only become visible once the droppings
have dried out, which may take several days.
The presence of mucus is
frequently associated with intestinal disorders or irritation.
The loss of fluid mucus via the
anus results in the discoloration of the hair in the perineal region. This
characteristic is an important diagnostic tool for confirming the diagnosis
of megacolon in spotted rabbits.
According
to anecdotal studies, megacolon rabbits may not produce cecal droppings.
However, Zippy did exhibit bending down towards his anus several times a day
and adopting the characteristic position of a rabbit ingesting its
"trophy."
A megacolon crisis is caused by
the passage of a particularly large hard dropping and is accompanied by
abrupt and violent abdominal spasms. Droppings collected at the end of such a
crisis often present an outgrowth. Their progression through the intestine
was accompanied by severe pain. Despite the administration of analgesic
medication, Zippy frequently exhibited signs of discomfort, including
pronounced abdominal discomfort and he would knock strongly onto his abdomen
with his nose during these episodes.
Help a Charlie rabbit during an acute crisis ?
The popularity of spotted
rabbits, including those with straight ears or lopped ears, is on the rise.
Therefore, it is essential to understand the causes of intestinal crises and
develop effective treatment methods. To date, there has been no consensus among
veterinarians and experts on this matter.
Crises are episodic, with sudden
outbreaks and calm periods. There are several potential triggers for these
issues, including dehydration, insufficient fiber intake, nutrient
deficiencies, and stress (e.g., unusual noise, abrupt weather changes).
During the crisis, Zippy was administered a painkiller (Metacam) and received
2 ml of virgin olive oil orally. This oil has been shown to stimulate
intestinal peristaltic movement. It acts gently, without causing intestinal
cramps (there is a risk of rupture of the caecum during these crises) in
contrast to chemical stimulants of the peristaltic movement (e.g.,
metoclopramide, cisapride). Zippy was kept hydrated
orally with a syringe. Hay and fresh or dried greens possessing carminative
or antispasmodic properties, such as celery branches, coriander, fennel,
thyme, lemon balm, or raspberry leaves, were given daily at the animal's
discretion. If he tolerates it, he will receive a gentle massage to his
abdomen and will be encouraged to exercise. The longest recorded crisis
persisted for a duration of nine hours. Fortunately, Zippy came out well
every time. The frequency of intestinal crises decreased after Zippy was
given sunflower seeds daily.
Zippy died at the young age of 4
years and some weeks after experiencing renal failure during the final weeks
of his life.
Acknowledgement
I would like to express my
gratitude to Michel Gruaz of Switzerland for his valuable insights on
megacolon in rabbits. I would also like to acknowledge Zippy for his
unwavering affection.
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