Rabbit Genetic Disorders | Dichrome Rabbitry

Other Genetic Disorders in Rabbits

WARNING! There are some images below which may disturb some viewers! This includes severe genetic disorders and necropsy photos of rabbits (including deceased rabbits and parts). Please proceed with caution.

Alfort Jumper (Sauteur d’Alfort)

Alfort Jumper rabbits have a mutation which causes them to walk on their front feet! Rabbits with this mutation also have eye deformities which result in reduced pupil reflexes, cataracts with lesions, glaucoma, entropion and ectropion, and papillary colobomas. It only takes one copy of the mutation (s^am) to cause the eye deformities but two to cause the odd movement.

The causative mutation is a reduction of function on the RORB gene. RORB is a transcription factor expressed in the nervous system, and especially in the spinal cord dorsal horn. Rabbits with the mutated form of the RORB gene have much less of the RORB transcription factor expressed in the spinal cord, causing a loss of saltatorial (hopping) gait. Instead, these rabbits often walk on their front legs when trying to make a faster escape.

Alfort Jumper rabbit showing the characteristic front leg walking.

Carneiro et al, 2021

Alford Jumper rabbit with eye deformities.

Carneiro et al, 2021

Earlessness

A rabbit born near the damaged Fukushima Dai-ichi nuclear plant was purportedly born without ears. It is just as possible (even likely) the kit instead had its ears chewed off by the mother at birth due to overzealous cleaning. Such occurrences are not exceptionally uncommon among rabbits. We could not find details to verify either way. It could also be a new mutation (or likely multiple mutations), so we are including it on this page.

Diaphragmatic Hernia

Newborn rabbits with this disorder die from respiratory failure. They may have external phenotypic problems like the diaphragm being missing. This is a recessive disorder. This mutation also has an incomplete penetrance, meaning that not all individuals with the mutation actually have the traits associated. The penetrance appears to be about 30%, so about 30% of individuals with two copies of the mutation are actually affected (Botha et al, 2014). Dh denotes normal, and dh denotes the mutated allele.

Figure: A: Plain X-ray of the thorax of a newborn with congenital diaphragmatic hernia (CDH). There are bowel loops in the left hemi-thorax, the mediastinum is displaced to the contralateral side and the space occupied by the lung is reduced. B and C: At laparotomy, a left, posterolateral diaphragmatic hernia was discovered. In B, small bowel loops can be seen entering the thorax through the orifice. In C, this is seen after reducing the contents of the hernia. D: The patient died of severe persistent pulmonary hypertension days later. At autopsy, extreme left lung hypoplasia and less severe right lung hypoplasia were discovered.

Adrenal Hyperplasia

This recessive disorder causes an excess secretion of adrenalin and death shortly after birth (Botha et al, 2014). A side phenotypic effect is feminization of affected kits. Ah denotes normal, and ah denotes the mutated allele.

Figure to the left shows bilateral adrenal hyperplasia.

Paralytic Tremors

This recessive, X-linked (sex-linked) disorder causes a wide range of neurological disorders (Botha et al, 2014). A few days after birth, the kit will develop shaky movements, almost as though it is dancing. Around 8 weeks, the hind limbs become paralyzed. Around 12 weeks, the kit will become completely paralyzed and die. However, the disorder has incomplete penetrance (not all with the mutation show any signs) and variable expressivity (some individuals have less or worse symptoms). Some individuals are so lightly affected that they can still breed. As it is X-linked, this disorder occurs mostly in males. Males, which have only one X chromosome, need only one mutated copy of the gene to be affected, whereas females need two copies. Plp denotes normal, and plp denotes the mutated allele.

Left Ostium Straightness

In this recessive disorder, the oviduct remains straight instead of curving to set with the ovary (Botha et al, 2014). The ovary also migrates to an abnormal location. This disorder has incomplete penetrance (not all individuals with the mutation show the phenotypic traits). Los denotes normal, los denotes the mutated allele.

Figure to the left shows the Left Ostium Straightness in rabbits. 1- kidney; 2- ovary; 3- fallopian tube; 4- oviduct

Cortical Renal Cysts

This disorder is caused by a recessive mutation with incomplete penetrance (not all individuals with the mutation are affected) of about 70% (Botha et al, 2014). Cysts appear in the kidneys when the rabbit is about 4 weeks old. They do not appear to affect kidney function. Rc denotes normal, and rc denotes the mutated allele.

Hypogonadia

This recessive disorder causes partial to complete infertility/sterility in both sexes (Botha et al, 2014). Affected males have much drastically reduced testicle size (only 13% of normal size) and females have smaller ovaries (8% of normal size) and no follicles. Hg denotes normal, and hg denotes the mutated allele.

Buphtalmia

Also known as hydroftalmia or congenital glaucoma, this recessive disorder shows incomplete penetrance (not all rabbits with the mutation are affected) (Botha et al, 2014). Affected rabbits It leads to the death of retinal ganglion cells and results in blindness via glaucoma. The gene involved in this form of glaucoma is located very close on the chromosome to albinism and is linked to Ruby Eyed White (REW) color. Most affected rabbits are REW, with only about 1% of affected rabbits being any other color. Bu denotes normal, and bu denotes the mutated allele.

Macrostomus

This recessive mutation has incomplete penetrance of about 30-35% (about 30-35% of individuals with the mutation are actually affected) (Botha et al, 2014). Affected rabbits have larger mouths and papillae (fleshy bumps) at the corners of the mouth. It appears to be linked to the dwarfing (Dw) gene. Mst denotes normal, and mst denotes the mutated allele.

The figure to the left shows a kit with Macrostomus on the left and a normal kit on the right.

Brachydactylia

This recessive disorder results in poorly formed toes and feet (Botha et al, 2014). The disorder is quite variable, with some affected rabbits having only minor shortening of the toes (brachydactylia) and others having complete loss of feet (acheiropodia). It can affect one to all feet. Br denotes normal, and br denotes the mutated allele.

Figure all the way to the left shows a rabbit with Brachydactylia (shortened toes) on the left and one with Acheiropodia (lack of feet). Figure to the right shows malformation of rabbit limb, x-ray outlining bone degeneration.

Hereditary vestigial pulmonary arterial trunk

This recessive disorder appears to have variable expressivity (more or less severe in different individuals) (Botha et al, 2014). Two different mutations are involved, and both are recessive. Affected rabbits must have two copies of each gene mutation. Therefore, It causes the pulmonary trunk will be vestigial or absent. Some individuals instead have a bulbous pulmonary trunk and the ductus arteriosus is vestigial or absent. Most individuals also have a high ventricular septal defect. In severe cases, the rabbit will be quickly lethal, but less severe cases may allow the rabbit to live for a short time. Vpt denotes normal, and vpt denotes the mutated allele.

Narrow axis

This recessive disorder causes a narrowing of the second cervical vertebra. It has variable expressivity, so some individuals have more or less severity (Botha et al, 2014). Nx denotes normal, and nx denotes the mutated allele.

Microphtalmia

This disorder is most likely recessive and causes a lowered rate of ovulation activity (Botha et al, 2014). Mi denotes normal, and mi denotes the mutated allele.

Anophtalmia

This disorder is thought to be recessive. It causes lack of eyes (Botha et al, 2014). There are also many possible environmental factors which may increase the risk of Anophtalmia and Microphthalmia (underdeveloped, small eyes), such as exposure to X-rays, chemicals, viruses, and drugs as a fetus.

Hereditary osteopetrosis

This recessive disorder results in skeleton deformations including tooth abnormalities, bone deterioration, and death of the kit by around the 5th week of age. (Botha et al, 2014). Os denotes normal, and os denotes the mutated allele.

Femoral luxation (Luxatio femoris congenitalis)

This recessive disorder causes rabbits to carry one or rarely two legs in an abnormally extended position and support themselves on their other legs (Botha et al, 2014). This occurs due to join laxity and subluxation. This occurs around the age of 2-4 months. Lu denotes normal, and lu denotes the mutated allele.

Figure to the left is a top view showing joint laxity and luxation of the shoulder in rabbit

Congenital absence of incisors

This disorder is caused by a dominant mutation (Botha et al, 2014). It causes a lack of either the primary incisor teeth or the second upper incisors (peg teeth). It is suggested it also has a lethal effect.

The figure to the left shows a lack of second upper incisors (peg-teeth). The figure to the right shows normal second upper incisors, for comparison.

Coloboma

This disorder is caused by a dominant mutation (Botha et al, 2014). It causes a hole in one of the structures of the eye, which fails to close entirely before the kit is born. The whole is most commonly present in the iris. It can happen in one or both eyes, and an an affected rabbit may be blind, partially blind, or have no vision problems.

Achondroplasia

This dominant mutation causes a shortening of limbs similar to that in a dachshund dog (Brown & Pearce, 2014). Other common physical traits associated with this mutation is extra folds of skins, a broad head and muzzle, extended and large abdomen, and lordosis of the spine.

The figure to the left shows two achrondroplastic dwarf kits compared to their normal litter mate (middle kit).

Distal Forelimb Curvature

This recessive disorder causes the forelimbs to curve, starting around 2 weeks of age, developing quickly until 2-3 months of age, in which the full and permanent presentation is found (Pearce, 1960). Fc denotes normal, and fc denotes the mutated allele.

The figures to the left shows two different views of an affected rabbit (A & B) and a normal rabbit leg (C, which is same perspective view as A).

The figures to the right show various affected rabbits.

Tables of Disorders

These tables from Botha et al. (2014) list various genetic abnormalities, the allele denotations, and the mode of inheritance. Some have been covered in this article and some have not.