A mutation in the KIT gene causes a dilatated colon, impaired intestinal motility, digestive problems and a decreased viability in Checkered Giant Rabbits (Oryctolagus cuniculus) with homozygous English spotting coat colour.
The English spotting coat colour locus in rabbits, also referred to as the Dominant white spotting locus, is controlled by an incompletely dominant allele (MC).
Rabbits that are homozygous for the recessive wild-type allele (N/N) have a uniform coat colour, while heterozygous N/MC rabbits display a typical spotted pattern. In contrast, homozygous En/En rabbits are nearly entirely white. Compared to the healthy N/N and N/MC rabbits, MC/MC rabbits are less vital due to an enlarged ('mega') cecum and ascending colon.
Megacolon Syndrome is a genetic disorder predominantly seen in English breed rabbits, marked by a unique coat pattern featuring white fur with dark patches. This syndrome is caused by the ‘MC’ gene, which exists in two variants: MC and N. Rabbits possessing two copies of the MC gene (MC/MC) are susceptible to developing Megacolon, which results in slower food passage through the gut and various digestive problems.
Rabbits affected by this condition often show symptoms such as a noticeable spine and ribs due to poor nutrient absorption, a swollen abdomen, and occasional bouts of pain. They are perpetually hungry and may experience pasty diarrhea. The syndrome can lead to severe complications like caecal obstruction.
Diagnosing Megacolon is difficult as there is no specific test for it. It is typically identified through clinical signs and post-mortem examinations, which reveal irregularities in the nerve supply to the gut. This condition is akin to Hirschsprung’s disease in humans, where a segment of the intestine lacks proper nerve connections, causing significant digestive issues.
Managing Megacolon involves providing a high-fiber diet, regular veterinary check-ups, and monitoring for signs of pain or distress. Although there is no cure, supportive care can enhance the quality of life for affected rabbits.
A DNA test is now available at Laboklin and can help breeders in reducing the occurance the variant in the population.
