DERMATOSPARAXIS IN WHITE DORPERS
By Darroll Grant & Wes Patton
Dermatosparaxis is caused by a simple recessive gene existing in a number of sheep breeds as well as
cattle, cats and humans. The genetic condition is the result of a genetically inherited flaw in the
composition of collagen. Normal collagen provides the skin with elasticity and strength. The recessive
homozygous condition results in skin fragility with tearing near the legs in wrinkled areas in very young
lambs. Stitching the skin is generally not successful and the lambs die of infection anyway.
The disorder was first identified in White Dorpers in the 1980s in The Republic of South Africa. More
recently it was manifest in Australia in 2006. A genetic test was developed and in use by late 2006 in
Australia. Subsequent testing found 20% of tested sheep to be carriers of the recessive gene. It appears
that some carrier genetics were exported to the US prior to discovery of the genetic flaw. The Australian
Dorper Society now notes individual animal status on the registration certificates.
The recessive gene exists within the US White Dorper population with the first double recessive lamb
born in 2007. This was the result of sire x daughter matings. More recently additional recessive lambs
have been born from a different bloodline. The two known sources that came into the US are rams
Highveld VP 1402 (RFVP1402AU) and Kaya 01-0608 (RF010608AU) who is also registered as Kaya
608 (RF608AU). If any other carrier lines are discovered, please contact the ADSBS President.
The gene has not been reported in Dorpers. However, if a Dorper flock has been upgraded from White
Dorpers, the possibility exists that the gene could be present.
A sheep can carry one gene for the trait and not give any indications. The problem is when two carriers
are mated. Theoretically one fourth of their off spring will have the pair of recessive genes and show the
condition, one half will be carriers and one fourth will be noncarriers.
That is the bad news. The good news is that there is a DNA test developed in the US by Gene Check of
Greeley Colorado (1-800-822-6740 or www.genecheck.com). This is the same lab that does scrapie codon
testing. To compound the good news their fee of under $25 is significantly less than those in Australia or
New Zealand. The same sample submitted for scrapie codon testing can be used to run the
Dermatosparaxis test. Since the lab maintains submitted DNA samples for at least 4 years, an email or
phone call can facilitate the test for recent codon tested sheep. This is the same lab that many use for
codon testing.
Cooperation between White Dorper breeders can minimize the cost of testing and speed the elimination
of the recessive gene from the gene pool. Publication of the flock number of carrier sheep would allow a
breeder to determine their possibility of exposure by use of the ‘Search for a Pedigree’ link on the
ADSBS website or by looking through the printed pedigrees of their sheep. The directions for use of the
website link are on page 4 in the recent Dorper Journal, thanks to Kathy Lewis. Fewer tests would need to
be run by testing offspring as close to an initial carrier as possible and then testing offspring from carriers.
Since this genetic defect has been detected early, it should be much easier to eliminate from the White
Dorper population in the US than, for example, spider lamb, where the condition was more deeply
imbedded in several breeds before eradication was initiated.
For the protection of buyers and sellers it is recommended that all White Dorper sheep going through
the 2012 Mid-America Sale be tested. For all sales in 2012 following the Mid-America Sale, testing of
White Dorpers will be REQUIRED. Any breeders selling bred or exposed ewes must meet the same
requirements for the service sires of the pregnancy. Furthermore, it is suggested that sellers notify buyers
of previously sold sheep of potential carriers of this condition.
The Board’s goals in taking these actions are (1) to maintain credibility with buyers of White Dorpers;
(2) to maintain the integrity of the Society, and (3) to maintain the long-term viability of the breed.
President McAnelly has appointed a committee to make recommendations to the Board of Directors for
a Society policy for this fatal genetic recessive. Ron Guenther is Chair, and the members are Wes Patton,
Philip Glass, Doug VanWell and Darroll Grant. Watch for more information in the near future, as the
phases of the ADSBS program to eliminate this condition are developed.