The names Karakachan and Bulgarian Shepherd Dog have been used interchangeably, but they are recognized as two breeds by official organizations in Bulgaria.
"The Karakachan official breed standard was written in 1991 and approved in 2005 by the State Commission for Animal Breeds within Ministry of Agriculture of Republic of Bulgaria. The breed has Certificate for recognition no. BG 10675 P2. They are registered in the International Karakachan Data Base in Bulgaria. Registrations will show MAKK or IKDA. Only those dogs are of the 'true' Karakachan bloodline."
There are long, complex stories behind each breed. See the links to both breeds for more info.
The two breeds look similar, but the Bulgarian Shepherd Dog is slightly taller (26-30") and bulkier, while the Karakachan is shorter (24") and has a lighter physical build.
The Bulgarian Shepherd generally has fluffy white fur with black markings; the Karakachan can have either short or long fur, white with black markings or black with white markings.*
"The Karakachan is a breed of dog that originated in Bulgaria as a mountain livestock guardian dog. Other names are Ovcharsko kuche and Thracian Mollos. The dog is named after the Karakachans, Balkan nomadic shepherds. Due to their conservative stock-breeding traditions, they have preserved some of the oldest breeds of domestic animals in Europe: the Karakachan sheep, Karakachan horse and the Karakachan dog."
*"Colour of hair: Two or tricolour, with spots. Most desired are clearly defined dark spots on white or big white spots on dark.
Uniform black has traditionally been the preferred colouring, but black-n-tan and dark brown dogs were also common, with many of them having small white markings. Examples having greater amounts of white on their bodies should have clearly marked black or black-n-tan patches on the head."
Click here to see the Wikipedia article: Karakachan_dog.
*"Colour of hair: Two or tricolour, with spots. Most desired are clearly defined dark spots on white or big white spots on dark.
Uniform black has traditionally been the preferred colouring, but black-n-tan and dark brown dogs were also common, with many of them having small white markings. Examples having greater amounts of white on their bodies should have clearly marked black or black-n-tan patches on the head."
Click here to see the Wikipedia article: Karakachan_dog.
About the family of Livestock Guardian Dogs...
“To this day flocks are guarded in the hills of Asia, Europe and Africa by powerful, robust dogs that are neither clumsy nor pacific. Despite the distances that separate them these breeds have much in common, and the Kuvasz is a member of this extended sheepdog family.”
From: Dr. Tibor Buzády, Dogs of Hungary, trans. Bernard Adams, Budapest, Hungary: Nóra Kiadó, 2002, p. 90.