The dog breeds that are most likely to carry disease-causing genetic mutations have been revealed, with Cavalier King Charles Spaniels unfortunately taking the top spot.

According to new research conducted by Uppsala University in Sweden, the small lap dogs have sadly been negatively affected by years of inbreeding and are now at higher risk of heart disease. In fact, scientists found the breed has genetic variants linked to myxomatous mitral valve disease (MMVD) — the most common acquired heart disease in small breed dogs.

Erik Axelsson, who published the findings in the journal PLOS Genetics, said years of breeding has caused many dogs to inherit genetic diseases.

"We find that individuals belonging to the breed affected by the most intense breeding – Cavalier King Charles Spaniel (cKCs) – carry more harmful variants than other breeds," he said in the paper. "[This indicates] that past breeding practices may have increased the overall levels of harmful genetic variation in dogs."

portrait of beagle standing on field,asturias,spainpinterest
DiegoArguelles / 500px//Getty Images
Beagles also made the list

As part of the research, the team sequenced entire genomes from 20 dogs from eight common breeds. While the Cavalier King Charles Spaniel was found to carry more harmful genetic variants than others, scientists discovered that Standard Poodles also carry damaging genetic variants than the others.

beautiful golden retriever dogpinterest
Carmen Martínez Torrón//Getty Images
Golden Retrievers are also at risk

"In the cavalier King Charles spaniel specifically, one or several of these mutations affect heart muscle protein NEBL and may predispose this breed to devastating heart disease," Erik adds.

Take a look at the breeds below which are now at risk of disease-causing genetic mutations:

  1. Cavalier King Charles Spaniel
  2. Beagle
  3. German Shepherd
  4. Golden Retriever
  5. Labrador Retriever
  6. Standard poodle
  7. Rottweiler
  8. West Highland White Terrier

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