Dog Blood Cell Study Reveals Breed Specific Variation

Royal Veterinary College study provides first ever large-scale analysis of blood cells in dog breeds

A Royal Veterinary College study, published in the journal PLOS ONE, provides the first ever large-scale analysis of blood cell parameters in different dog breeds.

The study demonstrates the potential of this species to identify the genes controlling blood cell numbers in health, many of which may also be involved in cancers and autoimmune diseases of the blood. It also underlines the pressing need to customize reference intervals in canine blood tests according to breed, sex, neutering status and age, to help improve veterinary clinical practice.

Aberrations of cell numbers play a part in immunodeficiency, autoimmune disease and malignancies of the blood (leukaemias) and the complete blood cell count (CBC) is a crucial diagnostic and screening tool in veteirnary as well as medical practice.

Professor Oliver Garden and colleagues at the Royal Veterinary College, working with Dr Lucy Davison of Oxford University, extracted information on the CBC of 6046 dogs with normal red and white blood cell parameters from a veterinary database. Seventy-five pure breeds plus a mixed breed control group were represented by 10 or more dogs.

Principal component analysis revealed 37 pure breeds with distinctive patterns of blood cell parameters. Furthermore, specific individual breeds and a mixed breed group showed significant differences between all haematological parameters except mean corpuscular haemoglobin concentration (MCHC).

Results found that concentrations of white blood cells (WBCs), neutrophils, monocytes, lymphocytes, eosinophils and platelets, but not red blood cell parameters, all varied with sex. Male dogs had higher concentrations of WBC, neutrophils, monocytes and eosinophils, but lower concentrations of platelets, than female dogs.

Neutering status had an impact on haemoglobin concentration, mean corpuscular haemoglobin (MCH), MCHC, and concentrations of WBCs, neutrophils, monocytes, lymphocytes and platelets.

All parameters other than MCHC varied with age. Though there is general recognition that puppies have a lower red cell mass and haemoglobin concentration than adult dogs, this is the first study to show a sustained increase in these parameters to up to four years of age, followed by a gradual decrease to 12 years of age and beyond.

The discovery of these changes in blood cell parameters with sex, neutering status and age offers the very exciting potential to streamline veterinary clinical practice in the future by the creation of much more specific reference intervals (‘normal ranges’), customized for individual dogs on the basis of their breed, sex, neutering status and age.

Personalizing this diagnostic test rather than applying the ‘one size fits all’ approach, which is currently the norm, will make CBCs a more powerful, refined diagnostic tool in the future.

Professor Garden said: “The dog is the most polymorphic terrestrial mammal on the planet, meaning that different phenotypes exist in the same population of a species. The creation of distinct breeds provides an unparalleled opportunity to dissect the genetic basis of complex traits. Studies that would require thousands of human subjects typically require fewer than 100 in the dog, which is why this species is rapidly gaining traction as a model in a number of biomedical disciplines.

“We have demonstrated that haematological traits in the domestic dog show breed-specific variation when the influences of age, sex and neutering status are accounted for, offering exciting potential to unravel the genetic constraints on haematological parameters in this species. Such studies are likely to have far-reaching, cross-species ramifications for our understanding of the formation of blood cell components in both health and disease.

“But closer to home, we have also demonstrated the need to generate customized reference intervals that account for breed, sex, neutering status and age in our day-to-day veterinary clinical practice. This is where the future lies: the days of generic, all-breed reference intervals for the canine complete blood cell count are numbered and will be a relic of the past in the next five to ten years. Our ongoing work in this area will advance veterinary clinical practice and could have implications for human medicine in due course.”

The study can be accessed via this link: http://dx.plos.org/10.1371/journal.pone.0081288

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