BLOOD PLATELETS IN CAVALIERS
More than half of all cavalier King Charles spaniels may have both an abnormally low number of blood platelets and oversized platelets.* In most breeds, platelets are usually smaller than a red blood cell. In the CKCS, the oversized platelets (called macrothrombocytes) are equal to or larger than a red blood cell.
Despite the low platelet counts, the typical cavalier’s blood platelets function normally, and the dog does not appear to experience any health problems due to either the smaller size or fewer numbers of its platelets. There are, however, limited exceptions to this typical situation.
*Other breeds reported to have similar conditions include the Japanese Akita, Cairn terrier, and Norfolk terrier.croplatelets
An excessively low platelet count normally is a sign which tends to alarm general practice veterinarians, and so it is vitally important that cavalier owners alert their vets about this benign condition in the breed when blood tests are ordered.
No treatment is recommended unless the dog shows other symptoms of a blood-related disorder. Cavaliers should not be treated for immune-mediated thrombocytopenia (IMT) as a precaution. A dog really suffering from IMT must be treated quickly, usually with intravenous doses of immunosuppressive drugs — steroids, azathioprine, cyclosporine A, and others — to save the dog’s life. Such treatments are severe and could do major damage to the healthy cavalier with nothing more than a low platelet count.
Most commercial laboratories use an automated counting system for blood cells, which determine cell types on the basis of their size and volume. Because some of cavaliers’ platelets are so large, automated blood cell counters may not recognize platelets as being platelets and undercount them (thinking they are the typically larger red blood cells), thereby inaccurately lowering the platelet count. Researchers have found that CKCS platelet counts using three different automated systems underestimated the actual counts determined manually. Antech Diagnostics, the largest veterinary diagnostic laboratory, has specifically stated on its website that:
“Platelets in this breed should be counted manually, because automated blood cell counters cannot distinguish the large platelets from erythrocytes and therefore underestimate the true platelet count.”
An accurate platelet count usually can be obtained by visually counting the cells. Also, because the large platelets are so fragile, any blood samples should be extracted very carefully. Therefore, all blood samples from cavaliers should be taken in a very careful manner and preferably only from the dog’s jugular vein, using a large bore needle, and then should be examined only under a microscope by an experienced clinical pathologist before making a diagnosis of low platelet count.
Absolutely no treatment is recommended unless the dog shows other symptoms of a blood-related disorder.
Cavaliers should not be treated for immune-mediated thrombocytopenia (IMT) as a precaution. Dog really suffering from IMT must be treated quickly, usually with intravenous doses of immunosuppressive drugs — steroids, azathioprine, cyclosporine A and others — to save the dog’s life. Such treatments are severe and could do major damage to the healthy cavalier with nothing more than a low platelet count.
It is essential that cavalier owners be aware of this benign platelet issue. Dogs undergo blood tests periodically for a variety of reasons, and platelet counts are standard elements of these tests. Veterinarians who are unaware that low platelet counts in CKCSs almost always are due to the fewer platelets being larger rather than to any serious blood deficiency (and, unfortunately, there are many such vets), may assume a life-threatening immune response disorder and perform completely unnecessary (and life-threatening) treatments, such as intravenous doses of steroids. Some vets have been known to start such treatments even before informing the dogs’s owners.
So, it is wise to inform the veterinarian, before any blood tests are performed, about this benign disorder.