New Study Reports Golden Retrievers Among Breeds with Low IgA Levels
Swedish researchers count Golden Retrievers among eight breeds in which 10 percent or more of adult dogs have low blood immunoglobulin A (IgA) levels. Low levels of IgA are often accompanied by recurrent infections and autoimmune and allergic diseases just as in humans with IgA deficiency.
The study was the first to evaluate IgA in several breeds of dog. Earlier research attributed low IgA levels to conditions such as atopic dermatitis and inflammatory bowel disease in German Shepherd Dogs (Tengvall, et al., 2013) and Chinese Shar-Pei. The current study found that 45 percent of Chinese Shar-Pei and 14 percent of German Shepherd Dogs were low in IgA levels.
“We found IgA concentrations to vary widely among breeds,” says researcher Katarina Tengvall, MSc, a doctorate
student in genetics at Uppsala University in Sweden. “This pronounced difference may explain why there is no established normal range of IgA and accepted cutoff value for low IgA in dogs.”
“These findings are important because low IgA may be associated with an elevated risk of atopic dermatitis (atopy) and inflammatory bowel disease (IBD),” says Rhonda Hovan, research facilitator for the Golden Retriever Club of America (GRCA) and member of the club’s Health & Genetics Committee.
“Atopy and IBD are autoimmune diseases, and Goldens appear to have an elevated risk for a number of autoimmune diseases. The category of autoimmune diseases also includes hypothyroidism (autoimmune thyroiditis), masticatory muscle myositis, autoimmune hemolytic anemia, lupus (systemic lupus erythematosus), Addison’s disease (hypoadrenocorticism), rheumatoid arthritis, and myasthenia gravis.”
A part of the secretory immune system, IgA is an antibody produced by plasma cells, which protect the lining of mucosal sites from pathogens. In people, IgA deficiency is associated with frequent respiratory illness and urinary tract and intestinal infections. In both dogs and people, there is no treatment for low blood IgA; rather, signs of disease are treated to help alleviate illness.
In the May 2014 issue of Veterinary Immunology and Immunopathology, the researchers indicated that low IgA in purebred dogs is likely due to founder effects, breeding practices and reproductive isolation.
“In an earlier study, we reported low IgA concentrations in wolves, the wild ancestor of the domestic dog,” Tengvall says. “Although that study used the Scandinavian wolf population, which is known to be highly inbred with very low genetic variation, this suggests that risk alleles predisposing to low IgA may have been transferred from wolves to dogs during domestication.”
A Model for IgA Deficiency
The Swedish study included 1,267 dogs representing 22 breeds. Blood samples were collected from healthy dogs and those affected by diseases living in the U.S., Sweden and Switzerland in cooperation with their owners and veterinarians. Disease-affected dogs suffered from conditions such as atopic dermatitis, Shar-Pei autoinflammatory disease, Addison’s disease, pancreatic acinar atrophy, diabetes mellitus, and steroid-responsive meningitis arteritis.
Besides 168 Golden Retrievers, the study included 141 Labrador Retrievers and 11 Nova Scotia Duck Tolling Retrievers. The findings showed that 13 percent of Golden Retrievers have low IgA, 12 percent of Labrador Retrievers and 20 percent of Nova Scotia Duck Tolling Retrievers.
The researchers evaluated the sex of the dogs and whether spaying or neutering contributed to low IgA. In both cases, they found no correlation.
Golden Retrievers were among six new breeds recognized as having an increased risk of low IgA. The other breeds were Hovawart, Norwegian Elkhound, Nova Scotia Duck Tolling Retriever, Bull Terrier, and Labrador Retriever.
Nearly half the Golden Retrievers in the study had signs of canine atopic dermatitis, yet their IgA levels were not much lower than those of unaffected dogs. Despite this finding, it is possible that low IgA levels could be a contributing factor to immune problems in the breed.
“Although a great deal of research has been done to identify the causes of human autoimmune diseases, much less research has been done in dogs,” Hovan says. “Still, the same overall principles of autoimmune disease apply to dogs.”
An online survey conducted by the Orthopedic Foundation for Animals for the Golden Retriever Club of America indicates that 13.4 percent of Golden Retrievers have skin disease, such as atopic dermatitis, says Ann Hubbs, DVM, PhD, chair of the GRCA health and genetics committee. She says about 5 percent of the owners of Golden Retrievers also reported gastrointestinal diseases.
Alan Mundell, DVM, DACBD, a board-certified veterinary dermatologist who practices in Edmonds, Washington, says, “Due to the frequency of skin problems in Goldens, we test for IgA levels as part of our diagnostic workup, especially if a dog shows signs of allergies and infections at a young age. In my experience, Golden Retrievers are among the top four breeds for low IgA levels. Environmental influences are important as well.”
Tengvall agrees. “Genetic and environmental factors contribute to diseases affected by low IgA. The connection between low IgA levels and atopic dermatitis seems to be unique in different breeds because in Golden Retrievers there was no correlation but in German Shepherd Dogs there was.”
“The genetic components of autoimmune diseases are very complex,” Hovan says. “Genes play a role in increasing susceptibility to autoimmune diseases, but environmental triggers initiate the onset of clinical signs. In dogs that are predisposed to autoimmune reactions, there are suspected triggers, but most of the time, it is impossible to know with certainty what triggers the onset of an autoimmune disease.”
The low IgA breeds identified in the study will potentially provide genetic models to help advance understanding of IgA deficiency in people. “Dogs offer an advantageous comparative model for human disease,” Tengvall says.
“We have identified six new potential genetic models of IgA deficiency.”
Thanks to this study, owners and breeders of Golden Retrievers that develop recurrent infections and autoimmune and allergic diseases can now recognize that IgA could be a contributing factor. Insights from the study also will help veterinarians who treat dogs to consider whether low IgA levels may contribute to the dog’s illness. However, as noted by the researchers, additional studies are needed to better understand the implications of low IgA levels in each specific breed, including the Golden Retriever.
Purina appreciates the support of the Golden Retriever Club of America and particularly Rhonda Hovan, the GRCA research facilitator, in helping to identify topics for the Purina Pro Club Golden Retriever Update newsletter.