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| Volume 4, Issue 1 |
International Parti Poodle Gazette |
January 2008 |
DAY BLINDNESS (HEMERALOPIA)Author: Heather BryanProdigy Standard Poodles www.standardpartipoodle.com In the past twenty years, I have seen science give the dog world seemingly marvelous tools to aid in the diagnosis and prevention of some serious genetic health issues. The ongoing research into the DNA of many breeds for specific known health issues offers great promises towards the future of overall dog health. Many of these research projects started as a collaboration of breeders who have had serious health issues crop up within their lines, veterinarians who diagnosed such issues, and universities who were willing to delve deeper into the problem. Addison’s, epilepsy, sebaceous adenitis, toe cancer, and Chrondro Dysplasia are a few of the more publicized issues being worked on by various universities. However, with all the innovations we have at our beck and call, it seems that more and more health issues are surfacing . . . some of which have been lying below the surface for an unknown period of time. It was mid July when I first noticed symptoms in one of our puppies. The litter was born at the end of May and, when they were about six weeks old, one of the females began showing signs of weak vision in the sunlight. I observed her for a few days, saying nothing until I was certain there was a problem. It seemed to only affect the puppy when she was outside in bright light: when the puppies were inside, her vision seemed normal. By the time the puppies were seven weeks old, a second puppy – also female – began showing signs of the same vision problem. This litter was a line breeding, doubling up on an outside line not related to our own. I immediately contacted the breeder of the sire of this litter and explained the symptoms to her as I had observed them. She confirmed she had also had several litters that had puppies with similar symptoms; that several of these puppies had been euthanized and necropsies performed on them. She agreed to have the necropsy reports forwarded to me via a mutual friend. Next, I turned to the Internet to see if I could find more information as well as a scientific diagnosis. My Google search for “day blindness in dogs” turned up a word I could barely pronounce, but that I soon became very familiar with over the ensuing months: Hemeralopia. So, what, you may ask, is Hemeralopia? I read an article by Dr. Kenneth Bourns titled Day Blindness which documented a line of Alaskan Malamutes who, back in the 1960s, produced puppies who seemed to have problems seeing properly during the daylight. It chronicled how the breeder was able to work with scientists through controlled breeding to help eliminate this disease from the line without destroying the existing breeding program. After reading the article, I knew I needed to track down the origin of the problem in the puppies. Over the course of the next few weeks, I contacted universities and ophthalmology research facilities, mostly, with little result. Most were not interested in opening research into what outwardly appeared to be an isolated case. It was by shear chance I received an email at the beginning of August from the University of Missouri, Columbia reporting the results from blood-work I had submitted in early June. The dog tested had been clear of the disease (which was wonderful news) but, more than that, the timing of the results could not have been more perfect. I quickly replied to the email giving a brief synopsis of the symptoms seen in my puppies, and it was forwarded to Dr. Gary Johnson, head of the genetics research lab. The University of Missouri, Columbia has done extensive research on NE (Neonatal Encephalopathy with Seizures) and recently provided a DNA test to screen Standard Poodles for the disease.
With the aid of UOM, we coordinated with a local office of the Eye Clinic for Animals to have an Electroretinagram (ERG) performed on the affected puppies. Dr. Narfstrom flew to Phoenix for the procedure. Two of the affected puppies were tested, as well as two unaffected puppies from different litters. The initial results were quite clear. The affected puppies did indeed have day blindness, and it was indeed genetic. The gene that produces day blindness is recessive, which means that both parents must be carriers for it to be produced. With both parents as carriers, typically 25 percent of the litter will be born affected, 25 percent will be carriers, and the remaining 50 percent will be unaffected. There were eight puppies in this litter. With two affected, it fell in line with the statistics. Because it takes two carriers to produce this disease and because there is currently no way to screen for it, it can go silently through a breeding program and be passed on from generation to generation without any puppies being affected. From the time I realized we had a litter of affected puppies, I made it perfectly clear that my intention was to help rid the breed of this disease. As soon as we recognized we had a genetic issue on our hands, we neutered both parents of the litter so there was no chance that either could ever pass this disease on in the future. Unfortunately, there has been some dissension from other breeders who would have preferred to have this matter kept from the public – a “code of silence” as it were. After publicizing our problem, we have been contacted by numerous breeders and owners who have known or witnessed affected puppies with similar symptoms. Perhaps it was by chance that this litter was born to us. I can’t speak for other breeders as to how they would have reacted to this problem, but I know it was ethically right to bring it out into the light to be examined and talked about. There have been more than a few breeders who criticized us for making it public, but there has also been great support from breeders who are doing all they can to help eliminate health issues in our beloved breed. In the timeline of research, this project is merely in its first breath of life. We strongly believe that the researchers at the University of Missouri, Columbia will be able to find more answers, and possibly a DNA marker. The most useful tool in any breeding program is information: the most detrimental is withholding information with the intention to detour blame. In the case of our puppies, vital information prior to the breeding could have prevented this. On the other hand, if these puppies had not been born, the threat of this disease would still be lurking undetected just beneath the surface.
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