It is only a couple more weeks until classes start up again and I have to make the long drive back to Pullman, and go back to long periods of sitting in class. So until that happens I’ve been trying to study for at least a couple hours each day in hopes that I haven’t forgotten everything I’ve learned in my first two years. I know studying during summer vacation is pretty nerdy but third year is supposed to be the most difficult.  Strange how it seems they say that about every year we are about to start. In any case the subject I was studying today is toxicology so I thought I would discuss 3 of the toxins from my notes.

Recently, word has spread that feeding grapes and raisins to dogs can be toxic. The first time I heard this I have to admit I was skeptical. It seems like whenever you hear that something is “bad” for your dog they can never tell you the why or how. So when we learned about grapes/raisins in class I was happy to finally have some solid information on the subject. Grapes/raisins are potential toxins that affect the kidneys. The problem is that there is no dose response recognized. What this means is that you or even your veterinarian cannot tell whether your dog will get sick by the amount of grapes/raisins your dog has consumed. Even more interesting is that not all dogs exposed become ill. The mechanism of action is also unknown at this time, i.e. how/why they damage the kidneys. If your dog is affected the signs will be pretty non-specific: vomiting characteristically occurs within 2 hours of ingestion, anorexia, diarrhea, depression, lethargy, and abdominal pain.

Cyanobacteria is another potential toxin that I had not heard about until veterinary school. Cyanobacteria, also known as blue-green algae, despite the name can be seen in many different colors ranging from black to pink. It may be found in salt or freshwater when the specific environmental conditions are in place for it to grow and to produce toxins. Not all cyanobacteria are toxic but all animals including humans are susceptible to the toxic producing variety making it a public health concern. Depending on the strain of cyanobacteria the liver or the nervous system may be affected. If your dog is affected, signs may include vomiting, abdominal pain, diarrhea, muscle rigidity, tremors, and paralysis. These signs would occur fairly soon after exposure within 1-4 hours. You can see some good pictures of cyanobacteria by searching in Google images. Since this is a public health concern if you suspect a bloom of cyanobacteria the Public Health department should be notified so they can test the suspected water.

The last potential toxin I’m going to discuss is Xylitol. This toxin is a sugar substitute that is now found in a wide variety of products including gum, toothpaste, mouthwash, candy, and sugar substitutes used for baking. Over-consumption can cause a severe hypoglycemia (low blood sugar) in dogs. Some dogs may even develop liver failure. The signs of hypoglycemia will generally develop 30-60 minutes after ingestion and include weakness, seizures, and vomiting.

These are just three examples of toxins that I felt are fairly unknown to the majority dog owners but can be very harmful.  If you think your dog has fallen victim to, or is experiencing any of the signs indicated here you should consult your local vet as soon as possible.

The 2009 AVMA convention was last weekend and I was fortunate to be able to attend several lectures given by Dr. Randall Fitch. These lectures were focused on localizing lameness in primarily the rear limb. I wish that they would have focused more on sports medicine as originally advertised, but we can’t have everything we wish for. During one of the lectures Dr. Fitch showed several pelvic radiographs from a bitch that was evaluated as OFA Excellent but turned out to be severally dysplastic.

This caught my attention since Indy, our gold border collie, has recently turned 2 years old and is now eligible to have his OFA radiographs submitted. There are two most popular screening organizations in the U.S. is the OFA and PennHIP. There is a lot of animosity and debate between the two groups as to which is the superior method and this doesn’t appear to be ending any time soon.

OFA has been around for a longer time period and is the more popular method of screening. Dogs must be at least 24 months of age to be certified and it is recommended that they be sedated for the procedure but it is not required. Radiographs are taken with the dogs lying on their backs with their rear legs extended and rotated slightly inward. When submitted the radiographs are subjectively measured on 7 points that takes into account evidence of hip laxity, osteoarthritis, or both. From this subjective evaluation the hips are rated into the seven different phenotypic classifications: excellent, good, fair, borderline, or mild, moderate, and severely dysplastic. These seven levels are used to help owners make informed decisions for breeding purposes. An advantage of OFA screening is that any veterinarian can take the radiographs and submit them as long as they are good quality. Also if the veterinarian is willing to take the radiographs without anesthesia they can be significantly cheaper then PennHIP. This is not advisable since tense muscles can make the radiographs appear better then they actually are. The OFA also maintains easily accessible records of all the submitted radiographs, which can be helpful when potential buyers are researching breeders.

PennHIP was developed to quantitatively assign a measure to hip joint laxity, the Distraction Index (DI). Since it has been recognized that there is a correlation between joint laxity and the development of osteoarthritis. PennHIP radiographs can only be taken by a certified veterinarian, which limits the availability of the procedure. Three views are taken and the dog must be under anesthesia or heavy sedation. The first view is the traditional rear limb extended view just like for OFA screening. The next two views, the compression and the distraction are done with the legs in a neutral or normal stance position while the dog is laying on it’s back. These are used in the measurement of the DI. The compression view is obtained by placing downward and inward pressure on the femur in order to place the femoral head into the acetabulum (hip socket). This allows for a visual evaluation of how well the femoral head fits into the acetabulum basically showing ideal congruency if no OA is present in the joint. The third view is the distraction view. A distractor is used to act as a fulcrum to displace the femoral heads from the acetabulums. The distractor is placed between the femurs with the rods placed over the femoral heads. Force causes the femur to distract from the acetabulum based on the inherent laxity of the joint. The DI is calculated and is given as a unit-less number between 0 and 1. As this number increases the joint is considered to have more laxity, and subsequently is more susceptible to arthritis. The laxity of the joint is the amount of displacement of the femoral head. Studies have shown that dogs that have DI <0.30 are virtually at no risk to develop arthritis. DI’s >0.30 are susceptible to arthritis. PennHIP screening can be performed as early as 4 months of age. Each report also contains a percentile ranking of the dog amongst others of the same breed. PennHIP advises that dogs below the 50^th percentile of their breed not be used for breeding.

Canine hip dysplasia continues to be a very prevalent disease in the canine population despite many years of working to decrease its occurrence. This is evidence of a screening method that is not accurate enough and has a low heritability. Which is the case with the OFA technique, which has been the most commonly used means of evaluating the dog for hip dysplasia for over 40 years. Despite this time, the prevalence of the disease has only decreased slightly. False negative results in the test are likely the main cause of the slow progress; i.e. dogs been graded acceptable when they are in fact dysplastic. The PennHIP technique has been found to have a negligible number of false negatives thereby minimizing the number of dogs with the genotype for hip dysplasia to be used in selective breeding programs. This is the main factor in decreasing the prevalence of the disease in the canine population. I believe, as more veterinarians are able to perform this screening technique the more popular it will become, and real progress can be made in eliminating hip dysplasia.