Grapes and Raisins

I thought another holiday treat post would be appropriate.  Raisins or grapes appear to be very toxic to some dogs.  Interestingly not all dogs seem to be susceptible.  In a study published in the Journal of Veterinary Internal Medicine in 2005, the authors examined records from AnTox, the database of the American Society for the Prevention of Cruelty to Animals Animal Poison Control Center.    They found records of 43 dogs from 1992 to 2002 that developed clinical signs and had blood tests indicating kidney dysfunction after eating grapes, raisins or both.  Just over half of the dogs survived.

All of the dogs vomited.  Other common clinical signs included diarrhea, lack of appetite, and lack of energy (lethargy).  A decrease in urine output, ataxia (lack of coordination, particularly in walking), or weakness were associated with a poor outcome.  Clinical signs (particularly vomiting and diarrhea) reportedly develop six to twelve hours after consuming either grapes or raisins, and renal failure can develop in one to three days.

The situation has not, to my knowledge been reproduced experimentally.  It appears to only affect a subset of dogs, since many dogs can apparently eat grapes and raisins in similar quantities and suffer no ill effects.  Until this condition is better understood, it is advisable to keep dogs away from grapes and raisins.  If a 20 lb dog eats more than 3 oz of raisins it could be at risk.  It looks like another good reason to give your dog, dog food instead of people food.

Water Hemlock

There are numerous plants that are poisonous to animals (many are also poisonous to the two legged animals known as humans).  Of those that grow in the Western United States, Water Hemlock (Cicuta douglasii) is the granddaddy of them all.  It causes the violent signs, and more often than not leads to death of the animal.  It only takes a little bit of the toxin, called cicutoxin, to be fatal.

Cicutoxin is a neurotoxin, which means that it affects the nervous system.  In this case it affects the brain, rapidly causing severe seizures, coma, and death.  Animals begin showing signs within a few minutes to a few hours after eating the plant, and can die as soon as 15 minutes after showing signs. 

Poisonings are likely in the spring when it first begins to grow.  The early leaves tend to have a very high concentration of cicutoxin.  Any animal that grazes on it is potentially susceptible.  I have even heard of geese being poisoned from eating the young plants in the early spring.  Poisonings also occur later in the year, particularly when the roots are larger and become available due to plowing, tromping in stream beds, cleaning ditches etc. 

Human poisonings may occur, because people mistake it for wild parsnips or other potentially edible plants.  The toxin is particularly concentrated in the root, and has been reported to have a carrot-like odor.  I recommend growing your own carrots and parsley (or buying them from your local grocer).

This is another situation where prevention is the most effective means of control.  Don’t graze animals where water hemlock is growing.  Another means is just plain luck.  In the lab where I am working there is a photograph of a field with more water hemlock than grass, and cattle are happily grazing around the plants.  If you try that technique I hope your luck is better than most farmers.

Blue-Green Algae

Pond with an algal bloom

Blue-green algae, or cyanobacterium, grows on the top of water.  If the nutrients are available and the temperature is warm, it can develop into a toxic algal bloom.  Add a little wind to push it all to one side of the water, and you have the perfect setup for a disaster.  Poisoning occurs when an animal drinks the affected water.  This can happen as a result of swimming in the water, ingesting some in the process.

Many species are susceptible, but simple stomached animals (dogs, cats, pigs, humans etc.) are less sensitive than ruminants (cattle, sheep, goats etc.).  Sensitivity also depends on the animal’s size and the amount of toxin it ingests.  Don’t let the fact that dogs are less susceptible than cattle fool you.  Many dogs have died from swimming in water with toxic algal blooms.

Microscopic image of blue-green algae

The toxins tend to fall into one of two groups.  Either they are neurotoxins (affecting the nervous system) or they are hepatotoxins (affecting the liver).  The neurotoxins cause a more rapid onset of clinical signs often within minutes of exposure, whereas the hepatotoxins typically take at least an hour before clinical signs appear.  Both are very dangerous.  Studies have found that animals can consume up to 90% of a lethal dose before they show any clinical signs.  As a result if clinical signs do appear there is a very good chance that without treatment the animal will die.

Affected animals may have muscle tremors, difficulty breathing, or diarrhea.  The most important piece of information necessary to diagnose this is the history of drinking or swimming in water with blue-green algae.

Prevention is clearly the key in blue-green algae poisoning.  If the only access animals have to water is a pond or lake that has algal blooms, the safest solution is to only allow access to the upwind side.  If you are lucky the wind will push enough of it to the other side that there will be no problems.  Don’t let dogs and other small animals swim in water during a bloom.  Avoidance is the best protection.

Blister Beetle (Cantharidin toxicosis)

Since the last two posts have been associated mostly with dogs I thought it might be nice to move to another species for this post.  The topic for this post is cantharidin, a nasty little compound found in blister beetles. A quick search on Google Scholar revealed a wide variety of species that have been affected, but the most commonly affected species are those that eat alfalfa hay.  Most reports are in horses, but there are also case reports in cattle, sheep, goats, rabbits, dogs, cats, various birds, and even people. 

            There are many different beetles that contain cantharidin.  The most common in the United States are those of the species Epicauta.  The adult beetles feed on the nectar of flowering plants.  As a result if alfalfa hay is cut when it is in bloom, there is a risk of smashing up swarms of these beetles in the process.  Therefore, if hay is cut before it flowers, or if it is cut before or after the adult beetles are active, it will reduce the risk of cantharidin exposure to the unsuspecting consumers.

Cantharidin is very irritating and can cause blisters on exposed skin.  You can imagine what it does to the mouth, throat, and stomach.  It causes erosions and ulcerations in the upper gastrointestinal tract (esophagus and stomach), and because it is excreted in the urine, it can also cause severe inflammation of the bladder. 

            Horses are likely the most susceptible and, according to several sources, as little as 4-6 grams of dried beetle can kill a horse.  Some reasonable prevention techniques are to feed first or last cutting hay.  Adult beetles emerge later in the spring, so typically first cutting is done before they are active.  Similarly the last cutting is typically after they are most active, reducing the likelihood of beetle contamination in the hay.  Feeding grass hay can also be an effective alternative.  If the number of animals you are feeding is small enough, you may find that simply inspecting each flake of hay before you feed is effective.  If you see beetle parts don’t feed the hay.  Even if the beetles are removed the cantharidin can, and very likely is still present on the stems of he hay.

Bread Dough

After I wrote my last blog my two daughters gave me the “teenage critique”.  Apparently “everyone knows that chocolate is poisonous to dogs”, and it was “boring”.  Thanks for the critique girls.  I’ll try to improve.  For today’s topic I tried to pick one that may be a little less known (at least in the teenage girl crowd).  The topic is bread dough toxicity (yeast based).  No one likes homemade bread or rolls more than I do especially when it comes with a nice smothering of homemade jam.  Unfortunately some of our pets (dogs are again the most likely) are impatient.  If they manage to get it before it makes its way into the oven it can be a recipe for disaster. 

The stomach is a nice warm, moist environment quite suitable for that ball of bread dough to rise.  As the yeast ferments (yes, if you didn’t know, that is how it works) two things happen.  First is the ball of dough expands.  This can put enough pressure on the stomach wall to decrease blood flow and cause damage similar to bloat in a dog.  It makes the dog want to throw up, but due to the nature of the bread dough it often doesn’t come up.

The second problem is typically the most severe.  One of the byproducts of fermentation is ethanol (alcohol).  As the fermentation process continues, and more alcohol is produced, the dog can start to stagger around.  That’s right the dog is essentially drunk.  The problem is that the fermentation process continues even after the dog passes out.  The blood alcohol can continue to rise until the dog dies.

My suggestion is cook the dough and eat it yourself.  Thanksgiving will be much more enjoyable with your belly full, and no trips to the emergency veterinarian.  However, if your dog does manage to swallow a big ball of dough, try to hurry.  At least that way your veterinarian may make it back home before the turkey is gone.