No portion of this article may be reproduced without permission of the copyright holder. Reprinted with permission from AKC Family Dog, July/August 2005. To subscribe:http://www.akc.org
People have always been fascinated by poisons. From Socrates and his hemlock to Romeo and Juliet, from Cleopatra and her asp to Arsenic and Old Lace, the ability of a substance (especially in small amounts) to kill a person or an annimal holds a morbid interest. Venomous animals that hunt or protect themselves using toxins (some of which are quite deadly) are particularly intriguing. Much folklore, myth, and phobia surrounds many of these venomous creatures. To come to understand something is to learn not to fear it.
Certainly no other animal is as entrenched in legend as the snake. From the Garden of Eden to Aesop's Fables, snakes represented evil and deceit. But the real animals bear little resemblance to those of the fables.
There are roughly 120 species of snake that inhabit the United States; only 21 of these species are venomous. Every state in the Union (except Alaska, Hawaii, and Maine) is home to at least one poisonous species. Become familiar with the indigenous poisonous snakes in your region. Two families of venomous snakes are found in the United States-the Elapids (two genera of coral snakes are found in Arizona and New Mexico and the other along the Gulf Coast states) and the Crotalids (rattlesnakes and their allies, the copperheads and water moccasins) The Crotulids are also known as pit vipers since these snakes possess heat-sensing facial pits between the nostrils and eyes that help them locate the small birds and mammals they eat. About 99 percent of all snake bites in this country each year are caused by pit vipers. Along with their facial pits, the Crotalids can also be distinguished by retractable fangs, elliptical pupils, and a triangular head. The true rattlesnakes have special keratinized rattles at the end of their tail that they vibrate when threatened. Many snakes (even nonvenomous species) will shake their tail when disturbed or agitated.
Coral snakes bear alternating bands of color-black, yellow (occasionally white), and red. A good rule of thumb is that if the head is black (only in the continental United States), or the yellow band touches the red, it is a coral snake. Also, coral snakes have no facial pits, always have round pupils, possess fixed front fangs, and their heads are not triangular. Many snakes mimic the coral's coloration. Fortunately, due to their small size, secretive behavior, and limited range, coral snakes pose little risk to dogs in this country. Far and away the most dangerous species to both people and their companion animals are the pit vipers.
Rattlesnake venom shoots from poison glands in the upper jaw through retractable, hollow fangs. The venom is designed to immobilize and predigest prey. While coral snake bites can be painful, the hallmark of a rattlesnake bite is tremendous tissue destruction, swelling, and bruising. Rattlesnakes can meter their venom, meaning that they can deliver different amounts of venom depending on the situation. If not agitated and striking a field mouse, they release a small amount. If threatened by a dog and biting to save their own lives, they may release all the venom they have. Younger snakes are already venomous and, in fact, have a higher percentage of toxic peptides in their venom.
Rattlesnake bites are a medical emergency. The majority of dogs seen at our practice for snake bite over the last 20 years have been bitten on the head and face; these wounds can be extremely dangerous. The single most effective therapy for rattlesnake bites in dogs is the intravenous administration of purified Crotalid antivenin, though a new vaccine can help alleviate the damage if given in advance. Antivenin can still be necessary for severe bites, even for vaccinated dogs. This material is expensive and severe bites may require multiple vials. It is most effective if given as soon as possible after the bite. If your dog is bitten, keep the animal quiet, remove any restrictive collars or harnesses and transport the animal quickly to a hospital that stocks antivenins. Many strikes by rattlesnakes are reported to be "dry bites." Do not assume so! Any dog bitten by a snake should be seen by a veterinarian. The best chances for successful therapy for snake bite come from early treatment. Antivenin also exists for certain coral snake species, though there is no vaccine.
Spiders rival snakes in our often intense phobias. They are the most successful terrestrial carnivores. There are over 38,000 known species, but many experts believe that this number is closer to 100,000. (Contrast this to the 4,000 species of mammals on the planet!) It is estimated that throughout your life you are never more than one meter from a spider. All spiders (except for two families) are venomous, but fortunately not all spiders possess the biting mouth parts necessary to pierce human and animal skin. Great stowaways, spiders can utilize human transport and heated cargo holds and safely arrive at destinations far outside their normal range. As a result, regional poison centers routinely record bites for species foreign to an area. Thankfully for is, most spiders are secretive, not aggressive, and prefer dark, quiet, draftless areas.
In the United States, the two best-known spider species are the Latrodectus (widow spiders) and the Loxosceles (recluse spiders), both of which can cause serious bites in humans and animals. Black widows are found throughout the United States. Females have the characteristic black coloration, spherical abdomen, and he familiar red hourglass marking n the bottom. Males are much smaller, inoffensive, and not involved in poisoning humans or animals. (Contrary to popular belief, black widow males are not always consumed by the female after mating.) Immature females are poisonous and can cause dangerous bites, but they lack the characteristic abdomen of the adult female and take on the color of their last insect meal--so they may go unrecognized.
Black widows may enter human habitations during cold weather. They are generally shy and will remain hidden if possible, though the females will protect their egg sac. The venom of black widows is highly toxic, thousands of times more deadly than necessary for killing the insects that they eat. Gram for gram, it is 100 percent more potent than rattlesnake venom. Luckily, their small size limits the amounts delivered.
For bites on dogs, the incident is rarely witnessed and the spider seldom seen. The bite area is inconspicuous and is further obscured by the animal's fur. In humans, black widow bites can go unnoticed but within a few hours are followed by dull pain or aching. Unlike bee stings, there is little swelling and, unlike snake bites, local tissue changes are generally absent. The area around the bite may redden, and the region may be dully sore. Classic signs to look for include abdominal muscle rigidity and tenderness. Cats seem much more sensitive to black widow venom than dogs, probably due to their smaller size. Dogs known to have been bitten by widow spiders should be seen by a veterinarian-a specific antivenin for black widow bites is available. Most likely, the majority of widow bites in dogs go unrecognized and untreated.
Brown recluse bites upon dogs can cause serious poisonings. These spiders generally live in the southern half of the United States, but can show up anywhere in shipments of produce and can survive in heated warehouses. The brown recluse is also called the fiddlebuck or violin spider because of the violin shaped marking on its back. (The neck of the violin points toward the abdomen.) The brown recluse is a nocturnal, secretive, nonaggressive spider-hence, the name recluse. Victims are generally unaware of being bitten by these spiders. The initial bite goes undetected, but hours later mild stinging, generalized soreness, and itchiness can arise. As the bite's lesion matures, a dark, northealing center may appear inside the reddened bite area. This central, deadened, ulcerative region is known as necrotic urachnidism. Cutting the area surgically used to be recommended, but now vets prefer to treat the wound conservatively. There is currently no specific antivenin for recluse bites.
Brown recluse bites on dogs can be potentially serious, one should seek veterinary care for any animal known to have been bitten. If your dog is bitten, try to find the spider and bring it to the veterinary hospital with the dog so that the species can be identified. If you happen to see a dog being bitten by a spider, take them both (if possible) to a veterinarian's office immediately.
Each year an average of 40 human deaths due to bee stings are reported in the United States-more than three times the number caused by poisonous snake bites. In addition, the prevalence of hymenoptera (bee sting) allergy in the general population of both dogs and people is reported to be around three percent. Furthermore, me appearance or so-called killer bees, or Africanized bees, has been documented in this country since 1990. For these reasons, it is important to be aware of the dangers that bees pose to dogs.
The stinging behavior of bees and wasps is primarily defensive and intended to protect the hive or nest. Only females possess stingers. Bee stingers have a barb that anchors in the skin and tears away from the bee, leaving the venom glands, the stinger, and a portion of the abdomen. As a result, bees can sting only once, then they die. Wasp and hornet stingers are straight and aren't lost, so the ani-ma-Is can sting multiple times and live. Unlike spider bites, wasp, hornet, and bee stings cause immediate pain and swelling. Stung dogs will often cry out. The majority of deaths due to anaphylactic (potentially life threateningly allergic) reactions to bee stings occur within one hour of the sting. Although many canine deaths result from immediate hypersensitivity, some result from dogs being stung multiple times. The majority of dogs, however, arrive at the vet's office with a solitary sting and local pain and swelling at the site.
Dogs that display a true allergic reaction, or animals stung multiple times, should receive veterinary care immediately. For most dogs, first aid for bee stings can be initiated at home. Waste no time searching for and meticulously removing stingers, since 100 percent of the venom is delivered within 60 seconds of the sting. Cool compresses, anti histamines, and bathing can help control the swelling and pain (but always check with your vet before administering medication, including antihistamines). Any questions regarding bee stings, or any dog who seems to be responding differently than lust to the pain of a small swelling, should be taken to your veterinarian. The venom of Africanized bees is not more toxic; rather, due to the aggressive nature of these bees, victims are more likely to be stung by many bees. Be careful bee stings can be quite painful, and potentially life threatening, and dogs do not seem to learn about bees even after being stung.
Imported fire ants arrived in the United States at the beginning of the last century. The black fire ant has been contained to central Alabama and Mississippi. The red fire ant, however, is now well entrenched in 13 southeastern states, from Texas to South Carolina. This insect is highly adaptive and has either replaced or interbred with local ants. In some areas, the hybrids make up 90 percent of the local population. Their spread has already caused health problems, since it is estimated that in ant infested areas, 60 percent of humans are stung at least once annu ally. Severe anaphylactic reactions have occurred in people and hypersensitivity reactions I have also been documented in large and small animals. In some areas of the Southeast, the fire ant is now the leading cause of insect sting hypersensitivity in humans, replacing bee stings. In dogs, it is the red fire ant that is most often involved. The potential for hybridization and for suitable habitat over much of the United States may make it a much more common problem.
Fire ants live in loose mounds with a single queen and as many as 100,000 individuals. If the mound is disturbed, pheromone controlled signals elicit a spectacular outpouring of aggressive ants. These ants bite and sting, first biting with powerful mandibles and anchoring to the skin, and then injecting venom through an abdominal stinger in a rapid series of stings rotating around the attached head. The stinger is smooth, is not lost, and fire ants, unlike bees, do not die after stinging. The stings are painful and cause redness at the site and a small lump that itches or burns. Afterwards, a blister develops. The area usually itches severely. Single stings do not generally require treatment: Relief of symptoms with anti-itch baths, antihistamines, cool compresses, and topical steroid creams may be helpful. Dogs with multiple stings may need to be hospitalized. To date, no prevention, control, or eradication programs of fire ants have been successful.
Snakes, spiders, bees, and ants represent the majority of poisonous animals that dogs encounter in the United States. The marine toad can cause poisonings in dogs, but these animals are generally confined to Hawaii, Florida, and the adjacent Gulf Coast states. Likewise, one species of venomous lizard, the Gila monster, exists in this country, but the range of these animals is now limited to a few counties in Arizona and New Mexico.
We should become aware of which poisonous animals live in our area and the first aid steps to take if our dogs are bitten or stung. Your veterinarian can answer any questions you have and treat specific bites or stings. Fortunately for most dogs, the odds of suffering a severe bite or sting are small.
Kevin Fitzgerald is a staff veterinarian at Alameda East Veterinary Hospital in Denver, and a frequent contributor to AKC FAMILY DOG.