Are Snakes Becoming More Toxic?


The May 2015 issue of Whole Dog Journal contains two in-depth articles about the venomous snakes in North America that are potentially dangerous or deadly to dogs. The main article discusses the rattlesnake vaccine and antivenom treatments, as well as practical tips for avoiding snakes and emergency first-aid for snake bites. The second article discusses snake-avoidance training methods that do not involve shock collars. Subscribers to the WDJ can check out these articles and more at — and in the hard copy of the magazine, in their mailboxes now.

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However, we ran out of room in the issue to discuss another important : Discussion of the evidence that venomous snakes may be developing increased toxicity.

In 2008, toxicologists at the Banner Poison Control Center in Phoenix, Arizona, one of the nation’s busiest poison centers treating rattlesnake bites, warned emergency physicians of a troubling trend.

“Over the last five or six years, we have noticed an increased incidence of critically ill rattlesnake bite patients being admitted to our service,” wrote Dr. Steven Curry, the center’s Director of Medical Toxicology. “The collective clinical findings in these patients mimic aspects of anaphylaxis and commonly include one or more of the following: rapid collapse within a few minutes of being bitten; hypotension and shock, commonly requiring epinephrine; rapid, profound third-spacing of fluids with hypovolemia and hemoconcentration, sometimes with only minimal or absent swelling; swelling or angioedema of the lips, tongue and throat, sometimes requiring emergency airway management; and profound weakness and/or diarrhea.”

Toxicologists could not say why so many bite victims experienced severe and life-threatening symptoms. In the few cases where physicians with Banner Poison Control Center were able to examine the snake responsible, it was a Mojave rattlesnake. However, in most cases, the rattlesnake was not identified.

“We never recommend that any attempt be made to capture or kill the offending snake because of the danger involved,” Dr. Curry said. “Therefore, we don’t know that Mojave rattlesnakes alone are responsible for an increasing frequency of severely envenomated patients.

“Physician toxicologists with Banner Poison Control Center have admitted about 50 to 75 rattlesnake bite patients annually for nearly 30 years,” Dr. Curry added. “Prior to 2002, we saw patients with the above findings about once every two or three years. Now we see several of these patients each year, and have recently become aware of similar patients in nearby states.”

Dr. Curry and his colleagues have communicated with poison center toxicologists in Tucson, Arizona, Southern California, and Colorado, where similar trends have been observed.

In June 2012, the San Diego Union-Tribune reported that in and around San Diego, California, rattlesnake bites were increasing in frequency and becoming more dangerous. The article quoted Dr. Richard Clark, director of the Division of Medical Toxicology at the University of California San Diego Health System and medical director for the San Diego office of the California Poison Control System. “While San Diego County is seeing a rise in snake bite cases each year,” he explained, “the more alarming factor is the toxicity of the bite. The symptoms and wounds we’re seeing are worse than in the past. Some speculate that with the modern world encroaching on nature, it could be survival of the fittest. Perhaps only the strongest, most venomous snakes survive.”

All the more reason to exercise caution in any area known for its rattlesnakes.