The toxicological affects of Bufotoxins

Cane toad toxin is a complex blend of chemicals produced by specialized glands on the toad's skin. Cane toads are poisonous at all life stages, including eggs and tadpoles.  Even a dead, dried cane toad can cause serious symptoms, since the toxins break down very slowly, and only once the dead toad is completely decomposed, are they considered safe.  A cane toad’s toxin can seep into the water around them, so poisoning can also occur if your pet drinks water from a bowl in which a toad was sitting, or water from a pond containing eggs.  The poison is an irritating, sticky substance that can adhere to a dog’s mouth, gums, tongue, nose, eyes or even an open wound, and enters the blood stream quickly.  It contains 3 main types of poison:  bufogenin, bufotoxin and bufotenin, which target the cardiovascular system.  Bufotenin also targets the central nervous and digestive systems. 

Both bufogenin and bufotoxin cause the heart to beat in an irregular rhythm, called an arrhythmia, which prevents it from pumping efficiently.  Bufotoxin also causes a narrowing of the blood vessels supplying the dog’s major body systems, like the brain, heart, lungs, digestive tract, muscles, and kidneys. The narrowed blood vessels cause an increase in the dog’s blood pressure, which in turn causes the heart to pump even harder to get the needed blood to those body systems.   Bufotenin causes stronger contractions of the heart, in an effort to increase the amount of blood being pumped. When the heart has an irregular rhythm, and high blood pressure and greater contraction of the heart are added to the equation, there becomes a considerable stress placed on the cardiovascular system.  When the heart can’t pump enough blood to the body, heart failure can occur.

Neurotransmitters play a role in nearly every function in the central nervous and digestive systems of a dog.  They are chemical messengers which carry a signal from one nerve cell to the next cell, and are required for the brain and nerves to work properly.  A type of Bufotenin found in cane toad toxin, called

5-Hydroxytryptophan, is transformed chemically within the dog to become the neurotransmitter serotonin. 

Serotonin is a naturally produced chemical within the dog’s body. However with exposure to cane toad toxin the levels become too high.  The resulting overstimulation of these chemical messengers in the brain, digestive system and nerves that control muscle movement, is a potentially life threatening condition.  It’s the central nervous symptom of seizures that are most worrying, as overheating due to prolonged seizure activity is the leading cause of death in extreme exposure cases.  

Not all canine poisonings via cane toad toxins are the same. Ultimately, the symptoms of cane toad poisoning experienced by a pet will depend on the amount of toxin absorbed, length of time from when the dog was exposed to the toxin, the size, age and general health of the dog. Once symptoms occur though, things tend to escalate very quickly.