The Woodhouse toad (Anaxyrus woodhousii) is a common amphibian found across much of the central and western United States. This species possesses toxic skin secretions that serve as a defense mechanism against predators. The toad is not considered poisonous, which would imply toxicity only upon ingestion, but rather it is venomous through its skin secretions that are absorbed through the mucous membranes of an attacker.
The Toxin and Its Secretion Mechanism
The toxicity of the Woodhouse toad is attributed to a complex milky substance known as bufotoxin. This defensive secretion is a mix of compounds, primarily bufadienolides, which are steroid derivatives that function similarly to cardiac glycosides. These chemicals are designed to quickly irritate and deter any animal that attempts to mouth or consume the toad.
The toxin is produced and delivered by a pair of large, bulbous parotoid glands located on the back of the toad’s head, positioned just behind the eyes. These glands produce the milky white substance. The toad secretes the toxin when it feels threatened, stressed, or is handled roughly, releasing the substance onto its skin surface.
Recognizing the Woodhouse Toad
The Woodhouse toad is a medium-sized amphibian, typically growing up to four or five inches in length, with a stout body, short legs, and warty, dry-looking skin. Its coloring is usually a light to yellowish-brown, often featuring darker, irregular blotches and a prominent, light-colored stripe running down the center of its back.
A distinctive feature is the pair of large, oval parotoid glands behind the eyes, which are separated by a space greater than the width of one gland. The toad also has bony cranial crests that run lengthwise from the front to the back of its eyes. The species is widespread, inhabiting areas from Mexico north to Washington and across to parts of the Midwest, thriving in habitats near permanent water sources like river valleys, irrigation ditches, and suburban backyards.
Symptoms and Emergency Procedures
Symptoms of Exposure
Exposure to Woodhouse toad secretions can cause significant distress, particularly in curious pets like dogs and cats. The initial and most common signs in pets are immediate, intense irritation of the mouth and gums. This irritation leads to profuse drooling, often appearing frothy, head shaking, and pawing at the mouth as the animal attempts to remove the irritating substance.
Systemic symptoms quickly develop, including vomiting, diarrhea, and visible discomfort. In more severe cases of exposure, the potent cardiotoxic and neurotoxic components of the bufotoxin can affect the animal’s major systems. This can result in loss of coordination, muscle tremors, seizures, and dangerous changes to the heart rate and rhythm, which can be life-threatening without prompt intervention. Human exposure, typically through accidentally touching the face or eyes after handling a toad, is generally limited to mild skin irritation, eye pain, or nausea if secretions are transferred to the mouth.
Emergency Procedures
Immediate action is necessary if a pet has mouthed a Woodhouse toad, as the rapid absorption of the toxin makes time essential. The first step is to immediately flush the pet’s mouth to remove unabsorbed toxins from the gums, tongue, and inner cheeks. This should be done carefully using a damp cloth or a gentle stream of water, sweeping from the back of the mouth toward the front to prevent the animal from swallowing the toxin-laced water.
Avoid using a strong hose, which can inadvertently force water into the pet’s lungs and cause aspiration pneumonia. Once the mouth has been flushed, the pet must be taken to a veterinarian or an emergency animal hospital immediately, even if symptoms appear mild. Pet owners should also contact an animal poison control center while en route for guidance. Treatment is supportive and focused on managing the neurological and cardiac effects.