Toxicology Tuesday, October 9

[Next week, I promise we will go back to the True/False format, and stop with the hard stuff. My sister says "It doesn't matter what the toxic principle is, if your pet eats poison, take it to the vet. You are being too picky with this series." But, the Science Chimp says "Knowledge is Good," or words to that effects, so bear with me one more time.]


The last poison in our rodenticide series is bromethalin, found in brand names like Rampage and Real Kill.


Remember the questions:

1) What is the toxic principle? (How does it kill?)
2) What are the signs/symptoms of poisoning?
3) Is there any treatment?
4) How bad is it - (On a relative scale of Fair - treatable if caught in time, Poor - might not survive even with treatment, or Grave - likely to be fatal even with treatment)

Give it a try, answer any or all questions, in part or in total. No one is laughed at for wrong guesses, and all attempts at answering will receive praise and public accolades.

Answer:

Bromethalin is a neurotoxin, and the signs are related to dysfunction of the CNS (Central Nervous System), primarily brain swelling. These signs are highly variable, depending on the dose ingested. Low doses in dogs lead to depression, anorexia, vomiting, and tremors, which may not show up for several days. Paresis (muscle weakness) or paralysis may also occur. High doses can cause a hyperexcitable state, tremors, increased reflexes, running fits, and localized or generalized seizures. In cats, the signs include depression, ataxia (incoordination), abdominal swelling, paralysis, and convulsions. Death can result from either high or low dose toxicity in both species.

These signs are non-specific; they are seen in many kinds of neurologic disease. If you don't have a history of exposure to the toxin, it might go undiagnosed, as it wouldn't show up in any of the routine laboratory work. It can take up to 4 days for initial signs to show in a dog, and may progress for one or two weeks before death from respiratory failure.

There is no antidote to bromethalin. It is rapidly absorbed into the system, and reaches peak blood levels a mere 4 hours after ingestion. If ingestion is observed, immediate decontamination (as discussed in previous posts) is the first course of action, and may be of some benefit. Otherwise, treatment is mainly supportive, including cautious use of IV fluids, diuretics, and steroids and mannitol to reduce brain swelling. The prognosis is grave in pets which are exhibiting symptoms.

Bormethalin was the second most common rodenticide I found when I shopped several local stores. About 75% of the products readily available were Vitamin K antagonists and about 25% contained bromethalin. I only found one store that carried one brand of cholecalciferol (Vitamin D) based mouse poison.

To sum up our three main types of mouse and rat poison:

1) Brodificoum, bromadiolone, and warfarin: Deplete the body's store of Vitamin K, causing bleeding problems. Antidote is Vitamin K. Prognosis: Fair. A good chance for recovery if treatment is started in time. Most common poison on the market.

2) Cholecalciferol: Vitamin D. Causes mineralization of soft tissues, especially the kidneys. No antidote, but early and aggressive treatment can speed the excretion of excess calcium, limiting the injury to major organs. Prognosis: Poor. Even with treatment, kidney or heart damage may leave animal with long-term health problems. Least common product available.

3) Bromethalin: A neurotoxin causing nonspecific signs. No antidote. Prognosis: Grave. Death is likely even with treatment. Second most common product.

So, how do you get rid of mice? Sticky traps are non-toxic, but I think we all agree that it is a cruel way for a critter to die. Old fashioned snap-traps are easy, quick, painless and non-toxic. If you can't stand to take the mouse off the trap, toss it - they're cheap. Unless you have a tiny pet, there is limited injury to "non-target organisms." Or, get a cat. I have one I will rent you.