A
couple of years ago, I noticed a sprinkling of dried mouse droppings on the
desk in my basement. I cleaned them up and,
except for setting traps in the basement, pretty much accepted the occasional debris
as an unavoidable nuisance. That changed
on the day I arrived at the desk to find that fiberglass from the nearby wall
had fallen on it, sodden with mouse urine and feces. Ewww! I decided to go after the little vermin with
a vengeance.
I
called my pest control guy, who strategically placed bait stations around my
basement. These were plastic mazes, the
payoff being a chunk of anticoagulant mouse poison at the end of the tunnel. Even though I don’t let my cats wander into
the basement, I told him I was concerned that they could be exposed to the
toxin if they happened to sneak down there.
He assured me that the point of the maze was to prevent pieces of the
poison from being removed from the bait station. The mice would help themselves to the toothsome
treat and leave. And then die.
One
of my cats, a rapscallion named Cam, became an expert at lying in wait for the
basement door to open and then streaking down the stairs. One day I chased after him and found him
licking a substantial chunk of grainy blue mouse poison. So much for “the mice
can’t remove the poison from the bait station!”
The bait stations were taken out the next day.
Rodenticides
can be grouped according to how they work.
The common ones we encounter in our practice are anticoagulants, which
stop normal blood clotting.
Bromadiolone, chlorophacinone, difethialone, brodifacoum, and warfarin
are examples of anticoagulants.
We
receive rodent poison-related calls at least a couple of times a month. The situations are sometimes similar to what
happened at my house. The most recent
one involved a dog that escaped through the front door, ran into a neighbor’s
garage and began eating a pellet of d-Con that was on the floor. In that case, the dog was lucky: The owner
knew what had happened and was able to get treatment right away. The tricky
thing about anticoagulant poisoning is that the pet owner usually has no
knowledge of the exposure, and the symptoms can be delayed for up to five
days. By that time, the owner has probably
forgotten that Fido disappeared into the neighbor’s shed for 10 minutes last
week. The pet is presented to us with physical
manifestations that aren’t specific to any one disease or syndrome: difficulty breathing, weakness, exercise
intolerance, lethargy, lameness, coughing, vomiting, and shaking. The
pet owner might not notice more specific signs, such as bruising, pale gums,
tarry black stools, or blood in the urine.
Treatment
for anticoagulants is supportive care, if indicated, and administering Vitamin
K1 for two to four weeks. If the owner
actually sees the pet eat the stuff, inducing vomiting (in some cases) followed
by activated charcoal might help prevent absorption. A pet with more severe clinical symptoms may
be in big trouble. Bleeding from rodent
poison is typically into the body cavities.
Massive blood loss into the abdomen and chest is common and is often the
cause of death.
Warfarin
– the same substance often prescribed for humans as a blood-thinning medication
– is what’s known as a first-generation anticoagulant poison and requires
multiple feedings to deliver a lethal dose.
Second-generation anticoagulants were developed when some resistance to
warfarin was discovered in rodents, and those can be lethal after just one
dose. After March 2015, consumers will
no longer be able to buy anything but first-generation anticoagulants or other
rodenticides, but pest control professionals will still be able to use the more
potent second-generation products.
According
to Audubon
Magazine, there’s no safe place or delivery system for second-generation
anticoagulants. Poisoning can occur from direct ingestion, but there’s also
something called “relay toxicosis”: after a rodent eats the poison, it gets
weak and becomes an easy, tasty meal for other animals such as raptors and
mammalian predators. That includes not only dogs and cats but foxes, bears,
bobcats, mountain lions, and wolves, among many others.
Here
are some sobering statistics:
- In California, rodenticides showed up in 79 percent of fishers, 78 percent of mountain lions, 84 percent of San Joaquin kit foxes, and 92 percent of raptors.
- In New York, rodenticides were found in 49 percent of 12 species of necropsied raptors. For great horned owls the figure was 81 percent. Rodenticides are also blighting raptors in Australia, New Zealand, Ireland, and Canada.
- In Great Britain, necropsies revealed the poisons in 92 percent of red kites, 91 percent of barn owls, and 80 percent of kestrels.
- Currently about 15,000 calls per year come in to the Centers for Disease Control from parents whose children have eaten rodenticides.
Scientists
and wildlife advocates recommend non-toxic pest eradication in most cases. There are certainly situations in which
rodents damage crops or homes, transmit disease, and even cause severe
ecological damage (entire island ecosystems have been destroyed by rats). But for the most part, use of second-generation
anticoagulants should be severely limited, even for pest control
professionals.
We
are the guardians of our children, pets, and wildlife; don’t use weapons of
mass destruction when a cherry bomb will do the job!
