Pumpkin spice lattes. Apple picking. Cute layering. But rats and mice???!!! Eek! The Fall is a wonderful time of year, but with the cooler weather comes the increased possibility of a rodent family moving into your warm home to snuggle up for the Winter. However, before you go purchasing any rat bait (i.e. a rodenticide), please educate yourself on the dangers of rat bait toxicity should your dog or cat accidentally ingest some and fall prey to potentially harrowing effects.
Types of Rodenticides
Vitamin K Antagonists (Anticoagulants)
Anticoagulant rodenticides are the most common category of rat baits. They contain ingredients that oppose the effects of vitamin K in the body. Vitamin K is utilized by the liver to form clotting factors, which are special proteins that aid in normal blood coagulation, a.k.a. blood clotting (the reason you don’t bleed to death after a little paper cut). (FYI: These products are very similar to common “blood thinners” used to prevent clot formation in humans.)
Anticoagulant rodenticides are meant to ingested by mice or rats to decrease vitamin K and clotting factor action enough to cause the rodents to bleed to death. However, if your inquisitive cat or dog eats the rat bait instead (or potentially consumes mice or rats that had ingested the poison), then your pet is at risk of hemorrhage as well. Signs of toxic effects are generally noted within 2-7 days after consuming the bait. Due to internal bleeding, you may observe pale gums (instead of the normal pink color), lethargy and decreased appetite, coughing and rapid or labored breathing due to bleeding inside the chest cavity, bloody vomit or dark stools, nose bleeds, or skin bruising.
If your pet is treated prior to the development of these clinical signs, prognosis is excellent; your vet will likely induce your pet to vomit, perform bloodwork, give an injection of vitamin K, and send your pet home with several weeks of oral vitamin K tablets to give with a fatty meal (to increase absorption of fat-soluble vitamin K by the GI tract). However, if your pet already has bleeding, your vet will perform special bloodwork to assess clotting ability (PT, PTT, ACT) and perhaps X-rays to assess bleeding in the chest or abdominal cavities. Once clinical signs have developed, prognosis is poorer, and your pet may require hospitalization with a blood transfusion, supplementary oxygen, and a possible chest or pericardial tap (thoracocentesis or pericardiocentesis, respectively) if there is bleeding around the lungs or heart.
Check your rat bait label for these anticoagulant ingredients: coumarin-based (such as warfarin; brodifacoum, bromadiolone, or difethialone) and indandione-based (such as diphacinone or diphenadione; and chlorophacinone). Examples of products: Havoc, Talon, d-CON, Maki, Contrac, Hombre, Generation, D-Cease, Diphacin, Ditrac, and Ramik.
Vitamin D (Cholecalciferol)-Based Products
Another group of rodenticides causes death in rats and mice by overdosing them with a form of vitamin D called cholecalciferol. Vitamin D normally functions in the body in concert with calcium and phosphorus for healthy bone development.
However, excessive levels of vitamin D rise levels of calcium high enough to form calcifications, or mineral deposits and plaques in multiple organs, including the GI tract, heart, and kidneys. This in turn causes organ dysfunction within 12-36 hours post-ingestion, seen as vomiting and diarrhea, dangerous heart arrhythmias (abnormal heart rhythms), kidney failure (causing increased urination and water consumption, or polyuria and polydipsia, respectively), and hemorrhage if mineralized plaques form in the walls of blood vessels and cause them to rupture.
If treatment is initiated quickly (before calcium deposits in the kidneys have formed), prognosis is generally good. However, if kidney calcifications have already developed (seen via ultrasound of the kidneys), prognosis is poor due to eventual demise from acute renal failure. If diagnosed early enough, your vet may administer cholestyramine, a bile acid derivative that binds fat-soluble vitamin D to prevent further kidney damage. Provided that your pet’s prognosis is good, your vet will prescribe a low calcium diet, anti-nausea medications, furosemide (Lasix®) and prednisone to promote increased excretion of calcium in urine, and other calcium-correcting drugs such as calcitonin or bisphosphonate and aluminum hydroxide. Treatments are generally ongoing over 2-4 weeks, during which time your vet will want to serially monitor your pet’s calcium levels via bloodwork.
Examples include Quintox, Tomcat, Ortho Rat-B-Gone and Mouse-B-Gone, and Muritan. Similar toxicity can occur following ingestion of Calcipotriene (or Dovonex®), a human psoriasis cream containing a cholecalciferol-like product.
Click here to learn more about your dog or cat’s nutrient requirements for vitamin D and vitamin K.
Bromethalin
Bromethalin is sold in a variety of forms such as tan or green pellets as well as “gummy” worms. Bromethalin is a rodenticide that personally haunts me, for one of my patients sadly died of this type of toxicity last Fall when she consumed bait that was set out by her unknowing owner’s landlord. Bromethalin affects the central nervous system by causing swelling of the brain and manifests in one of two ways depending on the dose consumed: paralytic syndrome or convulsant syndrome. Lower toxic doses cause paralytic syndrome which occurs within 1-5 days of ingestion and may last up to 12 days. Paralytic syndrome causes lethargy, vomiting , uncoordinated movement (ataxia), weakness (paresis), twitching eye movement (nystagmus), and decerebrate posture (in which the head is extended backwards and the front limbs are extended stiffly forward). These signs can progress to coma and failure to breathe adequately. (Note: Cats only exhibit the paralytic syndrome even if they consume a high toxic dose; in addition to the aforementioned signs, cats may also vocalize more loudly, have difficulty urinating, and have distended abdomens due to decreased intestinal activity.) If dogs receive a higher toxic dose of bromethalin, they may also exhibit the following signs of convulsant syndrome within 24 hours (as early as 4 hours) after eating the poison: muscle tremors or convulsions, loss of the ability to bark, bouts of running in circles, hyperthermia, paralysis, and unequal pupil size (anisocoria). Even with treatment, which involves the use of activated charcoal to “sop up” the toxin, anticonvulsants, and decreasing brain swelling (a difficult task), prognosis is very guarded, meaning the case could likely end in death. Examples of products: Assault, Rampage, Trounce, Vengeance, Hot Shot Sudden Death, Doratid, Fastrac, TopGun, Real Kill Mouse and Rat Killer, and Tomcat Mole Killer.
Zinc Phosphide
Zinc phosphide is typically sold as gray pellets or powder, which forms a toxic gas when it mixes with stomach acid. This gas has a strong fishy or garlic odor. Zinc phosphide affects the GI tract, respiratory system, and central nervous system, causing decreased appetite, vomiting, difficulty breathing (wheezing or gasping for breath), abnormal heart rhythm, convulsions, and shock. Toxicity occurs between 4-12 hours following ingestion (or as quickly as 15 minutes if your pet had a full stomach when he or she ate the poison). If caught early enough, your vet will try to trigger your pet to vomit out the contents and administer antacids or fluids to decrease stomach acid, liver protecting medications, and anticonvulsants. (Note: Do not try to induce vomiting at home because the toxic gas from the stomach contents can be hazardous to you as well!) Death can occur between 4-48 hours; however, even if your pet survives the first 48 hours, he or she may have long-lasting liver, kidney, or heart damage. Examples of products: Killrat, Mous-Con, Phosvin, Rumetan, Gopharid, Mole Nots, Ratol, Ridall-Zinc, Rodent Pellets, ZP-Rodent Bait Dragon, and Zinc-Tox. Related products include aluminum phosphide and magnesium phosphide.
Strychnine
Strychnine is one of the oldest types of rat poisons, and it is also one of the worse due to its horrible effects on the central nervous system. It is sold in a variety of products, in both pellet form and dyed grains to entice rats and mice; it may be colored pink, red, or green. Strychnine has a quick onset of action once consumed, typically within 15 minutes but up to 2 hours if your pet has a full stomach. Signs of toxicity include restlessness, over-excitability of the muscles and nerves, dilated eyes, arching of the neck backwards (opisthotonos), hyperthermia, and inadequate breathing (apnea). The most classic signs of strychnine poisoning are a “saw-horse stance” (in which all of the limbs are extended straight out in front of the animal without flexing easily), what appears to be a “grin” on the affected animal’s face (in which the corners of the mouth are pulled backwards due to lack of nerve control), and tonic seizures. Prognosis is typically fair with many animals dying of respiratory failure in less than 24 hours after ingestion, but prognosis may be good with early detection and treatment in which your vet will promote vomiting in your pet or administer activated charcoal to “soak up” the toxins, give muscle relaxants or anticonvulsants, and possibly place your pet on a ventilator if it cannot breath on its own. Examples of products: Gopher-Go, Milo Bait for Gophers, Gopher Getter, Force’s Gopher Killer, and Ro-dex.
What do I do if I think my dog or cat has ingested rat bait?
If you suspect that your dog or cat has ingested rat bait of any kind, prevent your pet from re-accessing the poison and immediately call your local veterinarian or after-hours emergency center. Your vet may also recommend that you contact the ASPCA Animal Poison Control Center (APCC) at (888) 426-4435. To aid your vet in treating your pet, please bring in the packaging of the rat poison as well as a sample to the clinic (wear gloves); if you observe what appears to be rat bait in your dog or cat’s vomit or feces, please bring a sample of that as well. If you are in a remote area and are unable to seek veterinary assistance, call the Animal Poison Control directly (fees may apply).
But what about the cute, furry little mice?
As a vet, I love animal of all kinds… not just dogs and cats. Yes, that means that I care for the well-being of wild mice and rats too. Instead of calling an exterminator or heading to the store to purchase rat bait or sticky pads, let’s discuss other means of pest control. I personally feel that rat baits and sticky pads are inhumane as these methods allow the rodent to suffer in a prolonged manner until death finally occurs… this can be days and days later. Plus, these poor animals can wander off to die inside a wall or other difficult-to-reach location, causing a horrible stench in your house. And as we’ve discussed, the use of rat poisons in your home can inadvertently expose your dog or cat to these toxins. A traditional mouse trap tends to be a quicker, more humane means of killing rodents, but what if you could get these furry pests out of your home while sparing their lives? I recommend a live mouse trap. I’ve personally used such traps, such as the Kness Tip-Trap, in my own home to great success. For this particular device, which is best for catching smaller mice, you simply open the trap and place a bit of food in the back of the trap to lure in the mouse (I recommend a dab of peanut butter). The mouse walks inside the trap’s door to the back and tips the trap over (like a child’s teeter-totter), causing the door to slam shut. You then take the entire trap outside (like the woods) and open the door to release the caught mouse. Win-win! (Be sure to walk a far enough distance from your house so that the mouse doesn’t follow you back home!)
For additional information on rodenticides, visit The American Veterinary Medical Association (AVMA). And be sure to check out The Meowing Vet later for future articles about other pet toxins, such as Snail Bait (Molluscicides) and Bird Bait (Avicides) as well as Medications and Drugs. In the meantime, please keep yourselves informed about human foods toxic to pets and poisonous household plants and mushrooms. download the APCC’s free mobile app for on-the-go pet safety info! As always, if you have additional questions, please feel free to contact us or follow us on Facebook.
– Maranda Elswick, DVM
