Did you know? Rodenticides to avoid!

DID YOU KNOW……….?
By Dr. Catherine Adams

All rodenticides are NOT created equal! Currently there are four separate categories of rodenticides available for general use. Each has a different and unique mechanism of action. This results in four different sets of clinical signs in both the target rodent population and our curious pets who might consume them. All of these rodenticides pose some potential for relay toxicity when animals eat rodents killed by the toxin.

Long-acting anticoagulants (LAACs): By far the most well-known and perhaps most widely used rodenticides are the LAACS. This family of products acts by interrupting the body’s ability to form coagulating or clotting factors. Once the body has used up its current supply of coagulating factors clinical signs of bleeding are seen. Common signs include nosebleed, bloody urine, large and soft lumps, anorexia, and pain. Lethargy and dullness are common. It generally takes 2-5 days for these signs to occur, but chronic ingestion shortens the time period. If there is any suspicion of ingestion, a prothrombin test, usually referred to as a PT test, supports the diagnosis. Fortunately, Vitamin K1, the antidote, is routinely found in most veterinary offices.

Bromethalin: Ingestion of this active ingredient causes early cerebral edema with subsequent central nervous system signs. Cats seem to be particularly sensitive to bromethalin and exhibit signs at much lower doses. Sadly there is no specific diagnostic test and no antidote. Treatment is symptomatic and
may require an extended amount of time.

Phosphides: Zinc, calcium, and aluminum phosphides are very rapidly hydrolyzed in the stomach to form phosphine gas. Early signs include gastrointestinal inflammation and abdominal distension followed by a rapid onset of severe pain, pulmonary congestion and edema, and cardiovascular and central nervous system effects. Phosphides have a very narrow margin of safety and survival depends on prompt and effective decontamination and supportive care. Special attention needs to be paid to ventilation as human beings are susceptible to the phosphine gas fumes.

Cholecalciferol (Vitamin D3): Vitamin D3 based rodenticides act to increase systemic phosphorous and calcium levels which ultimately results in acute renal failure. Early elevations in serum phosphorous along with significant elevations in serum calcium are used to diagnose and guide treatment in overdose situations. Again, the margin of safety is very narrow and a complicated, long term treatment regimen is usually required. Interestingly, one of the newer treatment options is pamidronate, a bisphosphonate medication used to prevent brittle bones in women!