Bromethalin Rodenticide Poisoning in Dogs

What is bromethalin rodenticide poisoning?

Bromethalin is one of the most common types of rodenticides currently on the market. It is found in several forms, including hard blocks, soft baits, pellets, worms or grubs, and meal or grain.

Dogs are commonly poisoned when they find loose blocks placed for rodent control, or when they access the bulk container. Relay toxicity, in which poisoning occurs when an animal ingests rodents that died from bromethalin, is possible but not demonstrated experimentally in dogs.

Once ingested, bromethalin is rapidly absorbed from the gastrointestinal (GI) tract and metabolized in the liver to its more toxic form. The primary target for bromethalin and its metabolite is the central nervous system (CNS). It causes depletion of energy in the CNS, ultimately resulting in swelling of various areas of the CNS, including the brain (cerebral edema), leading to severe neurologic signs. Depending on the amount ingested, clinical signs can develop as soon as a few hours after exposure and in rare situations, as long as seven days after exposure.

What are the clinical signs of bromethalin poisoning?

There are two syndromes seen with bromethalin toxicosis, dependent on dose: acute convulsant syndrome and delayed paralytic syndrome. Paralytic syndrome develops within one to seven days of exposure and progresses over one to two weeks. This syndrome has a more subtle onset, often starting with mild lethargy and decreased appetite. It progresses to rear limb weakness and ataxia and, ultimately, paralysis. 

Dogs may also develop fine tremors, seizures, abnormal body positioning, and altered brain activity or coma. Convulsant syndrome develops within 24 hours of exposure. This syndrome is characterized by severe tremors, seizures, hyperthermia, agitation, and running fits. These signs are worsened with stimulation from light and noise.

How is bromethalin poisoning treated?

There is no antidote for bromethalin, so early decontamination is extremely important. If a dog ingests a toxic dose of bromethalin, prompt decontamination can be lifesaving. Intravenous (IV) fluids are delivered to maintain hydration and close electrolyte monitoring is important to watch for elevated sodium levels. If clinical signs develop, medications are initiated to decrease cerebral edema. Clinical signs are then treated as needed.

What is the prognosis for bromethalin poisoning?

Unfortunately, prognosis is poor to grave if severe clinical signs develop such as seizures, paralysis, or coma. Patients with milder clinical signs may recover after several weeks but may have permanent neurologic damage. If clinical signs can be appropriately managed but there is no improvement after a week, prognosis is poor.

If you suspect or witness your pet ingesting rodenticide, call Pet Poison Helpline, a 24/7 animal poison center, at 1-855-764-7661 and take your pet to a veterinarian for treatment.

Pet Poison Helpline, an animal poison center based out of Minneapolis, MN, is available 24/7 for pet owners and veterinary professionals that require assistance treating a potentially poisoned pet. The staff provides treatment advice for poisoning cases of all species, including dogs, cats, birds, small mammals, large animals, and exotic species. As the most cost-effective option for animal poison control care, Pet Poison Helpline’s per-incident fee includes follow-up consultations for the duration of the poison case. Pet Poison Helpline is available in North America by calling 800-213-6680. Additional information can be found online at www.petpoisonhelpline.com.