Chlorfenapyr Poisoning

By Renee Schmid, DVM, DABVT, DABT; Ahna Brutlag, DVM, MS, DABT, DABVT

What is chlorfenapyr poisoning? 

Chlorfenapyr is a pesticide used to control both nuisance and destructive insects including roaches, bed bugs and termites in home settings and gnats, thrips and caterpillars in greenhouse-grown crops/ornamental plants. It is available as a liquid concentrate, aerosol spray and aerosol fogger. Chlorfenapyr disrupts the ability of an animal cell to produce energy which results in cellular death. Ingestion, inhalation, or skin absorption of chlorfenapyr can lead to poisoning in animals and people.  

What are the clinical signs of chlorfenapyr poisoning?  

Although reports of confirmed chlorfenapyr poisoning in the medical literature are sparse and limited to humans and dogs, it is suspected that any animal can develop clinical signs following toxic exposure. Acute signs in dogs include panting, vomiting, stiff rear-legged gait, collapse and death. These signs occur within 60 – 90 minutes of ingestion and are expected following consumption of a toxic dose. Later onset clinical signs including a high fever, wobbly gait, and agitated behavior are reported hours after ingestion in dogs. Case studies involving people describe delayed onset neurological symptoms including fever, muscular pain, limb weakness progressing to paralysis, loss of consciousness and death within 5 – 10 days following chlorfenapyr exposures. If you suspect your pet has been exposed to chlorfenapyr, please call your veterinarian or Pet Poison Helpline, a 24/7 animal poison control center, at 1-800-213-6680 right away. 

How is chlorfenapyr poisoning diagnosed? 

Chlorfenapyr poisoning is suspected if a pet has access to this pesticide and subsequently develops expected signs. It should also be suspected in a pet that is exhibiting signs and at risk of malicious poisoning. No specific changes in blood counts or serum chemistries are reported in dogs, but chlorfenapyr intoxicated humans have lab work indicating kidney injury, pancreatic inflammation and muscle breakdown. These same findings may occur in dogs. Magnetic resonance imaging (MRI) changes in people include fluid accumulation (swelling) and loss of myelin – the tissue that covers important nerves – in the spinal cord and brain. Again, this may also be possible in dogs. Confirmatory diagnosis of chlorfenapyr poisoning can be made by analyzing blood, tissue, stomach contents or suspected malicious bait for the presence of the toxin using specialized testing.  

How is chlorfenapyr poisoning treated? 

Due to a narrow margin of safety and high risk for death, pet owners should seek immediate veterinary care for any pet exposed to chlorfenapyr. Aggressive decontamination, including induction of vomiting, gastric lavage (stomach pumping), and activated charcoal, is advised following most ingestions. Inducing vomiting in cats should never be attempted at home unless under the instruction of a veterinarian. Hospitalization at a facility that provides continuous veterinary supervision is needed to monitor for clinical signs. Unfortunately, there is no antidote for chlorfenapyr poisoning. If signs occur, pets are administered intravenous (IV) fluids, muscle relaxants, cooling therapies, sedation/anesthesia, and mechanical ventilation for support. Other therapies may also be warranted, based on the progression of clinical signs.   

What is the prognosis for chlorfenapyr poisoning?  

Pets that develop clinical signs following chlorfenapyr ingestion are unlikely to survive and chronic complications may be present for survivors.

Pet Poison Helpline, an animal poison control 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


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