Organophosphate and Carbamate Toxicity in Dogs

Organophosphate (OP) and carbamate (CM) insecticides were once commonly used on animals as active ingredients in flea and tick medications. With the development of newer, safer insecticides, use of OP/CMs as parasite control for pets has declined. Concern of OP/CM toxicity in dogs is still warranted as these chemicals are widely used in agricultural and gardening herbicides.

Choking from excessive lung secretions, seizures, or respiratory arrest are the typical cause of death in OP/CM toxicity.

OP/CM products range from having very low to very high toxicity that can result in death. Prognosis depends on which product an animal has come into contact with, the dosage, and time between exposure and decontamination.

Exposure to any OP/CM containing insecticide or herbicide requires immediate veterinary care for decontamination and treatment. Emergency veterinary attention is necessary for any dog showing symptoms consistent with OP/CM toxicosis, whether exposure is known or not.

Symptoms can occur within 30 minutes of ingestion or inhalation, but skin exposure may delay onset of signs up to 12-24 hours.

Organophosphate and carbamate poisoning is caused by exposure to these classes of chemicals which are commonly used in herbicides. The complete list of chemicals in this class is extensive. Exposure can be through most routes, including ingestion, inhalation, and absorption through the skin. These chemicals have neurotoxic effects and in high enough doses can be life threatening.

OP/CMs overstimulate nerve endings and lead to the signs of toxicity.

Symptoms are grouped into nicotinic, muscarinic, and central nervous system effects.

Diagnosis is typically made based on symptoms together and known or suspected exposure. Additional tests to help confirm diagnosis are measuring cholinesterase activity in whole blood, measuring OP/CM levels of stomach contents, or an atropine response test.

Treatment consists of immediate life-saving care, decontamination, and supportive care.

Life-saving care consists of controlling seizures, oxygen support, and temperature regulation. Decontamination is achieved by bathing, inducing vomiting, or administering activated charcoal.

Note: induction of vomiting and administration of activated charcoal should only be performed by a veterinary professional. There is no safe way to decontaminate a pet’s stomach contents at home.

Supportive care includes specific medications to raise heart rate and reduce tremors. Intravenous fluid therapy helps with cardiovascular support and replace fluids and electrolytes lost through vomiting and diarrhea. Analgesics and anti vomiting medications may be needed if GI symptoms are severe.

The duration of signs varies depending on dosage and which specific OP/CM has led to poisoning. CMs are broken down quickly and symptoms are usually gone within 4 hours. OPs take longer for the body to eliminate and symptoms tend to have a longer duration. There are also effects of OP/CMs that may take days to weeks to appear after initial symptoms are noted.

Prevention is by reducing exposure risk and keeping all pesticides out of reach of animals. Mixing OP/CMs with organic fertilizers can increase the likelihood of exposure because the latter are very attractive to dogs. This condition is not contagious.

OP/CM toxicosis is common in dogs.

• Decontamination
• Anti-seizure medication
• Thermoregulatory measures
• Oxygen support
• IV fluid support
• Atropine
• Muscle relaxers
• Analgesics
• Antiemetics