Pesticide Poisoning in Dogs

Pesticide poisoning in dogs is a toxic illness caused by contact with a product that kills or repels pests. Organophosphates, carbamates, pyrethrins and pyrethroids, chlorinated hydrocarbons, and rodent and slug baits are the main causes. Dogs breathe the product in, absorb it through the skin or swallow it. Lawn products such as glyphosate are harmful if a dog swallows them or touches them while still wet. Symptoms include drooling, vomiting, diarrhea, tremors, seizures, difficulty breathing, weakness and irritation. If a dog eats a pesticide, start with the product name and label ingredients, then follow the five treatment steps. To keep dogs safe, remove pets, toys, bedding, and food and water bowls before application.

What Is Pesticide Poisoning in Dogs?

Pesticide poisoning in dogs is a toxic illness caused by contact with a product that kills or repels pests. Pesticide poisoning in dogs ranges from mild to life-threatening, depending on the specific substance and the amount ingested. Pesticides form an extremely large category. The category covers insecticides such as organophosphates and carbamates, and rodenticides such as bromethalin and cholecalciferol. Bromethalin is a neurotoxic rodenticide that damages the central nervous system. Cholecalciferol exposures have increased markedly in frequency in the US since the EPA regulatory changes. The poisons come from lawn and garden baits, outdoor sprays and product containers left within reach. Insecticide ingestion is consistently in the top 10 common toxicities for pets, according to the ASPCA Animal Poison Control Center. Michael J Murphy found in a 2002 study that rodenticides are second only to insecticides in pesticide exposure prevalence. The National Pesticide Information Center is a collaboration between Oregon State University and the United States Environmental Protection Agency. It gives objective, science-based information about pesticides. Treat every suspected case as an emergency and call a vet immediately.

Why Are Pesticides Poisonous to Dogs?

Pesticides are poisonous to dogs because they disrupt the nervous system. Dogs and other mammals experience insecticide toxicity in the same ways. A pesticide such as an organophosphate or carbamate insecticide blocks an enzyme called acetylcholinesterase. A 2015 study by Allister Vale in the Handbook of clinical neurology reports that both insecticide groups inhibit this enzyme. The block causes acetylcholine to accumulate. Blocked acetylcholinesterase leaves nerve cells overstimulated, which ultimately causes muscle tremors, paralysis and death. Malathion was one of the first organophosphate insecticides. Pyrethrin and pyrethroid insecticides overexcite the nervous system through sodium channels in the cell membrane. Imidacloprid is a systemic insecticide of the neonicotinoid class. It acts on the central nervous system of insects. Dose and route set the severity. The risk depends on the dose and on the toxicity of the pesticide to that type of animal. Allister Vale’s study titled Organophosphorus and carbamate insecticide poisoning gives a measure for delayed neuropathy. In organophosphate-induced delayed neuropathy, at least 70 percent of the neuropathy target esterase is phosphorylated and aged.

Can Pesticides Kill a Dog?

Yes. Pesticides can kill a dog, and pesticide poisoning can be deadly. With early diagnosis and aggressive therapy, the prognosis is typically good. In sudden and severe organophosphate poisoning, the primary signs may be breathing distress and collapse followed by death. Carbamate poisoning brings drooling, vomiting, sweating, small pupils, convulsions and fluid in the lungs, and ends in death. A 2014 study by Sheemona Chowdhary in Clinica chimica acta calls acute organophosphorus poisoning a potential cause of mortality. The risk is greatest in developing countries. Aldicarb is considered extremely hazardous by the EPA and the World Health Organization. It has been banned in more than 100 countries. Chlorpyrifos is considered moderately hazardous to humans (Class II) by the World Health Organization. Strychnine kills some animals too fast to detect the poison in the urine. Organic pesticides can have harmful effects on domestic species, fish and wildlife. A natural label does not remove the risk. A 1995 study by Steven S Nicholson from Louisiana State University tested a botanical insecticide spray on cats. A concentration of 5 and 10 times normal caused depression and recumbency lasting several days. The exact toxicity of a given product stays uncertain until a veterinarian reads its label and ingredients.

What Types of Pesticides Poison Dogs?

The types of pesticides that poison dogs are organophosphates, carbamates, pyrethrins and pyrethroids, chlorinated hydrocarbons, and rodent and slug baits. Key types include:

• Organophosphates: Organophosphate insecticides include azinphos-methyl, chlorpyrifos, coumaphos, diazinon, dichlorvos, dimethoate, disulfoton and malathion. Chlorpyrifos is an organophosphate pesticide used on crops, animals and in buildings to kill insects and worms. Organophosphates are a major cause of animal poisoning.
• Carbamates: Carbamate insecticides include aldicarb, carbaryl, carbofuran, methomyl and propoxur. Carbaryl is the organic compound 1-naphthyl methylcarbamate. A carbamate is a category of organic compounds with the general formula R2NC(O)OR.
• Pyrethrins and pyrethroids: Pyrethrins are naturally occurring compounds that act as the active insecticidal ingredients of pyrethrum. Wide use of these insecticides means wide exposure for dogs.
• Chlorinated hydrocarbons: Chlorinated hydrocarbon insecticides are general central nervous system stimulants. Their stimulation of the nervous system leads to tremors and convulsions.
• Rodent and slug baits: Outdoor baits for gophers and other rodents, and many slug and snail baits, can be highly toxic to pets. They are a frequent source of exposure.

A 2009 study by A Anadón reports that pyrethrin and pyrethroid insecticides are widely used in veterinary medicine. Their uses are agricultural and domestic. A study by Michael J Murphy at the University of Minnesota ranks rodenticides second only to insecticides in exposure prevalence.

What Are the Symptoms of Pesticide Poisoning in Dogs?

The symptoms of pesticide poisoning in dogs are drooling, vomiting, diarrhea, tremors, seizures, difficulty breathing, weakness and irritation. Organophosphate poisoning produces most of them. Key symptoms include:

• Drooling: Excessive drooling is an initial sign of organophosphate poisoning, together with small pupils and frequent urination. It appears early, so it gives the first warning.
• Vomiting and diarrhea: Vomiting, diarrhea and colic are initial signs of organophosphate poisoning. Owners who see them with drooling should contact a veterinarian immediately.
• Tremors and muscle spasms: Muscle spasms and weakness follow the initial signs. Tremors, trouble walking and nausea belong to the same picture.
• Seizures: Seizures come late, after nervousness, lack of coordination and apprehension. Seizures signal advanced poisoning.
• Difficulty breathing: Difficulty breathing is one of the initial signs. Breathing distress can progress to collapse in severe cases.
• Weakness or collapse: Weakness follows the spasms. Muscle paralysis can appear 24-96 hours after exposure in the intermediate syndrome.
• Irritation of the skin, eyes or mucous membranes: Insecticide poisoning irritates the skin, eyes and mucous membranes. This sign marks direct contact with the product.

Signs usually begin within hours after exposure but may be delayed for more than 2 days. A 1993 study by T C Marrs in Pharmacology & therapeutics states that diagnosis rests on clinical signs. It adds measurement of inhibition of erythrocyte acetylcholinesterase or plasma cholinesterase activity. Acetylcholinesterase inhibition in nervous tissue and at the neuromuscular junction produces the toxicity of organophosphate and carbamate insecticides. Allister Vale of the School of Biosciences reported in 2015 that cholinergic symptoms can relapse after apparent resolution.

Can Pesticides Cause Seizures in Dogs?

Yes. Pesticides cause seizures in dogs, and pyrethrin and pyrethroid poisoning is a documented cause. More severely affected animals can have severe tremors, seizures and death caused by respiratory failure. A 1995 study by Steven S Nicholson in Veterinary dermatology lists excessive salivation, tremors, ataxia, depression and hyperexcitability. It lists seizures and dyspnea as well. Pyrethroids reach the brain’s control of movement because they overexcite the nervous system through sodium channels. Chlorinated hydrocarbon insecticides cause tremors, convulsions and high fever as the most obvious signs of poisoning. Convulsions from chlorinated hydrocarbons may last from a few seconds to several hours and lead to coma. Metaldehyde is toxic if ingested in large quantities. Bromethalin is metabolised to n-desmethyl-bromethalin, which uncouples mitochondrial oxidative phosphorylation and lowers ATP synthesis. Atropine does not relieve the nicotinic effects of organophosphates. Muscle paralysis and death can still occur after massive overdoses.

Are Lawn Pesticides Harmful to Dogs?

It depends. Lawn pesticides such as glyphosate are harmful to dogs if the dog swallows them or touches them while still wet. Risk rises with exposure and with product toxicity, because a pet’s risk depends on how much pesticide the pet meets. Label directions set the safe return time. Pets stay away for the time on the label or until the spray has dried completely, whichever is longer. Granular products can need 24 or more hours while the granules dissolve and the surface dries. A 2006 study by Jelena Macan reports a relatively low risk to mammals from pyrethrins and pyrethroids. Rapid metabolism leaves no significant accumulation. The study titled Health effects of pyrethrins and pyrethroids by Jelena Macan warns of adverse effects. They occur more often in acute poisoning and after chronic exposure. A low-risk label does not remove the risk. A product labeled green is not necessarily safe for a dog that eats it. Organic pesticides can harm domestic species. Pets eat lawn and garden baits after application, dig them up and chew stored containers. The EPA announced a ban on the use of chlorpyrifos on food crops in the United States. The EPA Office of Pesticide Programs regulates the manufacture and use of all pesticides in the United States. The Federal Insecticide, Fungicide, and Rodenticide Act, revised in 1972, is the basis of current pesticide policy. The evidence for low risk to mammals is limited, so the real toxicity of an unfamiliar lawn product stays unknown.

How Do Dogs Get Exposed to Pesticides?

Dogs get exposed to pesticides when they breathe in the product, absorb it through the skin or ingest it. Permethrin is available for topical use as a cream or lotion, so skin contact is a route. Pesticides most often reach a dog when it licks the toxic substance from its feet or coat. Eating the product from a container left out is the other common route. A study by Jelena Macan in Arhiv za higijenu rada i toksikologiju confirms entry by ingestion, inhalation or skin contact. Walking on the lawn immediately after application of insecticide, then licking the feet, exposes the dog within the first hours. Eating dead or injured bugs that were sprayed with insecticide carries the poison into the gut. Eating grass or weeds near recently applied insecticide has the same result. Imidacloprid is one of the most widely used insecticides in the world, which spreads exposure into homes and yards. Susceptibility depends on the toxicity of the pesticide to the specific type of animal.

What Should Be Done if a Dog Eats Pesticide?

To act on what should be done when a dog eats pesticide, start with the product name and label ingredients. Call a veterinarian at once or call Pet Poison Helpline, because pesticide poisoning is an emergency. Determine how much and what type of product the dog consumed. Keep the packaging, or what is left of it, for the veterinary team. Contact a veterinarian immediately when vomiting, diarrhea, seizures, trouble walking, drooling, nausea or tremors begin. When exposure is by spraying, dipping or dusting, wash residue off with a thorough and gentle bath. Use detergents and large quantities of cool water, and skip the brushes. Seek emergency care when the dog has difficulty breathing, tremors, seizures, convulsions or collapse. Expect toxicity to differ between products, because organophosphates vary greatly in toxicity. Remember that the National Pesticide Information Center has no regulatory authority over pesticides. Care at a clinic then follows the active ingredient. A study by Franz Worek in Archives of toxicology states that standard drug treatment is atropine and an oxime.

Should Vomiting Be Induced if a Dog Eats Pesticide?

No. Vomiting should not be induced after insecticide ingestion at home when a dog eats pesticide, unless a veterinarian instructs it. Inducing vomiting after pyrethrin and pyrethroid ingestion is not usually recommended. Sheemona Chowdhary of the Department of Experimental Medicine and Biotechnology describes acute organophosphorus poisoning as a potential cause of mortality. The veterinary manual says vomiting should be induced if the dog swallowed an organophosphate less than 2 hours earlier. That advice does not apply when the dog is depressed. A dog that already shows clinical signs may be too late for safe vomiting. The risk is aspiration pneumonia. The sources differ on the timing window, so the veterinarian decides. Cholecalciferol reaches nontarget species typically through inadvertent ingestion of the bait product itself. Zinc phosphide needs an acidic pH, is severely corrosive and causes very rapid spontaneous vomiting with or without blood.

How Is Pesticide Poisoning in Dogs Treated?

To have pesticide poisoning in dogs treated, follow the 5 steps below. Atropine and pralidoxime are the antidotes for organophosphate poisoning.

1. Call the veterinarian at once and give the product name and label ingredients, because treatment depends on the product class. Carbamate poisoning is treated like organophosphate poisoning, since atropine injections help in both.
2. Let the veterinarian decide on decontamination, such as induced vomiting in the hospital or activated charcoal. Activated charcoal can help prevent absorption from the gastrointestinal tract, so it limits how much toxin the body takes in.
3. Wash residue off the skin with a gentle bath, using detergent and large quantities of cool water. Skip the brushes, because exposure by spraying, dipping or dusting calls for a gentle method.
4. Admit the dog for IV fluids and baseline blood tests when poisoning is severe. Blood tests are an important diagnostic aid, and a complete blood count, serum blood chemistry and urinalysis set the baseline. A depressed, dehydrated dog needs rehydration and nourishment intravenously or by stomach tube.
5. Give the antidote for the active ingredient, such as atropine and pralidoxime for organophosphates, and control seizures. Atropine sulfate blocks the central and peripheral muscarinic receptor-associated effects of organophosphates. Pralidoxime is an oxime that binds to organophosphate-inactivated acetylcholinesterase. An excited animal needs a sedative or anti-convulsant.

A 2020 study by Franz Worek in Archives of toxicology states that standard drug treatment is atropine and an oxime. It has been virtually unchanged for more than six decades. T C Marrs adds diazepam to the list in a 1993 study titled Organophosphate poisoning. The carbamate insecticides act like organophosphates, because they inhibit acetylcholinesterase at nerve synapses and neuromuscular junctions.

How Can Dogs Be Kept Safe From Pesticides?

To see dogs kept safe from pesticides, start by removing pets, toys, bedding, and food and water bowls. Keep pets near pesticide application out of treated areas until the pesticide has dried completely. Expect granular products to need 24 or more hours. Follow the label directions, which set the re-entry time. Select lower toxicity pesticides to cut the chance of a problem. Store pesticides securely in locations where pets cannot access them. Record what pesticides are used, when and where they were applied. Treat broadcast spraying of non-specific pesticides as a last resort. Integrated pest management chooses effective, less risky controls first. Use highly targeted chemicals, such as pheromones that disrupt pest mating, or mechanical control, such as trapping or weeding. Avoid Roundup and other weed killers that contain glyphosate where pets spend time. The EPA identified potential ecological risks from glyphosate to mammals and birds. Those risks are limited to the application area or areas near it. The Federal Insecticide, Fungicide, and Rodenticide Act requires the EPA to review pesticide registrations periodically. A Anadón reported in Veterinary journal (London, England : 1997) that these insecticides are widely used domestically.