Insecticides and dogs

There are dozens of products sold at hardware, home repair, and agricultural stores to kill ants, termites, wasps, garden pests, and other insects. Most of them contain organophosphates and carbamates as their active ingredients. With the development of pyrethrin insecticides that are equally effective but much less toxic, organophosphates and carbamates are being used less frequently.

Organophosphates and Carbamates: The organophosphates include chlorpyrifos, diazinon, phosmet, fenthion, cythioate, and tetrachlorvinphos. The common carbamates are carbyl and propexur. Most cases of organophosphate or carbamate poisoning occur because the dog ingested a poison bait. Exposure to high concentrations of chemicals in sprays and dusts also occurs. Signs of toxicity are hyperexcitability, excessive salivation and drooling, frequent urination, diarrhea, muscle twitching, weakness, staggering, collapse, and coma. Death is by respiratory failure.

Treatment: If you suspect that your dog has ingested an insecticide poison, immediately induce vomiting and notify your veterinarian. With any sign of toxicity, the first priority is to get your dog to the veterinarian as quickly as possible. The specific antidote for organophosphate poisoning (not carbamate poisoning) is 2-PAM (protopam chloride). Atropine is given for both organophosphate and carbamate poisoning to control excessive salivation, vomiting, frequent urination and defecation, and to reverse a slow heart rate. Seizures are controlled with diazepam (Valium) or barbiturates. In the event of skin exposure, give the dog a bath with soapy water and rinse thoroughly to remove residual insecticide.

Chlorinated Hydrocarbons: These compounds, of which the prototype is DDT, are added to sprays and dusts to control plant pests. Their use has been curtailed because of persistent toxicity in the environment. Only lindane and methoxychlor are approved for use around livestock. Chlorinated hydrocarbons are readily inhaled and easily absorbed through the skin. Toxicity can occur from repeated or excessive exposure. Signs of toxicity appear rapidly. They include hyperexcitability with twitching of the face, followed by muscle tremors that begin at the head and progress back to involve the neck, shoulder, trunk, and rear legs. Seizures and convulsions are followed by respiratory paralysis and death.

Treatment: There is no specific antidote. Treatment includes supporting life functions, removing ingested poison from the stomach, and controlling seizures.

Pyrethrins and Pyrethroids: These compounds are incorporated into many insecticidal shampoos, sprays, dusts, dips, foggers, and sprays. Pyrethrins and the synthetic pyrethroids are much safer to use on and around dogs (and humans) than are other insecticides, and they are being used more widely. Many over-the-counter topical flea-control products have concentrated pyrethrins as their active ingredients. Some dogs may be adversely affected by that level of pyrethrins. Common chemicals in this class include permethrin, allethrin, fenvalerate, resmethrin, and sumethrin. Signs of toxicity include drooling, depression, muscle tremors, staggering, vomiting, and rapid labored breathing. Toxicity occurs primarily in small dogs. Death is rare. Simultaneous exposure to organophosphates increases the toxicity of pyrethroids.

Treatment: Induce vomiting within two hours of ingestion. Call your veterinarian for further instructions. Do not induce vomiting if the product contains a petroleum distillate. With signs of toxicity, proceed immediately to the veterinary clinic. For topical exposure, remove residual insecticide by bathing the dog in lukewarm water and Dawn dishwashing soap or canine shampoo to strip out the chemicals. (Do not use flea shampoo.) Rinse very thoroughly. Bathing in hot or cold water may actually increase the rate of absorption or cause hypothermia, which increases toxicity. After bathing, keep the dog warm.

Prevention: Most cases of poisoning occur because of improper application of flea-control products. That may be because the product is being used more often than the instructions call for, or is being combined with another flea-control product. Follow all instructions carefully.

Arsenic: This heavy metal is used in herbicides, insecticides, and wood preservatives. Sodium and potassium arsenate are used in ant poisons. Arsenic has a very rapid action and therefore poses a major risk for accidental poisoning. Death can occur quickly, even before symptoms are observed. Fortunately, the use of arsenic has been greatly curtailed. Signs of poisoning include thirst, drooling, vomiting, staggering, intense abdominal pain, cramps, diarrhea, paralysis, and death. The breath of the dog has a strong garlic odor.

Treatment: Proceed at once to the nearest emergency veterinary facility. BAL (British Anti Lewisite) is a specific antidote and should be given as soon as the diagnosis is suspected.