Organophosphate Poisoning


Organophosphates are found in some older flea and tick rinses, and although there are many newer and safer alternatives, organophosphate poisoning is still one of the top three chemical agents responsible for deaths in animals. The other two are the anticoagulant rodenticides, and ethylene glycol (antifreeze).

There are many types of organophosphates, and they vary in how toxic they are, and how quickly they are excreted from a dog’s body. However, most have a very narrow margin of safety.

Poisoning usually occurs when a flea or tick rinse concentrate is incorrectly diluted and is used at a higher concentration than recommended. Another cause of poisoning is using more than one organophosphate-containing chemical at the same time, for example a flea rinse and a topical spot-on product.

When an organophosphate is used on a dog, it is stored in the body fat, and slowly released into the circulation. Leaner animals have less stored body fat, so there’s more available in the bloodstream to cause poisoning. Symptoms usually appear within hours of exposure but it can take up to 2 days for your dog to show signs of poisoning.

Organophosphate poisoning affects the nervous and musculoskeletal systems. A chemical called acetylcholine is involved in transmitting messages between nerve cells, or between a nerve cell and a muscle cell. When the acetylcholine has transmitted its message, it is destroyed by an enzyme. Organophosphates inactivate this enzyme, leaving the acetylcholine to send and resend the message.

Your dog will show any or all of the following symptoms – vomiting, diarrhea, depression, tremors and seizures, difficulty breathing, and constricted pupils. The dog may then become paralyzed, lapse into a coma and die due to respiratory failure and heart attack. Some organophosphates show a delayed effect on the nervous system, with dogs becoming wobbly and paralyzed up to 3 weeks after exposure.

If the chemical was applied to the skin, wash your dog thoroughly with a mild shampoo and warm water. There is a specific treatment for organophosphate poisoning, so take your dog to your vet immediately. The outcome varies, depending on how severely your dog has been affected.

To prevent organophosphate poisoning, use the product strictly according to directions. Don’t use at a higher concentration, and don’t use any more frequently than recommended. Better still, use one of the newer flea control products which are often more effective and much safer.

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