Pyrethroid Poisoning (Feline)

Pyrethrins are active insecticidal agents derived from flowers of the Pyrethrum plant. Pyrethroids are synthetic versions of these agents with better efficacy and stability and less toxicity than their natural counterparts. Pyrethroids are commonly used in topical and environmental flea control products. Permethrins are one of the more common types of pyrethroids used in flea control products. Cats are known to be sensitive to some pyrethroid formulations, especially those labeled for use on dogs only containing permethrin and less so to phenothrin. Aggressive early treatment is often successful.

Common name: Pyrethroid poisoning, Permethrin poisoning, Phenothrin poisoning
Scientific name: Pyrethroid toxicosis, Permethrin toxicosis, Phenothrin toxicosis

Diagnosis

Signalment
Cats are at risk of developing clinical signs from over exposure to some pyrethroids especially permethrin. Pediatric, geriatric and ill cats may have greater incidence of adverse reactions.

Incidence/prevalence
Pyrethroid toxicosis, typically involving permethrin, is one of the most commonly reported toxicities in cats to the ASPCA Animal Poison Control Center. Inappropriate exposure of cats to permethrin products results in as many as 97% showing clinical signs with 10.5% ending in death.

Geographic distribution
There is no known geographic predilection for this disease. However, it is expected to be more prevalent in climates where fleas are present.

Clinical signs (primary, most to least frequent, scientific term, synonyms)
Convulsions (seizures), Muscle fasciculations (twitching, tremors), Hypothermia (decreased body temperature),Hyperthermia (increased body temperature).

Clinical signs (secondary, most to least frequent, scientific term, synonyms)
Anorexia (loss of appetite), Vomiting, Death.

Cause (scientific, common term)
Pyrethroid insecticides, Permethrin insecticides, Phenothrin insecticides.

Organ system affected (most to least affected)
Central Nervous System, Gastrointestinal, Cardiopulmonary.

Diagnostic tests
History of exposure, Hair sample analysis.

Differential Diagnosis
Organophosphate insecticide poisoning.

Overview

Pyrethroid insecticidal products are neurotoxicants targeted toward the nervous system of fleas and other insects, and are used in topical spot–on and household products available over-the-counter and at veterinary hospitals. Topical flea control products are used commonly on pets due to ease of administration and overall good efficacy. Pyrethroids have replaced natural pryrethrins in may products to increase efficacy and stability. Products labeled for use on dogs-only and not intended or safe for cats are often mistakenly or purposely applied to cats. Cats are often intolerant of some insecticides and medications probably because of their livers reduced ability to metabolize some compounds. Adverse reactions can result from an unusual sensitivity at low doses, immune-based allergic sensitively or true toxic reactions at labeled or high doses. Pyrethroid toxicosis, typically involving permethrin, is one of the most commonly reported toxicities in cats to the ASPCA Animal Poison Control Center. Inappropriate exposure of cats to permethrin products results in as many as 97% showing clinical signs with 10.5% ending in death if not treated early and aggressively. Phenothrin flea control products may result in clinical signs of reduced severity in some sensitive cats even though these products may be labeled for use in cats. Clinical signs of permethrin poisoning in cats range from facial tremors and ear twitching to generalized muscle tremors and seizures. Some cats salivate profusely and vomit, but this is more likely from ingesting insecticide during grooming or inhalation of mist if sprayed. Cats often refuse to eat either out of anxiety or a physical inability to do so.

Treatment

Home Care
For cats only exhibiting increased salivation a bath in a hand dish washing soap to strip oils from the coat and thereby remove the product may be sufficient. The cat must be kept warm after the bath as low body temperatures increases the effects of the insecticide. Wrapping the cat in a towel warmed in a dryer is an excellent way to avoid low body temperatures during drying.

Professional Care
For pets exhibiting muscle tremors or seizure activity, or for which bathing did not help, hospital care is required. Muscle relaxants given by intravenous injection containing methocarbamol are highly effective at significantly reducing or eliminating muscle tremors. Repeat doses may be required. Close monitoring of body temperature is important to ensure that low body temperature does not occur which can increase effects of pyrethroids. Other supportive care including intravenous fluids and oral nutrition are important to speed recovery. On average, recovery time for symptomatic cats is two-three days.

Action
Any cat that develops clinical signs after application of any flea product, or is exhibiting clinical signs after being exposed to another pet which had the product applied should seek veterinary care.

Outcome
Immediate veterinary care designed to remove residual product, control tremors and seizures and maintain normal body temperature is often successful. Delayed care resulting in uncontrolled seizure activity can lead to death. All flea control products should only be used as strictly instructed by the EPA approved product label or the attending veterinarian.

Recommended Treatment
Pyrethrin, permethrin, phenothrin and other pyrethroid poisoning is life-threatening to the cat and requires immediate emergency veterinary care when muscle tremors are noted. If accidental application of a dog flea product to a cat is immediately recognized (no clinical signs), a detergent bath with a hand dishwashing detergent, drying with a towel and observation at home is typically sufficient.

References/Additional Readings

Sutton, Nicolas. Clinical Effects and Outcome of feline permethrin spot-on poisonings reported to the Veterinary Poisons Information Service (VPIS), London. In: Journal of Feline Medicine and Surgery 2007; Volume 9: 335-339.

Author

Patricia Wagner, DVM

Editor

Steven Hansen, DVM, MS, MBA

DABVT, DABT