Keeping cats safe

Lara Boland graduated from the Universityof Sydney, Australia, and initially worked infeline and general small animal practice. Shehas completed internships in small animaland emergency medicine. Lara undertookspecialist training at the University of Bristol,UK, via an International Cat Care sponsoredresidency in small animal medicine. Shecurrently works at the University VeterinaryTeaching Hospital, Sydney, at the Universityof Sydney, Australia.

Lara Boland BVSc (Hons I) MANZCVS (Feline Medicine)DipECVIM-CA Specialist in Small Animal Internal Medicine

Feline permethrin toxicity

Permethrin toxicity can cause severe and potentiallyfatal tremors and seizures in cats. Cats are usuallyexposed when their owners mistakenly apply spot-onflea products that are made for dogs. Exposed catsrequire immediate emergency treatment which focuseson three main aspects: decontamination to removeremaining toxin from the skin and fur, control of the tremors with medications, and supportive care.Prevention is always better than the cure and veterinarynurses have a key role to play in cat owner education tohelp to reduce the incidence of permethrin toxicity.

Permethrin is a pyrethroid insecticide.Pyrethroids are synthetic analogues of

pyrethrins, which are naturally occurringsubstances extracted from Chrysanthemumflowers. Permethrin is a neurotoxin that bindsto and blocks open sodium channels on thesurface of neurons. This interferes with nervefunction by causing the neurons to dischargerepetitively.

Cats are very sensitive to permethrin and aremore likely to develop signs of toxicity thandogs. Permethrin is metabolised by the liver. It is suspected that cats may be more proneto toxicity because they have different livermetabolic pathways to other species; inparticular they have a deficiency of theenzyme hepatic glucuronosyltransferase.

Routes of exposureExposure to even small quantities ofpermethrin can cause severe and fatalpoisoning in cats. Cats are usually exposed to permethrin when pet owners accidentallyapply permethrin-containing flea and tickspot-on products, which are made for dogs,to cats. These products usually come in asmall pipette and the liquid is applied the skin

on the back of the neck. The liquid isthen absorbed through the skin andinto the body. Permethrin containingspot-on products are used in manycountries around the world.

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Key point

Cats are usuallyexposed when wellintentioned ownersapply spot-on fleaproducts designed for dogs. They may also be exposed bygrooming or brushing againstrecently treated dogs.

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Keeping cats safe

Dogs are less sensitive to the toxiceffects of permethrin and theseproducts are safe to use on dogs butnot on cats. Often owners do notrealise that the products can only beused on dogs, accidentally mix updifferent dog and cat products orthey do not understand that theycan result in fatal toxicity if used on cats. Another route of exposureoccurs if a cat grooms a dog in thesame household that has had theproduct applied. It is not known forcertain how long cats should beseparated from dogs after dogshave had permethrin-containingproducts applied, but 72 hours isoften recommended.

Clinical signsSigns of toxicity are usually seenwithin a few hours but can take 1–2days to develop. Common signs oftoxicity include: muscle tremors,twitching, seizures, ptyalism, ataxia,hyperaesthesia, pyrexia andmydriasis. Clinical signs can varyfrom mild facial twitches topersistent severe generalisedtremors.

Diagnosis Diagnosis is based on a knownexposure to permethrin and clinicalsigns consistent with toxicity.

Differential diagnoses fortremors/seizures may include the following:Intra-cranial causes such as;• infectious disease (eg,toxoplasmosis, cryptococcosis,feline infectious peritonitis);

• inflammatory disease;• neoplasia;• trauma;• idiopathic epilepsy; or• vascular (eg, thrombosis orhaemorrhage).

Extra-cranial causes such as;• toxins (eg, lead, ethylene glycol,

organophosphates);• metabolic disease (eg, hepaticinsufficiency, hypoglycaemia,hypocalcaemia, hypo- orhypernatraemia, erythrocytosis).

TreatmentTreatment of cats with permethrinpoisoning can be very intensiveand expensive. There is no antidotefor permethrin toxicity.

There are three main aspects totreatment:• decontamination;• control of tremors;• supportive care.

DecontaminationMost cats are exposed after havingpermethrin products applied to theskin. Decontamination involvesthorough washing of the cat withlukewarm water and a mild handdishwashing detergent. Fur mayalso be clipped off at theapplication site. The aim is toremove as much of the oilyproduct as possible to stop furtherabsorption through the skin.

Treatment of muscle tremorsTreatment of muscle tremors mayinvolve the use of various differentmedications depending on theseverity of clinical signs and whatproducts are available.Methocarbamol is a centrallyacting muscle relaxant that is often

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Key pointTreatment focuses ondecontamination by washing theproduct off to reduce absorption,controlling tremors,and giving supportivecare. There is noantedote forpermethrin toxicity.

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used intravenously or can also begiven orally in less severe cases.Benzodiazepines such as midazolammay be used intravenously as abolus or as an intravenous infusion.Barbiturates such as phenobarbitonemay also be used. Severely affectedcats may require heavy sedation orgeneral anaesthesia to controlclinical signs; eg, a propofolintravenous infusion (Figure 1).

Lipid emulsion therapy Another treatment that may be used, in combination withmedications aimed at reducingtremor activity, is an intravenousinfusion of a lipid emulsion. Thistreatment may help to reduce thetime taken for clinical signs oftoxicity to resolve. Lipid emulsiontherapy can be used for treatmentof toxicity from lipid-soluble drugsor toxins and is thought to work byproviding a ‘lipid sink’ so that thetoxin is sequestered within theintravascular space and cannotreach its sites of action.

Supportive careSupportive care involves intravenousfluid therapy and close monitoring.

Affected cats are oftenhyperaesthetic and their tremorsmay worsen with handling andnoise. They may benefit fromhousing in a dark and quiet room.Heavily sedated or anaesthetisedcats may require supplementaloxygen, endotracheal intubation,temperature monitoring and activewarming if required, turning andocular lubrication to prevent thedevelopment of corneal ulcers.Other parameters to monitor mayinclude SpO2, ETCO2, bloodpressure and urine output.

Cats will usually require anywherefrom a few days to a week oftreatment in hospital before slowlyrecovering. Some cats with severesigns do not survive, requireprolonged hospitalisation or developcomplications such as corneal ulcersor aspiration pneumonia.

Prognosis With early treatment and intensivecare most cats will survivepermethrin toxicity, however, thecosts of treatment may beprohibitive for some cat owners.Publications from the UK, USA andAustralia report mortality rates of upto 37% (died or euthanased).

Prevention and the role ofveterinary nurses andtechniciansVeterinary nurses have a major rolein both the prevention and

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Key pointAs veterinary nurses andtechnicians you are often themain source of advice toowners on flea controlproducts. Educating ownerson the risks of using dog flea products on catsis vital to prevent further cases of toxicity.

Figure 1: Drugs used to control muscle tremors:methocarbamol and, in some cases, anaesthesiawith propofol will be required

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SignalmentJasper is a 5-year-old male neutereddomestic shorthair.

HistoryJasper’s owner split a permethrin-containing flea spot-on product,manufactured for use on large dogs,between Jasper, their small dog andtheir pet rabbit. Six hours later Jasperwas found unable to stand, drooling and with severe generalised tremors.Jasper’s owners contacted their localveterinary hospital with no idea of thecause of his clinical signs. The veterinarynurse on duty was able to advise themthat immediate veterinary attention was required and brief questioningdetermined that this was a possible caseof permethrin toxicity. The nurse advisedthe owners to bring the flea productpackaging into the hospital forconfirmation. The nurse alerted theveterinarian on duty and commencedpreparing equipment ready for Jasper’sarrival.

PresentationJasper had severe generalised tremors,marked ptyalism, hyperaesthesia andthere were greasy patches of fur wherethe flea product had been applied.

TreatmentCareful handling was required to be ableto place an intravenous catheter andimmediate treatment with midazolam,methocarbamol and intravenous fluidswas administered. Once his tremors hadreduced, blood was collected for anemergency analysis. Packed cell volume,total protein, electrolytes and urea werewithin reference intervals. The affectedregions of fur were clipped and he waswashed with a mild dishwashingdetergent.

Initially, Jasper’s tremors reduced inseverity, however, they later worsenedand, as a result, he became pyrexic. Hewas then treated with a propofolinfusion. Heavy sedation was required tocontrol the tremors and so Jasper hadan endotracheal tube placed (Figure 2).He was also treated with supplementaloxygen, temperature monitoring andregulation, ocular lubricants and wasturned every 2 h.

Jasper required intensive nursing careand monitoring. Every 4 h the propofoldose was reduced to assess forrecurrence of tremor activity.

Thirty hours later the propofol infusionwas able to be discontinued and Jasperwas extubated. At this stage he hadcontinued intermittent fine facial andlimb twitches. Twenty-four hours later hewas greatly improved with only mildintermittent limb twitches and feedingwas recommenced.

OutcomeThe following day Jasper was wellenough to be discharged from hospital.

Case study: Jasper’s accidental exposure to permethrin

Figure 2: General anaesthesia can be used tocontrol the tremors caused by permethrin toxicity

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treatment of feline permethrintoxicity. Nurses assist in educatingowners about routine preventivehealth care such as parasite control.Educating pet owners about whichflea and tick products are safe to useon cats, explaining appropriateadministration and ensuring that pet owners read and understandproduct labelling is essential.International Cat Care hascampaigned on this topic and aposter (Figure 3) is available todownload at:http://icatcare.org/sites/default/files/PDF/permethrin_poster_vet.pdf

Veterinary nurses are often the firstpoint of contact for pet ownerswhen they call a veterinary hospitalfor emergency advice aboutpossible toxicity. Understanding theimportance of rapid assessment andtreatment at a veterinary hospital isessential to be able to advise petowners. Veterinary nurses are also

key in the initial emergencyassessment and treatment of thesepatients and in their ongoinghospital care and monitoring.

Further reading• Boland LA and Angles JM. Feline

permethrin toxicity: retrospective studyof 42 cases. J Feline Med Surg 2010; 12:61–71.

• Draper WE, Bolfer L, Cottam E, et al.Methocarbamol CRI for symptomatictreatment of pyrethroid intoxication: areport of three cases. J Am Anim HospAssoc 2013; 49: 325–328.

• Haworth MD and Smart L. Use ofintravenous lipid therapy in three casesof feline permethrin toxicoses. J VetEmerg Crit Care 2012; 22: 697–702.

• Kuo K and Odunaya A. Adjunctivetherapy with intravenous lipid emulsionand methocarbamol for permethrintoxicity in 2 cats. J Vet Emerg Crit Care2013; 23: 436–441.

• Linnett PJ. Permethrin toxicosis in cats.Aust Vet J 2008; 86: 32–35.

• Malik R, Ward MP, Seavers A, et al.Permethrin spot-on intoxication of cats:literature review and survey of veterinarypractitioners in Australia. J Feline MedSurg 2010; 12: 5–14.

• Meyer EK. Toxicosis in cats erroneouslytreated with 45 to 65% permethrinproducts. J Am Vet Med Assoc 1999; 215:198–203.

• Peacock RE, Hosgood G, Swindells KL, etal. A randomized, controlled clinical trialof intravenous lipid emulsion as anadjunctive treatment for permethrintoxicoses in cats. J Vet Emerg Crit Care2015; 25: 597–605.

• Sutton NM, Bates N and Campbell A.Clinical effects and outcome of felinepermethrin spot-on poisonings reportedto the Veterinary Poisons InformationService (VPIS), London. J Feline MedSurg 2007; 9: 335–339.

Kill the flea.

Not the cat.Permethrin spot-on flea products for dogs can kill cats

Ask your vet for advice on safe flea treatments for your cat

icatcare.org/permethrin

Figure 3: International Cat Care’s permethrincampaign poster

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It is important to report felinetoxicities to the appropriate bodyin your country. This ensures thatup-to-date information is availableabout the incidence of toxicities incompanion animals and whattoxins are involved.

Report incidences of toxicity

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