Exam 2: Management of Ectoparasites in Dogs and Cats

catgeories of ectoparasiticides

• organophosphates (coumaphos)

• pyrethrins and pyrethroids (flumethrin)

• macrocyclic lactones (selamectin, moxidectin)

• formamidines (amitraz)

• chloroicotinyls (imidacloprid, nitenpyram, dinotefuran)

• phenylpyrazoles (fipronil)

• isoxazolines (afoxolaner, fluralaner, sarolaner, lotilaner)

organophosphates 

• inhibit acetylcholinesterase via irreversible binding at cholinergic synapse at muscle endplates 

• mimic acetylcholine leading to paralysis 

• extremely toxic to animals including people! 

  • block with atropine, then reactivate AChE with 2-PAM 

example of organophosphate

coumaphos- used in dipping vats to kill cattle fever ticks

pyrethrins and pyrethroids

• both interfere with parasite neuronal K+ and Na+ channels leading to paralysis and death

• toxic to fish, invertebrates, and CATS → immediate decomtamination and supportive care

• natural product of chrysanthemum

• fast knock down but apid degradation causing poor residual activity

example of pyrethrin or pyrethroid

fumethrin

Macrocyclic lactones 

• enhance the effect of glutamate at glutamate-gated Cl- channels, causing hyperpolarization and paralysis at neuromuscular junctions

• minor effects on GABA receptors 

• bad in dogs with MDR1 mutation 

examples of macrocyclic lactones

• selamectin- topical for ear mites in cats and dogs, sarcoptic mange

• moxidectin- pour on for cattle horn flies

chloronicotynyls

• chlorinated derivatives of nicotine binds to nicotinic receptors causing paralysis and death

examples of chloronicotinyls 

• imidacloprid- topical in combination with moxidectin (advantage multi) for fleas on dogs and cats 

• Nitenpyram (capstar) oral for fleas 

• Dinotefuran- topical in combination with pyriproxyfen+permethrin for fleas, ticks and mosquitoes 

Phenylpyrazoles

bindes y-aminobutyric acid and glutamate gated receptors, inhibiting Cl- flux into nerve cells

example of phenylpyrazoles

• fipronil- topical

• prolonged residual activity due to minimal systemic absorption(spreads in sebum)

• broad spectrum against fleas, lice, ticks and mites

isoxazolines 

block ligand gated chloride channels in insects (fleas), acarines (ticks)

examples of isoxazolines

• afoxolaner

• fluralaner

• sarolaner

• lotilaner

insecto development inhibitors and insect growth regulators (IDIs and IGR)

• do not directly kill adult parasites but interfere with growth and development

• not useful for rapid control of established adult populations

• useful for strategic seasonal preventive treatment

• chitin synthesis inhibitors (lufenuron), chitin assembly inhibitors (cyromazine), juvenile hormone analogs

juvenile hormones analogs 

• normal, fully developed larvae produce enzymes that destroy endogenous juvenile hormones

• these analogs bind to hormone receptors but are not enzymatically degraded so metamorphosis to the adult stage is prevented 

• good for fleas, but not ticks and mites due to incomplete metamorphosis 

• S-methopriene (frontline plus), Pyriproxyfen (Vectra 3D) 

Synergists

• not insecticidal

• piperonyl butoxide

• inhibitos breakdow of pesticides by mixed function oxidase systems in insects

• commonly combined with pyrethrins and pyrethroids to enhance activitu

other ectoparasite control options

• repellents- flumethrin, DEET and citronella

• biological control - Bacillus thuringiensis

• off host control - non return traps, chemically impregnated screens

comprehensive flea control programs should : 

• eliminate fleas on pets 

• eliminate existing environmental infestations 

• prevent subsequent re-infection 

• (life cycle 21-28) 

strategy for flea eggs

resistant to insecticides, susceptible to insect growth regulators and development inhibitors

strategy for flea larvae

susceptible to insecticides, IGR, IDI

strategies for flea pupae

very resistant to everything 

strategies for flea adults

adulticides and speed of kill

maintain flea control year round

IDIs and IGR in fleas

• ovicidal, larvicidal but NOT adulticidal

• recommended in combination with adulticides

• lag time of 5 weeks to reach >90%

• S-methoprene (frontline plus), Pyriproxyfen

isoxazolines for fleas 

• high efficacy, high speed of kill, kill fleas before they can lay eggs = prevention 

• sold as standalone drugs or in combinations with other actives for heartworms or GI 

• monthly, 12 week or annual 

• may be associated with neurologic adverse reactions 

flea prevention

• give year round preventative flea and tick products as soon as possible after birth

• ensure all dogs and cats in household are on prevention

• vacuu

• wash bedding

• professional exterminator

lice in dogs and cats

• considered a disease of neglect and associated with overcrowding, poor sanitation and or poor nutrition

• keep infested animals isolated

• good response to commonly available flea preventatives (fipronil, imidacloprid, selamectin)

flies of interest for control 

• flesh flies (Sarcophagidae)

• blow or bottle flies (Calliphoridae)

• Muscid flies (Muscidae) 

myiasis of new world screwworm

• if you suspect, report the case to the Louisiana Department of Agriculture and Foresry

treatment of Myiasis

• be prepared, the smell!

• cut hair and clean wound site with dilute hydrogen peroxide

• treat bacterial infection

• remove as manny maggots as possible manually and remove the whole organism

• nitenpyram may be used to kill (capstar)

treatment of cuterebra spp 

• may require ssedation or GA

• enlarge fistula and extract grub 

• important to try and remove grub intact to avoid a possible anaphylactic reaction 

• wound may be flushed with chlorhexidine solution 

treatment of sarcoptic mange in dogs

• isozazolines extra label in US

• selamectin and topical moxidectin/imidacloprid are labeled approved

• high dose ivermectin not recommended

prevention of sarcoptic mange

• routine use of isozazolines will likely prevent infestations (similarly fipronil, moxidectin/imidacloprid, selamectin)

treatment of Otodectes cynotis - ear mites 

• clean ears to remove debris 

• labeled products for dogs = selamectin or moxidectin/imidacloprid, extra label isoxazolines 

• labeled products for cats = topical selamectin or selametin + sarolaner, moxidectin/imidacloprid 

ear mite prevention

monthly treatment with isoxazolines, selamectin, moxidectin/imidacloprid

Cheyletiella spp (walking dandruff) treatment

• insecticidal preparations at 7-10 day intervals

• treat all animals on premises

• prevent with monthly administrations of moxidectin/imidacloprid or selamectin

localized canine demodicosis 

• <5 lesions or 1 mbody region 

• alopecia around eyes, commisures of mouth and or forelegs 

• most often pups 3-6months old 

• 90% spntaneous cure in 6-8 weeks so do not treat 

canine demodicosis generalized form

• >5 lesions or >1 body region

• secondary pyoderma is common

• increased TGF-B and decreased TNF-a

juvenile generalized canine demodicosis 

• usually starts as localized lesion then progresses 

• heritable - short haired and purebreeds 

• demodex specific T cell defect is suspected 

adult onset generalized canine demodicosis

• rare, poor prognosis if untreated

• usually secondary to underlying immune deficiency or immunosuppressive condition such as Cushings

treat localized canine demodicosis

• local topicals (benzoyl peroxide) can be used if client insists

• no steroids

treat generalized canine demodicosis 

• mild disease may resolve spontaneously in dogs <1 year 

• observation with repeated skin scrapings over 4-6 weeks is reasonable to mild disease

• adult dogs and young dogs with moderate to severe disease (pyoderma, pain, pruritus, malaise) will require treatment 

extra label canine demodicosis treatment

• isoxazolines

• continue treatment until obtaining two negative skin scrapings one month apart

• treat secondary bacterial infection

• spay/neuter when heritable

• investigate underlying immune deficiency or immunosuppressive condition

Demodex cati

• commensal and rarely cause disease

• localized form is normally self limiting

• generalized form may be associated with FeLV/FIV, diabetes, cushings, neoplasia, toxoplasmosis

• follicular mite so found in deep scrapings

feline Demodex gatoi 

• shorter body and found in low numbers, stratum corneum so found in superficial scrapings 

• contagious! Treat all cats in the household 

• scrape between shoulder blades and fecal float 

• more common along gulf coast 

treatment for feline demodicosis

• extra label treatment = isoxazolines

• demodex cati= investigate underlying immune deficiency or immunosuppressive condition

• demodex gatoi = treat all cats in household

treatment of ticks

• remove manually if only a few

• fast acting acaricide= isoxazolines

• year round use of control

• indoor control = professional exterminator for pyrethroids (esp important for Rhipicephalus sanguineus dog tick)

• outdoors= modify habitat