Ectoparasiticides Flashcards
What are the most common groups of ectoparasites? Why is treatment important?
- INSECTS - fleas, lice, lice
- ARACHNIDS - ticks, mites
they can transmit disease and cause allergic dermatitis
What are the 3 main characteristics of the ideal ectoparasiticides?
- an effective repellent and adulticide with persistence in the blood or skin surface
- formulation that is stable to sunlight and water/shampooing
- high efficacy with low toxicity to host
What is the feeding behavior of fleas and ticks?
FLEAS - engorge with with a blood meal from the host from 5 mins to 1 hr of infestation
TICKS - engorge longer periods
What are the main 3 mechanisms of action of ectoparasiticides?
- affect ectoparasite nervous system - AChE inhibitor, Na+ channel blocker, nAChR inhibitor, GABA/glutamate receptor Cl- channel inhibitor
- ectoparasite repellant
- block insect growth and development
What formulation is considered the safest ectoparasiticide? Most convenient?
powders - must be applied frequentyl
spot-on - ease of use and efficacy
How should shampoo ectoparasiticides be used? How do sprays compare?
little residual effect and must stay on the skin for at least 10 minutes
residual effect depends on active compound and concentration
What phenylpyrazole is commonly used as an ectoparasiticide? What 3 parasites does it work best on? What is it not effective against?
Fipronil (Frontline)
- adult fleas
- all stages of brown dog tick, American dog tick, Lone Star tick, and deer ticks
- biting fleas
preventing fleas from biting and feeding
What additional action does the formulation Frontline Plus have? What is fipronil approved for use in?
efficacy against flea eggs and larvae
dogs and cats > 8 weeks
What is the mechanism of action of Fipronil (Frontline)?
noncompetitively inhibits GABA-induced ion influx by targeting GABA-regulated Cl- channels, blocking Cl- influx and causing neural hyperexcitation, paralysis, and death
(500x selective toxicity to insects over mammals)
What are 3 signs of Fipronil (Frontline) toxicity?
- hyperactivity
- hyperexcitability
- convulsions
(wide margin of safety, non-teratogenic)
What 3 neonicotinoids are commonly used as ectoparasiticides? What is the mechanism of action?
- Imidacloprid (Advantage)
- Spinosad (Comfortis)
- Nitenpyram (Capstar)
competitive inhibition at the postsynaptic nicotinic acetylcholine receptors (nAChR); don’t bund effectively to nicotinic receptors in mammals
What biphasic response is characteristic of neonicotinoids?
increased frequency of spontaneous discharge followed by a complete block to nerve propagation
What parasite does Imidacloprid (Advantage) have efficacy against? What does it have limited activity against? What animals is it approved for use in?
adult and larval fleas (kills within 1 hour or exposure)
ticks
dogs and cats > 4 months
What formulation is Advantage Multi? What 4 additional effect does it have?
Imidacloprid + moxidectin —> dogs and cats
fleas, heartworm prevention, intestinal worms, ear mites
What does Spinosad (Comfortis) work best against? What is it not labeled for use against?
prevention and treatment of adult fleas in dogs and cats (works within 30 mins of exposure)
ticks
What is the mechanism of action of macrocyclic lactones?
act on glutamate-gated chloride channels (GluCl) and GABA receptors, inducing reduction of motor activity and causing flaccid paralytic effects on pharynx and somatic musculature