Ectoparasiticides Flashcards

1
Q

What are the most common groups of ectoparasites? Why is treatment important?

A
  1. INSECTS - fleas, lice, lice
  2. ARACHNIDS - ticks, mites

they can transmit disease and cause allergic dermatitis

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2
Q

What are the 3 main characteristics of the ideal ectoparasiticides?

A
  1. an effective repellent and adulticide with persistence in the blood or skin surface
  2. formulation that is stable to sunlight and water/shampooing
  3. high efficacy with low toxicity to host
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3
Q

What is the feeding behavior of fleas and ticks?

A

FLEAS - engorge with with a blood meal from the host from 5 mins to 1 hr of infestation

TICKS - engorge longer periods

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4
Q

What are the main 3 mechanisms of action of ectoparasiticides?

A
  1. affect ectoparasite nervous system - AChE inhibitor, Na+ channel blocker, nAChR inhibitor, GABA/glutamate receptor Cl- channel inhibitor
  2. ectoparasite repellant
  3. block insect growth and development
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5
Q

What formulation is considered the safest ectoparasiticide? Most convenient?

A

powders - must be applied frequentyl

spot-on - ease of use and efficacy

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6
Q

How should shampoo ectoparasiticides be used? How do sprays compare?

A

little residual effect and must stay on the skin for at least 10 minutes

residual effect depends on active compound and concentration

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7
Q

What phenylpyrazole is commonly used as an ectoparasiticide? What 3 parasites does it work best on? What is it not effective against?

A

Fipronil (Frontline)

  1. adult fleas
  2. all stages of brown dog tick, American dog tick, Lone Star tick, and deer ticks
  3. biting fleas

preventing fleas from biting and feeding

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8
Q

What additional action does the formulation Frontline Plus have? What is fipronil approved for use in?

A

efficacy against flea eggs and larvae

dogs and cats > 8 weeks

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9
Q

What is the mechanism of action of Fipronil (Frontline)?

A

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)

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10
Q

What are 3 signs of Fipronil (Frontline) toxicity?

A
  1. hyperactivity
  2. hyperexcitability
  3. convulsions

(wide margin of safety, non-teratogenic)

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11
Q

What 3 neonicotinoids are commonly used as ectoparasiticides? What is the mechanism of action?

A
  1. Imidacloprid (Advantage)
  2. Spinosad (Comfortis)
  3. Nitenpyram (Capstar)

competitive inhibition at the postsynaptic nicotinic acetylcholine receptors (nAChR); don’t bund effectively to nicotinic receptors in mammals

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12
Q

What biphasic response is characteristic of neonicotinoids?

A

increased frequency of spontaneous discharge followed by a complete block to nerve propagation

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13
Q

What parasite does Imidacloprid (Advantage) have efficacy against? What does it have limited activity against? What animals is it approved for use in?

A

adult and larval fleas (kills within 1 hour or exposure)

ticks

dogs and cats > 4 months

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14
Q

What formulation is Advantage Multi? What 4 additional effect does it have?

A

Imidacloprid + moxidectin —> dogs and cats

fleas, heartworm prevention, intestinal worms, ear mites

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15
Q

What does Spinosad (Comfortis) work best against? What is it not labeled for use against?

A

prevention and treatment of adult fleas in dogs and cats (works within 30 mins of exposure)

ticks

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16
Q

What is the mechanism of action of macrocyclic lactones?

A

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

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17
Q

What ectoparasiticide effects does Ivermectin have in swine, cattle, dogs, and cats/kittens?

A

SWINE - lice, mange mites

CATTLE - horn flies, grubs, biting and sucking lice, mites, ticks

DOGS - otodectic, sarcoptic, notoedric, and demodectic mange

CATS/KITTENS - adult ear mites

18
Q

In what species is Eprinomectin used as an ectoparasiticide? What parasites is it used against?

A

beef and dairy cattle

horn flies, biting and sucking lice, mites

19
Q

What 2 species is Doramectin commonly used as an ectoparasiticide? What parasites is it used against?

A

BEEF CATTLE - horn flies, grubs, biting and sucking lice, mites, ticks, screwworms

SWINE - sucking and mange mites

20
Q

In what species is Moxidectin used as an ectoparasite? What parasites is it used against?

A

dairy and beef cattle

horn flies, grubs, biting and sucking lice, mites, and ticks

21
Q

In what species is Selamectin used as an ectoparasite? What parasites is it used against? What additional use does it have?

A

dogs and cats

ear mites, adult fleas, sarcoptic mange, ticks

prevents the hatching of flea eggs

22
Q

In what species is Milbemycin oxime used as an ectoparasite? What parasite is it used against?

A

cats and kittens (> 4 weeks)

ear mites

23
Q

What 4 isoxazolines are used as ectoparasiticides? What is their mechanism of action?

A
  1. Sarolaner (Simparica)
  2. Afoxolaner (NexGuard)
  3. Fluralaner (Bravecto)
  4. Lotilaner (Credelio)

inhibit GABA-gated and glutamate-gated chloride ion channels, resulting in irreversible hyperexcitation in targeted parasites

24
Q

What 2 types of parasites do Isoxazolines work against?

A
  1. fleas —> Ctenocephalides felis and canis
  2. ticks —> Dermacentor reticulatus and veriabilis, Ixodes ricinus and scapularis, Rhipicephalus sanguineus, Amblyomma americanum andmaculatum,
25
Q

What are the 4 major species of ticks that are vectors of bacterial diseases in the US?

A
  • Dermacentor: Rickettsia rickettsii (Rocky Mountain spotted fever)
  • Ixodes: Borrelia burgdorferi (Lyme)
  • Dermacentor, Amblyomma, Rhipicephalus: Ehrlichia, Babesia
26
Q

What makes Isoxazolines so safe?

A

very selective for flea and tick CNS GABA receptors over mammalian receptors

27
Q

What are pyrethrins? What parasites are they used against?

A

extracts from chrysanthemum flowers (synthetic = pyrethroids)

  • fleas
  • flies
  • lice
  • cheyletiella
  • otodectes
  • mosquitoes
28
Q

What is the mechanism of action of pyrethrins?

A

disrupt neurological function by prolonging the opening of Na+ channels, resulting in repetitive membrane depolarization

(insect sodium channels can be 100x more sensitive than mammalian channels)

29
Q

How do pyrethroids compare to pyrethrins?

A
  • synthetic analogs with same MOA
  • more resistant to breakdown
  • extremely selective for insects
30
Q

What is the most commonly used pyrethroid?

A

3rd generation pyrethroid, Permethrin

31
Q

What unique property do both pyrethrin and pyrethroids contain?

A

repellents

  • avoids infection while treating current infestations
  • good for patients with allergies sensitive to simply contact with parasites
32
Q

What species is spot-on Permethrin used on? What is included in its K9 Advantix II formulation? What additional properties will it have?

A

up to 65% - dogs, NO CATS (lack glucuronidation enzymes)

Imidacloprid + Permethrin + Pyriproxyfen - manage fleas, ticks, mosquitos, lice, and biting flies

33
Q

What formulations of Permethrin are approved for use in dogs and cats?

A

sprays, shampoos, and dusts at lower concentrations (0.05%)

34
Q

How is Permethrin used in food animals?

A

sprays and pour-ons with short withdrawal times provided they are correctly applied

35
Q

How are pyrethrins and pyrethroids absorbed dermally?

A

LIMITED —> very lipophilic and have large molecular weights, making it difficult to entirely cross the keratin and intercellular lipids of the stratum corneum

36
Q

When is it common for pyrethrin and pyrethroid toxicity to occur? How does it present? How is it treated?

A

following ingestion from grooming or percutaneous absorption

salivation, tremors, and seizures (like OP and CM)

no specific antidote —> symptomatic treatment including bathing

37
Q

What are the 2 groups of insect growth regulators?

A
  1. juvenile-hormone analogs (JHAs)
  2. insect development inhibitors (IDIs)
38
Q

What are 4 approved juvenile-hormone analogs? What are the commonly formulated with? What is their mechanism of action?

A
  1. Methoprene
  2. Pyriproxyfen
  3. Fenoxycarb
  4. Cyromazine
    - adulticides

falsely signal the organism (ticks, fleas, flies) to remain in its immature egg or larval stage

39
Q

What is the main uses of Methoprene and Pyriproxyfen? What are they commonly formulated with?

A

control horn flies n cattle

sprays, spot-ons, collars for dogs and cats

Methoprene + Pyriproxyfen + fipronil = Frontline Gold spot-on

40
Q

What type of drugs act as insect development inhibitors (IDIs)? What is their mechanism of action?

A

Benzoylphenyl urea compounds - Diflubenzuron, Lufenuron (Program)

interfere with the development of the exoskeleton by inhibiting chitin synthesis or deposition also required for flea eggshells