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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
What are the 4 major species of ticks that are vectors of bacterial diseases in the US?
- Dermacentor: Rickettsia rickettsii (Rocky Mountain spotted fever) - Ixodes: Borrelia burgdorferi (Lyme) - Dermacentor, Amblyomma, Rhipicephalus: Ehrlichia, Babesia
26
What makes Isoxazolines so safe?
very selective for flea and tick CNS GABA receptors over mammalian receptors
27
What are pyrethrins? What parasites are they used against?
extracts from chrysanthemum flowers (synthetic = pyrethroids) - fleas - flies - lice - cheyletiella - otodectes - mosquitoes
28
What is the mechanism of action of pyrethrins?
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
How do pyrethroids compare to pyrethrins?
- synthetic analogs with same MOA - more resistant to breakdown - extremely selective for insects
30
What is the most commonly used pyrethroid?
3rd generation pyrethroid, Permethrin
31
What unique property do both pyrethrin and pyrethroids contain?
repellents - avoids infection while treating current infestations - good for patients with allergies sensitive to simply contact with parasites
32
What species is spot-on Permethrin used on? What is included in its K9 Advantix II formulation? What additional properties will it have?
up to 65% - dogs, NO CATS (lack glucuronidation enzymes) Imidacloprid + Permethrin + Pyriproxyfen - manage fleas, ticks, mosquitos, lice, and biting flies
33
What formulations of Permethrin are approved for use in dogs and cats?
sprays, shampoos, and dusts at lower concentrations (0.05%)
34
How is Permethrin used in food animals?
sprays and pour-ons with short withdrawal times provided they are correctly applied
35
How are pyrethrins and pyrethroids absorbed dermally?
LIMITED ---> very lipophilic and have large molecular weights, making it difficult to entirely cross the keratin and intercellular lipids of the stratum corneum
36
When is it common for pyrethrin and pyrethroid toxicity to occur? How does it present? How is it treated?
following ingestion from grooming or percutaneous absorption salivation, tremors, and seizures (like OP and CM) no specific antidote ---> symptomatic treatment including bathing
37
What are the 2 groups of insect growth regulators?
1. juvenile-hormone analogs (JHAs) 2. insect development inhibitors (IDIs)
38
What are 4 approved juvenile-hormone analogs? What are the commonly formulated with? What is their mechanism of action?
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
What is the main uses of Methoprene and Pyriproxyfen? What are they commonly formulated with?
control horn flies n cattle sprays, spot-ons, collars for dogs and cats Methoprene + Pyriproxyfen + fipronil = Frontline Gold spot-on
40
What type of drugs act as insect development inhibitors (IDIs)? What is their mechanism of action?
Benzoylphenyl urea compounds - Diflubenzuron, Lufenuron (Program) interfere with the development of the exoskeleton by inhibiting chitin synthesis or deposition also required for flea eggshells

Veterinary Pharmacology (35 decks)

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