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MODULE 7 - Skin and Bones > PHARMACOLOGY - Ectoparasiticides > Flashcards

PHARMACOLOGY - Ectoparasiticides Flashcards

1
Q

Why are ectoparasites so challenging to control?

A
  1. Large seasonal increases in ectoparasite populations
  2. Ectoparasites are widespread in the environment
  3. Ectoparasite populations increase rapidly
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2
Q

What are five of the main classes of ectoparasiticides used in veterinary medicine?

A

Organophosphates
Pyrethrins/Pyrethroids
Macrocyclic lactones
Insect growth regulators (IGRs)
Fibronil

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3
Q

What is the mechanism of action for organophosphates?

A

Organophosphates inhibit acetylcholinesterase leading to excessive accumulation of acetylcholine in the neuromuscular junction, causing paralysis

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4
Q

What is the spectrum of activity for organophosphates?

A

Psoroptes ovis
Blow flies
Ticks
Keds
Lice

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5
Q

Give an example of an organophosphate drug

A

Diazinon

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6
Q

Why do farmers require a certificate of confidence and SEPA licence before using organophosphate dips?

A

Organophosphates can be toxic to humans and animals and can persist in the environment if disposed of incorrectly

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7
Q

What is the difference between pyrethrins and pyrethroids?

A

Pyrethrins are a natural substance extracted from pyrethrum flowers whereas pyrethroids are synthetic analogues of pyrethrins

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8
Q

What is the mechanism of action for pyrethrins and pyrethroids?

A

Pyrethrins and pyrethroids inhibit the closure of pre-synaptic voltage-gated sodium channels, inhibiting repolarisation of nerve fibres, causing paralysis

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9
Q

What is the spectrum of activity for pyrethrins and pyrethroids?

A

Ticks
Keds
Lice
Fleas

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10
Q

What is the mechanism of selective toxicity for pyrethrins and pyrethroids?

A

If given orally, pyrethrins and pyrethroids undergo rapid metabolic detoxification in vertebrates which prevents the entry of the drug into the vertebrate central nervous system (CNS)

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11
Q

Why should pyrethrins and pyrethroids always be given in combination with a synergist?

A

Pyrethrins and pyrethroids can be enzymatically detoxified in ectoparasites so should always be given in combination with synergists to increase the persistence of the drug within the ectoparasite

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12
Q

Which synergist is commonly given in combination with pyrethrins and pyrethroids?

A

Piperonyl Butoxide (BPO)

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13
Q

What is the main advantage of pyrethroids over pyrethrins?

A

Pyrethroids are much more stable that pyrethrins

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14
Q

What causes pyrethroids to cause toxicity in cats?

A

When pyrethroid collars and spot-ons designed for dogs are applied to cats, this can cause pyrethroid toxicity as the dose will be elevated and cats do not metabolically detoxify the drug as well as dogs

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15
Q

How should pyrethroid toxicity in cats be treated?

A

Decontamination (bathing)
Neuromuscular blocking drug administration

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16
Q

Give three examples of pyrethroid drugs

A

Permethrin
Cypermethrin
Deltamethrin

17
Q

What is the mechanism of action for macrocyclic lactones?

A

Macrocyclic lactones stimulate glutamate-gated chloride channels in invertebrate nerve and muscle cells resulting in flaccid paralysis

18
Q

What is the spectrum of activity for macrocyclic lactones?

A

Macrocyclic lactones are endectocides so can be used against nematodes and ectoparasites including Hypoderma (warble flies), lice, fleas and mites

19
Q

Give an example of macrocyclic lactone

A

Ivermectin

20
Q

Which four dog breeds can suffer from ivermectin toxicity?

A

Collies
German Shepherd
Australian Shepherd
Shetland Sheepdog

21
Q

What makes particular dog breeds susceptible to ivermectin toxicity?

A

Ivermectin causes toxicity in dog breeds with a ABCB1 gene mutation which causing dysfunction in P-glycoproteins which would normally pump ivermectin out of the central nervous system (CNS)

22
Q

What are the six clinical signs of ivermectin toxicity?

A

Pupil dilation
Ataxia
Vomiting
Tremors
Salivation
Coma

23
Q

What are insect growth regulators (IGRs)?

A

Insecticides which does not stop egg deposition but do inhibit ectoparasite development

24
Q

Give four examples of insect growth regulators (IGRs)

A

Cyromazine
Dicyclanil
Lufenuron
Methoprene

25
Q

What is the mechanism of action for cyromazine and dicyclanil?

A

Cyromazine and dicyclanil inhibit larval development

26
Q

What is the mechanism of action for lufenuron?

A

Lufenuron inhibit chitin synthesis in fleas

27
Q

What is the mechanism of action for methoprene?

A

Methoprene inhibits juvenile growth hormone which inhibits egg, larvae and pupae development

28
Q

Why should lufenuron and methoprene be given in combination with an adulticide?

A

To also target the adult stage of the ectoparasite lifecycle to provide more efficient control

29
Q

What is the mechanism of action for fibronil?

A

Fibronil is a GABA and glutamate gated chloride channel antagonist leading to paralysis

30
Q

What is the spectrum of activity for firbonil?

A

Ticks
Lice
Fleas

MODULE 7 - Skin and Bones (22 decks)

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