Anthelmintics Flashcards

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1
Q

Define Anthelmintic

A

A chemotherapeutic agent used to control helminth infections

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2
Q

Define Chemotherapy

A

Use drugs to injure an invading organism without injury to the host - selective toxicity dependent

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3
Q

Anthelmintic action can have a ____ or a ____ spectrum

A

broad or narrow

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4
Q

What is the proper name for white drench? Give a specific example

A

Benzimidazoles - fenbendazole

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5
Q

What is the proper name for yellow drench? Give a specific example

A

Imidazothiazoles - levamisole

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6
Q

What is the proper name for clear drench? Give a specific example

A

Macrocyclic lactones - ivermectin

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7
Q

How do Benzimidazoles act on a helminth?

A

Block microtubule polymerisation causing inhibition of glucose intake = death

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8
Q

Give an example of a benzimidazoles Anthelmintic used against liver fluke

A

Triclabendazole

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9
Q

What is potency of Benzimidazoles determined by?

A

Duration of drug exposure

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10
Q

Will benzimidazoles be more potent in a dog or a ruminant? Why?

A

Ruminant - slower rate of passage of ingesta so longer exposure

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11
Q

How do Imidazothiazoles act on a helminth? How?

A

They cause spastic paralysis - accelerate neurotransmission

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12
Q

Give an example of an Imidazothiazole

A

Levamisole

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13
Q

How do Macrocyclic Lactones act on helminths? How?

A

They cause flaccid paralysis - blocking neurotransmission

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14
Q

What two types of Macrocyclic Lactones are there?

A

Avermectins and Milbemycins

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15
Q

Define Metaphylaxis treatment

A

Treatment of an animal whilst they are being exposed to the helminth

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16
Q

Define Prophylaxis treatment

A

Treatment of animal before they are let out to pasture to stop the pasture getting contaminated

17
Q

Describe the action of Praziquantal

A

Destroys tegument by increasing Ca2+ permeability - causing muscular spasm and release from gut wall

18
Q

How do Flukicides act on flukes?

A

The uncouple oxidative phosphorylation decreasing phosphate compound availability - starving parasite

19
Q

What are the three methods for anthelminthic delivery?

A

Oral, Parenterally (injection), Topical (trans-dermal)

20
Q

Give examples of treatment failures

A
Under dosing
Underestimation of bodyweight
Inadequate equipment
Poor technique
Use of incorrect drug
Reintroduction into heavily infested pastures
Anthelminitc resistance
21
Q

What is anthelmintic resistance?

A

ability of worm to tolerate a normally lethal dose

22
Q

How does anthelmintic resistance occur?

A

Resistance alleles are already present and spread slowly at first then rapidly as frequency increases

23
Q

When does anthelmintic resistance become detectable?

A

When allele frequency is >25%

24
Q

When does clinical failure of anthelmintics occur?

A

Normally after allele frequency has breeched 50%

25
Q

What tests can measure anthelmintic resisitance?

A

Drench tests and faecal egg count reduction tests