Anthelmintics

Question 1

Define Anthelmintic

Answer 1

A chemotherapeutic agent used to control helminth infections

Question 2

Define Chemotherapy

Answer 2

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

Question 3

Anthelmintic action can have a ____ or a ____ spectrum

Answer 3

broad or narrow

Question 4

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

Answer 4

Benzimidazoles - fenbendazole

Question 5

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

Answer 5

Imidazothiazoles - levamisole

Question 6

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

Answer 6

Macrocyclic lactones - ivermectin

Question 7

How do Benzimidazoles act on a helminth?

Answer 7

Block microtubule polymerisation causing inhibition of glucose intake = death

Question 8

Give an example of a benzimidazoles Anthelmintic used against liver fluke

Answer 8

Triclabendazole

Question 9

What is potency of Benzimidazoles determined by?

Answer 9

Duration of drug exposure

Question 10

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

Answer 10

Ruminant - slower rate of passage of ingesta so longer exposure

Question 11

How do Imidazothiazoles act on a helminth? How?

Answer 11

They cause spastic paralysis - accelerate neurotransmission

Question 12

Give an example of an Imidazothiazole

Answer 12

Levamisole

Question 13

How do Macrocyclic Lactones act on helminths? How?

Answer 13

They cause flaccid paralysis - blocking neurotransmission

Question 14

What two types of Macrocyclic Lactones are there?

Answer 14

Avermectins and Milbemycins

Question 15

Define Metaphylaxis treatment

Answer 15

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

Question 16

Define Prophylaxis treatment

Answer 16

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

Question 17

Describe the action of Praziquantal

Answer 17

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

Question 18

How do Flukicides act on flukes?

Answer 18

The uncouple oxidative phosphorylation decreasing phosphate compound availability - starving parasite

Question 19

What are the three methods for anthelminthic delivery?

Answer 19

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

Question 20

Give examples of treatment failures

Answer 20

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

Question 21

What is anthelmintic resistance?

Answer 21

ability of worm to tolerate a normally lethal dose

Question 22

How does anthelmintic resistance occur?

Answer 22

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

Question 23

When does anthelmintic resistance become detectable?

Answer 23

When allele frequency is >25%

Question 24

When does clinical failure of anthelmintics occur?

Answer 24

Normally after allele frequency has breeched 50%

Question 25

What tests can measure anthelmintic resisitance?

Answer 25

Drench tests and faecal egg count reduction tests