Anti-Parasiticides (Ecto and Endo)

Question 1

Name the 3 main types of parasiticides

Answer 1

1. Ectoparasiticides
2. Endoparasiticides
3. Endectocides

Question 2

When are anthelmintics used

Answer 2

Treating infections with parasitic worms/helminths

Question 3

Name the 3 main targets for anthelmintics

Answer 3

1. Beta-tubulin
2. Nictotinergic acetylcholine receptor
3. GABA receptor and Glutamate-gated chlorine channel

Question 4

Name the class of anthelmintic which targets Beta-tubulin

Answer 4

Benzimidazoles

Question 5

How do benzimidazoles work and what does this action cause

Answer 5

Bind to beta-tubulin
Inhibits/blocks polymerisation
Causes abnormal microtubule formation and disrupts intracellular homeostasis and energy metabolism

Question 6

Between Ach and GABA, which is the excitatory and inhibitory containing neurone

Answer 6

Excitatory = Ach containing neurone
Inhibitory = GABA containing neurone

Question 7

How do GABA agonists work as an anthelmintic and give some examples

Answer 7

Stimulate GABA receptor
Causes Chloride channels to open => influx of chloride ions
Hyperpolarises the neural membrane
Causes flaccid paralysis of the worm
Examples - Piperazine, Macrocyclic lactones

Question 8

How do nicotinic Ach agonists work as an anthelmintic and give some examples

Answer 8

Change the permeability at the post-synaptic membrane
Causes depolarisation => opens voltage-gated sodium channels
Causes excessive stimulation of muscle contraction => spastic paralysis of the worm
Examples - tetrahydropyrimidines, imidazothiazoles

Question 9

What type of paralysis do cyclic octodepsipeptides cause

Answer 9

Flaccid paralysis

Question 10

What type of paralysis do Aminoacetonitrile derivates cause

Answer 10

Hypercontraction and spastic paralysis

Question 11

What type of paralysis do spiroindoles cause

Answer 11

Flaccid paralysis

Question 12

How does resistance develop against anthelmintics

Answer 12

Mutation of the beta-tubulin or Ach receptors

Question 13

Name 4 reasons why ectoparasitic disease is very important

Answer 13

1. Animal welfare concern
2. Economic loss
3. Vectors of disease
4. Source of zoonotic infection

Question 14

Name the 4 non-chemical control-related factors of ectoparasitic control

Answer 14

1. Stage of parasite lifecycle to intervene at
2. Which animals to treat
3. Whether to employ environmental or physical methods of control
4. If there is a wider public health concern

Question 15

Which stage of the parasite lifecycle should you intervene

Answer 15

Depends
Commonly target the adult parasite
Can intervene at multiple stages

Question 16

Name the host factors associated with chemical control of ectoparasites (x4)

Answer 16

1. Species
2. Age restrictions
3. Suitable mode of action
4. Meat/milk withdrawal periods

Question 17

Name the drug factors which need considering when using chemical control of ectoparasites (x7)

Answer 17

Drug action required
Spectrum of activity
Speed of onset required
Duration of action/ frequency of application required
Specific contraindications
Safety
Development of resistance

Question 18

Name the 3 modes of action of drugs against ectoparasites

Answer 18

1. Neurotoxins
2. Insect growth regulators (IGRs)
3. Other - repellents, synergists, mechanical agents

Question 19

How do neurotoxins work as ectoparasiticides

Answer 19

Act on the CNS synapses, axons or neuromuscular junctions
Causing flaccid or spastic paralysis
All adulticidal (some ovoidal/larvicidal as well)

Question 20

Name the 6 main groups of neurotoxins used against ectoparasites

Answer 20

Nicotinic Ach receptor stimulants
Cholinesterase inhibitors
GABA inhibitors
GABA and chloride channel inhibitors
Chloride channel stimulator
Sodium channel stimulant

Question 21

Name the type of nicotinic Ach receptor agonist stimulator used and give a specific drug example

Answer 21

Neonicotinoids
Specific drug example - Imidacloprid

Question 22

Name the type of cholinesterase inhibitor used and give a specific drug example

Answer 22

Organophosphates
Example - Diazinon/dimpylate

Question 23

Name the type of GABA inhibitor used and give a specific drug example

Answer 23

Phenylpyrrazoles
Example - Fipronil

Question 24

Name the type of GABA and chloride channel inhibitor used and give some specific drug examples

Answer 24

Isoxazolines
Examples - fluralaner, sarolaner, afoxolaner

Question 25

Name the type of chloride channel stimulator used and give some specific drug examples

Answer 25

Macrocyclic lactones
Examples - avermectins (ivermectin, doramectin, eprinomectin), milbemycins

Question 26

Name the type of sodium channel stimulant used and give asome specific drug examples

Answer 26

Pyrethroids
Examples - Permethrin, Cypermethrin, Deltamethrin, Flumethrin

Question 27

How do insect growth regulators act as ectoparasiticides

Answer 27

Interrupt juvenile stages of an insects lifecycle
No adulticidal properties
Slow to act

Question 28

Name the 3 modes of action of insect growth regulators

Answer 28

1. Juvenile hormone analogues
2. Chitin synthesis inhibitors
3. Triazine derivatives

Question 29

Give 3 examples of juvenile hormone analogues (IGR’s)

Answer 29

S-methoprene
Pyriproxyfen
Fenoxycarb

Question 30

Give an example of a chitin synthesis inhibitor (IGR)

Answer 30

Lufenuron

Question 31

Give 2 examples of triazine derivatives (IGR)

Answer 31

Cyromazine
Dicyclanil

Question 32

Name a contraindication of the phenylpyrrazole Fipronil

Answer 32

Toxic to rabbits

Question 33

Name a contraindication of the isoxazolines (GABA and chloride channel inhibitors)

Answer 33

Caution using on patients with seizures

Question 34

Why has the use of organophosphates been reduced

Answer 34

Neurotoxicity concerns

Question 35

Name a contraindication of the Macrocyclic lactones

Answer 35

Generally - neurotoxic if the MDR1 gene is mutated, care of use in collies/herding breeds

Question 36

Name a contraindication of Ivermectin

Answer 36

Toxic to chelonians

Question 37

Name a contraindication of pyrethroids

Answer 37

Toxic to cats and aquatic life