Anti-Parasiticides (Ecto and Endo) Flashcards
Name the 3 main types of parasiticides
- Ectoparasiticides
- Endoparasiticides
- Endectocides
When are anthelmintics used
Treating infections with parasitic worms/helminths
Name the 3 main targets for anthelmintics
- Beta-tubulin
- Nictotinergic acetylcholine receptor
- GABA receptor and Glutamate-gated chlorine channel
Name the class of anthelmintic which targets Beta-tubulin
Benzimidazoles
How do benzimidazoles work and what does this action cause
Bind to beta-tubulin
Inhibits/blocks polymerisation
Causes abnormal microtubule formation and disrupts intracellular homeostasis and energy metabolism
Between Ach and GABA, which is the excitatory and inhibitory containing neurone
Excitatory = Ach containing neurone
Inhibitory = GABA containing neurone
How do GABA agonists work as an anthelmintic and give some examples
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
How do nicotinic Ach agonists work as an anthelmintic and give some examples
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
What type of paralysis do cyclic octodepsipeptides cause
Flaccid paralysis
What type of paralysis do Aminoacetonitrile derivates cause
Hypercontraction and spastic paralysis
What type of paralysis do spiroindoles cause
Flaccid paralysis
How does resistance develop against anthelmintics
Mutation of the beta-tubulin or Ach receptors
Name 4 reasons why ectoparasitic disease is very important
- Animal welfare concern
- Economic loss
- Vectors of disease
- Source of zoonotic infection
Name the 4 non-chemical control-related factors of ectoparasitic control
- Stage of parasite lifecycle to intervene at
- Which animals to treat
- Whether to employ environmental or physical methods of control
- If there is a wider public health concern
Which stage of the parasite lifecycle should you intervene
Depends
Commonly target the adult parasite
Can intervene at multiple stages
Name the host factors associated with chemical control of ectoparasites (x4)
- Species
- Age restrictions
- Suitable mode of action
- Meat/milk withdrawal periods
Name the drug factors which need considering when using chemical control of ectoparasites (x7)
Drug action required
Spectrum of activity
Speed of onset required
Duration of action/ frequency of application required
Specific contraindications
Safety
Development of resistance
Name the 3 modes of action of drugs against ectoparasites
- Neurotoxins
- Insect growth regulators (IGRs)
- Other - repellents, synergists, mechanical agents
How do neurotoxins work as ectoparasiticides
Act on the CNS synapses, axons or neuromuscular junctions
Causing flaccid or spastic paralysis
All adulticidal (some ovoidal/larvicidal as well)
Name the 6 main groups of neurotoxins used against ectoparasites
Nicotinic Ach receptor stimulants
Cholinesterase inhibitors
GABA inhibitors
GABA and chloride channel inhibitors
Chloride channel stimulator
Sodium channel stimulant
Name the type of nicotinic Ach receptor agonist stimulator used and give a specific drug example
Neonicotinoids
Specific drug example - Imidacloprid
Name the type of cholinesterase inhibitor used and give a specific drug example
Organophosphates
Example - Diazinon/dimpylate
Name the type of GABA inhibitor used and give a specific drug example
Phenylpyrrazoles
Example - Fipronil
Name the type of GABA and chloride channel inhibitor used and give some specific drug examples
Isoxazolines
Examples - fluralaner, sarolaner, afoxolaner
Name the type of chloride channel stimulator used and give some specific drug examples
Macrocyclic lactones
Examples - avermectins (ivermectin, doramectin, eprinomectin), milbemycins
Name the type of sodium channel stimulant used and give asome specific drug examples
Pyrethroids
Examples - Permethrin, Cypermethrin, Deltamethrin, Flumethrin
How do insect growth regulators act as ectoparasiticides
Interrupt juvenile stages of an insects lifecycle
No adulticidal properties
Slow to act
Name the 3 modes of action of insect growth regulators
- Juvenile hormone analogues
- Chitin synthesis inhibitors
- Triazine derivatives
Give 3 examples of juvenile hormone analogues (IGR’s)
S-methoprene
Pyriproxyfen
Fenoxycarb
Give an example of a chitin synthesis inhibitor (IGR)
Lufenuron
Give 2 examples of triazine derivatives (IGR)
Cyromazine
Dicyclanil
Name a contraindication of the phenylpyrrazole Fipronil
Toxic to rabbits
Name a contraindication of the isoxazolines (GABA and chloride channel inhibitors)
Caution using on patients with seizures
Why has the use of organophosphates been reduced
Neurotoxicity concerns
Name a contraindication of the Macrocyclic lactones
Generally - neurotoxic if the MDR1 gene is mutated, care of use in collies/herding breeds
Name a contraindication of Ivermectin
Toxic to chelonians
Name a contraindication of pyrethroids
Toxic to cats and aquatic life
