Ectoparaciticides Flashcards
What drugs affect acetylcholine?
Organophosphates
carbamates
What drugs affect axonal sodium channels?
Pyrethroids
What drugs affect the octopamine system?
Amidines
What drugs affect the chloride channels?
Avermectins, fipronil, isoxazolines
What drug acts on insect growth regulators - juvenile hormones?
Methoprene
What drug acts on insect growth regulators - chitin synthesis inhibitors?
Benzoyl urea derivatives
What are 4 modes of application of ectoparasiticides?
Systemic treatment of the host
Topical application
Dips
Bands, collars and tags
How do organophosphates kill ectoparasites?
Irreversibly inhibits acetylcholinesterase
Causes flaccid paralysis
How do carbamates kill ectoparasites?
Reversibly inhibits acetylcholinesterase
Causes flaccid paralysis
How are organophosphates administered?
All routes - absorbed systemically by host
How are carbamates administered?
Topically
How does Imidacloprid (neonicotinoid) kill ectoparasites?
Partial agonist at nicotinic ACh receptors in
insect CNS
Causes depolarising block and flaccid paralysis
How is Imidacloprid administered?
Spot on
How do pyrethroids kill ectoparasites?
Opens sodium channel
Causes prolonged depolarising afterpotential
How are pyrethroids selectively toxic?
Temperature dependence - insects colder
Metabolic rate - insects slower
Body size - small less chance to metabolise
How are pyrethroids administered?
Topically
How do amidines kill ectoparasites?
Agonists of the octopamine receptor
What is octopamine?
Invertebrate equivalent of noradrenaline neurotransmitter
What is the consequence of amidines on parasites?
CNS hyperexcitability
Death
How are amidines administered?
Topically
What do pyrethroids always end in?
-thrin
How does fipronil kill ectoparasites?
Antagonist of GABA receptors
Causes hyperexcitation in the CNS, convulsions and death
How is fipronil administered?
Spray or spot on
Stored in sebaceous glands for 3 months
What is a side effect of fipronil?
Hypersalivation if licked
How do avermectins kill ectoparasites?
Activate the GABA receptor which inhibits neurotransmission
How are avermectins administered?
Systemically by injection or orally
What are avermectins used to treat?
Arthropod ectoparasites Fleas Mites Lice Nematodes
What is a new ectoparasiticide that can help with resistance? How?
Isoxazolines
Acts at a different binding site to the other GABA antagonists
How does methoprene and pyriproxyfen affect ectoparasites?
Prevent metamorphosis by mimicing insect juvenile hormone
How do benzoyl ureas affect ectoparasites?
Inhibit the enzymes than synthesise chitin
Affects the development of the fleas offspring
How are benzoyl ureas administered?
Orally
