Lecture 20 4/10/24 Flashcards
What allows us to use chemical agents against parasites without harming patients?
-size of the animal
-route of exposure
-evolutionary distance; can attack targets that are absent in vertebrates
How do parasites differ from other animals?
-surface area to volume is higher in smaller creatures
-some ion channels are unique to parasites
-have unmyelinated neurons; differences in synaptic structure and neuromuscular junctions
-differences in enzyme and amino acid synthesis
-unique insect hormones
-organelles unique to parasites
-periods of torpor
How are parasites similar to other animals?
-eukaryotes
-fertilization and early embryological development
-oxygen requirement/respiratory systems
-neurotransmitters; flaccid and spastic paralyses
-immune systems
-sensory systems
-digestive systems
What are the characteristics of DDT?
-selectively absorbed by chitinous cuticle; acts on nervous system
-banned due to environmental contamination, effects on non-target invertebrates, egg shell thinning
-significant toxicity in cats
What are the characteristics of carbon tetrachloride?
-irritating to mucous membranes
-slowly absorbed in intestine
-CNS depression and cardiovascular collapse
What are the characteristics of cats and combination products?
-fipronil is labeled for cats for flea/tick control
-canine products add pyrethrin derivatives which are toxic to cats/cause neuro signs
What are the characteristics of monensin?
-fermentation product of Streptomyces
-forms ionophores that affect mitochondrial transport of ions
-used in cattle/goats/poultry for coccidiostatic activity
-causes fatal cardiomyopathy/cardiac necrosis in horses/swine
How are new parasiticides approved?
-screening of agents for efficacy
-estimate of mammalian toxicity
-experiments on target hosts and parasites
-FDA New Animal Drug Application
-tissue residue and excretion rate for food animal use
-EPA environmental impact statements
-worker safety information
-independent laboratory analysis of efficacy
What prevention measures can be used in place of parasiticides?
-engineering controls
-traps
-fly masks
-vaccination
-chemotherapy
-biological controls
-fecal removal and composting
-repellants
How should husbandry be improved in order to prevent parasites?
-reduce stress
-good plane of nutrition
-reduce population density
-selective breeding/purposing
What are the delivery methods for endoparasiticides?
-oral
-spot ons
-injectables
What are the chemical groupings for anthelmintics?
-trematodocides (ivomec plus)
-cestodocides (droncit)
-piperazine
-benzimidazoles (panacur/safeguard)
-imidazothiazoles (levasole)
-tetrahydropyrimidines (strongid)
-macrocyclic lactones/macrolides (heartguard, interceptor)
-cyclic depsipeptides (profender)
-arsenicals (immiticide, diroban)
How do benzimidazoles/probenzimidazoles work?
affect tubulin and microtubule assembly; affect repro.
How do tetrahydropyrimidines work?
acetylcholine agonist; membrane depolarizer
How do imidazothiazoles work?
acetylcholine agonist; membrane depolarizer
How do macrocyclic lactones work?
affect glutamate-gated chloride channels
How do isoquinolines work?
affect cell membrane permeability
How do arsenicals work?
unknown/may affect glycolysis
How does piperazine work?
GABA and acetylcholine agonist
Which parasites do benzimidazoles/probenzimidazoles target?
-nematodes
-trematodes
-cestodes
Which parasites do tetrahydropyrimidines target?
-nematodes
-cestodes
Which parasites do imidazothiazoles target?
nematodes
Which parasites do macrocyclic lactones target?
-nematodes
-ectoparasites
Which parasites do isoquinolines target?
-trematodes
-cestodes
