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
Which parasites do cyclic depsipeptides target?
nematodes
Which parasites do benzene sulfonamides target?
trematodes
Which parasites do arsenicals target?
nematodes
Which parasites do heterocyclics target?
nematodes
Why is praziquantel used for platyhelminths?
-impairs function of suckers
-increases contraction of strobila
-increases calcium ion flux into parasite
What is the MOA for benzene sulfonamides?
inhibits enzymes of the glycolytic pathway; impaired energy production
What are the adverse effects of isoquinolones?
-typically safe
-cats may vomit
-transient injection site pain
-occasional drowsiness and weakness
What is most important in cestode and trematode control?
-separation from sources of reinfection
-consider snails/IH
-consider mammal and arthropod IH for cestodes
Why is pyrantel used for nematodes?
mimics action of excitatory neurotransmitters, leading to spastic paralysis, muscle contraction, and starvation
What are the adverse effects of piperazine?
-almost non-toxic
-ascarid impaction/rupture
-emesis
-diarrhea
-incoordination/head pressing
Which parasites CANNOT be treated with piperazine?
hookworms
Which parasite is the main target of piperazine?
ascarids
What are the adverse effects of benzimidazoles?
-usually very safe; prolonged exposure needed for effective treatment
-can cause abortion in ruminants and dogs
-teratogenic in sheep
-liver disease in dogs
-bone marrow suppression in dogs
-thromboischemic pinnal necrosis in dogs
What are the characteristics of benzimidazole resistance?
-cyathostome resistance and ascarid resistance in horses
-Cooperia/trichostrongyle resistance in cattle
-Haemonchus resistance in small ruminants
-hookworm resistance
Which animals should benzimidazoles NOT be used in?
-lactating dairy cattle/dairy cattle
-veal calves
What are the adverse effects of imidazothiazoles/levamisole?
-mimics organophosphate toxicity
-similar MOA to pyrantel/morantel; should not be co-administered
-antagonistic to piperazine
What are the adverse effects of tetrahydropyrimidines?
-side effects unlikely
-low incidence of vomiting in puppies
-antagonistic of piperazine
-similar MOA to levamisole
Which animals are treated with benzene sulfonamides?
-cattle
-sheep
-llamas
Which animals are treated with isoquinolones?
-dogs
-cats
-horses
-sheep
-goats
-chickens
Which animals are treated with piperazine?
-dogs
-cats
-poultry
-swine
-safe in neonates
Which animals are treated with benzimidazoles?
-dogs
-cats
-cattle
-horses
-sheep
-goats
-pigs
-rabbits
-rodents
-camelids
-birds
-reptiles
Which animals are treated with imidazothiazoles?
-cattle
-sheep
-swine
Which animals are treated with tetrahydropyrimidines?
-dogs
-cats
-horses
-swine
-cattle
-goats
-sheep
-rabbits
-camelids
-birds
