Lecture 33: Ectoparasites Flashcards
What 4 things should a good ectoparasiticide do
- Effective adulticide and repellant
- Persist at an effective dose on the skin for extended period (1-3 months)
- Be stable in sunlight, shampoo, water
- Cause minimal contamination in the local environment (reduce risk of resistance)
Individual ectroparasiticide agents are __ molecular weight
Large
What large molecular weight of ectoparasiticides allows for what 4 things to occur
- Slow dermal absoprtion
- Low systemic bioavailability
- Large volumes of distribution
- Long tissue and plasma half lives
What are some advantages of topical ectoparasiticides
Avoid degradation in the GI tract, avoid first pass metabolism in the liver
What are some disadvantages of topical ectoparasiticides
Risk of overdose (licking collar or skin), prolonged withdrawal times in food animals
What are the routes of absoprtion for trans-epidermal absoprtion
- Transceullar- active transport
- Intercellular
What are the routes of absoprtion for trans follicular absoprtion
- Trans-epidermal
- Sweat pore- accumulation of sebaceous glands
What species has the thickest and thinnest epidermal skin
Thickest: pigs
Thinnest: cats
What are some indications for pyrethrins/pyrethroids
- Fleas and tickets
- 3rd generation chemicals have some mite and lice coverage
What 3rd generation pyrethrins/pyrethroids tx fleas, ticks, mites and lice
Permethrin
As you go from 1st generation to 4th generation pyrethrins/ pyrethroids how does stability and potency change
Increase
What is the PD for pyrethrins/pyrethroids
Activates Na+ channels in nerves—> repetitive depolarizations leading to parasite death
2nd generation pyrethrins pyrethroids are absolutely toxic to ___ because requires ___
Cats, requires glucoronidation metabolism
What are some signs of toxicity to pyrethrins/ pyrethroids
SLUDGE, miosis, tremors, convulsions, dyspnea
What are 2 examples of drugs that are synergistic with pyrethrins
- Piperonyl butoxide
- N-octal bicycloheptene dicarboximide
What is the PD of piperonyl butoxide and N-octyl bicycloheptene dicarboximide
Blocks cytochrome p450, inhibits oxidative and hydrolytic metabolism, prevents enzymatic breakdown of pyrethrins
What are some adverse effects with piperonyl butoxide
Prevents breakdown of pyrethrins in cats and increases toxicity
Organophosphate are used for what
Pesticide control, anti-nematode agents, flea collars
What is tetrachlorvinphos
Organophosphate collar to protect against fleas, ticks
What is the PD of organophosphates
Long lasting, irreversible inhibitors of AChE
What are some signs of AChE inhibitor toxicity
SLUDGE, miosis and muscle spasms, bronchoconstriction, bradycardia, hypotension, seizures, respiratory paralysis, death
What cattle breeds are sensitive to organophosphates
Brahman, charolais, and simmental
What dogs are sensitive to organophosphates
Greyhounds and whippets
What broad species is sensitive to organophosphates
Cats
What is pralidoximine chloride used for
Reversible agent for AChE toxicity caused by organophosphotases
What is the PD for pralidoxime chloride
PAM binds organophosphate so it can’t bind to AChE receptor