26 – Ecto-parasiticides Flashcards
Many ectoparastiticide formulations
- ear tags
- collars
- immersion baths
- topical dusts
- shampoos
- premise application (fleas!)
- pour-on
What are the different acetylcholinesterase inhibitors?
- Organophosphates
- Carbamates
Acetylcholinesterase inhibitors: organophosphates
- mechanism: IRREVERSIBLE binding to AChE
- HIGHLY toxic to mammals
- Environmental concerns
What are the different compounds and formulations of acetylcholinesterase inhibitors: organophosphates?
- Diazinon ear tags (control horn flies and face flies in cattle)
- Many other compounds
Acetylcholinesterase inhibitors: carbamates
- Mechanism: competitive inhibitor of AChE (reversible)
- Less toxic than organophosphates, still toxic though
o Given small amount for a large animal
What are the different compounds and formulations of acetylcholinesterase inhibitors: carbamates?
- Carbaryl dusting powder for control of mites, fleas, lice, ticks, and flies in various food animal species
(Amitraz)
- Inhibits monamine oxidase
- Toxicity: activation of alpha2 receptors
- Prevention of ticks
- NOT in Canada
Pyrethrins (basic from chrysanthemum flower)/Pyrethroids (synthetically modified compounds)
- ‘natural’
- Highly LIPIDLY soluble
- Topical formulations stay in stratum corneum
o NO systemic absorption
o Considered pesticides - *TOXIC IN CATS
Examples of drugs that are pyrethins/pyrethroids
- Permethrin (ex. vetolice)
- Cypermethrin
- Cyfluthrin (CyLence)
What is the mechanism of pyrethrins/pyrethroids?
- Most act on Na+ channels (stuck in OPEN state) or other NT functions
What are the formulations of pyrethrins/pyrethroids?
- Shampoos
- Sprays
- Dips
- Dusts
- Ear-tags
What are pyrethrins/pyrethroids active against?
- Fleas
- Ticks
- Flies: probably the best fly control
- Lice
- (Mites: not as good)
- *ENVIRONMENTAL CONTAMINATION
Pyrethins/pyrethroids is toxic in cats
- Due to grooming of topical products?
- Poor hepatic glucuronidation?
- *especially in environmental decontamination
o ALSO TOXIC FOR FISH! - *persist in environment for a long time
Neonicotinoids
- Like nicotine, but more stable
- Non-ionized at physiological pH (so crosses BBB)
- Minimal environmental impact (but it is what is killing bees, due to using it on plants to kill bugs)
What is the mechanism of neonicotinoids?
- Activates INSECT nicotinic receptors
- No effect on vertebrate nicotinic or muscarinic receptors
- First depolarizes neuron (Na channels open), but eventually STOPS neural transmission
Examples of neonicotinoids
- Imidacloprid
- (Nitenpyram (Capstar))
Imidacloprid
- TOPICAL formulations for dogs and cats (monthly)
- Minimal transdermal absorption, but surface ‘translocation’ over skin
- Kills ADULT and LARVAL fleas and lice
o Limited activity against ticks (not on host often) - Generally very safe for mammals
- Ex. advantage/KD Advantix
Imidacloprid and lice
- Will get both adults and eggs
Imidacloprid and fleas
- can still have environmental reservoir
(Imidacloprid and Moxidectin)
- Also get heart worms
- *won’t get TAPEWORMS!
Nitenpyram (Capstar)
- ORAL tablet (DIN) FLEA adulticide in dogs and cats
- Administered DAILY if fleas observed on animals
- 100% oral bioavailability
- Effective against fipronil-resistance fleas
- Generally very safe
Insect growth regulators
- Analogues of HORMONES which regulates insect LARVAL DEVELOPMENT
- No effect on ADULT insect
- Exposure results in ‘arrested development’ of larval stage
- Generally little toxicity in mammals
- *takes weeks to see effect since no effect on adults
o Often used with other adult insect pesticides - Ex. LuFEnuron (old: Methoprene, pyriproxyfen)
LuFEnuron
- Block development of insect exoskeleton by inhibiting chitin synthesis or utilisation (if no chitin=can’t get out of egg=die)
- *used to control FLEAS at egg and larval stages
- Program for cats
o Monthly oral suspension
o SC injection (6 month duration) - Sentinel tablets for dogs (w/milbemycin)
- Use in aquaculture for prevention of sea lice
*Isoxazoline (“Langer”) ectoparasites
- ANTAGONISTS of GABA and glutamate gated Cl-channels
o Lack of hyperpolarization=excess neural activity
o Opposite effects of macrocylic lactones - *effective for control of fleas and ticks
- *all classified as drugs (DIN)
- *DON’T WORRY ABOUT SPECIFIC NAMES (Ex. Bracvecto: fluralaner)
- *know they end in ‘laner’
o Most oral products and mixed with something else (ex. Avermectin)
o Also have topical solutions - *CAN CAUSE SEIZURES
Ticks and fleas
- Takes time as there is an environmental component
- Ex. HOT WASHING THE BEDDING
When using topical isooxazoline what do you need to be careful for?
- WATCH FOR TRANSFER TO OWNER
o No cuddling or sharing a bed with animal
o At least 48 hours
o Wear gloves!
Can Praziquantel be topically absorbed?
- Apparently
