Ectoparasites

Question 1

Organophosphates

Answer 1

*NOT in cats! (young animals, eq)
*most toxic ectoparasiticides , contact poison
*choline-esterase irreversible inhibition (P-esterifaction sites) -> spastic paralysis , works on both muscarinic and nicotinic receptors.
*Highly lipophilic, sensetive to alkaline PH (use soap to inactivate)
*good absorption
*sheep- dipping (mange mites) ,honeybees strips.
*excellent distribution -BBB
*liver inactivation , urine excretion
*biological accumilation
*Spectrum: AN, flea,ticks, Demodex, lice, flies
*SE: mAch-SLUDGE
nAch- muscle spasms. PS (miosis) , death.
*ANTIDOTE: i.Atropine (muscarinic R only- not for convulsions)
ii.ACh Enzyme reactivation→ Pralidoxime, Obidoxime . BEST, first 24h only
*dipping (0,05 % solution), spraying, collars, spot-on, pour-on, organophosphates:
i.Diazinon (Dimpylate)→ large animals
ii.Coumaphos→ honeybees(Varroa destructor)
iii. Phoxim
iv. Fenthion-systemic pesticide
*PO:
i.Cythioate- small animals
ii.Haloxon, Metriphonate - large animals
*Anti-nematodial:
i. Dichlorvos (Sus (premix,Eq,Ca, Fe)
ii. Trichlorfon (Eq, Ca)
iii. Cythioate(Ca, Fe)
iv. Naftalofos, Haloxon, Coumaphos, Crufomate(Ru)

Question 2

Carbamates

Answer 2

• reversible inhibition of AChE
• Spectrum: flea, tick, lice
• safer than organophosphates but less lipophilic, same side effects + carcinogenic
• ANTIDOTE: Atropine
• i.Carbaryl
  ii. Propoxur (+ Pyrethroids/ Juvenile hormone analogues combi)

Question 3

Pyrethroids

Answer 3

• NOT for cats in spot on! (Foresto is ok)
• most freq. used + has REPELLENT EFFECT!
• contact poision, Na influx->excitation->death
• lipophilic , short lasting
• spectrum: ticks , flies, mosquitos (dec. for fleas or mange mites)
• SE:tremors, seizures, excitation =>hyperthermia. fish killing when entering the sea.
• NO ANTIDOTE but intralipid 20%+ anticonvulsive agent (first 24h)
• toxicosis same as organophosphate but MYDRASIS instead of miosis.

*1st gen: Tetramethrin (NeoStomosan)-sensitive to light + humidity,lower stability + shorter duration, residual activity(bathing solun.)
*2nd gen: longer action , more toxic
i. Permethrin (Advantix, Vectra)
ii. Deltamethrin (Scalibor)
iii. Flumethrin (Kiltix, Foresto)
spot on ,collar.

Question 4

Formamidine

Answer 4

AMITRAZ

• NOT in cats, chihuahua and eq(-GI motility , paralytic ileus)
• MAO inhibitor (catecholamine uptake in synaptic cleft inhibitior)
• Alpha2-agonist
• agonist at OCTOPAMINE (NT) receptor - only in parasite. (continued excaitation-> energy depletion) can cause noradernaline,dopamine,serotonine reuptake - animal exciatation
• modernate absorption , slow release, long HL in dog
• spectrum: only 8-legged arthropods- mange mites (dipping in 0.025% solution),demodex,ticks,varroa (-honeybees above 14 degrees).
• SE: narrow TI , PO more toxic. α2 agonist→sedation, bradycardia, hypothermia, emesis, hyperglycaemia(-not in DM)
• sensitive to light and air →fresh solution
• ANTIDOTE: Atipamizole

Question 5

Endectocides (Macrocyclic lactone)

Answer 5

• Glutamate-gated Chloride ion channels and GABA agonist -> hyperpolarization->flaccid paralsis (animals are safe due to thier P-glycoprotein pumps in BBB)
• spectrum: AN, fleas (Selamectin), demodex spp. (Moxidectin 1xW/Milbemycin 1xD) , mange mites ear mites, myiasis, (ticks)
• MDR gene mutation dogs are suseptible because the lack of P-glycoporotein pump . (e.g:collies)
• PO (NexGard, Milbemax, Milprazon) ,SO (bervecto plus),IV

Question 6

Phenylpyrazoles

Answer 6

FIPRONIL (Frontline)

• NOT in rabbits and bees
• GABA Antagonist ->excitability>spasms
• insecticide,acaricide (mites,ticks)
• good distribution,residual activity, minimal systemic effect.
• slow but long duration of action
• low water solubility (no water for 2d)
• good against Dermatophagoides farina (house dust mites) by residues in shadded hair.
  (i) Pyriprole: derivative, dog’s fleas and ticks, more effective, slow+better absorption. not in cats and rabbits

Question 7

Indoxocarb

Answer 7

*sodium channel blocker→ hyperpolarisation → paralysis
*Prodrug, kills fleas (adults,larvae,eggs)
but not ticks
*good for FAD (flea allergy dermatitis)
*good for cats+dogs
*also used in agriculture

Question 8

Neonicotinoid insecticide

Answer 8

*Ach agonist>excitation>death
*fastest acting group
*effective against FAD
*safe,more toxic to the environemnt
*1st gen:
i. Imidacloprid: fles,lice, adulticide, epithelial debris
-combi: +Permethrin(ticks, NOT in cats-adventix)
+Flumethrin(ticks,+cats - foresto,slow)
+Moxidectin (+cats - advocate)
ii.Nitenpyram (Capstar tablet, not in Hungary): PO, urine excretion,safe for pregnant animals.
*3rd gen: better,lower dose
i.dinotefuran: Vectra 3D=→ Dinotefuran+ Permethrin (not for cats) + Pyriproxyfen (all flea life stages)

Question 9

Isoxazolines

Answer 9

• GABA antagonist, Glutamate-gated Chloride channel antagonist > excitation>death
• very safe,give with food (vomiting), accumilation in adipose tissue
• bile excretion
• Spectrum: FIRST LINE for Demodex spp!!. act against mosquitoes, fleas and ticks ,mange mites , Demanyssus gallinae .
• SE: only when overdosing x3 = tremors, x5 convulsions in puppies , disappear after 24h
• collar SO: contact dermatitis in small dogs, paws are suseptible.
  i. Fluralaner (3m), food dependent, safe for pregnant, lactating+MDR1
  ii. Afoxolaner (1m), +kidney excretion (not in kidney patients)
  iii. Sarolaner (1m), most toxic
  iv. Lotilaner
• combi: i. Sarolaner+ Selamectin (Stronghold Plus)
  ii. Afoxolaner+ Milbemycin oxime (NexGard)

Question 10

Insect growth regulators (IGRS)

Answer 10

• act only on developmental stages (metamorphosis), not adulticide.
• not aginst mites and ticks (no metamorphosis)

(1) Juvenile hormone analogues:
very long duration of action (over 48d), light sensitive, residual activity.
i.Methoprene (Frontline Combo, highly toxic to fish)
ii.Pyriproxyfen (Vectra, more stable)
iii.Fenoxycarb
*often in combination with pyrethroids or Fipronil

(2) Chitin synthesis inhibitors:
* mainly used in agriculture
* interferes with polymerisation and deposition of chitin, killing developing larvae either within the egg or after hatching.
* spectrum: flea (not adulticidal), fungi
* SE: unkown toxic effect.
i. Lufenuron ii.Novaluron iii.Diflubenzuron