Antiparasitics: Ectoparasiticides

What parasite does Pyrethrins, pyrethroids and organochlorides target? What is their MOA?

• Arthropods on skin and environment

• Binds to voltage gated Na+ channels → prolonged Na+ influx → delay of depolarization → Spastic paralysis

What parasite do Neonicotinoids (Imidacloprid, nitenpyram, thiamethoxam) target? What is their MOA?

• Fleas

• Blocking on nicotinic acetylcholine receptors → Decreased ACh activity → flaccid paralysis

What parasite does Phenylpyrazoles (Fipronil) target? What is its MOA?

• Ticks, mites, fleas,lice

• GABA-gated Cl- channgels antagonist → spastic paralysis

What parasite does Isoxazolines (Afoxolaner, Fluralaner, Sarolaner) target? What is its MOA?

• Ticks, mites, fleas,lice

• GABA-gated Cl- channgels antagonist → spastic paralysis

The exact same as Phenylpyrazoles

What parasite does Chitin synthesis inhibitors (Lufenuron) target? What is their MOA?

• Fleas

• Interferes with chitin synthesis of larvae and eggs

What parasite do Juvenile hormone analogues (S-Methoprene, Pyriproxyfen) target? What is their MOA?

• Fleas

• Arrested development of eggs and larvae

Ectoparasiticides are drugs that act against _____ ______

External Parasites

What are the 2 categories of Ectoparasiticides that we discuss?

1. Drugs that affect neurotransmission

2. Drugs that affect arthropod growth regulation

Most Ectoparasiticides drugs affect _________, what are the 2 that do not?

• Neurotransmission

1. Chitin synthesis inhibitors 

2. Juvenile hormone analogs

Organophosphates used to be a common drug that treated most ectoparasites, why is it not used as commonly anymore?

• Resistance

• They are available OTC

Pyrethrins and Pyrethroids are ________ poison for arthorpods

Contact

Pyrethrins and Pyrethroids are not given to what animal? Why?

• Cats

• It is neurotoxic to them

  • They cannot metabolize it since they are deficient in glucuronidase

T/F: It is safe to give a dog Pyrethrins and Pyrethroids (K9 Advantix) that lives in the same house as cats

False, Pyrethrins and Pyrethroids are contact parasitic drugs, cats could groom or come into contact with it (1-8 times the lethal dose in cats)

Which particular species of flea has developed resistance to Pyrethrins and Pyrethroids?

Cetonocephalides felis (The Cat Flea)

What is the difference between a contact insecticide and a systemic insecticides?

• Contact

  • Only on skin, can kill the ectoparasites before they bite

• Systemic

  • Kills ectoparasites after they bite

Tetracyclic macrolides (Spinosad) treat what particular ectoparasite?

Fleas

What are the 2 types of Neonicotinoids? How does each vary?

• Imidacloprid (Seresto)

  • Contact insecticide for fleas/lice

• Nitenpuram (Capstar)

  • Systemic insecticide (requires blood meal from host)

What is the concern with Neonicotinoids regarding pharmacokinetics?

• It is quickly excreted in the urine without being metabolized first

  • Active form can be excreted into the envrionment

• Also is only present in host for 24 hrs

Which antiparasitic drug targets Nematodes (worms) and arthropods? What is its MOA?

• Macrocyclic lactones

Phenylprazoles (Fipronil) are not approved in _________

Canada (but are approved in the US)

What type of insecticide would be best for dogs with flea-allergy dermatitis?

Contact insecticides

Phenylprazoles (Fipronil) should not be given to which species? Why?

• Rabbits

  • GI signs, lethargy → seizures → death

Fipronil = Fluffer

Isoxazolines are _______ arthorpod poison, they treat fleas, ticks, mites, and one other ectoparasite, what is it and why is it important? (HINT)

• It kills mosquitoes

  • Prevents further transmission of Dirofilaria immitis (does not protect the dog from getting it

    • (systemic insecticide, mosquito has to have a blood meal it first))

Simparica TRIO is a combination of what anti-parasitics?

1. Sarolaner (Isoxazolines)

2. Moxidectin (Macrocyclic lactones)

3. Pyrantel (Tetrahydropryrimidines)

Amidines (Amitraz) is a unique ectoparasitic, why?

• It is a contact posion for arthropods (applying it will cause active/attached ectoparasites to drop off and die)

Why is Amidines (Amitraz) not commonly used?

It is very toxic to a wide variety of animals and can cause poisoning in humans 

T/F: Chitin Synthesis Inhibitors target both larval, hatching, and adult ectoparasites

False, they don’t affect adults

What is the MOA of Lufenuron?

• Chitin synthesis inhibitors

  • Interfere with chitin synthesis → Prevents viable molting of larval stages and hatching of eggs

What is the MOA of S-Methoprene and Puriproxyfen?

• Juvenile hormone analogs

  • Arrest mthe development of eggs or larvae

T/F: Juvenile homrone analogs have no adulticide effects

True (“Juvenile“)