Parasitology: Ectoparasites Flashcards
Define eradication
Implies the disease or pest is to be eliminated and will not return, eg smallpox
Eradication is difficult and expensive, and is rarely an objective
Define parasite control
Reduction of parasite load or vector population –> reduce transmission.
Objective is to reduce the disease/pest to a level which is acceptable
Most ectoparasiticides act as neurotoxins that act on CNS synapses, axons or neuromuscular junctions, what does this cause?
spastic or flaccid paralysis
What are the risks of using neurotoxins for parasite control?
insects and mammals have many neurotransmitters in common –> toxicity risks (to animal and humans)
How do organophosphates work?
Cholinesterase inhibitors eg. Fenthion
How do carbamates work?
Cholinesterase inhibitors eg. propoxur, carbaryl, fenoxycarb
How do triazepentadienes (formamidines) work?
Octopamine receptor stimulant
eg. amitraz
How do phenylpyrrazoles work?
GABA inhibitor eg. fipronil, pyriprole
How do neonicatinoids work?
Insect nicotinic Ach receptor stimulant eg. Imidacloprid, Nitenpyram, Dinotefuran
How do pyrethrins work?
Na channel activator eg. dichlorvos, fenitrothion
How do pyrethroids work?
Na channel activator eg. Permethrin, cypermethrin, flumethrin
How do semicarbazones work?
Na channel blocker eg. indoxacarb
How do macrocyclic lactones work?
What are the two subgroups?
Cl channel blockers
Avermectins: ivermectin,selamectin, doramectin
Milbemeycins: milbemycin, moxidectin, oxime
How do isoxazolines work?
GABA and cl channel inhibitor eg. afoxolaner, flurolaner, sarolaner, lotilaner
How do spinosyns work?
Nicotinic Ach receptor stimulant and GABA agonist eg. spinosad
What do Insect growth regulators do?
All with no adulticidal properties
Effective in interrupting environmental stages of flea life cycle but slow to act (eg 60-90 days for lufenuron) –> Often used with adulticides
What are the types of IGR?
Juvenile growth hormone analogues: S-methoprene, pyrlproxyfen, dicyclanil, fenoxycarb
Chitin synthesis inhibitors: Lufenuron
Triazine derivatives: Cyromazine
What products contain juvenile growth hormone analogues?
Collars, spot ons and house sprays
What products contain juvenile growth hormone analogues?
Collars, spot ons and house sprays
What can we use to repel ectoparasites?
Pyrethrins/pyrethroids
Diethyltoluamide (DEET)
What can we use to desiccant ectoparasites?
sodium polyborate - carpet powders
What can we add to antiparasitics to synergise?
Piperonyl butoxide - inhibits the insects detoxification pathways
Use esp. with pyrethrins
What are the pros and cons of spot-ons?
Good compliance
But concern:
» Human toxicity immediately after application, esp children
» Ingestion of product (including by other pet) – NB esp collies/herding breeds with macrocyclic lactones
» Occasional skin lesions at site of application
» Wetting/bathing may compromise action, especially if not absorbed systemically
» ?Concentration gradient with distance from site of application if not absorbed systemically
What are the pros and cons of sips and sprays?
Care re operator exposure
Care re appropriate storage and disposal
» Dips: ideally pesticide binds to skin/hair, leaving residual wash depleted of chemical
What does the Deltamethrin Collar protect against?
sandflies, mosquitoes, ticks
What does the imadicloprid/flumethrin collar protect against?
fleas, ticks
What are the cons/considerations with using collars?
» Remove during swimming/washing to avoid depletion of drug from collar +/- contamination of aquatic life– but insecticidal activity may take 1-2 days to re-establish
» Occasional contact irritation
» Care to prevent animal chewing/swallowing collar
» Use immediately once opened
What are the quickest acting anti-parasitics?
Nitenpyram – very rapid onset (95-100% kill in 6 hours) but short action
Spinosad and izoxazolines – very rapid onset, last 1-3 months –> very effective
What are the contraindications of pyrethroids?
Pyrethroids/Permethrin
» Some cats highly sensitive, even to small amount of permethrin spot-on products à neurotoxicity. Care to avoid contact with dog spot-ons
What are the contraindications of Macrocyclic lactones, especially ivermectin?
Multi-drug resistance gene (MDR1) encodes for P-glycoprotein, responsible for pumping drugs out of the CNS. In dogs with MDR1 mutation, drug crosses blood brain barrier –> neurologic signs/death.
Especially collies/herding breeds.
Always stay within label use for these breeds, and use off label with caution in others
What are the contraindications of fipronil?
Reports of fatalities in rabbits – do not use
What are the contraindications of spinosad?
Contraindicated in dogs with epilepsy
What are the contraindications of Advocate (moxidectin/imidacloprid) ?
Contraindicated with any other macrocyclic lactone (eg Milbemax (milbemycin/praziquantel endoparasiticide))
What are the contraindications of Amitraz?
Should not be applied by people taking monoamine oxidase inhibitors (antidepressants) or with diabetes mellitus
Never use concurrently with alpha-2 adrenergic agonists (eg medetomidine)
What is modelling and forecasting used for?
To help predict seasonal patterns of particular ectoparasites
Help vets/farmers to Integrate chemical/non-chemical control techniques and use ectoparsiticides prophylactically
What are the ideal conditions for fleas?
Ideal conditions 25’C and 75% RH
» <3’C will kill eggs and pupae
» >38’C and <33% RH is lethal to larvae
What physical control can we employ for fleas?
Washing pet blankets, rugs, and pet carriers to remove flea eggs and larvae >60C
Hoover crevices in sofas and chairs, and areas beneath sofas or beds where flea eggs/faeces may drop from the pet and accumulate.
Pupa is unaffected by all treatments (‘pupal window’), so how long can it take to eradicate fleas?
up to 3 months
How do flea treatments work?
May act topically by dispersing on the skin and hair coat, eg imidacloprid, fipronil or they may act following systemic absorption and redistribution to the skin, eg lufenuron (oral), selamectin/moxidectin (topical)
