Ectoparasite control Flashcards
Give an example where you may intervene at multiple stages of a parasites life cycle?
fleas:
- adulticide to animal
- spray environment to affect juvenile stages
Why might it be more effective to target certain stages of a parasite’s life cycle?
Some stages, like larvae (e.g., blowfly strike), are more vulnerable than adults.
What two key characteristics of a parasite are essential to know when deciding which animals to treat?
If the parasite is contagious to others of the same species
If the parasite is species-specific
What are two non-chemical control strategies for ectoparasites?
Avoiding contact with the parasite
Producing conditions unsuitable for the parasite to live or reproduce
How can contact with parasite be avoided (non-chemical)?
barriers
Most useful where only part of life cycle on host, so harder to control
How can conditions be made unsuitable for parasite to live/reproduce (non-chemical)
Change host environment
- e.g., minimise pasture worm burden/ tail docking => reduce myiasis of sheep
Change off-host environment
- e.g., management of dung to avoid attracting flies
What public health implications may influence ectoparasite treatment?
Zoonosis (e.g., sarcoptic mange)
Parasites as disease vectors (e.g., ticks transmitting Lyme disease).
What are some methods used in chemical ectoparasite control?
Neurotoxins (kill parasite)
Insect growth regulators (arrest parasite development)
Repellents, desiccants, and mechanical agents
What drug-related factors need to be considered when choosing a drug for ectoparasite control?
Spectrum of activity (what parasite at which life stage)
Speed of onset required
Duration of action/frequency of application (compliance, animals that get wet)
Contraindications and drug interactions
Safety (patient, owner and humans, environment, non-target species)
Development of resistance
Cost and licensing (many are expensive and POM-V)
What host-related factors need to be considered when choosing a drug for ectoparasite control?
species
age restrictions
suitable mode of application
meat/milk withdrawal periods (production animals)
Describe the action of neurotoxins
Most ectoparasiticides
Act of CNS synapses, axons or neuromuscular junctions => spastic or flaccid paralysis
All adulticidal & some ovicidal/larvicidal also
What extra safety considerations should we be aware of when using neurotoxins?
Insects and mammals have many neurotransmitters in common – better safety profile if drugs act on non-mammalian mechanisms
Give examples of different types of neurotoxins
Describe Neonicatinoids
Nicotinic acetylcholine (Ach) receptor stimulant
Used for fleas in small animals
examples:
- Imidacloprid (topical application)
- Nitenpyram
- Dinotefuran
Describe organophosphates
Cholinesterase inhibitors
example:
- diazinon (dimpylate) (sheep dip vs wide range of ectoparasites)
Describe phenylpyrazoles
GABA inhibitors
against fleas & ticks
example:
- Fipronil (topical application, toxic to rabbits)
Describe Isoxazolines
GABA + chloride channel inhibitors
fleas & ticks
Rapid onset of action
- kills fleas before eggs laid so most likely to be effective if environmental treatment not feasible
Absorbed systemically
Caution in patients with seizure history
Examples:
- Fluralaner
- Sarolaner
- Afoxolaner
Describe Macrocyclic lactones
Chloride channel stimulator
Absorbed systemically
Ectoparasites & endoparasites
cause neurotoxicity in collies/herding breeds (MDR1 gene mutation)
Describe Pyrethroids
Sodium channel stimulant
adulticide for fleas, flies, lice, keds, ticks & some mites
Also repellant
Toxic to cats & aquatic life
Examples:
- Permethrin
- Cypermethrin
- Deltamethrin
- Fluemethrin
What stage of life cycle do insect growth regulators act on?
interrupt juvenile stage (no adulticidal properties)
- very slow to act
- often used in conjunction with rapid acting adulticide
What are the 3 types of insect growth regulators
Juvenile hormone analogues
Chitin synthesis inhibitors
Triazine derivatives
Describe juvenile hormone analogues
Mimic activity of juvenile hormone so development of egg/larva arrested
Commonly in environmental flea sprays (also collars & spot-ons)
examples:
- S-methoprene
- Pyriproxyfen
- Fenoxycarb
Describe chitin synthesis inhibitors
Prevent normal development of the exoskeleton –> stop larvae developing
All dogs/cats in household must be treated for product to work
example:
- Lufenuron
Describe Triazine derivatives
Disrupt cuticle turnover – moult inhibitors
Preferential efficacy for Dipteran fly larvae –> prevention of cutaneous myiasis (sheep and rabbits)
examples:
- Cyromazine
- Dicyclanil
give examples of repellents
Most important is the Pyrethroids – used as repellant
Commonly for tick repellant action – but time to kill slow (>48h);
Some licensed for sandfly repellency (Leishmaniasis preventative)
Cattle ear tags for fly repellency
Repellant products for Culicoides midges (horse)
Describe mode of action of synergists
Inhibits insect detoxification pathways –> increase available concentration of insecticide.
Used especially with pyrethrins to reduce insecticide content.
example:
-Piperonyl butoxide
Describe lime sulphur dip
Traditional pesticide. Also fungicidal, bactericidal.
Unpleasant odour, may stain light coats, must prevent ingestion.
Describe desiccants
Used in environment, e.g. carpet powders
example:
- Sodium polyborate
Describe mechanical agents
Used in environment, e.g. carpet powders
sharp particles that damage exoskeleton
example:
- Diatomaceous earth
What are the steps for diagnosing an ectoparasite?
- Identify likely parasite(s) based on host, history &clinical signs
- Select appropriate diagnostic tests
- Perform tests correctly & collect representative samples.
- Examine sample systematically
- Identify the parasite.
What is the best test for fleas?
Coat brushing/comb onto paper
What is the best test for lice?
Coat brushing/comb onto paper or into LP
unstained acetate tape strip
trichograms (egg on hair).
Visible with naked eye, but microscopy needed to assess if chewing/sucking louse +/- to speciate
What is the best test for surface mites
Cheyletiella:
- coat brushing into LP
- unstained acetate tape strip
- superficial skin scraping
- hair pluck
Neotrombicula:
- unstained acetate tape strip
- superficial skin scraping
Otodectes:
- Otic exudate in LP
Microscopy x4
What is the best test for deeper mites
Deep skin scraping
hair pluck
Microscopy x4
Sarcoptes – scrape into epidermis
Demodex – deeper - scrape until blood oozes.
In what situations is serology used?
Psoroptes antibody serology - sheep scab
Sarcopted IgG serology - canine
Flea IgE serology
Describe the best practice for sampling/microscopy of ectoparasites
Primary lesion
Multiple samples
Scrape until capillary bleeding seen
View area systematically
x4-10
Condenser diaphragm partially closed
Look in house (mites are short lived)
What is the best place to find parasites on a sheep scab (Psoroptes)
superficial scraps at the leading edge of the lesion
How can skin scrapings be used to monitor treatment for canine/feline demodicosis
Repeated monthly - treat until 2 consecutive sets of -ve scrapes
scrape same sites and record number of each life stage and % live vs dead
How can insects & arachnids be differentiated
How can fleas, flies & lice be differentiated
How can chewing/biting lice vs sucking lice be differentiated
How can ticks vs mites be identified
How can soft vs hard ticks be identified
How can surface vs burrowing mites be identified
What is Damalinia spp. and what are its host species
Chewing lice
horse, cattle, sheep, goats
What is Felicola spp. and what are its host species
Chewing lice
Cats
What is Trichodectes spp. and what are its host species
Chewing lice
Dogs
What are Lipeurus, Cuclotogaster, Menacanthus and what are its host species
Chewing lice
Birds
What are Gliricola sp and Gyropus sp and what are its host species
Chewing lice
Guinea pig
What is Haematopinus spp. and what are its host species
Sucking lice
Cattle, pigs, horses
What is Linognathus spp. and what are its host species
Sucking lice
Cattle, sheep, goats, dogs
How do you distinguish Psoroptes from other surface mites
What is Cheyletiella and what is its host species
Surface mite
dogs, cats, rabbits
Heart-shaped
What is Otodectes sp. and what is its host species
Surface mite
Dogs, cats
In ears
What is Psoroptes and what is its host species
Surface mite
Cattle, sheep, horses, camelids, rabbits
What is Chorioptes spp. and what is its host species
Surface mite
Cattle, sheep, horses, camelids
What is Dermanyssus and what is its host species
Surface mite
Red mite
Poultry, wild birds
What is Ornithonyssus and what is its host species
Surface mite
Northern fowl mite
poultry, wild birds
What is Chirodiscoides and what is its host species
Surface mite
guinea-pig
What is Listrophorus and what is its host species
Surface mite
Rabbit
What is Neotrombicula and what is its host species
Surface mite
Harvest mite
dogs, cats, horses
What is Sarcoptes and what is its host species
Burrowing (round) mite
Dog!, horses, cattle, sheep, pigs, human, cat
Terminal anus
What is Notoedres and what is its host species
Burrowing (round) mite
Cat
Dorsal anus
What is Trixacarus and what is its host species
Burrowing (round) mite
Guinea pig
What is Knemidocoptes and what is its host species
Burrowing (round) mite
Birds
Cause of scaley leg & beak
What is Demodex and what is its host species
Burrowing (cigar-shaped) mite
Dogs, hamsters
Highly host specific
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