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Module 7 > Control of Ectoparasites > Flashcards

Control of Ectoparasites Flashcards

1
Q

what are the reasons to control ectoparasites (5)

A
  1. debilitating irritant to host
  2. source of infestation –> animals and humans
  3. vectors of disease
  4. economic loss
  5. compromise animal welfare
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2
Q

why are ectoparasites difficult to control

A
  1. large seasonal increases in populations –> tick population increases in spring/autumn, blowflies increase in late spring and early summer, midges peak in summer and autumn
  2. infestations can be highly contagious –> stocking density, location - transport
  3. can be widespread in the environment –> although some are more localized
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3
Q

what are the basic strategies to control ectoparasites (7)

A
  1. deployment and application of drugs to kill and repel insects and arachnids (all)
  2. legislation to report and treat (scab and warble)
  3. quarantine and treatment of incoming stock (scab)
  4. treatment of all in contact animals (sarcoptic mange)
  5. treatment of the local environment/habitat (flea allergic demodecosis)
  6. vaccines against ectoparasites (rhipicephalus tick)
  7. mechanical removal –> traps and vacuums (tetse fly and fleas)
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4
Q

what are the pharmological interventions to prevent ectoparasite infestation

A

selective toxicity –> target a feature of the parasite that is different from the host

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5
Q

what is selective toxicity

A

target specific ion channels that are in the CNS of vertebrates but in the PNS of ectoparasites

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6
Q

what are the mechanisms of action of selective toxicity

A
  1. exploit the fact that metabolism is slower in insects than endotherms
  2. target receptors that vertebrates do not have
  3. have greater affinity for equivalent ectoparasite receptor
  4. target proteins, like chitin, that vertebrates lack
  5. bio-activation of the drug in the gut of the insect to kill parasite
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7
Q

what are the methods of delivery of ectoparasiticides

A
  1. ear tags, tapes, collars for farm animal species
  2. pour on for large and small animals
  3. spot on solutions
  4. collars for cats and dogs
  5. dips
  6. oral tablets or suspensions
  7. sprays
  8. injectable
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8
Q

what is the mechanism of action of organophosphates

A

selective inhibition of acetyl cholinesterase –> accumulation of acetyl choline in synaptic celft –> neuromuscular paralysis

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9
Q

what is the spectrum of organophosphates

A

ticks and mites; flies, feals and lice

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10
Q

what is the toxicity of organophosphates

A

safely margin is limited for animals and man and products carry operator warnings –> certificate of competence for OP dip

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11
Q

what are the mechanism of action of pyrethrins and pyrethroids

A

prevent closure of presynaptic voltage gated sodium channels

nerves cannot repolarize

cause paralysis

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12
Q

what is the spectrum of pyrethrins and pyrethroids

A

lice, fleas, flies, keds

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13
Q

what is the toxicity of pyrethrins and pyrethroids

A

low if given orally, fish and some aquatic invertebrates are highly sensitive

dip formulations banned

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14
Q

how is pyrethrins and pyrethroids selectively toxic

A

rate of metabolism is more rapid in vertebrates

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15
Q

how is permethrin toxic in cats

A

life threatening toxocosis

spot ons for dogs applied to cats

high surface/weight ratio –> elevated dose

lower detoxification/excretion

can cause tremors, twitches, hyperthermia, seizures

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16
Q

how is permethrin toxicity in cats treated

A

methocarbamol i.v (centrally acting muscle relaxant)

seizure control; barbiturates, diazepam, inhalant anaesthetics

dermal decontamination by bathing

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17
Q

what are examples of avermectins and milbemycins

A

invermectin, doramectin, selamectin, moxidectin, milbemycin

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18
Q

what is the action of avermectins and milbemycins

A

bind to glutamate gated (ectos) or GABA gated chloride channels (host)

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19
Q

what is the toxicity of avermectins and milbemycins

A

sensitive animals including some dog species, kittens, some species of birds, turtles, fish and reptiles

20
Q

what is toxicosis of ivermectin

A

contraindicated in some species and some dog breeds

unable to pump out drug from CNS

toxicosis syndrome, dilation of pupil, depression, tremor, ataxia, vomiting, salivation, coma

21
Q

what are uses of avermectins and milbemycins

A
  1. invermectin: very many formulations –> Ivomec
  2. selamectin: stronghold (spot on, dogs and cats)
  3. doramectin: dectomax (cattle, sheep, pigs)
  4. moxidectin: cydectin (sheep and cattle) with imidacloprid (advocate)
22
Q

what are examples of neonicotinoids

A

nitenpyram and imidacloprid

23
Q

what is the mechanism of action of neonicotinoids

A

block nicotinic receptors

inhibits cholinergic transmission causing paralysis and death

24
Q

what is the spectrum of neonicotinoids

A

fleas/lice in cats, dogs rabbits, ferrets

25
Q

what is the toxicity of neonicotinoids

A

low but toxic to bees

26
Q

what are the trade names of neonicotinoids

A

nitenpyram –> Capstar

imidacloprod –> Advantage

imidacloprid + permethrin –> advantix (fleas, ticks, lice)

imidaclorpid + moxidectin –> advocate (sarcoptic mange, demodecosis)

27
Q

what is the effect of cyromazine and methoprene

A

insect growth regulators (IGR)

effect deposition of chitin in cuticle

28
Q

what are the uses of cyromazine and methoprene

A

blowfly strike –> domestic rabbits –> reargard (cyromazine)

blowfly strike –> sheep –> clik/clikzin pour on (dicyclanil)

29
Q

what is the withdrawal period of cyromazine and methoprene

A

7 days for meat

not to be used in sheep producing milk for human use

30
Q

what is juvenile hormone (methoprene) used for

A

fleas, ticks and biting lice (dogs and cats)

spot ons –> kill adult fleas and inhibit development of egg

larvae and pupae

31
Q

what is an example of benzoyl urea derivative

A

lufenuron

32
Q

what is the mechanism of action of benzoyl urea derivative

A

inhibits chitin synthase in fleas

also kills eggs and larvae

33
Q

what is the pharmacokinetics

A

absorption improved in presence of food

highly lipophylic and accumulates in adipose tissue

34
Q

what is the administration of benzoyl urea derivative

A

oral suspension or tablets (monthly with food)

injectable for cats (six monthly)

35
Q

what is the mechanism of action of fipronil

A

an antagonist to GABA and glutamate gated chloride channels

greater affinity for insect receptors

reservoir in skin

36
Q

what are examples of fipronil

A

frontline

37
Q

what is the spectrum of fipronil

A

fleas, ticks, biting lice in cats and dogs

kills adults before eggs are laid

combined with IGR (methoprene): frontline plus; fiprotec combo; fleascreen combo for flea control

38
Q

what is the toxicity of fipronil

A

toxic to some gallinaceous birds and some fish

39
Q

what is oxadiazine insecticides

A

indoxacarb

sodium channel blocker

needs bioactivation

adult fleas

40
Q

what is an amidine

A

amitraz is the class member used for ectoparasites

41
Q

what is the mechanism of action of amidines

A

alpha2 receptor antagonist –> stimulates alpha adrenergic receptors

octopamine receptor antagonist –> alters brain function

leads to insect hyperactivity, paralysis and death

also detaching behaviour; inhibition of oviposition; reduces egg hatchability

42
Q

what are examples of amidines

A

aludex

43
Q

what is a strategy to sheep scab control

A

sheep scab is difficult control –> highly contagious –> control needs 100% efficiency –> residual activity > 17 days

44
Q

how is sheep scab treated

A

effective treatment by plunge dipping –> organophosphate dip kills 24 hours, residual effect –> 28 days

sheep in dip for atleast 60 seconds –> head immersed twice –> operator/environmental issues

injectables:

ivermectin (2, no residual) –> move to mite free environment

doramectin (1, 14-17 days residual) –> move to mite free environment

moxidectin 2% (1, 60 days residual)

emerging resistance of mite to Mls recently reported

mobile dipping contractors increasingly being used

45
Q

what does scab control require

A

all in contact animals must be properly treated

minimize impact of outbreak –> inform neighbours of risk –> coordinate treatment across farms

promote biosecurity –> good fencing, all incoming animals, quarantine, test and treat for 3 weeks

recognize common grazing as high risk infection

46
Q

what are pyrethroid products and their uses

A

permethrin: Advantix for dogs, Auriplak tag for cattle, Flypor pour on cattle, Xenex spot on for small furries

Cypermethrin: Crovet sheep, Dysect cattle and sheep, Excis pour on salmon, Deosect horses spray

Deltamethrin: AMX salmon, Butox swish cattle, Coopers spot on cattle and sheep, Scalibor collar large dogs

Flumethrin: Bayvarol strips, against varroa mites

Module 7 (50 decks)

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