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Parasitology > Lice, Scabies, Bed Bugs, Resistance to Pest Control > Flashcards

Lice, Scabies, Bed Bugs, Resistance to Pest Control Flashcards

1
Q

Lice - features

A

Wingless
Ectoparasites
Bite often

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2
Q

Types of lice and infestations

A

Head louse - Pediculus humanus capitis
Pediculosis capitis - head infestation

Body louse - Pediculus humanus humanus
Body infestation - Pediculus corporis

Pubic/crab louse - Phthirus pubis
Pediculosis pubis - infestation of pubic hair
Pediculosis ciliaris - infestation of eyelashes
Pediculosis - Lice infection

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3
Q

Epidemiological factors - head lice

A

Kids mostly affected
Females affected > males
European descent affected > african descent

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4
Q

Epidemiological factors - body lice

A

Poverty
Poor hygeine
Crowding

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5
Q

Epidemiological factors - pubic lice

A

Sexually active

Young adults

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6
Q

Life history - lice

A

Three growth stages:
Egg - nits, laid singly attached to hair/clothing (cementing substance to attach)
Larva - nymph, feeds on host
Adult

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7
Q

Head Lice transmission

A

Direct contact - person to person

Indirect contact - clothing, bedding, brushes

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8
Q

Head lice features

A 
Pointed in front
5 jointed antennae 
Claws present 
Bi lobed at end - female
Pointed end - male
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9
Q

Pruritis

A

An unpleasant sensation that provokes the desire to scratch.

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10
Q

Sensitization

A

Immunesystem produces protein, called an antibody, in response to any substance it considers abnormal

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11
Q

Excoriation

A

urge to pick at one’s skin

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12
Q

Signs+symptoms of crab louse

A

-Intensely pruritic - due to Allergic reaction to lice saliva
-Sensitization occurs in about 4-6wks
-This causes morbilliform rash (circular rose-red lesions)
Excoriations
Hyperpigmentation

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13
Q

Complications - lice

A

Excessive scratching can break skin barrier leading to bacterial infection -Dermatitis - Scratching and secondary infection

Lice can transmit bacteria causing infections:

  • Vectors:
  • Epidemic typhus - Rickettsia prowazeki
  • Relapsing fever - borrelia
  • Trench fever - Rickettsia quintana
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14
Q

Diagnosis - lice

A

Visualise nymphs/adults

If nits are >6.5mm from scalp then not active infestation

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15
Q

Control - lice

A

Permethrin 1% (Nix/Kwellada shampoo)
Removal via fine combing with diluted vinegar solution
Clean clothing in hot water with detergent
Regular infestations
Oral ivermectin

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16
Q

Ricksettsiae

A

Gram -ve coccobacilli
Two groups:
Spotted fever group
Rickettsia rickettsii - RMSF - tick bites

Typhus group
Rickettsia prowazeki - Epidemic typhus - lice feces
Rickettsia typhi - Murine typhus (endemic typhus) - rat fleas

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17
Q

Rickettsia is weak gram -ve to giesma stain used (T/F)

A

True

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18
Q

Why is rickettsia intracellular

A

-intracellular b/c can’t make NAD+ and CoA so requires cells

Attach to endothelial cells and invade.

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19
Q

Scabies etiology

A

Skin conidition caused by mites - Sarcoptes scabei

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20
Q

Scabies risk factors

A

Crowding
Skin to skin
—direct and prolonged
Fomites (furniture, chairs, beds) - happens in one type of scabies –survive 1-1.5 days

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21
Q

Pathogenesis - scabies

A

Female mite secrets proteolytic enzymes - allows entry into epidermis
Eggs laid
Larvae hatch

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22
Q

Types of scabies

A

Classic

Pruritic

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23
Q

Classic scabies pathogenesis

A

Classic
Eruption of small erythematous paules
-appearance of “knots on a rope”

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24
Q

Pruritic scabies pathogenesis

A

Pruritic

  • -severe at night
  • -3-6 wks after colonization due to delayed sensitivity
  • -1-3 days if reinfestation occurs
  • -Response could be caused due to allergens in mites fecal pellets
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25
Q

Classic scabies papules locations

A

Webs of fingers
Axillae
Areola
Genitalia

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26
Q

Crusted scabies has less mites present than classic scabies (T/F)

A

False, more mites present in crusted scabies

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27
Q

Transmission via fomites is not common in crusted scabies (T/F)

A

False

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28
Q

Crusted scabies/Norwegian scabies is found where on the body?

A

Hands, feet, scalp

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29
Q

Diagnosis - Scabies

A

Microscope - eggs/mites
Often clinical diagnosis
-Pruritis
-Crusting, scaling fissuring

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30
Q

Treatment - Scabies

A

Topical permethrin

Ivermectin

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31
Q

Bed bugs features

A
  • -Wingless; flat insects
  • -Feed at night
  • -Not much physical harm done
  • -Hidden in crevices of bed frames and mattresses
  • -Difficult to find
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32
Q

Persons become sensitive to bed bug bites in infestations (T/F)

A

True

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33
Q

Bed bug life cycle

A

Eggs laid
Eggs hatch in 6-10 days
Nymphs look for blood meal
Immature nymphs molt 5 times before adulthood

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34
Q

Environmental signs of bed bugs

A

Dark specks - along mattress seams - bedbug excrement.
Empty exoskeletons - from molting
Rusty or reddish stains - blood from accidental crushing of bed bug

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35
Q

Bed bugs - symptoms

A

Bed bug bites may form line/ zigzag pattern
Red, papular erosions of skin
Burning, painful sensation

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36
Q

Areas of the body with bites - bed bugs

A 
neck
face
hands
shoulders
arms
legs
37
Q

Papule

A

Solid elevation of skin; no visible fluid

38
Q

Scabies Drugs History

A

Scabies Drugs
Lindane - toxic to humans - paralyses mite - resistance
Permethrin - safer choice - resistance
benzyl benzoate - toxic to nervous system of mites - skin irritation - cheaper
Ivermectin - broad range medicine - no resistance for scabies

39
Q

Bed bugs drugs history

A

Synthetic pyrethroids - for Cimex spp -resistance
Pyrethroid+neonicotinoid - combo for resistance
Chemical alternatives: organophosphates, Carbamates - developing resistance - current treatment

40
Q

Head lice Drugs History

A

Permethrin, phenothrin (pyrethroid), malathion (organophosphate), lindane
Lindane - resistance - toxicity to humans
Malathion - inflammability+application issues - resistance
Permethrin and henothrin - synthetic pyrethroids - resistance
Invermectin - current treatment

41
Q

Domestic livestock Illnesses

A

Sheep scabies, poultry mites, sea lice

42
Q

Sheep scab pathogen

A

Pathogen: Psoroptes ovis - not fatal - frequent itching leading to bact. infection in sheep, weight loss due to not eating

43
Q

Drugs History - Sheep scabies

A

Lindane - toxic residues in meat - not used
Diazinon and propetamphos - organophosphates - dipping treatment - exposure to farmers to chemicals causing muscle spasms, flu like symptoms - harm to wildlife
Flumethrin and cypermethrin - synthetic pyrethroids
Invermectin and moxidectin - macrolytic lactones

44
Q

Sheep scabies - control - issues

A

Too many treatment options - no consistent control strategy

45
Q

Poultry mites pathogen

A

Dermanyssus gallinae - infests chickens - anemia in hens = less egg production

46
Q

Poultry mites are difficult to treat, why?

A
  • difficult to treat b/c mites hide well in dark corners and feed at night
47
Q

Poultry mites - Drug history

A

Acaricides - spray for mites -organophosphates - tetrachlorvinphos, dichlorvos, malathion - synthetic pyrethroids - permethrin, delatherin - carbamates - carbaryl

Ivermectin - ineffective
Permethrin, amitraz, carbaryl - resistance

48
Q

Poultry mutes - control - issues

A

Farmers spray more than needed = growing resistance - toxic acaricide in eggs and meat

49
Q

Sea lice pathogen

A

Salmon louse - Lepeopophtheirus salmonis - infects atlantic salmon

50
Q

Effect of sea lice on farmers

A

Juvenile stages - attach to skin - feed on mucus and blood when adults - tissue loss = low value of fish

51
Q

Sea lice - Drug history

A

Dichlorvos and azametiphos - Organophosphates - resistance
Cypermethrin - synthetic pyrethroids
Ivermectin - supercded by avermectin, emamectin benzoate
Hydrogen peroxide - topical
Deltamethrin - resistance

52
Q

Sea lice - control issues

A

-Resistance- Cost of multiple treatments

53
Q

Organophosphates MoA

A

(e.g. malathion, diazinon) - block activity of acetylcholinesterase (AChE) = paralysed athropod

54
Q

Resistance response to organophosphates

A
  • increase in esterases and cytochrome P450 = drug metabolised before it has an effect - increase transcription of (AChE)
55
Q

Synthetic pyrethroids MoA

A
  • target voltage gated Na+ channels = paralysis
56
Q

Synthetic pyrethroids resistance response

A

Resistance due to mutations in target genes

57
Q

Macrolytic lactone resistance in sea lice

A

Macrolytic lactones are not a common resistance problem except for in sea lice.
Emamectin benzoate - decreased GABA channels = resistance

58
Q

Macrolytic lactones MoA - nematodes

A

-target GABA and glutamate gated chloride channels = chlorine ions in cells = paralysis and death

59
Q

Resistance response to Macrolytic lactones

A

Mutations in genes encoding channels

Increased transcription of ATP binding transporters = metabolise drugs before they affect

60
Q

Factors influencing fast spread of resistance genes

A

Short life cycle of parasites + high fecundity

61
Q

Methods to counteract resistant parasites

A

Possible methods: Move livestock from pastures with infective larvae to unused pastures - less potential to get resistant parasites
Slowing treatment method - treat select individuals with certain symptoms

62
Q

Issue with slowing treatment method

A
  • treat select individuals with certain symptoms - slows development but no eradication
63
Q

Insect growth regulators have not been as exploited (T/F)

A

true

64
Q

IGRs - def’n

A

Group of drugs - mimics arthropod hormones+enzymes that inhibit growth and development

65
Q

IGR categories

A
  • juvenile hormone analogues (JHAs such as methoprene and hydropene), chitin synthesis inhibitors (diflubenzuron) - blocks chitin production - available for plants more than livestock
66
Q

JHAs - elevated juvenile hormone - usage

A
  • interferes with reproduction in arthropod - used against crop and household pests - not used for human parasites - resistance in house fly
67
Q

Biological control, why is this used?

A

Safer for environment

68
Q

Bio control alternatives

A 
Azadirachtin
Spider venom peptides 
Lippia multiflora 
Chamomile extract 
Tea tree oil 
Fungi
69
Q

Azadirachtin - found where? - MoA

A

Naturally found in neem tree - deters feeding in locusts and mites - disrupts growth - non toxic to humans

70
Q

Spider venom peptides - Found where? MoA

A

Found in arachnids - target Ca+ and Na+ channels = paralysis - peptides need to be nontoxic to humans

71
Q

Lippia multiflora (bush tea) - pathogens

A

Treats head lice and scabei

72
Q

Chamomile extract - pathogens

A

Psoroptes cuniculi - rabbit ear mite

73
Q

Tea tree oil - treat what pathogens

A

Head lice - acaricidal - S scabei

74
Q

Fungi - MoA

A

Conidia penetrating mites on host

75
Q

Vaccination for parasites is more feasible for veterinary parasites than human ones (T/F)

A

True; can’t vaccinate all persons at risk

76
Q

Primary control of cattle ticks

A

acaricide = env pollution + resistance

based on tick gut antigen - exploits haematophagous habits

77
Q

Cattle tick vaccine MoA

A
  • based on R microphilus Bm86 gut antigen - haematophagous habits exploited
78
Q

Cattle tick vaccine advantages

A

Tick control possible with vaccine - less need for acaricides
-sheep can mount protective immune response

79
Q

What causes lesion development in parasitic infestations?

A

Eosonophil production causes inflammation

80
Q

IgE levels effect in goats against parasitic infestation

A

IgE levels = Protective immunity against scabies

81
Q

Early IgG response effect in immunity

A

Early IgG response = clearing infection w/o drugs

82
Q

Which livestock infestation has no protective immunity available

A

No protective immunity for sea lice and poultry mites

83
Q

Other than immune response, what is another criteria for a successful vaccine?

A
  • > If antibodies are taken up by parasite
  • -poultry mites + sea lice - blood feeders - ingest antibodies
  • -sheep scab + scabies mites - ingest antibodies via serous exudate not blood
  • —Gut proteases - possible vaccine
84
Q

Subolesin

A

conserved protein inticks, which can provide protection against sometickspecies

85
Q

Vaccine-Salmon louse

A

Homologue (close relation to) of tick subolsin called my32 - found in salmon louse - Caligus rogercresseyi - vaccine - 57% decrease in lice

86
Q

Other salmon louse potential vacine

A

Trypsin

87
Q

Natural treatments for parasites

A

Cinammon, cassia, tea tree oils - effective in vitro

88
Q

Bed bugs and head lice has no vaccine, why?

A

no vaccine b/c too high number of susceptible persons and short lived life cycle

Parasitology (10 decks)

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