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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
Classic scabies papules locations
Webs of fingers Axillae Areola Genitalia
26
Crusted scabies has less mites present than classic scabies (T/F)
False, more mites present in crusted scabies
27
Transmission via fomites is not common in crusted scabies (T/F)
False
28
Crusted scabies/Norwegian scabies is found where on the body?
Hands, feet, scalp
29
Diagnosis - Scabies
Microscope - eggs/mites Often clinical diagnosis -Pruritis -Crusting, scaling fissuring
30
Treatment - Scabies
Topical permethrin | Ivermectin
31
Bed bugs features
- -Wingless; flat insects - -Feed at night - -Not much physical harm done - -Hidden in crevices of bed frames and mattresses - -Difficult to find
32
Persons become sensitive to bed bug bites in infestations (T/F)
True
33
Bed bug life cycle
Eggs laid Eggs hatch in 6-10 days Nymphs look for blood meal Immature nymphs molt 5 times before adulthood
34
Environmental signs of bed bugs
Dark specks - along mattress seams - bedbug excrement. Empty exoskeletons - from molting Rusty or reddish stains - blood from accidental crushing of bed bug
35
Bed bugs - symptoms
Bed bug bites may form line/ zigzag pattern Red, papular erosions of skin Burning, painful sensation
36
Areas of the body with bites - bed bugs
``` neck face hands shoulders arms legs ```
37
Papule
Solid elevation of skin; no visible fluid
38
Scabies Drugs History
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
Bed bugs drugs history
Synthetic pyrethroids - for Cimex spp -resistance Pyrethroid+neonicotinoid - combo for resistance Chemical alternatives: organophosphates, Carbamates - developing resistance - current treatment
40
Head lice Drugs History
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
Domestic livestock Illnesses
Sheep scabies, poultry mites, sea lice
42
Sheep scab pathogen
Pathogen: Psoroptes ovis - not fatal - frequent itching leading to bact. infection in sheep, weight loss due to not eating
43
Drugs History - Sheep scabies
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
Sheep scabies - control - issues
Too many treatment options - no consistent control strategy
45
Poultry mites pathogen
Dermanyssus gallinae - infests chickens - anemia in hens = less egg production
46
Poultry mites are difficult to treat, why?
- difficult to treat b/c mites hide well in dark corners and feed at night
47
Poultry mites - Drug history
Acaricides - spray for mites -organophosphates - tetrachlorvinphos, dichlorvos, malathion - synthetic pyrethroids - permethrin, delatherin - carbamates - carbaryl Ivermectin - ineffective Permethrin, amitraz, carbaryl - resistance
48
Poultry mutes - control - issues
Farmers spray more than needed = growing resistance - toxic acaricide in eggs and meat
49
Sea lice pathogen
Salmon louse - Lepeopophtheirus salmonis - infects atlantic salmon
50
Effect of sea lice on farmers
Juvenile stages - attach to skin - feed on mucus and blood when adults - tissue loss = low value of fish
51
Sea lice - Drug history
Dichlorvos and azametiphos - Organophosphates - resistance Cypermethrin - synthetic pyrethroids Ivermectin - supercded by avermectin, emamectin benzoate Hydrogen peroxide - topical Deltamethrin - resistance
52
Sea lice - control issues
-Resistance- Cost of multiple treatments
53
Organophosphates MoA
(e.g. malathion, diazinon) - block activity of acetylcholinesterase (AChE) = paralysed athropod
54
Resistance response to organophosphates
- increase in esterases and cytochrome P450 = drug metabolised before it has an effect - increase transcription of (AChE)
55
Synthetic pyrethroids MoA
- target voltage gated Na+ channels = paralysis
56
Synthetic pyrethroids resistance response
Resistance due to mutations in target genes
57
Macrolytic lactone resistance in sea lice
Macrolytic lactones are not a common resistance problem except for in sea lice. Emamectin benzoate - decreased GABA channels = resistance
58
Macrolytic lactones MoA - nematodes
-target GABA and glutamate gated chloride channels = chlorine ions in cells = paralysis and death
59
Resistance response to Macrolytic lactones
Mutations in genes encoding channels | Increased transcription of ATP binding transporters = metabolise drugs before they affect
60
Factors influencing fast spread of resistance genes
Short life cycle of parasites + high fecundity
61
Methods to counteract resistant parasites
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
Issue with slowing treatment method
- treat select individuals with certain symptoms - slows development but no eradication
63
Insect growth regulators have not been as exploited (T/F)
true
64
IGRs - def'n
Group of drugs - mimics arthropod hormones+enzymes that inhibit growth and development
65
IGR categories
- juvenile hormone analogues (JHAs such as methoprene and hydropene), chitin synthesis inhibitors (diflubenzuron) - blocks chitin production - available for plants more than livestock
66
JHAs - elevated juvenile hormone - usage
- interferes with reproduction in arthropod - used against crop and household pests - not used for human parasites - resistance in house fly
67
Biological control, why is this used?
Safer for environment
68
Bio control alternatives
``` Azadirachtin Spider venom peptides Lippia multiflora Chamomile extract Tea tree oil Fungi ```
69
Azadirachtin - found where? - MoA
Naturally found in neem tree - deters feeding in locusts and mites - disrupts growth - non toxic to humans
70
Spider venom peptides - Found where? MoA
Found in arachnids - target Ca+ and Na+ channels = paralysis - peptides need to be nontoxic to humans
71
Lippia multiflora (bush tea) - pathogens
Treats head lice and scabei
72
Chamomile extract - pathogens
Psoroptes cuniculi - rabbit ear mite
73
Tea tree oil - treat what pathogens
Head lice - acaricidal - S scabei
74
Fungi - MoA
Conidia penetrating mites on host
75
Vaccination for parasites is more feasible for veterinary parasites than human ones (T/F)
True; can't vaccinate all persons at risk
76
Primary control of cattle ticks
acaricide = env pollution + resistance | based on tick gut antigen - exploits haematophagous habits
77
Cattle tick vaccine MoA
- based on R microphilus Bm86 gut antigen - haematophagous habits exploited
78
Cattle tick vaccine advantages
Tick control possible with vaccine - less need for acaricides -sheep can mount protective immune response
79
What causes lesion development in parasitic infestations?
Eosonophil production causes inflammation
80
IgE levels effect in goats against parasitic infestation
IgE levels = Protective immunity against scabies
81
Early IgG response effect in immunity
Early IgG response = clearing infection w/o drugs
82
Which livestock infestation has no protective immunity available
No protective immunity for sea lice and poultry mites
83
Other than immune response, what is another criteria for a successful vaccine?
- > 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
Subolesin
conserved protein in ticks, which can provide protection against some tick species
85
Vaccine-Salmon louse
Homologue (close relation to) of tick subolsin called my32 - found in salmon louse - Caligus rogercresseyi - vaccine - 57% decrease in lice
86
Other salmon louse potential vacine
Trypsin
87
Natural treatments for parasites
Cinammon, cassia, tea tree oils - effective in vitro
88
Bed bugs and head lice has no vaccine, why?
no vaccine b/c too high number of susceptible persons and short lived life cycle

Parasitology (10 decks)

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