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Lice and Fleas Flashcards

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1
Q
  • What is an ectoparasite?
A

o A parasite that lives outside the host like a flea
o The opposite of ectoparasites are endoparasites which live inside the host

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2
Q
  • What are the two types of ectoparasites?
A

o Facultative
o Obligatory

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3
Q
  • What is the difference between obligatory and facultative ectoparasite parasite?
A

o Obligatory is just like it sounds, the parasite requires the host to complete development.
o Facultative is the opposite, where the host is technically not necessary (optional), depending on the conditions. It can live independently or as a parasite.

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4
Q
  • What adaptions do fleas and lice have that enable them to be better ectoparasites?
A

o The body shape and size, allowing them to be small and cryptic
o The heads have smaller eyes with short antennas to prevent organ damage and detection
o The thorax is modified for grasping and jumping between hosts

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5
Q
  • What is the foraging range of fleas and lice?
A

o Fleas and lice remain in close association to their hosts

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6
Q
  • What kind of ectoparasites are fleas?
A

o Obligatory ectoparasites, they require the host. This is why their foraging range remains near the host.

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7
Q
  • What kind of ectoparasites are lice?
A

o Just like the fleas, lice are obligatory parasites, requiring the host to survive

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8
Q
  • How are the legs morphologically adapted in ectoparasites?
A

o The legs of ectoparasites are adapted in a way that enable them to attach to the host or habitat

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9
Q
  • How do claws benefit ectoparasites?
A

o Claws that cling, or grasp to the host prevent the host from scratching off the parasite

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10
Q
  • How do forelegs benefit the ectoparasite?
A

o On fleas, the front legs have large claws that allow them to hitchhike and grasp on a passing host

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11
Q
  • How do large hind legs benefit ectoparasites?
A

o The large hind legs of fleas facilitate the shuffling between hosts by enabling fleas to jump long distances

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12
Q
  • How are sensory structures morphologically adapted to benefit the ectoparasite?
A

o Like the other arthropods, the sensory structures are adapted to locate and recognize the host through multiple sensors:
 Motion
 Vibration
 Temperature
 Moisture
 CO2
 Chemical substance
 Visual cues

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13
Q
  • What are the primary sensory organs of insects?
A

o Antennas and eyes
o Antenna of blood-feeders can detect molecules emitted from the host

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14
Q
  • Why do eyes benefit an ectoparasite?
A

o Visual perception allows the ectoparasite to locate and orient itself toward the host

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15
Q
  • Why have lice and fleas morphologically adapted to have small or no eyes?
A

o To prevent damage to sensory organs
o Also, because fleas and lice do not need eyes to detect a host

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16
Q
  • Why is thermotaxis beneficial for fleas and lice?
A

o Thermotaxis is the process of locating warmth
o This warmth could mean to the ectoparasites that a warm host is present

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17
Q
  • Can fleas solely rely on thermotaxis?
A

o No, many sensory cues are required such as olfactory and movement cues. Just heat can be misleading.

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18
Q
  • How do lice and fleas detect the location of capillaries?
A

o There are receptors on the tip of the mouthparts that detect capillaries beneath the host skin

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19
Q
  • What is the classification of lice?
A

o Domain: Eukarya
o Kingdom: Animalia
o Phylum: Arthropoda
o Class: Insecta
o Order Psocodea
o Family: Pediculidae

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20
Q
  • In sucking and chewing lice, what are the three main sub-orders and which one do we care about the most?
A

o Trogiomopha
o Troctomorpha
o Psocomorpha
o We care about troctomorpha because the sub-order contains the two families Pthiridae (pubic lice) and Pediculidae (human lice)

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21
Q
  • How long have lice been around on earth?
A

o Evidence of lice can be traced back to the late Jurassic/early Cretaceous periods

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22
Q
  • What are the general characteristics of the Troctomorpha?
A

o 2 to 4 mm in the adult stage
o The head is narrower than the thorax
o Piercing mouthparts for feeding
o Wingless
o Dorso-ventrally flattened
o Reduced or lack of eyes
o Tibio-tarsal claws (claws at the end of the leg that aid in clasping to hairs and other surfaces)

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23
Q
  • What is the global distribution of lice?
A

o Lice are co-distributed with their host
o Since hosts and domestic animals are found everywhere, so are lice

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24
Q
  • In what kind of conditions are body lice found in?
A

o Crowded and unsanitary conditions. This is why lice are found predominantly on unhoused or displaced people, or in economically developing nations

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25
Q
  • What sub species of lice do humans care about for disease transition?
A

o Pediculus h. humanus (the body louse). Conversely, the P. humanus capitis is a head louse and does not transmit disease

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26
Q
  • What is the difference between P. humanus humanus and P. humanus capitis?
A

o P. humanus humanus is the body louse, while P. humanus capitis is the head louse
o They each occupy different habitats and do not mix
o P. humanus humanus is an example of how evolution has enabled the head lice to evolve with humans with the invention of clothing

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27
Q
  • What kind of life cycle do lice have?
A

o Incomplete metamorphosis (hemimetabolous) meaning that the lice look roughly the same after it hatches

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28
Q
  • What are the three stage of life in lice?
A

o Egg (nits)
o Nymph (3 stages)
o Adult

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29
Q
  • What is the difference in habitat between the adult and immature stages of lice?
A

o The habitats are the same. Both live permanently on humans clinging to the fibers of clothing

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30
Q
  • How long is the complete life cycle of the lice?
A

o 14 to 21 days

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31
Q
  • How do female lice lay eggs?
A

o By glueing 8 to 12 eggs per day onto the fibers of clothing seams, preferring underclothes
o Body lice multiply rapidly

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32
Q
  • What are the characteristics of lice eggs?
A

o 1 mm long
o Oval
o White
o Distinct operculum (cap) with small perforations for air exchange

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33
Q
  • How long does the egg stage of lice last?
A

o 5 to 11 days except it can take 2 to 3 weeks to hatch under cool conditions such as discarded clothing. After a month, the eggs will not hatch, so it is safe to wear clothing that has sat out for over a month

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34
Q
  • What does a lice nymph look like?
A

o Just like an adult but without gonads

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35
Q
  • What does a louse nymph feed on?
A

o Also blood, like an adult, as it passes through the three nymphal instars

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36
Q
  • How long does it take for lice to go through the nymph stage?
A

o 7 to 14 day to become an adult

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37
Q
  • What can alter how long it takes for a nymph to turn into an adult?
A

o How frequently the clothing is worn because this alters the temperature as well as food availability

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38
Q
  • How long will a body louse live?
A

o 20 to 30 days and the multiply rapidly

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39
Q
  • What are the characteristics of adult lice?
A

o Small (2.3 to 3.6 mm long)
 Like a sesame seed
o Pale beige or greyish color
o Wingless
o Soft
o Leathery
o Dorsoventrally flattened
o Small black eyes
o Short five segmented antenna
o Stout, well-developed legs that ends in a curved claw

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40
Q
  • What kind of mouthparts do lice have?
A

o The nymph and adult stages all have piercing-sucking mouthparts

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41
Q
  • How is the mouthpart of the lice different from other parasitic insects?
A

o The labrum, not the labium, forms a snout-like structure (haustellum) around the mouthpart

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42
Q
  • How do lice feed?
A

o The labrum will be everted (turned inside-out) exposing teeth that will grip onto the skin of the host. The stylets inside the head will penetrate the host. The ventral stylet has teeth that will pierce the skin

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43
Q
  • What is the main sensory organ of human lice?
A

o The antennae

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44
Q
  • What kind of senses do lice use?
A

o This is done through many sensory structures (sensilla)
o Olfactory
o Taste
o Thermo-hypo recognition (temperature and humidity)
o Mechanoreceptors

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45
Q
  • How do lice move?
A

o They can move rapidly on a host when it requires feeding

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46
Q
  • How long may a louse remain on a host?
A

o The louse can blood-feed off a host for 30 days

47
Q
  • How are body lice spread between individuals?
A

o From close contact between hosts (normally hosts can carry 100 lice on their body)
o This is why lice are found in overcrowded conditions and with poor hygiene where individuals rarely wash or change their clothes

48
Q
  • Where on the body may body lice be found?
A

o Areas in close contact with clothing such as underwear or waistline

49
Q
  • What is the feeding behavior of lice?
A

o Lice are solenophages meaning that they feed by sucking on the blood through a hollow dorsal stylet

50
Q
  • Which sex of lice feed on blood?
A

o Both

51
Q
  • When do lice feed?
A

o During the day and at night
o Usually, 3 to 5 blood meals a day
o The lice will sit in the clothing and go onto the host’s body to feed

52
Q
  • How do lice feed?
A

o Needlelike stylets will thrust into the skin
o Saliva will be injected into the wound to prevent clotting
o The lice will suck the blood where it will enter the stomach for digestion
o As the lice feeds, it may excrete dark red feces as well

53
Q
  • How long can a lice survive without a blood meal?
A

o One to two days

54
Q
  • Where will female lice go for oviposition?
A

o Female lice will look for a particular temperature zone that is covered
o The female will lay eggs and glue them to the hosts clothing

55
Q
  • Can oviposition occur on hair?
A

o No, it only occurs on clothing in seams and creases

56
Q
  • What louse-borne diseases do we care about?
A

o Bacterial infections:
 Epidemic typhus by Rickettsia prowazekii
 Louse-borne relapsing fever by borrelia recurrentis
 Trench fever by bartonella quintana
o Pediculosis

57
Q
  • What is a large infestation of lice on a human host called?
A

o Pediculosis, this pertains to both head and pubic lice

58
Q
  • What is the case fatality rate of typhus?
A

o 60% without antibiotic treatment

59
Q
  • What is the extrinsic incubation period of typhus?
A

o 4 to 12 days

60
Q
  • What happens during the extrinsic incubation period of typhus?
A

o The R. prowazekii will multiply in the gut epithelium of the lice. The gut epithelium cell will lyse, releasing rickettsiae into the feces of the lice

61
Q
  • What is the mode of transmission of typhus?
A

o Biological, propagative, meaning that it just multiplies since it is a bacteria developing in the louse

62
Q
  • What is the route of transmission of typhus?
A

o Stercorarian, meaning through contaminated feces. Remember in the typhus book where individuals will scratch themselves and microlesions open the wound for infection with the bacteria
o Since the epithelium cells lyse, it is no wonder that infected lice end up dying

63
Q
  • How long is the intrinsic incubation period of typhus?
A

o 7 to 14 days

64
Q
  • Does the louse have to be alive for R. prowazekii to live?
A

o No, in fact, the louse can be dead for weeks harboring live R. prowazekii. In feces, R. prowazekii, may remain for 100 days

65
Q
  • At which stage of the louse life cycle can typhus be transmitted?
A

o All stages since all stage feed on blood

66
Q
  • What are the transmission prevention methods of Rickettsia prowazekii?
A

o This is targeting the host and the vector
o To prevent transmission, methods include personal protection and dusting powders
o To target the vector, IVM methods such as education, fumigation, dusting, heat treatment of clothing and linens, and ivermectin is used
o Lice can only survive 5 days without a blood meal, so just leaving the location for over 5 days can kill off lice

67
Q
  • What is the classification of fleas?
A

o Domain: Eukarya
o Kingdom: Animalia
o Phylum: Arthropoda
o Class: Insecta
o Order: Siphonaptera
o Family: Pulicidae

68
Q
  • What kind of parasite are fleas?
A

o Ectoparasites, they reside outside of the host

69
Q
  • What is the distribution of fleas?
A

o Fleas are found all over the world with a concentration in temperate (mild or moderate) regions

70
Q
  • What family of fleas are we concerned about medically?
A

o Pullicidae

71
Q
  • How long have fleas been on this earth?
A

o Fossil records show fleas dating all the way back to the Jurassic period, 165 million years ago

72
Q
  • What are the common characteristics of the Pullicidae?
A

o 0.1 to 0.32 cm adult
o Bilaterally compressed
o Absent wings
o Powerful legs, with hind legs made for jumping
o Tough cuticle with many bristles
o Broad flattened spine
o Triangular head
o Compound or absent eyes
o Downward facing mouthparts

73
Q
  • What is the life cycle of the flea?
A

o Metamorphosis (Holometabolous)

74
Q
  • What are the life stages of the flea?
A

o Egg
o Larva
o Pupae
o Adult

75
Q
  • What is the duration of the flea life cycle dependent on?
A

o The life cycle can range from a couple weeks to month because temperature and humidity levels play a huge factor in timing

76
Q
  • What kind of environment do fleas prefer for their life cycle?
A

o 70 to 80 degrees with 70% humidity

77
Q
  • What are the characteristics of flea eggs?
A
  • What are the characteristics of flea eggs?
    o 0.1 to 0.5 mm
    o Ovoid
    o White or yellowish
    o No visible pattern
78
Q
  • How many eggs can fleas lay?
A

o 300 to 1000 eggs in batches of 3 to 25 per day

79
Q
  • What is the flea egg hatching time dependent on?
A

o The species, humidity, and temperature
o Usually, eggs hatch within 2 to 5 days
o Yet, eggs cannot survive longer than 4 weeks without hatching. So, if you get clothing that hasn’t been worn for over a month, there is no concern for fleas

80
Q
  • What are the characteristics of flea larvae?
A

o 4 to 10 mm
o Legless
o Eyeless
o Stout body setae
o Sclerotized head capsule
o Robust chewing mandibles

81
Q
  • What is the activity level of flea larvae?
A

o Very active and free living

82
Q
  • Where is the larvae habitat of fleas?
A

o Larvae hate light and will find shelter in cracks and crevices, in debris, nests or animal burrows
o Fleas can be found in dirty clothing or beds

83
Q
  • What do flea larvae feed on?
A

o Organic debris and adult flea feces

84
Q
  • How long is the larval period for fleas?
A

o 2 to 3 weeks

85
Q
  • What is the resilience of flea larvae in climates as compared to adults?
A

o If the humidity is outside the optimal range, flea larvae will die, unlike the adults

86
Q
  • What are the characteristics of flea pupae?
A

o Exarate (externally projecting appendages)
o Surrounded by a loose silken cocoon
o Sticky and the coccoon can attach to things camouflaging them

87
Q
  • What is the resilience of pupae to external conditions?
A

o The pupae stage is most resilient to external conditions

88
Q
  • How long is the pupae stage in fleas?
A

o 5 to 14 days depending on the temperature and a stimulus
o The stimulus can be vibration, like when a host moves

89
Q
  • Why do the pupae stages require another stimulus such as vibration?
A

o Remember, the fleas need to feed when adults, so if there is no vibration, there is no host, so it is safer to remain as a pupae until a host appears at the dwelling
o The adults can remain in the cocoon for 4 to 12 months, or even over a year, until living conditions are favorable

90
Q
  • What other stimuli may flea pupae require besides vibration to enter the adult stage?
A

o CO2
o Humidity increase

91
Q
  • What are the characteristics of adult fleas?
A

o Small (1 to 8 mm)
o Wingless
o Bilaterally compressed
o Heavily chitinized
o Enlarged hind legs for jumping
o One or more combs (ctenidia) as a row of enlarge, sclerotized spines

92
Q
  • What kind of mouthparts do fleas have?
A

o Piercing-sucking mouthparts
o The labrum (epipharynx) and paired serrated maxillary laciniae pierce the skin and suck the blood

93
Q
  • How can you tell the difference between adult male and female fleas?
A

o Males have an upward pointed abdomen
o Females have a downward sloping abdomen

94
Q
  • How do fleas move?
A

o Walking or running along the surface or host
o Jumping
 Fleas can somersault during the jump

95
Q
  • What kind of hosts do fleas have?
A

o Rodents
o Dogs
o Cats
o Rabbits
o Humans
o Birds

96
Q
  • How have sensory capabilities enabled fleas to exploit and locate their hosts?
A

o Stimuli have evolved to increase chance of locating a host. Such stimuli include:
 Body warmth
 Air movement
 Vibration
 Change in light intensity
 Host odor such as urine of CO2
o Sensilium, antennae, and eyes also aid in host detection

97
Q

When will a flea visit the host?

A

o Fleas will visit a host to feed

98
Q
  • What cues will initiate a flea to start feeding on a host?
A

o Body warmth
o Skin secretions
o Host odors

99
Q
  • Why are fleas anautogenous?
A

o This means that they require a blood meal to produce eggs

100
Q
  • How does a flea feed on blood?
A

o The maxillary and labial palp sensory structures help the flea find the feeding site
o Labium and labial palps will guide the stylets onto the host skin
o The stylet tip will pierce the capillary
o Cibarial and pharyngeal muscles will facilitate feeding

101
Q
  • What does it mean that the fleas are solenophageous?
A

o The fleas feed directly from the blood vessel

102
Q
  • Where will flea oviposition occur?
A

o A rodent fleas will leave the host and look for debris to deposit eggs into
o Human or domestic animal fleas will lay eggs onto the host, but the eggs are not sticky and will fall off the host. This is why in these cases eggs can be found where the host spends a large amount of time

103
Q
  • Which flea borne disease do we care about?
A

o Bacteria
o Cestoda (tapeworm)

104
Q
  • What is the causative agent of the plague?
A

o Yersinia pestis

105
Q
  • Which flea species can transmit yersinia pestis?
A

o Xenopsylla Cheopis (found worldwide)
o Oropsylla montana (found in the US)

106
Q
  • What is the case fatality rate of the plague if left untreated?
A

o 30 to 60%

107
Q
  • What are the types of plague?
A

o Bubonic
o Septicemic
o Pneumonic (person to person)

108
Q
  • What is the extrinsic incubation period of yersinia pestis?
A

o About 7 to 31 days inside the flea, but can shorten to 5

109
Q
  • What is the intrinsic incubation period of yersinia pestis?
A

o 1 to 7 days

110
Q
  • What is the mode of transmission for yersinia pestis?
A

o Propagative, meaning that they multiply (remember that this is a bacteria, no need to develop)

111
Q
  • What is the route of transmission for the plague?
A

o Regurgitative
o Yersinia pestis will multiply rapidly, blocking the gut preventing the flea from eating, forcing the flea to regurgitate its contents into the host with the blood meal
o When the flea has a blocked gut, it will have a difficult time feeding, resulting in many aggressive feeding attempts on multiple hosts, increasing transmission

112
Q
  • What are the transmissibility prevention methods for yersinia pestis?
A

o This is the relationship between the host and the vector
o Prevention methods include sanitation, hygiene, and using repellant
o Targeting the vector, prevention methods include IVM methods such as education, vacuuming, steam cleaning, IGR, reservoir control, and using insecticides
o Focus on areas where pets and humans spend the most such as bed

113
Q
  • What are the susceptibility prevention methods for yersinia pestis?
A

o This is the relationship between the vector and host
o Prevention methods include vaccines

Vector Biology (4 decks)

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