Module 6 Lice

Question 1

two groups of lice

Answer 1

1. chewing lice (birds, marsupials, placental mammals)

2. sucking lice (oblate hematophagous; placental mammals)

Question 2

lice anatomy

Answer 2

small, highly modified
no wings or eyes
dorsoventrally flattened
numerous setae
strong tarsal/tibial claw

Question 3

lice development

Answer 3

hemimetabolous (egg - X3 nymph - adult)
eggs called nits
females can produce 10 eggs / day

Question 4

phoresy

Answer 4

transportation over short distance by hitching a ride on a non-host organism

Question 5

chewing lice taxonomy

Answer 5

order Phthiraptera

suborder Mallophaga

Question 6

chewing lice characteristics

Answer 6

most diverse
obligates of birds, marsupials, placental mammals
most feed fur, hair, or skin (not blood)
not medically important

Question 7

Trichodectes canis

Answer 7

Dog Biting Louse

• chewing lice
• tapeworm uses louse as host, louse eats its eggs, humans accidentally eat the infected louse

Question 8

sucking lice taxonomy

Answer 8

order Phthiraptera

suborder Anoplura

Question 9

sucking lice characteristics

Answer 9

blood feeders
stylets consist of labium, hypo pharynx, and 2 maxillae
capable of transmitting diseases

Question 10

human body louse

Answer 10

Pedicules humanus humanus

• infest clothing and lays eggs here (exception!)
• not common in developed nations
• most important medically (only species to transmit pathogens)
• overcrowding/unsanitary conditions

Question 11

human head lice

Answer 11

Pediculus humanus capitus

• infects head/scalp
• eggs cemented to hair
• very common especially among children
• person to person contact
• no major health concerns

Question 12

plica polonica

Answer 12

matting of hair and human head lice parts
can develop secondary fungal infections
mainly in peasants

Question 13

human crab / pubic lice

Answer 13

Phthirus pubis

• large claws for gripping thick pubic hair
• transfer thru intimate contact
• very short lifespan off of host
• cause intense itching/purple lesions
• not know to transmit disease

Question 14

pediculosis

Answer 14

infestation of 1 of 3 species
skin becomes tough/pigmented
weariness/irritability caused by repeated injection of saliva

Question 15

epidemic typhus

Answer 15

• caused by infection of Rickettsia prowazekii
• louse-borne fever
• Rickettsia invade gut of louse then burst cells and kill louse
• infection occurs when feces of infected louse is rubbed into abrasions
• bacteria can live up to 60 days in feces so lice usually not found on human when he/she gets sick

Question 16

louse-borne relapsing fever

Answer 16

• caused by borrelia recurrentis
• parasite invades body of louse and kills it (but doesn’t reach feces)
• infection occurs when the louse is rubbed into abrasions

Question 17

trench fever

Answer 17

• caused by Bartonella quintana
• parasite multiplies in lice gut but doesn’t kill it
• parasite is voided in feces
• infection occurs when feces is rubbed into abrasions

Question 18

body louse control

Answer 18

limit contact with infested people
wash bedding/clothing in hot water
insecticides

Question 19

head lice control

Answer 19

shampoos, lotions (but only kills adults)
repeated treatments needed
use fine toothed comb

Question 20

public lice control

Answer 20

change bed linens
shampoo
shaving of hair
awareness of sexual partner