Lecture 2.2 - Lice Flashcards
What is the order of lice and about how many species are there?
Order: psocodea
about 11,000 species
What three lice are harmless to humans?? (book and bark lice)
pscomorpha
trogiomorpha
liposcelidae
What do these harmless lice eat and what can they damage?
eat moss, lichen, organic material on trees
booklice can damage books by eating glue
Phtiraptera
parasitic lice
What is the host of parasitic lice?
strict host association (obligately ectoparasitic) - only limited number of closely related species or even a single species of host
often highly specialized to feed on specific hosts (size, color, morphology, behavior)
What is the pigeon Lous (columbicola Columbae) size is influenced by what?
via selection on the ability to hide between feather barbs and resist preening
only live ON host rather than inside
What is the haematomyzus sp. (rhynchophthirina) specialized to feed on?
to feed on elephants and warthogs
The 1st fossil wasn’t described until 2003, dates to 44 mya, at the time this was the youngest order of insects. Genomic data suggested that the group is at least 15 million years old. What does this tell us?
feathered dinosaurs may have harbored lice
Pediculidae
class of lice that we focus the most on
What does Pediculus schaeffii feed on?
chimpanzees, bonobos
What does Pediculus mjobergi feed on?
new world capuchin, howler, spider monkeys
What does Pediculus humanus humanus feed on?
human body louse (cooties)
What does Pediculus humanus capitis. feed on?
human head louse
Do the four pediculus lice stated feed on other mammals?
NO they are obligate primates who feed on specific mammals
Where are head lice found?
almost exclusively on the scalp, only lay eggs in hair
Where is body lice found?
rarely on the head, primarily lay eggs on clothing
P. h. humanus and P. h. capatis are obligate blood feeders and require multiple blood meals a day to survive, how long can each survive off of the host?
P. h. humanus: can survive 5-7 days off the host
P. h. capatis: can survive 1-2 days off the host
Can P. h. humanus and P. h. capatis mate?
in captivity yes
in nature no
P. h. humanus and P. h. capatis diverged from a common ancestor about 30,000 to 110,000 years ago.
What may have started during this time to contribute to the divergence of these species?
we started wearing clothes
P. humanus capitis transmission:
direct head-to-head contact
or
sharing combs, brushes, and head gear
Felicola subrostratus
cat lice
chewing, eats skin
Trichodectes canis
dog lice
chewing
Linognathus setosus
dog lice
sucking lice (blood feeding)
Can you get lice from pets? Can pets get lice from you?
no and no
lice are highly host specialized and generally do not have distantly related hosts
P. humanus humanus transmission:
exposure to bedding/clothing infested with lice
thrives in crowded, unsanitary conditions
can survive several days off of host (they are only the the host to feed and will retreat)
What is easier to spread P. h. humanus or P. h. capitis?
P.h. humanus due to the fact it can survive several days off of host making it easier to spread
How do P.h. humanus feed?
with their tarsal claws that allow attachment to host
Pthirus pubis
pubic lice
What is the only genus in the order of Pthiridae that has two extant species?
Pthirus (pubic lice)
What are these, and what do they feed on?
Pthirus pubis:
Pthirus gorilla:
Pthirus pubis: human pubic or crab louse
Pthirus gorilla: gorilla louse
What does Pthirus pubis do?
infects pubic hair, body hair (esp. in men), sometimes eyelashes (rare)
What is the transmission of Pthirus pubis and how long can it survive off of host? What does it cause?
close contact (sexual)
only about 24-48 hours off of host (rare to find off host)
causes itching and irritation (reaction to louse saliva)
Is Pthirus pubis linked to disease transmission?
no
How did Pthirus jump from gorillas to humans?
occupation of gorilla nests by humans
gorilla hunting
What is Pediculosis?
condition of being infested with lice
considered to be a disease itself
What is pediculosis associated with?
allergic reaction to bites: itchy, distracting, sleep impairment
dermatitis and secondary infection in severe cases (in worst cases, fecal material and matted hair provide medium for fungal growth, hair becomes cemented together in solid mass: aka plica polonica)
What are the treatments to Pediculus humanus capitis?
launder all bedding/clothes affected
treat with OTC insecticidal shampoo
remove nits (combing)
What are the treatments to Pediculus humanus humanus?
showering with regular soap
launder all bedding/clothes affected and dry in machine
What are the treatments to Pthirus pubis?
insecticidal lotions
ivermectin (oral)
launder all bedding/clothes affected and dry in machine
Is pubic lice considered an endangered species?
it depends on the location
decline is correlated with pubic hair removal; however, some countries and cultures do not believe in that and lice is not endangered in those places
What is the medical significance of each lice we have learned about?
P. h. capitis:
P. h. humanus:
Pthirus pubis:
P. h. capitis: no known pathogens transmitted, nuisance pest
P. h. humanus: Rickettsia prowazekii, causative agent of epidemic typhus
Pthirus pubis: no known pathogens transmitted, nuisance pest
What are the three distinct typhus diseases?
1) Scrub typhus
2) Murine typhus
3) Epidemic typhus
Scrub typhus-
Agent:
Vector:
Sylvatic host:
Symptoms:
Treatment:
Prognosis:
Agent: Orientia tsutsugamushi-alphaproteobacterial, formerly Rickettsia
Vector: Trombiculidae, aka chiggers (mites)
Sylvatic host: rodents
Symptoms: fever, headache, cough, GI issues (early stages) pneumonitis, encephalitis, myocarditis (later stages)
Treatment: doxy/tetracycline
Prognosis: often fatal if untreated, effectively treated with antibiotics
Murine typhus-
Agent:
Vector:
Sylvatic host:
Symptoms:
Treatment:
Prognosis:
Agent: Rickettsia typhi -Alphaproteobacteria
Vector: bites and feces of oriental rat flea (Xenopsylla cheopsis), cat flea (Ctenocephalides felis)
Sylvatic host: rodents, cats, possums
Symptoms: fever, headache, rash
Treatment: doxy/tetracycline
Prognosis: rarely fatal, even if untreated, effectively treated with doxycycline
Epidemic typhus-
Agent:
Vector:
Sylvatic host:
Symptoms:
Treatment:
Prognosis:
Agent: Rickettsia prowazekii-Alphaproteobacteria
Vector: feces of body louse (P. h. humanus/corpis)
Sylvatic host: flying squirrels (Glaucomys Volans)
Symptoms: fever, headache, rash, shortness of breath
Treatment: Vaccine, doxy/tetracycline
Prognosis: about 40% fatality rate if untreated
What is the epidemic typhus associated with?
refugees
war (soldiers in close quarters)
jails
homelessness
Which typhus do some humans serve as asymptomatic carriers serving as reservoirs?
epidemic typhus
What has shaped history?
typhus
430-427 plague of Athens
1489 Grenada war
17th-18th century Gaol fever
1853-1856 crimean war
1914-1918 WWI
1939-1945 WWII
2002 Fulton county resident infected
How many reported cases of typhus in the US since 1976 has there been?
47
Howard Taylor Ricketts
American biologist
identified that ticks vectored the causative agent of Rocky Mountain spotted fever (FIRST to do so)
died while investigating an outbreak of murine typhus
Henrique da Rocha Lima
identified R. prowazekii as the causative agent of epidemic typhus (he did this with Prowazek)
Stanislaus Josef Mathias von Prowazek
contracted and died from typhus while working with with da Rocha Lima (which is why it is named after him)
What is the life cycle of Rickettsia prowazeckii in louse?
acquire bacteria while feeding on infected human, bacteria invades gut of louse, bacteria multiplies and bursts into gut cells releasing bacteria back into the gut of the lumen where the louse eventually dies
bacteria is then transmitted to another person in louse feces or body fluids if the lice is crushed, bacteria then enters the human through bite site, scratched into the skin (not infected from the bite but the bacteria getting in from area where bite occurred)
What is the life cycle of Rickettsia prowazeckii in humans?
invades vascular endothelial and/or immune cells, escapes vacuoles, replicates in the cytosol killing cell, invades neighboring cells
results in compromised vascular tissue, leading to edema, hypotension, hypovolemia (eventually organ failure)
Ricketts understood that ticks were the vector of RMSF, but he couldn’t figure out if it were a virus or a bacterium due to the fact he could not culture it. Why?
they are obligate intracellular and cannot be cultured in isolation from host cells
diverse, largely arthropod associated and many have symbiotic partners
alphaproteobacteria, the same lineage that mitochondria evolved from
What family are black flies in?
Simuliidae
Where do black flies like to live and lay their eggs?
like fast flowing water
eggs laid on aquatic substrates (cold, fast moving water)
How do black fly larvae feed?
filter feeders (cephalic fans enable filter feeding)
What do black flies do?
1) hook on posterior of the abdomen
2) pupae spin silk cocoons and anchor to substrates (respiratory filaments allow for breathing)
3) adults emerge using a bubble of air and pop out of the water
What do adult black fly females need for eggs and how do males find females?
females: often require a blood meal to develop eggs (anautogeny)
males: DON’T use pheromones, primarily use vision (can distinguish female up to 50 meters away
How might host-seeking be different for a black fly vs. a louse?
lice: feed on host
black fly: male feeds on nectar female feeds on blood AND nectar
What systems do flies rely on to find hosts?
olfactory: host odor and CO2
visual: attracted to blue, repelled by white
Preferred hosts vary by species, but many feed on what?
mammals
Why do black flies feed on blood?
for production to develop eggs
blood proteins -> yolk proteins
What is autogeny?
they do not have a blood meal before reproduction
What is primiparous autogeny
yes they feed on blood before reproduction but not the first cycle
What is anautogeny?
they always have a blood meal before reproduction
Where do primiparous and autogenous black flies get their protein for yolk?
pollen
How might autogeny/anautogeny influence disease transmission?
anautogeny is a better disease vector they have multiple opportunities to pick up a parasite
primiparous are also good disease vectors
What is larval feeding like for large river species of black flies?
larval food is abundant and high quality
What is larval feeding like for small stream species of black flies?
larval food less abundant/lower quality in clear water
How do black flies blood feed?
they create lacerations then lap up host blood - pool feeding
once they start feeding they are hard to dislodge and will persist
different species target different regions of the body
Can you find black flies indoors?
not really
diurnal, almost exclusively outdoors
