Download Quyen Vu Lice Outbreaks: Transmission and Avenues for Treatment

Quyen Vu
Lice Outbreaks: Transmission and Avenues for Treatment
Introduction & Title Slides (Slides 1, 2)
Goal/Thesis (Slide 3)
1. Understanding the differences between three types of lice: how to tell them apart, and the
relevant/appropriate strategies for treatment and prevention for each type. (Mostly in the first
part of the presentation)
2. Humanitarian crises: how body lice are a serious issue due to disease risk. Three main diseases
carried by body lice. High risk for mortality. Explained in more detail in a Burundi case study.
Vector Biology (Slide 4)

Head lice found anywhere on the head (typically hair, but also can be found on the
eyebrows.)

Body lice: typically found on the clothing, except when they need a blood meal. They
then move to the skin (but usu found on the clothing NOT the skin)

Pubic lice: usu found in pubic hair but are adapted to any other type of coarse hair
(armpit region etc.)

All of the lice types are six-legged

Differ on the basis of morphology (see pictures, especially pubic lice), where they can be
found as discussed above, and size

Photo Credit and Source: CDC http://www.cdc.gov/parasites/lice/index.html
Vector Biology (Slide 5)

Ectoparasite: lives on surface of host, as opposed to inside the body (endoparasite) as
with many other parasites we’ve seen. Do need blood meals to survive.
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
Move by crawling: as opposed to flying or hopping, which affects the control and
prevention measures needed.

Feet are specifically adapted to human hair (cannot survive for that long if they fall off a
human.) They can only live 1-2 days if they fall off of a human host. See photo on the top
right of the slide for a zoomed-in look at the hooks on louse feet adapted to clinging to
human hair.

Humans as only host. There is no animal reservoir, which makes control measures
different and potentially simpler than other parasites.

Photo Credit and Source: CDC
http://www.cdc.gov/parasites/lice/head/gen_info/faqs.html
Lice Life Cycle (Slide 6)
1. Egg/nit

The egg/nit is usually located no more than 1/4 inches from the base of the human hair
scalp.

It's attached by a sticky glue-like substance secreted by the adult louse, which is what
allows it to stick to the human hair.

Takes 8-9 days to hatch.
2. Nymph

There are three molting stages. Takes the nymphs approximately one week in total to
move into the adult stage.

The nymphs must take a blood meal in order to move on the next molting stage (therefore
need three blood meals in total.)
3. Adult stage.
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
Can live up to 30 days on the human host. Die within 1-2 days without the human host.

All adult lice need a blood meal in order to survive (nutrients). Females need it in
particular for oviposition.

All of these stages are SMALL! See reference photo of the stages.

Source: CDC http://www.cdc.gov/parasites/lice/body/biology.html
History of Lice & Humans (Slide 7)

Humans host two genera of lice: Pediculus (also found in chimpanzees) and Phthirus
(also found in gorillas)

Host-parasite associations are shown on the phylogenetic tree on the slide

Study looked at DNA, suspecting that lice species distribution is related to speciation
events between humans and primates

The chimpanzee and human Pediculus species split off from each other ~6 million y/a
(approx same time as chimps and humans split off from each other.)

Phthirus species (gorillas and human lice) split off from each other 3-4 million years ago,
while the hosts (gorillas and humans) split off from each other far before that: 7 million
y/a.

Takeaway point: Lice have been around for a long time!! They are closely linked to our
own species evolution.

Source (slide information and figure): Reed et al. BMC Biology.
History of Lice & Humans (Slide 8)
Photo Credit: iStockphoto (http://www.istockphoto.com/stock-photo-4127789-bushmenpaintings-and-rock-art.php)
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
Body lice are typically found on the clothing and not on the skin (discussed previously in
lice behavior)

This means that body lice probably originated close to when humans started using
clothing!

Find when body and head lice split = find approx date when humans started using
clothing (anthropologically interesting)

DNA sequencing: found ~72,000 years ago. Pretty recent.

Skepticism: there's little other concrete evidence on clothing. but we know that
Neanderthals lived ~500,000 years ago in cold places (unlikely that they didn't have
clothing then...)

Source credit: Travis, Science News.
Lice in the News (Slide 9)

46 results in Google News (search done March 8, 2012). as compared to 1600 for "E Coli
outbreak"!

Points to the well-controlled nature of lice in the United States

Stories mostly related to elementary schools and some college campuses. But nothing
sounds life-threatening or scary (sensationalist reporting with some of the other disease
outbreaks, e.g. nothing like "plague outbreak"!)

A few editorial tone type pages, like "how to keep your kids lice free" -- very everyday,
mundane type of tone. Lice just an inconvenient part of life...
Symptoms (Slide 10)
Symptoms associated with head lice: mostly due to the lice biting (people are somewhat allergic
to the bite.) = itching
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
Difficulty sleeping: This is due to vector biology -- the lice are more active at night, so
biting and itching are more likely to occur at night.

Sores and secondary bacterial infection: Caused by scratching the itchy bites (and
bacteria that's on the fingers or on the scalp can get into the bite.) This is a minor
symptom and isn't observed as often as the common itching!

Photo Credit: Medicimage http://children.webmd.com/ss/slideshow-lice-overview; Photo
Researchers Inc.
Symptoms Continued (Slide 11)

Body lice typically characterized by intense itching (more so than head lice usually
because there are more lice.)
o If infection is ongoing for a long period time (lots of lice bites), there can be skin
discoloration and thickening in the areas with lots of bites.
o As with head lice, secondary bacterial infection is possible from scratching =
open wound, bacteria can enter from hands or surrounding skin area
o Red rash appears where the lice have bitten.

Pubic lice: Itching and burning of the pubic area.
o Infection possible (like the other types of lice)
o Like head lice: itching can be worse at night b/c that's when the lice are more
active.

Photo Credit: iStockPhoto, CDC
Disease (Slide 12)

Important to emphasize here that head and pubic lice DO NOT SPREAD DISEASE!
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Their symptoms are a nuisance and inconvenient, but they do not cause clinically serious
symptoms or fatalities.

Body Lice are associated with a variety of really serious bacterial diseases (list on slide)

Photos on right show lesions from epidemic typhus

Photo Credit: Raoult et al.
Body Lice Diseases (Slide 13)

Louse-borne relapsing fever: B. recurrentis.
o High case-fatality (10%) in WWII; mortality is 30-70% without tx
o More severe than the tick-borne version.
o Often found in epidemics amid poor-living conditions (and in war, like WWII) -developing world.
o Spread when an uninfected human crushes an infected louse. B. recurrentis is
spread via mucous membranes and then invades bloodstream
o No animal reservoir
o Can alter the protein surface (causes relapses "relapsing fever")

Trench fever: B. quintana
o soldiers in WWI infected w/ Trench Fever.
o rarely fatal
o symptoms serious: acute fever onset (five days), headache, myalgias, rashes,
splenomegaly (less common)

Epidemic typhus: R. prowazekii
o Significant contributor to worldwide mortality (millions) before antibiotic
treatment
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o Classified as a category B bioterrorism agent (second most severe category):
moderately easy to disseminate
o More info on this later in the presentation!!

Source: CDC, Pittendrigh et al. (see reference section at end of this presentation)
Diagnosis by Direct Visualization (Slide 14)

Definitive diagnosis only happens with direct observation of live nymphs or adult lice

Finding nits is suggestive of infection but not definitive
o Nits are very small, and it is difficult to correctly identify them
o Are often mistaken for other things in the hair: dandruff, droplets of hairspray,
etc.
o Old nits can persist in the hair for a long time after infection (due to the sticky
substance holding them to hair), so finding these old nits only indicates an old
infection. Not necessarily an active infection that is still ongoing.

Lice are small, quick, and avoid the light (are most active at night.)
o Use a fine-tooth comb and magnifying glass to find them

In body lice, because lice are not normally found on the skin, you should look for them
on the clothing. They can typically be found in the seams (along with nits.) See photo of
this on the slide.

Photo
Credit:
CDC
(bottom
two)
+
Medline
http://www.nlm.nih.gov/medlineplus/ency/imagepages/17207.htm
Epidemiology & Risk Factors (Slide 15)

Head Lice: "head to head" transmission
Plus
(ADAM):
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o Lice do not live very long (1-2) without a human host. And they are not adapted
to walking along smooth surfaces that do not have human hair.
o Therefore transmission really only occurs with direct "head to head" contact
o Typically occurs more often w/ children and in schools
o Pretty prevalent among children in the United States
o Not associated with poor hygiene. Can really happen anywhere that head to head
contact occurs.
o Girls at a higher risk than boys, this is thought to be b/c of more social contact,
playing with hair, etc.
o African Americans at lower risk because the lice are specifically adapted to
clinging the best to certain types of human hair.
o Photo Credit: Photo: iStockPhoto (http://0.tqn.com/d/childparenting/1/0/5/B/-//iStock_children_group_heads_touching.jpg)
Epidemiology & Risk Factors Cont (Slide 16)

Pubic lice, aka. crabs
o Current estimates are worldwide prevalence of 2%, although it is generally
difficult to find data and statistics on lice.

Likely due to underreporting, b/c not considered a serious condition and
easily treated. For pubic lice because it's considered an STI this could also
lead to underreporting.
o Spread through sexual intercourse
o Like the other types of lice: can be spread indirectly via belongings but this is
unlikely because the lice do not live long when separated from a human body.
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o Because pubic lice are usually only found on adults, finding them in children is
potentially an indication of sexual abuse

(Could also simply be caused by close and direct contact. But sexual abuse
is a possibility here.)
o Pubic lice also not associated with hygiene. Therefore can be found worldwide!
Epidemiology & Risk Factors Cont (Slide 17)

Unlike head and pubic lice, body lice is associated with situations of poor hygiene (where
people can't bathe, and where they don't have a change of clothes)

Particularly relevant to humanitarian crises and other events that cause people to be
displaced and living in close quarters.

Crowded living conditions promote lice transfer from one person to another

Normally this would be remedied via regular bathing and a change of clothes, but this is
not possible in these crisis situations

In the United States, body lice only found among populations w/ little access to sanitation
and hygiene
o In jails and among transient populations
o Still, these are small pockets of the population and are relatively easy to treat w/
only small outbreaks.

Photo
Credit:
Getty
Images
Doug
Menuez
(http://cache1.asset-
cache.net/xc/SO000531.jpg?v=1&c=IWSAsset&k=2&d=EDF6F2F4F969CEBDB62146
EFFEB6FBBC34C14AC0481B67D45168F001BDD89321)
Epidemic Typhus (Rickettsia prowazekii) (Slide 18)

Basic info about bacteria and its animal reservoir in North America
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
First described in Italy in 1083: It's been around for a long time! And has been a
significant contributor to mortality throughout history

In 1812: more French soldiers under Napolean died because of typhus infection than
were killed by Russian forces

WWI: millions of deaths in Russia, Poland, and Romania.
o Delousing stations set up for control effort
o Fatality 10-40% of those infected.
o 1918-1922: 20-30 million cases total

WWII: spread along w/ armies (North Africa, Egypt, Iran)
o Particularly devastating in Nazi concentration camps
o Vaccine developed during this time
o DDT spraying (will elaborate on this more later in the presentation)

Featured in popular literature, often to highlight poor living conditions (orphanages, jails,
etc.) Examples given on slide

Sources: Weindling, P. (see references)

Photo
Credit:
WWII
US
Medical
Research
Centre
http://med-
dept.com/testimonies/george_mcl.php
Epidemic Typhus (Rickettsia prowazekii) (Slide 19)

The different names for this disease speak to the sorts of environmental and living
conditions associated with this disease.

As previously mentioned, this is one of the 3 diseases spread by body lice (ONLY body
lice and not head or pubic lice!!)
1. Transmission occurs when an uninfected louse feeds on an infected human
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2. R. prowazekii bacteria develops inside the louse's gut (the body louse is a biologic vector
3. R. prowazekii excreted in louse feces
4. The infected louse then bites a new uninfected human, who scratches the bite because it's
itchy. This rubs the feces into the open wound, causing the transmission event.

Clinical symptoms (similar to some of the other diseases transmitted by body lice):
severe headache, sustained high fever, rash, muscle pain

Can be treated with antibiotics
o However important to note that mortality is really high!! 10-60% without
treatment
o In these crisis situations, unlikely that infected people will have access to
antibiotics.
Humanitarian Crisis in Burundi (Slide 20)
Transition from a discussion of epidemic typhus in general into a specific case.
Setting the context: Burundi very unstable due to civil war 1993-2005

Began with ethnic tensions between Hutus and Tutsis (although this was an arbitrary
designation left over from Belgian colonization)

Supposed differences in appearance between the groups, but difficult to tell

Violence began when a Hutu elected president was assassinated by Tutsi extremists

Other countries also had violence between Hutus and Tutsis (Rwandan Genocide):
overall very unstable time for the entire region.

Refugees (in other countries) and internally-displaced persons (in Burundi) recent
estimates
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o ~100,000 IDP's in Burundi
o 352,640 in Tanzania; 4400 in Rwanda; 17,777 DRC

Source: Globalsecurity.org, CIA
Jail Fever Outbreak in Burundi (Slide 21)

A nurse observed clinical symptoms in several patients, unsure about diagnosis
o Symptoms: abrupt fever up to 40 degrees C + rash
o Body louse outbreak also going on in the jail at the same time
o Serologic testing (samples from nine males), confirmed R. prowazekii (typhus)
diagnosis
o Lice were also obtained from the clothing of several patients. Confirmed R.
prowazekii in the lice.

Poor jail conditions noted as risk factors in the paper.

This confirmed outbreak particularly significant due to the instability of the country and
region
o Potential link (not confirmed) with a larger outbreak occurring in the country
o This is particularly worrisome because jail populations are constantly in flux in a
country that is undergoing war and violence
o Outbreak spread to larger population very possible

Photo Credit: Photo Credit Image by Flickr.com, courtesy of the_kid_cl

Source: Raoult et al.
Large Epidemic Typhus Outbreak (Burundi) (Slide 22)

Jail outbreak in Raoult et al study: cases late 1995 and 1996

Potential connection with larger regional outbreak in 1997: largest outbreak in 50 years!
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o Very likely to be connected with general upheaval in the region
o Refugee camps in the province where initial cases reported
o Because of refugee flow, risk identified in neighboring countries of Zaire and
Rwanda

Efforts by the WHO to treat cases w/ doxycycline (antibiotic) -- epidemic contained.

Source: WHO
Lice Treatment (Slide 23)
Define terms

Pediculicidal: kills live lice

Ovicidal: kills eggs
There are several over the counter medications available.
For all treatments, it is important to remember to re-treat after ~9 days in order to make sure you
kill the nits in addition to the adults/nymphs.

Pyrethins are derived from chrysanthemums. Approved for kids > 2 y/o

Permethrin 1%: tends to be the most commonly used. Brand name "Nix" shampoo. Safe
for kids > 2 months

Photo Credit: Photo Credit: Photononstop http://children.webmd.com/ss/slideshow-liceoverview
Lice Treatment (Continued) (Slide 24)
Prescription medications available in addition to OTC, these tend to be stronger and also have
more side effects.
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
Malathion: an organophosphate. Kills eggs in addition to adults (a more "complete"
treatment). Use should be limited because it can be irritating to the head and scalp. Use
recommended for children > 6 y/o. It's also flammable.

Benzyl alcohol lotion: Recommended for children > 6 mo. It kills the adults but not the
eggs. Can cause irritation.

Lindane shampoo 1%: Can cause neurologic toxicity in immunocompromised or
vulnerable patients: premature infants, women pregnant or breastfeeding, HIV patients,
people w/ sores, elderly, and underweight people (<110 lbs)
Which treatments should be used? (Slide 25)

First line treatment: OTC (Permethrin 1%).

If this doesn't work: move to prescription options
o Malathion, Benzyl alcohol (make sure to re-treat to kill the nits)
o Lindane not currently recommended because of potential neurologic effects.
Should only
be used if none of the other treatments work! (Last resort
treatment)
Photo Credit: Glow Images http://children.webmd.com/ss/slideshow-lice-overview
Additional Lice Treatments (Slide 26)
o Oral ivermectin study: 812 patients assigned to ivermectin and malathion (existing
topical medication.) Primary end point = absence of lice on day 15 of treatment.
o 97.1% of ivermectin group patients lice-free on day 15; 89.8% of the malathion
group
o Oral ivermectin: twice a day, given on days 1 and 8.
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o Topical 0.5% malathion lotion: 400 micro g / kg of body weight, given days 1 and
8
o Previously, some studies found ivermectin had limited efficacy. FDA did not
approve...until recently!
o Sklice lotion: one application. Clinical trials very successful: 76.1% of Sklice-treated
patients lice-free without nit-combing after 2 weeks, 16.2% in placebo group.
o Side effects (<1% patients): conjunctivitis, eye irritation, dandruff, dry skin, skinburning
o Applied for 10 mins. No longer need to comb for nits!
o Source: Chosidow et al.; Hand, L.
Additional Lice Treatments (Continued) (Slide 27)
o This type of treatment is the most relevant to humanitarian crises (and diseases
associated with body lice).
o Fumigation (chemical spraying) + dusting w/ chemical insecticides
o Can cover a LARGE tract of land all at once
o Makes the most sense when distribution of medications and antibiotics is
impractical or not feasible.
o First used in WWII: used dust anywhere that can come into contact w/ lice and an
infected person (the patient themselves, as well as objects in contact, and other
members of the household)
o The success of the dusting method is related to vector biology: lice are not able to
hop or fly. The dust can get into crannies and spaces that the lice are able to be,
and thus reaches them effectively.
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o DDT dusting found to be highly effective: lice mortality of 99% from 1% DDT; lice
mortality of 96% from 0.1% DDT.
o Photo Credit: user otisarchives4 on flickr.
http://www.flickr.com/photos/27337026@N03/2590000499/sizes/m/in/photostream/
o Source Credit: Blanton, F.; Lepes, T.
Prevention (Slide 28)
o Avoid methods of transmission: particularly important for the types of lice more
prevalent in the United States (head lice and pubic lice)
o Head lice: avoid "head-to-head" contact, particularly with small children who are
in school. Take special precautions if the children have recently been exposed to
another person with lice (e.g. if a note comes home saying there was a lice
outbreak.)
o Pubic lice: practice safe sex and/or avoid sexual contact w/ an infected person
o Body lice: is easy to prevent w/ regular and improved hygiene/sanitation
o A regular change of clothes (body lice like to spend time in the clothing)
o Regular bathing: lice are unable to swim
o Laundry & soaking in hot water: unlikely that lice will be spread through contact w/
objects. However, lice and eggs are killed at exposure of 5 mins and temps > 128.3
degrees F. This is an extra precaution you can take.
o Domesticated pets do not spread lice. Lice are very host-specific (human lice only affect
humans.)
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o Photo Credit: Photocredit: iStockPhoto (http://www.istockphoto.com/stock-photo19058410-applying-liquid-soap-for-hand-washing.php); Peter Cade / Iconica
(http://children.webmd.com/ss/slideshow-lice-overview)
Prevention in Schools: No-Nit Policy Controversy (Slide 29)
o No-Nit Policy developed by National Pediculosis Association as a program to prevent
head lice transmission in schools
o Focuses on objective criteria and strict guidelines: if a child has nits, they go
home
o Is a strong education and prevention program
o American Academy of Pediatricians have issued guidelines opposing this strict no-nit
policy
o Effects of the strict no-nit means that children have to stay home from school,
even when the clinical effects of head lice are not that serious.
o The AAP focuses on safe treatment of head lice (management of chemicals,
supervision, etc.)
o Advocates "common sense": safe treatment, a reasonable amount of preventative
measures. Subjective based on the teachers and caregivers.
o Photo Credit: National Pediculosis Association
Summary Slide (Slide 30)
Communication with Expert
I sent the following email to Dr. Peavey but did not receive a response (most likely due to time
constraints...)
Quyen Vu