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Lice Outbreaks: Transmission and Avenues for Treatment Quyen Vu. Goals. Understand the main differences between the three types of lice affecting humans Morphology and vector biology Disease risk Most effective treatments Prevention strategies

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Lice Outbreaks: Transmission and Avenues for Treatment Quyen Vu

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  • Understand the main differences between the three types of lice affecting humans
    • Morphology and vector biology
    • Disease risk
    • Most effective treatments
    • Prevention strategies
  • Learn about the disease risks associated with body lice, especially in situations of humanitarian crisis
    • Burundi case study
    • Appropriate control strategies
vector biology
Vector Biology

Three types of lice:

  • Head lice: Pediculushumanuscapitis (2-3 mm long)
  • Body lice: Pediculushumanushumanus (2.3-3.6 mm long)
  • Pubic lice (crabs): Phthirus pubis (1.1-1.8 mm long)
vector biology5
Vector Biology
  • All three types of lice:
  • Are ectoparasites: lice live on the surface of the host
  • Move by crawling, as opposed to flying
  • Have humans as their only host
  • Have similar life cycles

Head Lice

Body Lice

Pubic Lice

lice life cycle
Lice Life Cycle
  • Lice stages:
  • Egg/nit
  • Nymph (3 molts)
  • Adult
  • Both nymphs and adults take blood meals from the human host.
history of lice humans
History of Lice & Humans
  • DNA evidence suggests that human lice split off from gorilla lice approximately 3-4 million years ago
history of lice humans8
History of Lice & Humans
  • Pediculushumanuscapitis(head lice) and Pediculushumanuscorporis(body lice) diverged when humans started using clothing
  • Used DNA sequencing to estimate how long ago common ancestors lived
  • Body lice usually found in clothing
  • Diverged ~72,000 years ago
lice in the news
Lice in the News
  • Outbreaks do show up in national news!
  • Not severe: most of the stories related to school and campus outbreaks
  • “Head Lice Epidemic Closes Anderson Schools” 1973
  • “Lice Outbreak Cancels Classes” 1980

Head Lice

  • Itching
  • Difficulty sleeping
  • Sores and secondary bacterial infections from scratching
symptoms continued
Symptoms (Continued)
  • Body lice: Intense itching
    • Skin discoloration/thickening
    • Secondary bacterial infection also possible from prolonged scratching
    • Red rash
  • Pubic lice “crabs”: Itching
  • Head lice: does not spread disease
  • Body lice spreads bacterial disease!
  • Pubic lice: does not spread disease
body lice diseases
Body Lice Diseases
  • Louse-Borne Relapsing Fever (Borreliarecurrentis)
    • 1 Million cases observed in North Africa (WWII)
    • Case fatality rate 10%
    • Related to tick-borne relapsing fever (B. duttonii)
  • Trench Fever (Bartonellaquintana)
    • Less serious, rarely fatal
    • Characteristic five-day fever
  • Epidemic typhus (Rickettsia prowazekii)
diagnosis by direct visualization
Diagnosis by Direct Visualization
  • Observation of live nymphs or adult lice.
  • Finding nits is suggestive of infection but not definitive.
  • Use fine-tooth comb and magnifying glass.


epidemiology risk factors
Epidemiology & Risk Factors

Head lice: “head-to-head” transmission

  • 6-12 million cases/yr in the United States in children age 3-11
  • Found worldwide
  • Girls at higher risk than boys
  • African Americans lower risk than other racial groups
epidemiology risk factors continued
Epidemiology & Risk Factors (Continued)

Pubic Lice (“Crabs”):

  • Current worldwide prevalence estimated 2%
  • Spread through sexual contact and is considered an STD
  • Can be spread through fomites: contact with clothing, linens, and towels belonging to an infected person.
  • Pubic lice found on children can be an indicator of sexual abuse.
epidemiology risk factors continued17
Epidemiology & Risk Factors (Continued)

Body lice: humanitarian crises & disenfranchised groups

  • Associated with poor hygiene and crowded living conditions
  • In the United States: prisons, homeless transient populations
epidemic typhus rickettsia prowazekii
Epidemic Typhus (Rickettsia prowazekii)
  • Pathogen type: gram negative bacteria
  • In North America, animal reservoir is the flying squirrel
  • Was first observed and described in Italy in year 1083
  • Typhus epidemics associated with extremely high mortality throughout history
    • Civil War
    • WWI: 3 million deaths in Russia
    • WWII
  • Featured in literature
    • Jane Eyre, Lolita, Doctor Zhivago, among others!
epidemic typhus rickettsia prowazekii19
Epidemic Typhus (Rickettsia prowazekii)
  • Also known as: “jail fever”, “camp fever”, “famine fever”
  • Body lice
  • Transmission:

1. Louse feeds on human infected w/ R. prowazekii

2. R. prowazekii grows in louse’s gut

3. R. prowazekii excreted in louse feces

4. Human scratches louse bite, rubs feces into wound

  • Symptoms:
    • Severe headache, sustained high fever, rash, muscle pain
  • Can be treated with antibiotics
humanitarian crisis in burundi
Humanitarian Crisis in Burundi
  • Civil war ongoing 1993-2005
    • Ethnic divisions: Hutus, Tutsis
    • Hutu president was assassinated by Tutsi extremists
    • Further aggravated by regional violence between Hutus and Tutsis (Rwandan Genocide)
    • Many refugees and internally-displaced persons
    • Total estimated death toll: 300,000
jail fever outbreak in burundi
Jail Fever Outbreak in Burundi
  • Nurse observed clinical symptoms in prisoners (1997)
    • Abrupt fever of up to 40 degrees C.
    • Serologic testing: R. prowazekii confirmed.
    • Body lice in jail
    • Conditions noted: “cold weather, poor hygiene, poverty”
    • “Confirmation of a typhus outbreak in Burundi is of concern, given the relative political instability…”
large epidemic typhus outbreak burundi
Large Epidemic Typhus Outbreak (Burundi)
  • Jail outbreak in 1995-1996 predates large outbreak in Burundi 1997
  • World Health Organization identified 24,000 cases in Bujumbura Province (Burundi).
    • Cases were later identified in six provinces
    • Largest outbreak in 50 years
    • Risk identified: Burundi, Zaire, Rwanda
lice treatment
Lice Treatment

OTC Medications

  • Pyrethins: kill live lice but not the nits
  • Permethrin lotion 1%: similar to Pyrethin, kills the adult lice but not the nits.
lice treatment continued
Lice Treatment (Continued)

Prescription Medications

  • Malathion lotion 0.5%: kills live lice and partially ovicidal (kills some eggs.) Can be irritating to skin/scalp.
  • Benzyl alcohol lotion 5%: does not kill live eggs
  • Lindane shampoo 1%: not recommended as first-line therapy because can cause neurological damage
which treatments should be used
Which treatments should be used?
  • Most parents use the “Nix” shampoo: Permethrin 1%.
    • Usually cited as the standard treatment.
  • If Permethrin is unsuccessful, move to prescription treatments
    • Lindane is currently not recommended by the American Academy of Pediatrics (AAP): should only be used if all the other treatments are ineffective.
additional lice treatments
Additional Lice Treatments
  • Several studies have looked at oral ivermectin administration as an alternative to topical medications
    • Oral ivermectin was found to be more effective than topical malathion lotion
    • Important given issues of resistance to existing topical treatments
  • Recent news! The FDA has approved a topical ivermectin-based lotion (brand-name Sklice)
additional lice treatments continued
Additional Lice Treatments (Continued)

Fumigation and dusting with chemical insecticides: DDT, 1% malathion, or 1% permethrin.

  • First used in WWII: U.S. military dusted DDT powder on troops and refugees.
  • 10% DDT louse powder on patient, clothing, bedding and members of household
  • Highly effective (lice mortality of 99% from 1% DDT; lice mortality 96% in 0.1% DDT)
  • Avoid methods of transmission (head-to-head contact, sexual contact)
  • Improved hygiene/sanitation for body lice
    • Regular change of clothes
    • Regular bathing
  • Laundry and soaking in hot water
  • Pets do not play a role in lice outbreaks
prevention in schools no nit policy controversy
Prevention in Schools: No-Nit Policy Controversy
  • No-Nit Policy: Education, screening, and treatment of children with lice in order to prevent transmission and maintain “nit-free” environments
    • Emphasize accurate diagnosis
    • Education about prevention techniques
    • Temporary dismissal of children with lice
  • American Academy of Pediatricians oppose the strict no-nit policy
    • Causes lost classroom time for children
    • (Head) lice aren’t a severe medical problem
    • Recommend: common sense
  • Body lice are more serious than pubic or head lice because they can transmit disease.
  • Diseases associated with body lice are severe!
    • Epidemic typhus (R. prowazekii)
  • Refugees and those affected by humanitarian crises are particularly at risk.
  • Insecticide spraying is an important control measure

Blanton, F. S. (1952). The Control of Epidemic Typhus. Journal of the New York Entomological Society, 60(3), 153-156.

Burundi Civil War.

Chosidow, O., Giraudeau, B., Cottrell, J., Izri, A., Hofmann, R., Ph, D., Mann, S. G., et al. (2010). Oral Ivermectin versus Malathion Lotion for Difficult-to-Treat Head Lice. NEJM, 362, 896-905.

Hand, L. 2012. FDA Approves New Lotion for Head Lice Treatment. Medscape Today. http://

Head lice. PubMed Health, 2012.

Lepes, T. J. (1960). Susceptibility of Body-lice to DDT in a Heavily Treated Area of Yugoslavia. World Health Organization Bulletin, 22, 515-518.

Lice. Mayo Clinic, 2012.

Parasites – Lice. CDC, 2012.

references cont
References (Cont.)

Raoult, D. et al. Jail Fever (epidemic typhus) outbreak in Burundi. Emerging Infectious Diseases, 1997. 3(3) 357-360.

Reed, D. L., Light, J. E., Allen, J. M., & Kirchman, J. J. (2007). Pair of lice lost or parasites regained : the evolutionary history of anthropoid primate lice. BMC Biology, 11, 1-11. doi:10.1186/1741-7007-5-7

Travis, J. (2003). The Naked Truth? Lice Hint at a Recent Origin of Clothing. Science News, 164, 118.

Weindling, P. (2000). Epidemics and Genocide in Eastern Europe, 1890-1945. Oxford University Press.