Pediculosis or headlice

Victorian statutory requirement

Notification is not required.

School exclusion: readmit the day after appropriate treatment has been commenced.

Infectious agent

Pediculus humanus var. capitus is the infective agent.

Identification

Clinical features
Pediculosis is commonly said to be associated with an itchy scalp however this is an unreliable sign. Itching is only experienced in 14–50% of people with head lice. Head lice can be present for weeks or even months without causing an itch. Secondary scalp infections resulting from scratching can occur but are rare.

Method of diagnosis
Early detection makes treatment and control of head lice easier. Traditional scalp inspection is a poor method of detecting lice. It can result in 30% false positive and 10% false negative findings.

The technique known as ‘conditioner and combing’ is the most effective method for detection. This involves combing white hair conditioner through dry, brushed hair. The next step is to divide the hair into smaller sections and to comb each section using a head lice comb. After each combing the comb is wiped on to a tissue. This allows lice and eggs to be easily seen. The aim is to cylindrically coat each hair in conditioner and continue to comb hair until the majority of conditioner is removed.

Incubation period

The life cycle consists of three stages: egg, nymph and adult. The eggs are known as nits and hatch in six to seven days. There are three nymphal forms that each last one to eight days.

The female lays the first egg one or two days after mating and can lay approximately three to eight eggs per day for the next 16 days. After a life span of 32–35 days the louse dies.

Public health significance & occurrence

Head lice have been associated with humans for 10 000 years. Head lice occur worldwide. Anyone can get lice and given the opportunity head lice will move from head to head without discrimination. They are frequently associated with children.

Information on the prevalence of head lice varies around the world. In 2002 the prevalence of head lice among primary school children in Victoria was found to be 13%. Females were more than twice as likely to have head lice as males.

The prevalence of head lice in primary school aged children in other parts of Australia is reported to be up to 60%.

Head lice are not vectors of infectious disease. Louse-borne relapsing fever, trench fever and typhus, none of which occur in Australia, are all associated with the body louse Pediculus humanus var. corporis.

Reservoir

Humans are the only reservoir. The lice of other animals are not transmissible to humans.

Mode of transmission

Pediculosis is transmitted through direct head to head contact with a person with head lice. Nymphal and adult lice survive, dependent on the humidity of the environment, and according to Queensland research usually die within 24 hours of being stranded away from the head. There is no significant risk of transmission from the environment.

Period of communicability

Communicability continues as long as lice or their nymphs remain alive.

Susceptibility & resistance

Everyone is susceptible to infection.

Control measures

Preventive measures
Regular checking using the method known as ‘conditioner and combing’ allows early detection of head lice and will limit the establishment of large outbreaks.

Control of case
Treatment should concentrate on the head. There is no evidence that the environment is a significant cause of reinfection.

The conditioner and combing method can be repeated every second day until no lice are found for ten days.

If using an insecticidal product it is important to use a ’registered’ or ’listed’ product which should have two applications seven days apart. Applying with the least amount of water possible and the removal of as many eggs as possible will optimise the treatment.

Increasing resistance to the products has been reported and each head lice product should be tested after 20 minutes to ensure it has killed the lice.

Control of contacts
Contact tracing is recommended.

All household members or people who have had head to head contact with the case should be examined for head lice. Preferably this should be done using the conditioner and combing detection method and repeated every two days for ten days.

Special settings
Hairdressing salons
Head lice rarely fall from the head. Data from James Cook University show head lice on combs and brushes are easily killed by immersion in hot water at 60°C for one minute. There is then no subsequent risk of transmission from the comb or brush to the next client.

Outbreak measures

Schools
While head lice are often associated with schools they are not necessarily spread in schools. Schools experiencing difficulty should encourage families to check for lice using the combing and conditioner method on a weekly basis, or more often during an outbreak. Even on receipt of a single case report of head lice, parents or guardians of all children from the class should be asked to screen their child at home utilising the conditioner and comb method. Parents or guardians should then report any active head lice following the synchronised home screening.

If there is a cluster of cases in a class, for example 10% of pupils, a further school wide management program could be considered (see resources for schools, www.health.vic.gov.au/headlice)

Additional sources of information

De Maeseneer, J, Blokland, I, Willems, S et al. 2000, ‘Wet combing versus traditional scalp inspection to detect head lice in school children: observational study’, BMJ, vol. 321, no. 7270, pp. 1187–8.
Spear, R, Thomas, G, Cahill, C 2002, ‘Head lice are not found on floors in primary school classrooms’, Aust N Z J Public Health, vol. 26, no. 3, pp. 208–11.
Victorian Department of Human Services
www.health.vic.gov.au/ headlice

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