Pediculosis (head lice)

Notification requirement for head lice

Notification is not required.

Primary school and children’s services centre exclusion for head lice

Exclude until the day after appropriate treatment has commenced.

Infectious agent of head lice

Pediculus humanus var. capitis is the infective agent.

Identification of head lice

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 per cent 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.

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 per cent false positive and 10 per cent 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 a tissue. This allows lice and eggs to be easily seen – the presence of eggs alone does not necessarily indicate active infestation. The aim is to cylindrically coat each hair in conditioner and continue to comb hair until the majority of conditioner is removed. This method has a sensitivity of 90 per cent and a negative predictive value of 99 per cent in children with low infestation intensity. This is in comparison to visual inspection alone, which has a sensitivity of 20–30 per cent. The detection of nits (live eggs), especially when close to the scalp, suggests active infestation; however, nits may persist for months after successful treatment.

Incubation period of Pediculus humanus

The life cycle consists of three stages: egg, nymph and adult. The eggs are known as nits and hatch in 7–10 days. There are three nymphal forms that each last 1–8 days.

The female lays the first egg 1 or 2 days after mating and can lay approximately 3–10 eggs per day for the next 16 days. After a lifespan of 32–35 days, the louse dies.

Public health significance and occurrence of head lice

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 – girls are more frequently infested than boys.

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 per cent. 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 per cent.

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 of Pediculus humanus

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

Mode of transmission of Pediculus humanus

Pediculosis is transmitted through direct head-to-head contact with a person with head lice. Nymphal and adult lice 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 of head lice

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

Susceptibility and resistance to head lice

Everyone is susceptible to infection.

Control measures for head lice

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 re-infestation.

The conditioner and combing method can be repeated every second day until no lice are found for 10 days.

If using an insecticidal product, it is important to use a ’registered’ or ‘listed’ product. Some treatments have two applications 7 days apart. Applying with the least amount of water possible and the removal of as many eggs as possible will optimise the treatment. Other occlusive products containing dimethicone are silicon-based products applied to clean, dry hair and washed out after 15 minutes. Spray gel and liquid gel products contain nerolidol, which also kills lice eggs. Each head lice product should be tested after 20 minutes to ensure that it has killed the lice.

Increasing resistance to the products has been reported. .

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 2 days for 10 days.

Special settings

Hairdressing salons

Head lice rarely fall from the head. Data from James Cook University show that head lice on combs and brushes are easily killed by immersion in hot water (60 °C) for 1 minute. There is then no subsequent risk of transmission from the comb or brush to the next client.

Outbreak measures for head lice

Although head lice are often associated with schools, they are not necessarily spread in schools. Schools experiencing difficulties should encourage families to check for lice using the conditioner and combing 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 using the conditioner and combing 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 per cent of pupils – a further school-wide management program could be considered.