INTRODUCTION
The human head louse, Pediculus humanus capitis
De Geer (Anoplura: Pediculidae) is a worldwide public health concern.
Head lice generally affect children, primary girls, aged 3-12 years, in
both the developed and the developing countries. This ectoparisite feed
by sucking blood and cause pruritus and subsequent skin excoriation may
lead to secondary infection. In addition, chronic irritation and secondary
infection may disrupt behavior and school performance (Bailey and Prociv,
2000) and cause psychological distress (Dodd, 2001; Mumcuoglu, 1999).
Recently, two studies have suggested that head lice can transmit Bartonella
quintana Brenner (Causative agent of Trench fever) (Sasaki et al.,
2006) and Richkettsia prowazekii da Rocha-Lima (Robinson et
al., 2003). In certain epidemiologic school surveys conducted in different
countries the prevalence of head lice has been found to be 6.8% in Turkey
(Kokturk et al., 2003), 8.9% in Belgium (Willems et al.,
2005), 13% in Australia (Counahan et al., 2004), 35% in Brazil
(Borges and Mendes, 2002), 5.8% in Korea (Sim et al., 2003) and
52% in Ukraine (Kurhanova, 2006).
Prevalence of infestation was reported from 0.68% (Motovali
Emami et al., 2003) to 52% (Kurhanova, 2006) in different studies
that may be affiliated with social situation, genetic and characteristics
of a population. Resistance to pediculicides such as lindane and permethrin
is common in populations where these pediculicides have been heavily used
(Elson, 2005).
Drug resistance has also increased the risk of infestation
among other schoolmates and family members and there fore, presents a
public health problem that is difficult to solve. Since 2003 numerous
earthquake in Kerman County (the biggest county in Iran) have been caused
environmental and socioeconomic changes, so health authorities are persuaded
to evaluate the impact of control strategies.
This study was undertaken to assess the prevalence of
and epidemiological factors associated with, head lice infections in all
the Kerman primary schools in 2006 and evaluate data on the therapeutic
efficacy of lindane shampoo.
MATERIALS AND METHODS
A total of 40586 children (19774 boys (48.72%) and
20812 girls (51.28%)) from 198 Government primary schools in Kerman, were
screened for head lice between March and June 2006.
Ethical approval was obtained form the Kerman University
of Medical Science Ethics Committee (ethics approval number: K-85/34).
There was a large variation in School size across the county with total
enrolments varying form 9 to 1511.Thirty one Schools were in rural areas
and the remainder in urban areas.
Before examining the students, a detailed structured
questionnaire was submitted to the parents and written informed consent
was obtained. In this proforma, the sex, age, family size, parent`s education,
bathing facilities in the house and hair washing (per week) were recorded
for each child.
A team of health specialists and general practitioners
skilled in the detection of head lice and trained in study procedures
conducted the screening under the supervision of the co-investigator dermatologist.
The diagnosis of head lice infestation was confirmed
by clinical inspection of scalp and hair for the presence of adult lice
nymphal stage, or eggs (nit) by line-toothed head lice comb, a validated
method of detection (Mottram, 2000).
The viability of nits was confirmed by stereomicroscopic
inspection. A history of previous head lice infestation was obtained from
medical records and parental anecdotes.
All children infested with lice were treated with lindane
shampoo (1% gamma benzene hexachloride). Children were reexamined at 2
weeks after treatment for head lice infestation. A dermatologist or general
physician performed examinations of scalp and hair. We defined treatment
failures as the presence of adult lice and nymphal stage, or viable eggs
(nits).
All infested children and their parents were given information
on how to prevent reinfestation. The washing of house hold clothes bed
linens and pillowcases in hot water in an automatic washing machine, immersing
fomites such as combs and brushed in hot water at a temperature of 70°C
or greater and treating other infested individuals in close contact with
the patient were recommended.
Statistical analysis: Statistical analysis of results was performed using
SPSS version 11.0. Standard statistical method including chi-square test
was used in order to analyses the data. Statistical significance was assumed
at a p<0.05.
RESULTS
Of the 40586 children (all primary children in Kerman county) examined,
the mean age of the children was 8.1±1.9 years (range, 6-11 years).
Demographic data and prevalence of infestation are shown in
Table 1.
The overall prevalence of head lice infestation was 1.8%.
In 29 (4%) of the 721 positive children, only egg residues were found,
whereas in the other 692 children, at least one of the lived (viable)
instars of development was observed.
The prevalence of infestation was significantly higher
in girls (2.9%) than in boys (0.6%) (p = 0.000).
As shown in Table 1 infested children aged 6-8 years
exhibited a statistically significantly higher rate than children aged
9-11 years and above.
Only 4071 students (10%) were living in families with
family size >10 and this prevalence was greater (3.51%) than among
others. In addition, the infestation rate was greater among pupils who
were living in rural areas (4.6%) than those in urban areas (1.5%).
Of the 721 children with a positive examination result,
424 pupils (58.8%) were reported as having been infested with head lice
in the previous 6 months.
Mother`s education level was a significant risk factor
in this model (p<0.05).
The analysis of other variables, such as father`s education
level, bathing facilities in the house and the frequency of hair washing,
in relation to infestation showed no significant differences between infested
and noninfested subjects.
At 2 weeks after the primary treatment, the success rates of treatment
were 49%.
| Table 1: |
Prevalence of head louse infestation
in primary school children in Iran 2006-2007 |
 |
DISCUSSION
Pediculus humanus capitis is an obligate ectoparasite
that lives only on human hair and feeds on the blood from the skin. The
prevalence is generally 1 to 3% in industrialized countries; however,
it may on occasion exceed 25% in elementary schools (Roberts, 2002).
In Iran, as in other countries, there is often a more
serious consequence than physical problems for those affected, because
social stigma is associated with having head lice.
The present study shows that the overall prevalence (1.8%)
of head lice infestation in Iran has decreased. In Iran, it was previously
reported that the prevalence of pediculosis was 0.68% (Motovali Emami
et al., 2003) to 27% (Alempour Salemi et al., 2003). The
prevalence of active pediculosis detected among all primary school students
in present study (1.8%) was lower than previous reported in Kerman city
by kamiabi and Nakhaei in randomized study (3.8%) (Kamiabi and Nakhaei,
2005). There may be a number of likely explanations for this difference
including, a bias due to the detection method or the sampling strategy
used, deficient population groups, variation in the study design, earthquake
in Kerman county three years before our survey and consequently increase
of Government attention to health of schools.
Because the adult louse moves quickly through dry hair
it is useful to look for lice when the hair is wet (Koch et al.,
2001). This has the effect of slowing them down, which gives the examiner
extended time to find them. Active infestation by head lice is evidenced
by the presence of adult lice, nymphs or live eggs, whereas hatched or
dead eggs point to inactive infestation. An additional complication in
diagnosis is the presence of pseudo nits. These are objects detected in
the hair that might be confused with nits, such as dandruff. Lice typically
lay nits within 1-2 mm of the scalp and for practical purposes; nits within
1 cm of the scalp should be counted as a sign of active infestation (Frankowski,
2004). Also we are of the opinion that comprehensive survey in our work
showed the better future of the disease and related factors.
In the present survey, girls are found to show a significantly
higher infestation rate than boys. Most previous studies have shown the
prevalence to be higher in girls (Motovali Emami et al., 2003;
Kokturk et al., 2003; Counahan et al., 2004; Sim et al.,
2003). Difference in behavior patterns between boys and girls might have
affected transmission rates and susceptibility to head lice infestation.
Transmission of head lice most commonly occurs through close physical
contact, especially head- to-head contact, but fomites, such as hats also
play a role. Girls in Iran use kerchief in the classroom situation and
outside during daily activities. They occasionally replace their kerchief
to each other that would in theory be an ideal situation for the transfer
of head lice. In addition we observed that most of the boys have very
short hairs, however a number of studies have failed to show a relationship
between hair length and head lice infestation (Chouela et al.,
1997; Slonka et al., 1977). Differences in the head louse distribution
rates between age groups are not supported by many studies (Kokturk et
al., 2003; Borges et al., 2002; Kamiabi and Nakhaei, 2005),
but in some reports, it has indicated that there is a increase in the
infestation rate with age (Amr and Nusier, 2000; Shakkoury and Abu Wandy,
1999) or no statistical significance relationship (Motovali Emami et
al., 2003; Zabihi et al., 2006).
Although some children with infestation are asymptomatic,
the most common symptom is pruritus, which occurs due to sensitization
to either louse salivary or fecal antigens. Children bellow 5 years may
not immediately feel the physical effect of having head lice but older
children especially over 10 years old become aware sooner.
In present study, urban areas had lower prevalence of
head lice infestation than rural areas, which is attributed to better
hygiene, because more often urban school have health teacher or supervisor.
Some researchers have claimed that head louse is found in all socio-economic
classed (Kokturk et al., 2003; Counahan et al., 2004; Borges
et al., 2002), whereas others have reported that head louse is
more frequent in rural area with socio-economic classes (Sim et al.,
2003; Kamiabi and Nakhaei, 2005). It has been proposed that in areas of
high social disadvantage, larger families may pay less attention to hair
care due to lake of support and financial limitations.
School may have to recognize that they need to play a
more active role in the control of Pediculus capitis.
We found that there was a relationship between the rate
of infestation and mother`s education. This is agreement with results
of a number of previous studies (Kamiabi and Nakhaei, 2005; Motovali Emami
et al., 2003).
Mothers with low education may be unaware of how to detect
infestation with head lice and may use techniques of how sensitivity.
Among the infested subjects, 58.8% reported in the questionnaire
that they had previous infestation and received prior treatment. We believe
that in order to lower significantly the infestation prevalence is a community;
a systemic strategy is required for a global and simultaneous thrust in
a semiclosed community, such as school, together with joint action on
the part of health staff, teachers and parents to maintain epidemiologic
surveillance.
Other factors such as fathers education, bathing facilities
in the house and frequency of hair washing had no statistically significant
influence on the prevalence of head lice infestation (p>0.01) in this
study.
The success rate of treatment at the 2 weeks follow-
up was 49%. Lindane shampoo is widely used as pediculicides in Iran health
centers. Lindane (Gamma benzene hexa chloride 1% shampoo) is pediculicidal
but it has limited ovicidal activity. Given lindane`s increased side-effect
potential including neurotoxicity and bone morrow suppression. Unfortunately
resistance to lindane is common in populations where these pediculicide
have been heavily used (Elson, 2005). Meinking et al. (2002) in
a recent study, showed 1% lindane was the slowest and least effective
pediculicide with no lice eradicated after 10 min and killing only 17%
of lice after 3 h. Ingestion or frequently repeated applications of lindane
increase the risk of toxicity. A nymph that has been exposed to a pediculicide
can shed its exoskeleton and receive only a sublethal dose, which contributes
to resistance (Meinking, 2004).
To slow the emergence of resistance, therapeutic agents
can be rotated (Meinking et al., 2002). Patterns of resistance
often appear to follow patterns of drug use in different areas of the
world (Berker and Sinclair, 2000; Downs et al., 2002). We believe
that education campaigns by health care officials, physicians and teachers
are expected to be helpful for head lice control. It is essential that
governments should be supported form cooperation between the school authorities
and public health centers to successful control head lice infestation
in primary school. Also there is an urgent need to identify safe, novel
insecticides for proved efficacy.
This project received financial support from vice chancellorship
for research affairs of Kerman University of Medical Sciences (Project
No. 85/11).
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