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Introduction
Head lice infestation is a public health issue leading to apparent morbidity among school children worldwide. This infection is caused by an ectoparasite (i.e., Pediculus humanus capitis) of humans found on the hair and belongs to the order Anoplura (1). The head louse cannot fly or jump, and therefore, it is commonly transmitted through physical or direct contact with the hat, scarf, comb, bedding, and clothing of the infected person (1, 2). In addition, it is not a disease vector; however, it sucks human blood for its nourishment, and therefore, leads to head itching, irritations, discomfort, sleep loss, and the pruritus secondary bacterial infec­tions, such as impetigo. Furthermore, its saliva may lead to allergy and other psychological effects that hinder students from attending school (3).
The head lice infestations caused by pediculus capitis are often associated with poor com­munities in neglected conditions leading to considerable health problems in many societies, especially among children between 3 and 14 years of age (4). Epidemiologic studies indicated that the prevalence rates of pediculosis were 6.8%, 26.6%, 23.32%, and 26.4% in Turkey (5), Jordan (6), Thailand (7), and Nigeria (8), respectively. In the United States, 6-12 million people are infested every year with an estimation of $100 million being spent annually on the treatment (9).
Some investigations have been conducted in Iran on the epidemiology of the head louse and its related risk factors. Sev­eral studies from various regions in Iran have reported the rates of head lice infestation varying between 28.5% and 0.47% (10). However, previous studies conducted in different areas in Iran showed the infestation rates of 0.7%, 10.25%, and 12% mostly in the school children in Kashan, Meshkinshahr, and Boushehr, respectively (11-13).
 
Pediculosis is a public health problem in different countries. The factors related to the host that can be associated with head lice prevalence include race, age group, gender, socioeconomic status, and hair characteristics. Given that Mashhad attracts plenty of international tourists and pilgrims every year, it is of utmost importance to investigate the risk factors influencing pediculosis. This study was conducted to determine the pediculosis prevalence rate and the effective factors in the elementary school-aged female students in Mashhad, Iran, from 2017 to 2018. The obtained results can be used to develop programs in order to manage the prevalence of this condition among elementary schools across Iran.
Materials and Methods
This study was conducted based on a descriptive and analytical design. In total, 20 state elementary schools were selected randomly from all districts in Mashhad, Iran. Out of these schools, 3062 female students were selected using a multistage-systematic random sampling. All students (first- to sixth-grade students) were examined for head lice infestation by health experts. Furthermore, the diagnosis of pediculosis capitis was confirmed by clinical inspection of scalp and hair under the light of a reading lamp using a manual magnifier for the presence of adult lice, or eggs (i.e., nits). Before examining the students, demographic characteristics form covering information, such as age, school grade, sleeping in a common room, using shared personal instruments, personal health care, family size, parents' educational level, parents' occupational status, and hair shape, were recorded for each student (14).   
 
 
Data Analysis
The data were analyzed in SPSS software (version 11.0). Moreover, the Chi-square test was used to compare the qualitative variables. A P-value less than 0.05 was considered statistically significant.
 
Ethical Considerations
With respect to the ethical considerations, written informed consent was obtained from all participants. Moreover, they were informed about the confidentiality of their information.
 
 
Results
 
Out of 3062 elementary school students, 417 (13.6%) cases were identified infested with head lice. The results obtained from the relationship between fathers’ occupational status and head lice infestation rate revealed that the students whose fathers were unemployed (17.1%) obtained the highest rate of infestation. On the other hand, the lowest rate of infestation was observed among those whose fathers had a government job (10.3%). However, this difference was not statistically significant (P=0.14, Table 1). Regarding the family size, the majority of the students with head lice infestation were from fami­lies with 2 members; however, there was no statistically significant difference between family size and the infestation rate (Table 1).
On the other hand, a significant difference was observed between age groups and school grades regarding the prevalence of pediculosis among students (P=0.0001, Table 1). Furthermore, the health expert presence at school was not correlated significantly with the prevalence of head lice infestation among schoolchildren (P=0.175). The pediculosis prevalence rates at schools with and without health experts were 87.5% and 85.8%, respectively.
Additionally, the rates of infestation among students using shared and non-shared personal instruments (i.e., combs and scarf) were 81.77% and 18.23%, respectively (Table 2). There was a significant difference between the prevalence rate of pediculosis and using shared instruments (P=0.0001). Furthermore, a significant difference was observed between the prevalence of pediculosis and parents' educational level (P<0.05, Table 2). In the present study, the rates of infestation with and without considering the personal hygiene were obtained at 11.5% and 48.3%, respectively, which was statistically significant (P<0.05, Table 2). Similarly, Table 2 depicts a significant relationship between the prevalence of pediculosis and the hair shape (P>0.05).
 
 
                                                                               
Discussion
Despite the advances in hygiene practices in communities, pediculosis still remains the main health concern in poor and developing countries. Previous studies indicated the presence of pediculosis in different areas of Iran (14). In this study, the prevalence rate of pediculosis was estimated at 13.6% among children in Mashhad. Similar relevant studies reported the pediculosis prevalence rates among elementary schools in different parts of Iran, such as Mazandaran (5.7%) (15), Hamadan (1.3%) (16), and Sanandaj (7.7%) (17). According to the results of a systematic review study in Iran, the prevalence rate of pediculosis was estimated at 9% among female schoolchildren (18).
In a similar vein, the findings in the present study revealed that the prevalence of pediculosis was higher in Mashhad, compared to other cities in Iran. This significant difference can be attributed to the increasing rate of migration, the emergence of marginal communities, and the lack of proper health education in Mashhad, Iran. In this study, the prevalence rate of head lice infestation correlated with the age groups and the school grades. Several investigations revealed the differences between the infesta­tion rates and the age groups  (age range: 6-13 years) (13,19). This difference may be due to the increased awareness of the students in higher school grades regarding health issues and their observance of personal hygiene to prevent the spread of infectious diseases.  
 
The findings also suggested a decrease in the rate of infestation among the children of employed and educated parents since they had greater knowledge and attitude regarding personal hygiene and pediculosis. In general, a higher level of the parents’ education led to more suitable health behavior throughout the family, which is consistent with the finding of other studies (20). In this study, the rate of pediculosis infestation was lower in families with 2 persons.
Head lice are considered as well-known obligate ectoparasites of mammals, especially humans, and they spread by direct contact from person to person (21). Therefore, the prevalence of pediculosis is expected to be higher in crowded families. In a similar study conducted in Belgium, the lice infestation rate was significantly increased in families of low socioeconomic status, individuals with large families, and those with long hair (22). Parents of large families are less likely to pay attention to their children's health status, which in turn increases the prevalence of pediculosis. Furthermore, the larger the family size, the more the utilization of shared personal belongings.
According to the current study, there was a significant relationship between the hair shape (i.e., long straight and tangled hair) and infection rate since this type of hair is brushed with difficulties. On the other hand, wearing scarves with long hair can provide the temperature needed for the growth of this insect. This can be one of the reasons for the increase in head lice among females who have long straight hair.
In this study, no significant relationship has been found between the pediculosis and the hairstyle, which is in line with the results of a study conducted by Doroodgar et al. In the aforementioned study, 88.2% and 11.8% of the cases had straight and curly hair, respectively (20), which was in line with the findings obtained from this study.
The majority of the students with head lice infestation had a history of using shared instruments in the present study. This finding was significant and consistent with the results of studies performed by Wafa and AL-Megrin (2015) and Dehghanzadeh et al. (2015) in which they reported the effect of using shared instruments at homes and schools on the increased rate of pediculosis (23, 24). Head lice generally spread through direct transmission via head-to-head contact with an infected person or indirect transmission by sharing common instruments.  
Considering the obtained results, a statistically non-significant difference was noticed among the students in primary schools with and without health experts though the presence of health experts at elementary schools plays a crucial role in the reduction of pediculosis rate. It seems that health experts do not have sufficient knowledge about pediculosis. However, this finding is not consistent with the results of a study conducted by Jahandideh (25).
In the present study, no significant relationship was observed between the hair condition and lice infestation rate, which was in line with the findings reported by Soultana et al. (26) and inconsistent with the results of a study carried out by Rafinejad et al. (27). The results of the present study are in accordance with those of the previous findings indicating that good hair care and personal hygiene will go a long way in reducing the prevalence of lice infestation (14, 28).
Previous studies have shown that regular brushing with the wooden fine-toothed comb has mostly been used as a physical preventive method that not only reduced the prevalence of the infestation but also healed it (29). According to the results of this study, sleeping in a common room was one of the factors con­tributing to the infestation rate, and the pediculosis rate was higher among students living in large families. It is worth mentioning that as soon as a family member is infested, the other family members have a high risk of getting infested due to using shared instruments (30).
Conclusion
It is necessary to provide parents, teachers, and students with health education and prevention methods regarding the management of pediculosis capitis through holding workshops and training sessions to reduce the prevalence rate of this infection.
 
 
Acknowledgment
 
The authors would like to thank the staff of the health and treatment office in Mashhad, Iran,  as well as the health experts at schools, officials, and staff of the Ministry of Education in Mashhad, Iran. Moreover, the authors show their sincere gratitude to school principals and teachers for their cooperation with conducting this study.
 
Funding
The study protocol was approved under approval No. 10204. Moreover, this study was conducted and financially funded by Mazandaran University of Medical Science, Sari, Iran.
 
Conflicts of Interest
The authors declare that they have no conflict of interest regarding the publication of this study.