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Anais Brasileiros de Dermatologia

Print version ISSN 0365-0596

An. Bras. Dermatol. vol.84 no.6 Rio de Janeiro Nov./Dec. 2009 



Metal microchanelled fine-toothed comb use in the diagnosis of pediculosis*



Patricia Elena NeiraI; Luis Rodrigo MolinaII; Alejandra Ximena CorreaIII; Nelson Ramón Américo MuñozIV; David Eduardo OschilewskiV

IMaster in Biological Sciences, Focus on Parasitology, Full Professor and Head of Parasitology, Department of Preclinical Care. Medical School, Universidade de Valparaíso - Chile
IIGeneral Practitioner, Resident Physician of Gynecology, Hospital Carlos van Buren Valparaíso, Chile
IIIGeneral Practitioner, Hospital de Quillota - Chile
IVLaboratory Technician, Area of Parasitology, Department of Preclinical Care, Medical School, Universidade de Valparaíso - Chile
VGeneral Practitioner, ongoing graduate studies in Dermatology, Professor Rubem David Azulay, Santa Casa de Misericórdia do Rio de Janeiro, Associate Professor of Parasitology, Department of Preclinical Care. Medical School, Universidade de Valparaíso - Chile

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BACKGROUND: Methods for the diagnosis of Pediculus humanus var. capitis are controversial and most studies are based on direct visual exam.
The objective of this study was to compare the diagnosis efficacy of both direct visual exam and the use of a metal microchanelled fine-toothed comb.
946 children and teenagers 4 to 19 years of age were examined. Each individual's hair was examined twice to determine whether there was infestation by lice or nits, through direct visual exam and the use of a metal microchanelled
fine-toothed comb.
The visual diagnosis detected infestation in 30.7% of the cases, while the metal comb detected infestation in 51.5%. Females were the most affected. The forms of parasites detected through direct visual exam were: only lice (adults and/or nymphs) 1.4%, only live nits 64.8% and live nits and lice, 33.8%; with the metal comb the percentages were 6.4%, 23.6% and 70%, respectively. The average time to find a louse was 57 seconds with the fine-toothed comb and 116.4 seconds through the direct visual exam.
Diagnosis with the microchanelled fine-toothed comb is twice as fast and 3.6 times more efficient than through direct visual exam.The direct visual exam detects non-active, past infestations, and
underestimates active ones.

Keywords: chile; scalp dermatoses; lice infestations; pediculus capitis




Among permanent human ectoparasite arthropods there is head lice Pediculus humanus var. capitis (Insecta: Phthiraptera), stenoxenic insect (adapted to a species)1 of hematophagic habits that develop all its life cycle over the host.

Pediculosis is a disease that has affected the humanity throughout its whole history 2,3. Its high prevalence was related with limited water availability and deficient hygiene practices 4, a situation that improved in the first half of the 20th century owing to general social betterment. However, in the 60's, there was significant regrowth of pediculosis in the world prevalence 2, a fact that was correlated with new characteristics of way of living in some subcultures, such as worsening in personal hygiene habits, increased sexual promiscuity and use of long hair among younger people 4.

In Chile, as well as in other countries, this parasitosis is not a compulsory reportable disease and there is no active surveillance that leads to knowledge of infestation rates in the childhood population. In the second half of the 90's, studies performed with primary school students in Santiago, coming from the North, East and West areas of the city, showed prevalence of 14.8% among men and 31.6% among women; those who came from the southern region of the capital showed 10.9% and 79.2% prevalence among men and women, respectively 2. In the region of Valparaiso (to the North from the capital), prevalence studies with school-aged children from rural areas showed difference from 0.8 to 46.8% 5, higher in children coming from suburban areas, amounting to 52.4% 6 and lower in hospitalized psychiatric adults, reaching 7.2% 7.

Most of the studies performed with pediculosis used as diagnostic tool the technique of direct visual examination to identify parasites 8-12, which is characterized by manual search and visual observation of the different parasite stages. In infested patients, there are more nits than pedicles (imagos and/or nymphs), reason why the initial diagnostic search in practice can be made by visualizing them 10.

There are different types of fine-toothed combs: plastic, aluminum, steel, thermal or electronic, which are used and recommended as medical treatment 13, but their efficacy for diagnosis has not been assessed. Steel metallic combs, whose manufacturer states that it is appropriate to remove nits, have not been used for diagnostic purposes, but the correct separation between the teeth, its resistance and the fact that they are microchanneled, which would enable easier removal of nits and imagos by dragging, formed the ideal diagnostic tool. Owing to the presented information and because there are no systematic studies to define the best method to be used, the purpose of our study was to compare the efficacy of direct visual examination and the use of Assy 2000 steel metallic microchanneled comb to diagnose Pediculus humanus var. capitis.




Assy 2000 steel metallic microchanneled comb (Laboratório Andrómaco) (Figure 1) is manufactured with stainless steel and weighs 42 grams. It has a 65 mm rounded handle (with four anti-sliding rubber pads on both sides) that are used for gripping the comb that has 33 circular and channeled steel teeth. The teeth end in microscopically rounded tips that prevent scalp damage. The teeth measure 38 x 1.5 mm.




The total examined population corresponded to 946 children and adolescents, 489 women and 457 men aged 4 to 19 years, whose records were part of foundation Children International-Chile in the city of Quillota (latitude -32,88 and longitude -71,25), Province of Valparaíso - Chile, who were included by the assistants of the healthcare program of the referred institution. The study was performed with the support of healthcare monitors of the foundation, who were previously trained with theoretical and practical course by the Discipline of Parasitology, Medical School, Universidade de Valparaíso,14 to involve and build awareness of the local community about this healthcare problem.

The examining team was protected with consistent biosafety measures using white gown with elastic cuffs, covered by a plastic apron from the chest to the knees. The hair was tied up for women and protected in both genders by a hair cap or tight turban. Even though the study was performed as part of the healthcare program of the foundation, parents and/or guardians were asked to consent for the participation, after having received information about the objectives and the activities to be performed.

Each child or adolescent was examined twice using direct visual examination and the microchanneled metallic comb. Their hair was previously untangled with a large plastic comb with separated teeth to avoid excessive pulling and to facilitate the visual examination and the metallic comb diagnostic procedure. Visual direct examination was performed under appropriate light conditions for diagnosis (Figure 2). The search for parasites started at the occipital and retroauricular region and extended to the rest of the head. The hair was separated with the fingers, looking for imagos, nymphs, alive or dead nits. Later, a second examiner placed in another room used the metallic comb (Figure 3), which was used from the hair basis to the tips to remove any parasite by dragging. The contents of the comb were emptied in a white tray to differentiate parasites from any other type of hair waste.





If necessary, a magnifying glass was used to differentiate live nits from dead ones and other types of morphologically waste seen by naked eye. Once the examination was finished, decontamination of the trays, the plastic and the metallic comb was made with boiling water, and the comb was brushed with a fine toothbrush to eliminate any residue and/or parasite. The instruments were them dried with hot air. The time until detection of the first louse was measured by a stopwatch by another member of the team and recorded with other patient information. Data were recorded using Microsoft Excel XP and analyzed by the department of statistics of the university, using software Stata version 8.0 (Statacorp, 2004) and chi-square test, with significance level of 5% and determination of odds ratio.



Foundation Children International-Chile, in the city of Quillota, Province of Valparaíso, comprises 1,061 children and adolescents aged 4 to 19 years. In this study, 89.2% of the parents consented with the procedure (amounting to a total of 946 examined subjects).

Prevalence of infestation by Pediculus capitis using a metallic microchanneled teeth comb was on average 51.5%, ranging from 27. 8 to 70% in different areas. In comparison, the prevalence detected using direct visual examination was 30.7%, ranging from 7.4 to 47.7% (Table 1). It is important to point out that all positive cases by the visual examination were confirmed using the metallic comb.



In both techniques, there were more affected women than men. There were 64.7% positive girls and 35.3% positive boys with metallic comb, and 65.9 and 34.1%, respectively, with visual direct examination.

Concerning the stages of Pediculus humanus var. capitits, we can say that through direct visual examination the following were detected: only lice (nymphs and/or adults) in 1.38%; only live nits in 64.8%, and lice + live nits in 33.8% cases diagnosed by this method (Graph 1). The stages found by metallic comb technique were: only lice in 6.4%; only live nits in 23.6%, and finally lice + live nits in 70% of the cases (Graph 2). Dead nits were found in 389 cases with direct visual examination and in 541 cases with metallic comb use. These cases were not considered as diagnostic. Graph 3 presents a comparison between both methods and the detected parasite forms.







The statistical analysis indicated that metallic comb detected on average 213 times more adult lice than direct visual method, with odds ration = 161 and CI = 70 - 368. In male gender, metallic comb led to 146 times more detection of adult lice than direct visual method. In female gender, this number went up to 249 times, or 3.64 higher than in men.

The mean time for detection of the first lice on the head of the examined patient was 57 seconds for the metallic comb and 116.4 seconds for direct visual examination, on average.



In Chile, there is the trend to underestimate pediculosis caused by Pediculus humanus var. capitis because classically this parasite is seen as not having pathogenic microorganism vector that causes other diseases 2. This is a controversial issue given that Muray and Torrey managed to experimentally infect Pediculus humanus var. capitis with Rickettsia prowazekii, etiological agent of epidemic typhoid fever 15 and Sasaki et al. isolated Bartonella Quintana from nits, which cause the so-called Trench fever.16 Pediculus capitis may parasitize subjects from different economic backgrounds, but in our society, there is the generalized tendency to state that this parasite is distributed mainly among less-privilege social groups and in those with poor hygiene habits. Global prevalence of 51.5% detected in the city of Quillota, Province of Valparaíso, Chile, confirms that this parasitosis has high prevalence in our population, showing that it is still a public health problem and an indicator of deficient cultural level.

Classically diagnostic methods used for different epidemiological and clinical studies have been used for lice direct visualization (adults and nymph states) or mainly nits located close to the hair scalp. Conversely, the recommendation for use of different types of fine-teethed combs is essential as a supporting measure in drug treatment 17, described only in a study for diagnostic purposes. De Maeseneer et al. (2000)18 compared 224 patients using fine-teethed combs used in wet hair and direct visual examination. The experiment revealed greater sensitivity for the comb, but the authors pointed out the need for further studies to validate the technique. Since then, nothing has been published in the world literature about this issue, showing that there is not great interest for pediculosis in general.

The main difference in prevalence found when comparing the microchanneled teeth metallic comb (51.5%) and direct visual method (30.7%) (Table 1) confirmed the important application of the comb for diagnosis purposes. The better diagnostic rate with the metallic comb may be explained by its structure: the space between the teeth (0.094 mm) is smaller than the size of nits (0.2 mm) and lice (0. 7 mm), enabling their dragging from the hair scalp to the hair tip, leading to their elimination. The teeth length (38mm) increased dragging useful area, enabling removal of nits with fewer passes, ensuring effectiveness in all hair types: long, short, straight, curly, fine, thick or abundant. Given that it is resistant to flexion, it enables sliding of the comb through the hair without causing too much tension over the handle, which is important in curly hair. Moreover, the comb had many advantages, such as: rounded tips that avoided hair scalp trauma; anti-sliding rubber pads that provided good gripping, and finally its stainless steel basis enabled disinfection with boiling water for many times, an important fact considering community applications. Thus, the main difference found between the two methods makes us seriously question the real prevalence of pediculosis in different parts of the world, based on studies that are performed with direct visual examination.

The confirmation diagnosis is based on finding adult or juvenile forms of the parasite, which is not frequent in direct visual examination, except for massive infestations, owing to the fact that adult forms and nymphs are photophobic and tend to get protected in hair thickness when it is touched. There is, therefore, higher likelihood of detecting nits, which tend to present as small ovoid formations firmly adhered to the hair basis. The previously mentioned situations are confirmed by our results (Graphs 1, 2 and 3). Nits placed longer than 6mm from the scalp are not viable because they will be ruptured 5 to 10 days after laying. As hairs grow between 10-32 mm per month, this fact would serve as a basis to diagnose non-active infestations when there are only nits found in a subject.

Hair length and its relation with higher risk of infestation is a controversial topic. In many texts, it is not reported and this element is considered unimportant and not the cause of infestation 13; however, in other studies, there seem to be a positive relation about this fact 8,19. In female patients, more cases are associated with long hair, which is also favored by inappropriate hygiene practices 8,19. In our observations, women with parasites denied the infestation and adopted complementary measures such as to color the hair and to have it cut in some specific areas of the head, especially in the occipital area, a fact performed without any scientific basis and consequently without satisfactory results, which was confirmed by the high positive rate of diagnosis in this group. In boys, longer hair on the frontal region compared to the rest of the head (trendy hairstyle) enabled higher concentration of movable parts in this area, providing better habitat, a fact that was observed in minors who had parasites and had this type of haircut during the study (unpublished data).

The infestation detected according to the subsectors ranged between 27.8 and 70% (Table 1); in Quillota, rural habits and limited financial resources of the diagnosed subjects prevented access to effective treatment, factors that would favor and explain the maintenance of high levels of infestation that were observed.

The great prevalence of Pediculus capitis, its implication to public health and the evident predominance in the studied population justify the approach of the topic focused from a sanitary medical perspective, so that prophylaxis can be seriously planned. It is essential to make the community participate in their health problems, especially adults responsible for underage subjects, such as the case in our study, who maintain the situation because of ignorance or negligence. In many cases, we observed that pediculosis was dealt with by myths and poorly founded practices that seemed to increase the risk (unpublished data).



The direct visual method underestimates active manifestations and detects non-active already finished infestations. Based on the high prevalence that was detected (51. 5%), we can state that the diagnosis of the infestation by Pediculus capitis is twice faster and 3.6 times more efficient when using the microchanneled teeth comb, reason why it is confirmed as a sensitive and reproducible method of great utility for epidemiological studies and daily medical practice.



1.  Downs AM, Stafford KA, Cole GC. Head lice: prevalence in schoolchildren and insecticide resistance. Parasitol Today. 1999;15:1-4.         [ Links ]

2.  Schenone H, Lobos M. Pediculosis capitis, un permanente y renovado problema. Bol Chile Parasitol. 1997;52:73-6.         [ Links ]

3.  Mumcuoglu KY. Prevention and treatment of head lice in children. Paediatr Drugs. 1999;1:211-8.         [ Links ]

4.  Schenone H, Saavedra T, Rojas A. Infestación por Pediculus humanus capitis. Un prolongado problema de salud pública. Bol Chile Parasitol. 1986;41:16-20.         [ Links ]

5.  Neira P, Goecke I, González W, Muñoz N. Ectoparasitosis en escolares rurales de la 5º Región, Valparaíso, Chile - 1986. Bol Chile Parasitol. 1987;42:87-9.         [ Links ]

6.  Neira P, Arenas C, Neira G, Valenzuela N, Subercaseaux B. Infecciones parasitarias en niños de una escuela de Reñaca Alto. Rev Med Valparaíso. 1981;34:56-60.         [ Links ]

7.  Garibaldi R, Muñoz N, Neira P, Subercaseaux B, Villalón L. Entero y ectoparasitosis en la 5º; Región, Chile. Estudio en el Hospital Psiquiátrico de Putaendo. Bol Chile Parasitol. 1990;45:83-5.         [ Links ]

8.  Cazorla D, Ruiz A, Acosta M. Estudio clínico-epidemiológico sobre pediculosis capitis en escolares de Coro, estado Falcón, Venezuela. Invest Clin. 2007;48:445-57.         [ Links ]

9.  Milano AF, Oscherov EB, Legal AZ. Pediculosis y otras ectoparasitosis en una población infantil urbana del nordeste argentino. Parasitol Latinoam. 2007;62:83-8.         [ Links ]

10.  Borges R, Silva JJ, Rodrigues RM, Mendes J. Prevalence and monthly distribution of head lice using two diagnostic procedures in several age groups in Uberlândia, State of Minas Gerais, Southeastern Brazil. Rev Soc Bras Med Trop. 2007;40:247-9.         [ Links ]

11.  Catalá S, Junco L, Vaporaky R. Pediculus capitis infestation according to sex and social factors in Argentina. Rev Saúde Pública. 2005;39:438-43.         [ Links ]

12.  Calderón-Arguedas O, Solano M, Sánchez C. El problema de la pediculosis capitis en escolares del área metropo litana de San José, Costa Rica. Parasitol Latinoam. 2003;58:177-80.         [ Links ]

13.  Speare R, Canyon DV, Cahill C, Thomas G. Comparative efficacy of two nit combs in removing head lice (Pediculus humanus var. capitis) and their eggs. Int J Dermatol. 2007;46:1275-8.         [ Links ]

14.  Neira P, Undurraga O, Muñoz N, Silva P, Saínz M, Molina L. Capacitación sobre pediculosis en líderes comunitarias. Anuario Escuela de Medicina Universidad de Valparaíso. 2003;7:217-24.         [ Links ]

15.  Murray ES, Torrey SB. Virulence of Rickettsia prowazekii for head lice. Ann N Y Acad Sci. 1975;266:25-34.         [ Links ]

16.  Sasaki T, Poudel SK, Isawa H, Hayashi T, Seki N, Tomita T, et al. First molecular evidence of Bartonella quintana in Pediculus humanus capitis (Phthiraptera: Pediculidae), collected from Nepalese children. J Med Entomol. 2006;43:110-2.         [ Links ]

17.  Rosso RO, Ramírez MS, Torres M. Pediculus capitis: terapias disponibles. Rev Chil Infect. 2003;20:111-6.         [ Links ]

18.  De Maeseneer J, Blokland I, Willems S, Vander Stichele R, Meersschaut F. Wet combing versus traditional scalp inspection to detect head lice in schoolchildren: observational study. BMJ. 2000;321:1187-8.         [ Links ]

19.  Schenone H, Falaha F, Villarroel F, Rojas A, Szekely R, Rojo M, et al. La infestación por Pediculus humanus capitis en Santiago de Chile. Bol Chil Parasitol. 1973;28:31-3.         [ Links ]



Mailing Address:
Patricia E. Neira.
Cátedra de Parasitología. Departamento de
Preclínicas. Escuela de Medicina, Facultad de
Medicina, Universidad de Valparaíso, Hontaneda
2653-Valparaíso, Chile PO Box 92-V.
Valparaíso Chile
Fono: 56-32-507349, Fax: 56-32-507321.

Conflict of interest: None.
Study awarded as Best Investigation Poster, Congress of Dermatology 2008.



* Study carried out by the Discipline of Parasitology, Department of Preclinical Care, Escola de Medicina, Faculdade de Medicina da Universidade de Valparaíso - Chile.

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