Lice

Background

Lice! Visions of unclean hair and vermin are conjured by the sound of this organism. There is an alarming trend toward organisms which are becoming increasingly resistant to most over the counter medications.

OUTLINE

Epidemiology

Laboratory/Radiologic/Other Diagnostic Testing

Gross Appearance and Clinical Variants

Prognosis and Treatment

Commonly Used Terms

EPIDEMIOLOGY CHARACTERIZATION

SYNONYMS Nits
Pediculosis capitis

INCIDENCE

Secular trends in the epidemiology of pediculosis capitis and pubis among Israeli soldiers: a 27-year follow-up.

Mimouni D, Grotto I, Haviv J, Gdalevich M, Huerta M, Shpilberg O.

Israel Defense Forces Medical Corps and Dermatology Department, Rabin Medical Center, Petah-Tiqva, Israel.
Int J Dermatol 2001 Oct;40(10):637-9 Abstract quote
BACKGROUND: Pediculosis capitis and pubis are not mandatorily reported diseases in most countries. Thus, the reported rates of these diseases in large populations are usually inaccurate and based on estimations.

OBJECTIVE: To describe the global epidemiology of pediculosis capitis and pubis in the Israeli Defense Force.

\METHODS: We analyzed the data obtained from the routine and mandatory reporting of every individual case of pediculosis capitis and pubis to the Army Health Branch Epidemiology Department since 1972 and 1973, respectively.

RESULTS: During this period, epidemics of pediculosis capitis and pubis were observed between 1973 and 1985 and 1972 and 1987, with 17.7- and 3.9-fold increases in incidence, respectively. These two epidemics were followed by a sharp decline in morbidity (113.6- and 13.6-fold between 1981 and 1999 and 1984 and 1999, respectively) to the present.

CONCLUSIONS: A number of factors could be responsible for the observed decline in morbidity, e.g. socioeconomic, pharmacologic, environmental, or prevention policy modifications. The rates of pediculosis capitis and pubis have continuously declined since the last epidemic of 1972-1987, indicating the influence of these and possibly other factors.

GROSS APPEARANCE/
CLINICAL VARIANTS CHARACTERIZATION

GENERAL

Louse comb versus direct visual examination for the diagnosis of head louse infestations.

Mumcuoglu KY, Friger M, Ioffe-Uspensky I, Ben-Ishai F, Miller J.

Department of Parasitology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.

Pediatr Dermatol 2001 Jan-Feb;18(1):9-12 Abstract quote
The techniques used for diagnosis of head louse (Pediculosis capitis) infestation are a source of controversy. Most epidemiologic and diagnostic studies have been done using direct visual examination.

The main objective of this study is to compare the efficacy of direct visual examination versus the louse comb method. The hair of each child was examined twice; one team used a screening stick and another team used a louse comb. Seventy-nine boys and 201 girls, 7-10 years old were examined. Examination with a louse comb found that 25.4% of the children were infested with both lice and nits, while another 31.3% had nits only. Boys were significantly less infested with lice and nits than girls (lice: 15.2 and 29.6%; nits: 21.5 and 35.4%, respectively). The infestation rate with lice and nits was significantly higher in children with long (68.9%) and medium-length (63.9%) hair than in children with short hair (44.0%) (p < 0.01). Direct visual examination found that 5.7% of the children were infested with both lice and nits, and another 49.0% with nits only. The average time until detection of the first louse was 57.0 seconds with the comb as compared to 116.4 seconds by direct visual examination.

Diagnosis of louse infestation using a louse comb is four times more efficient than direct visual examination and twice as fast. The direct visual examination technique underestimates active infestation and detects past, nonactive infestations.

PROGNOSIS AND TREATMENT CHARACTERIZATION

PROGNOSTIC FACTORS

RESISTANCE

Widespread insecticide resistance in head lice to the over-the-counter pediculocides in England, and the emergence of carbaryl resistance.

Downs AM, Stafford KA, Hunt LP, Ravenscroft JC, Coles GC.

Department of Dermatology, University of Bristol, Bristol, BS2 8HW, UK.

Br J Dermatol 2002 Jan;146(1):88-93 Abstract quote
BACKGROUND: Increasing resistance to insecticides used for the control of head lice infestation has been documented over the last decade. Treatment failure and tolerance to insecticides have been validated in a number of studies undertaken in several U.K. centres.

OBJECTIVES: To establish the extent of insecticide resistance in head lice and acetylcholinesterase activity in the presence of carbaryl in head lice.

METHODS: Head lice were collected from school children in four centres across England (Exmouth, Loughborough, Leeds and South Shields), and tested in their response to the insecticides permethrin, phenothrin, malathion and carbaryl. Data were compared with information collected in Bristol and Bath in 1998 and with susceptible body lice. The activity of louse acetylcholinesterase was measured with and without carbaryl in head lice collected in Bristol, Leeds, Loughborough and in body lice. The efficacy of a 1% carbaryl lotion was compared in children in Bristol and Leeds.

RESULTS: Compared with body lice, head lice from all six centres were significantly different in their response (P < 0.0001) to permethrin, phenothrin and malathion after 2-h exposure tests. There were significant differences in louse acetylcholinesterase activity in body lice, and head lice collected in Loughborough and Bristol in the presence or absence of carbaryl (P < 0.001), indicating enzyme inhibition. However, the difference for lice from Leeds was not significant (P = 0.363) suggesting that the enzyme was resistant to carbaryl. Eighty-nine per cent of children treated in Leeds with carbaryl were cured compared with 100% in Bristol.

CONCLUSIONS: The data suggest head lice resistance is present in many parts of England to over-the-counter products containing synthetic insecticides (permethrin, phenothrin and malathion). They further suggest that resistance is starting to develop to carbaryl in head lice in Leeds and that extensive use of this product would lead to significant resistance.

TREATMENT

Permethrin-resistant human head lice, Pediculus capitis, and their treatment.

Yoon KS, Gao JR, Lee SH, Clark JM, Brown L, Taplin D.

Department of Entomology, University of Massachusetts-Amherst, MA 01003, USA.

Arch Dermatol. 2003 Aug;139(8):994-1000. Abstract quote
OBJECTIVE: To compare the pediculicidal activity of Ovide lotion and its active ingredient, 0.5% malathion, with Nix and its active ingredient, 1% permethrin, in permethrin-resistant head lice.

DESIGN: In vitro pediculicidal product and active ingredient comparison. The presence of knockdown resistance-type mutations (T929I and L932F) was validated by DNA sequencing.

SETTING: University of Massachusetts-Amherst; University of Miami School of Medicine, Miami, Fla; Plantation and Homestead, Fla; and Mathis, Tex.Other

PARTICIPANTS: Lice were collected in 3 geographical regions within the United States and in Yamburara, Ecuador, from healthy but infested individuals.Intervention Within 3 to 6 hours of collection, lice were given a blood meal, exposed to products or active ingredients, and observed at regular intervals.

MAIN OUTCOME MEASURES: Percent mortality of lice at regular intervals after exposure to products or active ingredients and presence of T929I and L932F mutations.

RESULTS: South Florida lice exhibited a significantly slower mortality response to permethrin compared with susceptible Ecuadorian lice. Ovide and malathion killed permethrin-resistant lice faster than Nix or permethrin. The presence of T929I and L932F in permethrin-resistant south Florida lice was confirmed by DNA sequencing. The population of Texas lice from Mathis was slightly resistant to permethrin and included 13% with resistant genotypes.

CONCLUSIONS: The presence of the T929I and L932F mutations was confirmed by DNA sequencing in lice collected from children in south Florida that were resistant to the pediculicidal effects of permethrin and the leading permethrin-based head lice product, Nix. Malathion resistance was not observed in this study. The data also show that Ovide killed these same permethrin-resistant head lice approximately 10 times faster than permethrin or Nix.

Comparative efficacy of treatments for pediculosis capitis infestations: update 2000.

Meinking TL, Entzel P, Villar ME, Vicaria M, Lemard GA, Porcelain SL.

Department of Dermatology and Cutaneous Surgery, University of Miami School of Medicine, PO Box 016960, R-117, Miami, FL 33101, USA.
Arch Dermatol 2001 Mar;137(3):287-92 Abstract quote
OBJECTIVE: To evaluate the pediculicidal and ovicidal activity of 5 head lice products.

DESIGN: In vitro pediculicidal and ovicidal product comparison.

SETTING: Tropical field station in Panama.

PARTICIPANTS: Head lice and eggs were harvested from healthy children infested with Pediculus capitis.

INTERVENTION: Within 2 hours of capture, lice were placed in continuous, direct contact with the pediculicide products and observed at regular intervals. Fresh, viable eggs were immersed in the pediculicides for 10 minutes, rinsed, air-dried, and incubated for 2 weeks.

MAIN OUTCOME MEASURES: Percentage of lice dead at regular observation intervals between 5 minutes and 3 hours of continuous exposure to the pediculicide and percentage of eggs not hatched after 2 weeks.

RESULTS: All lice treated with Ovide lotion (0.5% malathion) were dead within 10 minutes and none of the eggs hatched. There was no significant change in the effectiveness of 0.5% malathion lotion or A-200 shampoo compared with the results of an earlier study (1986). There were significant declines in the pediculicidal activity of RID and the ovicidal activity of lindane. Nix (1% permethrin), which was not on the market at the time of the original study, killed lice in less than 30 minutes, and ovicidal activity ranged from 73% to 90% (diluted and undiluted, respectively).

CONCLUSIONS: Ovide lotion (0.5% malathion) was the fastest-killing pediculicide and the most effective ovicide. One percent lindane shampoo was the slowest-acting pediculicide and least effective ovicide. Nix was highly effective in both undiluted and diluted forms.

Comparative In Vitro Pediculicidal Efficacy of Treatments in a Resistant Head Lice Population in the United States

Terri L. Meinking, BA; Lidia Serrano; Bruce Hard, MA; Pamela Entzel, JD, MPH; Glendene Lemard, MA; Elisabeth Rivera; Maria Elena Villar, MPH

Arch Dermatol. 2002;138:220-224 Abtract quote

Objective
To compare the pediculicidal activity of 5 head lice products available in the United States on head lice from south Florida.

Design
In vitro pediculicidal product comparison.

Setting
Lice Source Services, Inc, located in Plantation, Fla, a clinic for the treatment and grooming of individuals with pediculosis capitis.

Participants
Head lice were collected from healthy clients with Pediculus capitis that came to Lice Source Services, Inc, to seek their services.

Interventions
Within 2 to 6 hours of capture, lice were placed in continuous direct contact with the pediculicide products and observed at regular intervals. Results were compared with findings of a recent study of a treatment-sensitive population of head lice conducted in Panama.

Main Outcome
Measure Percentage of lice dead at regular observation intervals between 5 minutes and 3 hours of continuous exposure to the pediculicides.

Results
Two prescription products, Ovide lotion (0.5% malathion) and 1% lindane shampoo, were ranked in the same order as in 2 previous studies (first and last, respectively). The order of effectiveness from most to least effective was as follows: Ovide lotion, A-200 shampoo (a natural pyrethrin product synergized with piperonyl butoxide), undiluted Nix (1% permethrin), diluted Nix, RID (a natural pyrethrin product synergized with piperonyl butoxide), and 1% lindane shampoo.

Conclusions
There were statistically significant differences in the efficacy of all the products when compared with the results found in the recent study in Panama, except for Ovide lotion. Of those tested, Ovide was the only pediculicide in the United States that had not become less effective. The difference in efficacy of 1% lindane, Nix, and pyrethrins between the Panama and Florida studies supports the argument that some head lice in the United States have become resistant to these treatments.

Henry JB. Clinical Diagnosis and Management by Laboratory Methods. Twentieth Edition. WB Saunders. 2001.
Rosai J. Ackerman's Surgical Pathology. Eight Edition. Mosby 1996.
Sternberg S. Diagnostic Surgical Pathology. Third Edition. Lipincott Williams and Wilkins 1999.
Robbins Pathologic Basis of Disease. Sixth Edition. WB Saunders 1999.
DeMay RM. The Art and Science of Cytopathology. Volume 1 and 2. ASCP Press. 1996.
Weedon D. Weedon's Skin Pathology Second Edition. Churchill Livingstone. 2002
Fitzpatrick's Dermatology in General Medicine. 5th Edition. McGraw-Hill. 1999.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fourth Edition. Mosby 2001.

Commonly Used Terms

Basic Principles of Disease
Learn the basic disease classifications of cancers, infections, and inflammation

Commonly Used Terms
This is a glossary of terms often found in a pathology report.

Diagnostic Process
Learn how a pathologist makes a diagnosis using a microscope

Surgical Pathology Report
Examine an actual biopsy report to understand what each section means

Special Stains
Understand the tools the pathologist utilizes to aid in the diagnosis

How Accurate is My Report?
Pathologists actively oversee every area of the laboratory to ensure your report is accurate

Got Path?
Recent teaching cases and lectures presented in conferences

Internet Links

Pathologists Who Make A Difference
Search for a Physician Specialist

Last Updated 8/26/2003

PROGNOSIS AND TREATMENT	CHARACTERIZATION
PROGNOSTIC FACTORS
RESISTANCE
Widespread insecticide resistance in head lice to the over-the-counter pediculocides in England, and the emergence of carbaryl resistance. Downs AM, Stafford KA, Hunt LP, Ravenscroft JC, Coles GC. Department of Dermatology, University of Bristol, Bristol, BS2 8HW, UK.	Br J Dermatol 2002 Jan;146(1):88-93 Abstract quote BACKGROUND: Increasing resistance to insecticides used for the control of head lice infestation has been documented over the last decade. Treatment failure and tolerance to insecticides have been validated in a number of studies undertaken in several U.K. centres. OBJECTIVES: To establish the extent of insecticide resistance in head lice and acetylcholinesterase activity in the presence of carbaryl in head lice. METHODS: Head lice were collected from school children in four centres across England (Exmouth, Loughborough, Leeds and South Shields), and tested in their response to the insecticides permethrin, phenothrin, malathion and carbaryl. Data were compared with information collected in Bristol and Bath in 1998 and with susceptible body lice. The activity of louse acetylcholinesterase was measured with and without carbaryl in head lice collected in Bristol, Leeds, Loughborough and in body lice. The efficacy of a 1% carbaryl lotion was compared in children in Bristol and Leeds. RESULTS: Compared with body lice, head lice from all six centres were significantly different in their response (P < 0.0001) to permethrin, phenothrin and malathion after 2-h exposure tests. There were significant differences in louse acetylcholinesterase activity in body lice, and head lice collected in Loughborough and Bristol in the presence or absence of carbaryl (P < 0.001), indicating enzyme inhibition. However, the difference for lice from Leeds was not significant (P = 0.363) suggesting that the enzyme was resistant to carbaryl. Eighty-nine per cent of children treated in Leeds with carbaryl were cured compared with 100% in Bristol. CONCLUSIONS: The data suggest head lice resistance is present in many parts of England to over-the-counter products containing synthetic insecticides (permethrin, phenothrin and malathion). They further suggest that resistance is starting to develop to carbaryl in head lice in Leeds and that extensive use of this product would lead to significant resistance.
TREATMENT
Permethrin-resistant human head lice, Pediculus capitis, and their treatment. Yoon KS, Gao JR, Lee SH, Clark JM, Brown L, Taplin D. Department of Entomology, University of Massachusetts-Amherst, MA 01003, USA.	Arch Dermatol. 2003 Aug;139(8):994-1000. Abstract quote OBJECTIVE: To compare the pediculicidal activity of Ovide lotion and its active ingredient, 0.5% malathion, with Nix and its active ingredient, 1% permethrin, in permethrin-resistant head lice. DESIGN: In vitro pediculicidal product and active ingredient comparison. The presence of knockdown resistance-type mutations (T929I and L932F) was validated by DNA sequencing. SETTING: University of Massachusetts-Amherst; University of Miami School of Medicine, Miami, Fla; Plantation and Homestead, Fla; and Mathis, Tex.Other PARTICIPANTS: Lice were collected in 3 geographical regions within the United States and in Yamburara, Ecuador, from healthy but infested individuals.Intervention Within 3 to 6 hours of collection, lice were given a blood meal, exposed to products or active ingredients, and observed at regular intervals. MAIN OUTCOME MEASURES: Percent mortality of lice at regular intervals after exposure to products or active ingredients and presence of T929I and L932F mutations. RESULTS: South Florida lice exhibited a significantly slower mortality response to permethrin compared with susceptible Ecuadorian lice. Ovide and malathion killed permethrin-resistant lice faster than Nix or permethrin. The presence of T929I and L932F in permethrin-resistant south Florida lice was confirmed by DNA sequencing. The population of Texas lice from Mathis was slightly resistant to permethrin and included 13% with resistant genotypes. CONCLUSIONS: The presence of the T929I and L932F mutations was confirmed by DNA sequencing in lice collected from children in south Florida that were resistant to the pediculicidal effects of permethrin and the leading permethrin-based head lice product, Nix. Malathion resistance was not observed in this study. The data also show that Ovide killed these same permethrin-resistant head lice approximately 10 times faster than permethrin or Nix.
Comparative efficacy of treatments for pediculosis capitis infestations: update 2000. Meinking TL, Entzel P, Villar ME, Vicaria M, Lemard GA, Porcelain SL. Department of Dermatology and Cutaneous Surgery, University of Miami School of Medicine, PO Box 016960, R-117, Miami, FL 33101, USA.	Arch Dermatol 2001 Mar;137(3):287-92 Abstract quote OBJECTIVE: To evaluate the pediculicidal and ovicidal activity of 5 head lice products. DESIGN: In vitro pediculicidal and ovicidal product comparison. SETTING: Tropical field station in Panama. PARTICIPANTS: Head lice and eggs were harvested from healthy children infested with Pediculus capitis. INTERVENTION: Within 2 hours of capture, lice were placed in continuous, direct contact with the pediculicide products and observed at regular intervals. Fresh, viable eggs were immersed in the pediculicides for 10 minutes, rinsed, air-dried, and incubated for 2 weeks. MAIN OUTCOME MEASURES: Percentage of lice dead at regular observation intervals between 5 minutes and 3 hours of continuous exposure to the pediculicide and percentage of eggs not hatched after 2 weeks. RESULTS: All lice treated with Ovide lotion (0.5% malathion) were dead within 10 minutes and none of the eggs hatched. There was no significant change in the effectiveness of 0.5% malathion lotion or A-200 shampoo compared with the results of an earlier study (1986). There were significant declines in the pediculicidal activity of RID and the ovicidal activity of lindane. Nix (1% permethrin), which was not on the market at the time of the original study, killed lice in less than 30 minutes, and ovicidal activity ranged from 73% to 90% (diluted and undiluted, respectively). CONCLUSIONS: Ovide lotion (0.5% malathion) was the fastest-killing pediculicide and the most effective ovicide. One percent lindane shampoo was the slowest-acting pediculicide and least effective ovicide. Nix was highly effective in both undiluted and diluted forms.
Comparative In Vitro Pediculicidal Efficacy of Treatments in a Resistant Head Lice Population in the United States Terri L. Meinking, BA; Lidia Serrano; Bruce Hard, MA; Pamela Entzel, JD, MPH; Glendene Lemard, MA; Elisabeth Rivera; Maria Elena Villar, MPH	Arch Dermatol. 2002;138:220-224 Abtract quote Objective To compare the pediculicidal activity of 5 head lice products available in the United States on head lice from south Florida. Design In vitro pediculicidal product comparison. Setting Lice Source Services, Inc, located in Plantation, Fla, a clinic for the treatment and grooming of individuals with pediculosis capitis. Participants Head lice were collected from healthy clients with Pediculus capitis that came to Lice Source Services, Inc, to seek their services. Interventions Within 2 to 6 hours of capture, lice were placed in continuous direct contact with the pediculicide products and observed at regular intervals. Results were compared with findings of a recent study of a treatment-sensitive population of head lice conducted in Panama. Main Outcome Measure Percentage of lice dead at regular observation intervals between 5 minutes and 3 hours of continuous exposure to the pediculicides. Results Two prescription products, Ovide lotion (0.5% malathion) and 1% lindane shampoo, were ranked in the same order as in 2 previous studies (first and last, respectively). The order of effectiveness from most to least effective was as follows: Ovide lotion, A-200 shampoo (a natural pyrethrin product synergized with piperonyl butoxide), undiluted Nix (1% permethrin), diluted Nix, RID (a natural pyrethrin product synergized with piperonyl butoxide), and 1% lindane shampoo. Conclusions There were statistically significant differences in the efficacy of all the products when compared with the results found in the recent study in Panama, except for Ovide lotion. Of those tested, Ovide was the only pediculicide in the United States that had not become less effective. The difference in efficacy of 1% lindane, Nix, and pyrethrins between the Panama and Florida studies supports the argument that some head lice in the United States have become resistant to these treatments.

Epidemiology
Laboratory/Radiologic/Other Diagnostic Testing
Gross Appearance and Clinical Variants
Prognosis and Treatment
Commonly Used Terms

EPIDEMIOLOGY	CHARACTERIZATION
SYNONYMS	Nits Pediculosis capitis
INCIDENCE
Secular trends in the epidemiology of pediculosis capitis and pubis among Israeli soldiers: a 27-year follow-up. Mimouni D, Grotto I, Haviv J, Gdalevich M, Huerta M, Shpilberg O. Israel Defense Forces Medical Corps and Dermatology Department, Rabin Medical Center, Petah-Tiqva, Israel.	Int J Dermatol 2001 Oct;40(10):637-9 Abstract quote BACKGROUND: Pediculosis capitis and pubis are not mandatorily reported diseases in most countries. Thus, the reported rates of these diseases in large populations are usually inaccurate and based on estimations. OBJECTIVE: To describe the global epidemiology of pediculosis capitis and pubis in the Israeli Defense Force. \METHODS: We analyzed the data obtained from the routine and mandatory reporting of every individual case of pediculosis capitis and pubis to the Army Health Branch Epidemiology Department since 1972 and 1973, respectively. RESULTS: During this period, epidemics of pediculosis capitis and pubis were observed between 1973 and 1985 and 1972 and 1987, with 17.7- and 3.9-fold increases in incidence, respectively. These two epidemics were followed by a sharp decline in morbidity (113.6- and 13.6-fold between 1981 and 1999 and 1984 and 1999, respectively) to the present. CONCLUSIONS: A number of factors could be responsible for the observed decline in morbidity, e.g. socioeconomic, pharmacologic, environmental, or prevention policy modifications. The rates of pediculosis capitis and pubis have continuously declined since the last epidemic of 1972-1987, indicating the influence of these and possibly other factors.