Essential Oils as a Potential Treatment Option for Pediculosis.

Pediculosis is a prevalent ectoparasite infestation caused by lice. The head louse (Pediculus humanus capitis) and body louse (Pediculus humanus humanus) are obligatory parasites whose only known hosts are humans. Pediculosis is probably the most common ectoparasitic infestation, affecting up to 80% of the population in several countries, and particularly prevalent in the infant population worldwide. Several treatment options, including shampoos and creams containing insecticides, have been introduced for the treatment of pediculosis. Recently, the use of synthetic chemicals to control human lice has raised concerns pertaining to human health and the environment. Therefore, increasing efforts have been undertaken to develop effective pediculicides with low environmental toxicity and minimal environmental residual activity. In this study, we focus on the essential oils derived from 22 plant genera, their constituents, and the major factors that play important roles in the effectiveness of these oils in the treatment of pediculosis. Furthermore, we discuss the advantages and limitations of the mentioned essential oils, and ultimately suggest those demonstrating the most effective in vitro pediculicidal activities. The genera such as Aloysia, Cinnamomum, Eucalyptus, Eugenia, Lavandula, Melaleuca, Mentha, Myrcianthes, Origanum, Pimpinella, and Thymus appear to be more efficient against lice. These genera are rich in anethole, 1,8-cineole, cinnamaldehyde, p-cymene, eugenol, linalool, limonene, pulegone, terpinen-4-ol, and thymol compounds.

In vitro efficacy of five essential oils against Pediculus humanus capitis.

Treatment of head lice has relied mainly on the use of topical insecticides. Today, conventional topical pediculicides have suffered considerable loss of activity worldwide. There is increasing interest in the use of natural products such as essential oils for head louse control, and many of them are now incorporated into various over-the-counter products presented as pediculicides, often without proper evaluation. The aim of the present study was to assess the in vitro efficacy of five essential oils against adults of Pediculus humanus capitis using a contact filter paper toxicity bioassay. The chemical composition of the essential oils from wild bergamot, clove, lavender, tea tree, and Yunnan verbena was analyzed by gas chromatography-mass spectrometry. All treatments and controls were replicated three times on separate occasions over a period of 11 months. In all, 1239 living lice were collected from the scalp of 51 subjects, aged from 1 to 69 years. Clove oil, diluted either in coco oil or sunflower oil, demonstrated the best adulticidal activity, reaching > 90% mortality within 2 h in lice submitted to a 30-min contact. Yunnan verbena oil diluted in coco oil showed also a significant efficacy. Other essential oils showed a lower efficacy. The oil's major component(s) differed according to the tested oils and appeared chemically diverse. In the case of clove oil, the eugenol appeared as the main component. This study confirmed the potential interest of some of the essential oils tested, but not all, as products to include possibly in a pediculicidal formulation.

Ineffectiveness of Insecticide Bendiocarb Against a Cimex lectularius (Hemiptera: Cimicidae) Population in Paris, France.

Bed bugs, nocturnal ectoparasites adapted to feed on humans, have demonstrated a global resurgence since 1990s, presumably due to increased international travel and insecticide resistance. Resistance to insecticides has restricted the ability to manage bed bug populations. We evaluated the susceptibility of Cimex lectularius L. (Hemiptera: Cimicidae) collected from five districts in Paris against bendiocarb, a carbamate insecticide. The susceptible strain of C. lectularius from London included in our experiments as a control. Mortality of adult bed bugs was assessed after exposure to a fixed concentration of bendiocarb (80%) at intervals ranging from 15 min to 72 h. Mortality in samples ranged from 14% in Bobigny to 0% in Paris 15th arrondissement and Drancy. Bioassays with bendiocarb insecticide on C. lectularius revealed high levels of resistance in Paris.

Do drowning and anoxia kill head lice?

Chemical, physical, and mechanical methods are used to control human lice. Attempts have been made to eradicate head lice Pediculus humanus capitis by hot air, soaking in various fluids or asphyxiation using occlusive treatments. In this study, we assessed the maximum time that head lice can survive anoxia (oxygen deprivation) and their ability to survive prolonged water immersion. We also observed the ingress of fluids across louse tracheae and spiracle characteristics contrasting with those described in the literature. We showed that 100% of lice can withstand 8 h of anoxia and 12.2% survived 14 h of anoxia; survival was 48.9% in the untreated control group at 14 h. However, all lice had died following 16 h of anoxia. In contrast, the survival rate of water-immersed lice was significantly higher when compared with non-immersed lice after 6 h (100% vs. 76.6%, p = 0.0037), and 24 h (50.9% vs. 15.9%, p = 0.0003). Although water-immersed lice did not close their spiracles, water did not penetrate into the respiratory system. In contrast, immersion in colored dimeticone/cyclomethicone or colored ethanol resulted in penetration through the spiracles and spreading to the entire respiratory system within 30 min, leading to death in 100% of the lice.

Molecular Survey of Head and Body Lice, Pediculus humanus, in France.

Human lice, Pediculus humanus, are obligate blood-sucking parasites. Phylogenetically, they belong to several mitochondrial clades exhibiting some geographic differences. Currently, the body louse is the only recognized disease vector, with the head louse being proposed as an additional vector. In this article, we study the genetic diversity of head and body lice collected from Bobigny, a town located close to Paris (France), and look for louse-borne pathogens. By amplifying and sequencing the cytb gene, we confirmed the presence of clades A and B in France. Besides, by amplifying and sequencing both cytb and cox1 gene, we reported, for the first time, the presence of clade E, which has thus far only been found in lice from West Africa. DNA from Bartonella quintana was detected in 16.7% of body lice from homeless individuals, but in none of the head lice collected from 47 families. Acinetobacter DNA was detected in 11.5% of head lice belonging to all three clades and 29.1% of body lice. Six species of Acinetobacter were identified, including two potential new ones. Acinetobacter baumannii was the most prevalent, followed by Candidatus Acinetobacter Bobigny-1, Acinetobacter calcoaceticus, Acinetobacter nosocomialis, Acinetobacter junii, and Candidatus Acinetobacter Bobigny-2. Body lice were found to be infected only with A. baumannii. These findings show for the first time, the presence of clade E head lice in France. This study is also the first to report the presence of DNAs of several species of Acinetobacter in human head lice in France.

In vitro activity of ten essential oils against Sarcoptes scabiei.

BACKGROUND: The development of alternative approaches in ectoparasite management is currently required. Essential oils have been demonstrated to exhibit fumigant and topical toxicity to a number of arthropods. The aim of the present study was to assess the potential efficacy of ten essential oils against Sarcoptes scabiei. METHODS: The major chemical components of the oils were identified by GC-MS analysis. Contact and fumigation bioassays were performed on Sarcoptes mites collected from experimentally infected pigs. For contact bioassays, essential oils were diluted with paraffin to get concentrations at 10, 5, and even 1% for the most efficient ones. The mites were inspected under a stereomicroscope 10, 20, 30, 40, 50, 60, 90, 120, 150, and 180min after contact. For fumigation bioassay, a filter paper was treated with 100 µL of the pure essential oil. The mites were inspected under a stereomicroscope for the first 5min, and then every 5min until 1h. RESULTS: Using contact bioassays, 1% clove and palmarosa oil killed all the mites within 20 and 50min, respectively. The oils efficacy order was: clove > palmarosa > geranium > tea tree > lavender > manuka > bitter orange > eucalyptus > Japanese cedar. In fumigation bioassays, the efficacy order was: tea tree > clove > eucalyptus > lavender > palmarosa > geranium > Japanese cedar > bitter orange > manuka. In both bioassays, cade oil showed no activity. CONCLUSION: Essential oils, especially tea tree, clove, palmarosa, and eucalyptus oils, are potential complementary or alternative products to treat S. scabiei infections in humans or animals, as well as to control the mites in the environment.

Efficacy assessment of biocides or repellents for the control of Sarcoptes scabiei in the environment.

BACKGROUND: Sarcoptes scabiei infection is a contagious disease affecting both humans and animals. The transmission occurs either by direct contact or from the environment where mites could survive several days remaining infective. The number of products available for environmental control of S. scabiei is very limited. The objective of the present study was to assess the efficacy of biocides or repellents against S. scabiei var suis. METHODS: Tested products included pyrethroids: permethrin, esdepallethrin and bioresmethrin, bifenthrin, cypermethrin and imiprothrin, cyfluthrin, tetramethrin and sumithrin. We also tested repellents: DEET, icaridin and IR3535. Sarcoptes scabiei var suis mites were collected from experimentally-infected pigs. For each test, 20 live mites of all motile stages were placed in a plastic Petri dish and sprayed uniformly by each product. Control mites were sprayed by distilled water. The study was performed in triplicate under room conditions and the mites were inspected under a stereomicroscope at intervals (5, 10, 15, 20, 25, 30, 40, 50, 60 min, 2, 3, 4, 5 and 24 h) after exposure to the products. RESULTS: All the products, except the combination of tetramethrin and sumithrin (A-PAR), were able to kill all mites within 24 h. The median survival time was 50 ± 30.4 min, 120 ± 309 min, 10 ± 5.9 min, 40 ± 36.8 min, 15 ± 7.3 min, 180 ± 417 min and 1440 ± 600 min when mites were exposed to permethrin 4 %, permethrin 0.6%, esdepallethrin and bioresmethrin, bifenthrin, cypermethrin and imiprothrin, cyfluthrin, tetramethrin and sumithrin, respectively. The median survival time was 20 ± 6.5 min, 15 ± 4.3 min, 30 ± 42.1 min and 15 ± 4.9 min for DEET 25, DEET 50, icaridin 20 and IR3535 20%, respectively. CONCLUSIONS: The results of the present study could support evidence-based use of biocides and repellents in households, hospitals and farms.