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Background Fine tooth lice combs fall into two classes based on the material from which their teeth are made: plastic or metal. Metal combs are further divided into those that are made from a flat sheet of metal, and hence have rectangular teeth, and those that have cylindrical teeth embedded in a plastic base. Methods The efficacy of two fine tooth combs [Lice Meister comb (metal) and Lady Jayne comb (plastic)] in removing head lice ( Pediculus humanus var. capitis) and their eggs from the hair of children was evaluated after treatment with a viscous head lice product (Lice Blaster; Emerald Forest Pharmaceuticals Pty Ltd, Currumbin, Qld, Australia). The hair of 27 children was divided into two sections sagitally, and each comb was randomly assigned to one half of the hair, and the lice and eggs removed by the combs were counted. Results In 96% of subjects, the Lice Meister comb removed more eggs than the Lady Jayne comb, with an average of three to four times more hatched, dead, and live eggs removed. The Lice Meister comb removed more lice than the Lady Jayne comb in 10 subjects, the same in eight subjects, and less in nine subjects. Conclusion Overall, the Lice Meister comb is recommended as a more effective comb for use in controlling head lice infestations, whether employed with conditioner or with insecticide treatment. This appears to be the first study investigating the efficacy of nit combs in vivo. Further research is needed to determine which characteristics of fine tooth combs are the most important in removing head lice eggs. [ABSTRACT FROM AUTHOR]

Background Pediculosis, caused by head lice (Pediculidae: Pediculus humanus var. capitis), is experiencing a global resurgence, with the prevalence in primary schools averaging as high as 40% in some areas regardless of socioeconomic factors. Control efforts using chemical treatments are becoming increasingly ineffective, with insecticide resistance recorded in several countries. Prevention using repellents and oils would be useful if they limited transmission. Many commercially available substances reputedly have effective repellent qualities, but remain untested. Methods This study tested the preventative efficacy of N, N-diethyl-3-methylbenzamide (DEET) against several commercially available botanicals to clarify their value as transmission inhibitors, irritants, repellents, and antifeedants. Results The transfer of head lice to treated hairs was limited by the slippery nature of the oils rather than their repellent qualities. Irritancy was not important because lice proceeded despite being highly irritated, except in the case of coconut. Tea tree and peppermint caused the most repellence, and tea tree and lavender prevented some blood feeding on treated skin. Comparatively, tea tree oil was most efficacious, with DEET ranking equal second overall with coconut, peppermint, and a botanical mixture. Conclusions Neither DEET nor any of the botanicals tested showed sufficient preventative efficacy to be endorsed. [ABSTRACT FROM AUTHOR]

Although head lice, Pediculus humanus capitis, are globally prevalent blood-sucking ectoparasites, the amount of blood imbibed by head lice has not been determined. This study investigated this parameter, as regular loss of a small quantity of blood may lead to an iron deficiency and anaemia. Adult female lice (66), adult males (46), and nymphs (152) were weighed before and after feeding in groups of 17–109 lice. The average amounts of blood imbibed at a single feed were: adult female louse (0.0001579 ml), adult male (0.0000657 ml) and nymph (0.0000387 ml). Assuming three feeds per day by an average infection of 30 lice (10 females, 10 males, and 10 nymphs), the average child with active pediculosis would loose 0.008 ml of blood per day. This amount of blood loss is of no clinical significance even in iron-deficient children. The most heavily infected child observed with 2657 lice could be expected to loose 0.7 ml/day or 20.8 ml/month, which may be of clinical importance in a child on an adequate diet, and would be significant in an iron-deficient child. However, if head lice feed more often than three times a day, a heavy infestation would have a greater potential to lead to iron deficiency. The frequency of feeding of head lice on the head of the human host needs to be determined. [ABSTRACT FROM AUTHOR]

Although the global increase in pediculosis is well known, little is known about the exact nature of head lice (Pediculus capitis ) transmission. Several mechanisms have been proposed such as head-to-head and fomite transmission, but some contention remains concerning the primary transmission route. This study investigated spatial and kinetic factors influencing the dynamics of hair-to-hair transfer to clarify further how head lice transmit from head to head. Forty-eight factorial experimental trials, with 10 replicates each, were conducted using 480 freshly caught P. capitis from primary school children. In the trials, each louse was placed on a stationary suspended hair or a mobile hair and was presented with mobile or stationary hairs for transmission. All hair passes involved contact between the uninhabited hair and the lice. Hairs without a louse were presented dorsally, laterally, and ventrally to the louse. They were also passed from head to tail or from tail to head and were moved at speeds of 8 m and 4 m per min. The proportion of P. capitis transmission was highly dependent on the specific setting. The tail-to-head direction, slow movement, and a parallel direction all proved favorable for transmission. The highest transfer proportion of P. capitis (85%) was observed in the setting where the presented hair was laterally slow moving in a parallel way from tail to head. No transmission at all was observed under an angle of 90 degrees. Hair-to-hair P. capitis transmission occurred more frequently when hairs were in particular physical and kinetic relationships. This suggests that head lice are less likely to take advantage of many proposed fomite transmission scenarios and are most likely to rely on head-to-head contact for transmission. [ABSTRACT FROM AUTHOR]