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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.

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]