Spatial and Kinetic Factors for the Transfer of Head Lice (Pediculus capitis) Between Hairs

Abstract

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.

Genetic Analysis of Lice Supports Direct Contact between Modern and Archaic Humans

“…We are confident that “direct contact” would be required for a host switch because these obligate parasitic lice cannot move between individuals without direct physical contact (Buxton 1946; Durden 2001; Canyon et al 2002; Burgess 2004) and furthermore, they die within 24 h of being removed from their host. However, an examination of Pthirus pubis, the human pubic louse, might shed light on the subject of human admixture because unlike head and body lice, pubic lice are primarily transmitted during intercourse.…”

“…The lice found on primates are quite host specific, with most species occurring only on a single species of host (Durden and Musser 1994). Host specificity is reinforced by the fact that primate lice require direct physical contact between hosts for transmission (Buxton 1946; Durden 2001; Canyon et al 2002; Burgess 2004). Host specificity often goes hand in hand with long-term coevolutionary patterns between hosts and parasites (Page 2003), making primate lice excellent candidates for inferring host evolutionary history.…”

Ectoparasitoses e saúde pública no Brasil: desafios para controle

“…A principal via de transmissão ocorre de cabeça a cabeça, sendo necessário um contato repetido e prolongado para atingir taxas de transmissão significantes (Canyon et al, 2002). A transmissão por meio de fômites é bastante discutí-vel.…”

Milben, Läuse und Flöhe

“…Am weitaus häu figs ten wer den Kopf läu-se durch di rek ten Kopf-zu-Kopf-Kon takt über tra gen. Ex pe ri men tell konn te ge zeigt wer den, dass für das Über wan dern eine lang sa me Par al lel be we gung des be nach barten Haa res in Schwanz-Kopf-Rich tung la teral vom In sekt am güns tigs ten ist [6]. Der in di rek te Über tra gungs weg über Kopf bede ckun gen, Kis sen, Käm me, Bürs ten und an de res spielt eine weitaus ge rin ge re Rol le [26].…”