Transmission and risk factors

[Extract]\ud It can be tempting to examine the global spread of pediculosis in terms of transmission risks because most countries have experienced increases in the detection of Pediculus capitis since the 1900s. Reducing transmission is arguably the most important factor controlling the spread of infestations. However, the spread of emergent and\ud resurgent diseases due to increased population movement is well documented and pediculosis is no exception. Of far more importance is the issue of reinfestation, which is a common problem in the control of pediculosis. Reinfestation is a highly problematic social and economic transmission issue that even effective pediculicides cannot easily resolve.\ud This chapter considers factors that have a bearing on the transmission of head lice. This has not been a clear-cut topic and there has been difficulty in estimating the importance of head-to-head versus fomite-to-head transmission. This has resulted in some time being invested during the last decade to determine the mechanisms in P. capitis transmission so that control programs do not squander limited resources. Some of these studies are field-based while others involve laboratory experimentation under controlled conditions. As can be expected, results from these two sources do not always agree