Conclusions Human body lice

Public Health Significance of Urban Pests 297 to transmit disease. The widespread distribution of homeless people with positive sero- logy for trench fever indicates that this disease is probably transmitted regularly when lousy individuals come in contact with and are exposed to infected louse faeces Jackson Spach, 1996. This also indicates that infestation with body lice may be widespread and that, as there is no mechanism for monitoring the infestation due to the withdrawal of appropriate environmental health services, the level of lousiness in society may be consi- derably higher than previously thought. It is unlikely that epidemic typhus or LBRF could enter Europe or North America under current conditions, although individual cases, resulting from travel to endemic areas, could arise; in those circumstances, howe- ver, onward transmission would be highly unlikely. Unforeseen social disruptions in the future, however, could alter this position.

9.9. Conclusions

The majority of environmental health and public health workers currently consider body lice a low priority. The exception to this is a small group of investigators who have iden- tified residual body louse populations as potentially active vectors of disease causing orga- nisms, mainly rickettsiae – some of which are zoonotic. The survival of both body lice and the diseases they have carried for the past half century, despite intensive efforts to eradicate them in the middle of the 20th century, indicates that they are not in decline. Indeed, the limited and often anecdotal information about body louse infestation in populations in high- and middle-income countries suggests that levels of infestation are increasing slowly, despite various efforts to reduce poverty and deprivation. Irrespective of the possibility of body louse prevalence increasing, the risk of disease trans- mission to a larger segment of the populace remains, because rickettsial organisms are spread primarily by dried faecal matter that can drift on air currents from the clothing of infested individuals to others in the vicinity that are not infested. Any services directed towards the homeless also require some matched services for the remainder of society, because body lice carry a greater stigma than other infestations and because the public facilities established long ago for dealing with this infestation have now disappeared from most countries. To reduce the risk of disease from body louse infestations, some policy options should be consi- dered by environmental and public health services as a first stage of the process: • make voluntary organizations that offer assistance to homeless and vagrant people more aware of body lice and their disease vector capacity; • monitor lousiness through medical services directed towards the homeless community, especially when an infestation is associated with febrile illness; • advise the homeless about louse-borne disease, with the aim to encourage them to seek help; • increase the availability of treatment options for lousiness – such as disinfestation or replacement of clothing, the use of impregnated materials, and possibly group iver- mectin therapy Foucault et al., 2006 – to reduce the prevalence of lice; and Human body lice 296 control, although the actual resistance of body lice throughout most of the world is cur- rently completely unknown. Following the use of pyrethrin and DDT in controlling outbreaks of louse-borne typhus in North Africa and central Italy during the Second World War, neurotoxic insecticides – first DDT, then lindane, followed by malathion and permethrin – became the treat- ments of choice until resistance rendered most of them ineffective in mass treatment pro- grammes Hurlburt, Altman Nibley, 1952; Kitaoka, 1952; Nicoli Sautet, 1955; Miller et al., 1972; Cole et al., 1973; Sholdt et al., 1977; Gratz, 1985.

9.7.3.1. Impregnated fabric

Fabrics impregnated with insecticides are one way to prevent or restrict body louse infes- tations. Where deemed a viable option, treating the garments of people likely to be affec- ted is the approach of choice. For example, among other functions, impregnation of mili- tary uniforms with permethrin may help to prevent their infestation should exposures arise – say, through contact with refugees or prisoners of war who have acquired a body louse infestation. Impregnation of clothing of so-called at-risk groups, such as vagrants in high- and middle-income communities or people living in areas where body louse infestation is endemic, is often impractical, as it is usually easier to provide alternative means of control – for example, by offering replacement clothing or by treating garments with heat. Under some circumstances, it may be possible to use impregnation as a control measure – for example, under conditions of social disruption. Products applied to skin are inappropriate for control of body lice, as the insects colonize clothing rather than the skin.

9.8. Benchmarks for lice management