Louse infestation in Europe and North America

Public Health Significance of Urban Pests 293 confirm this British Department of Health and Social Security, 1987; Lindsay, 1993. However, the appearance of resistance to the most commonly used insecticides is belie- ved to have had an impact on the number of children infested in most communities in high- and middle-income countries Burgess Brown, 1999; Downs, Harvey Kennedy, 1999; Meinking, 1999. The studies by Lindsay 1993 and Willems and colleagues 2005 showed that socioeconomic factors influence both the risk of infestation and the ability to cure it, indicating a broader spectrum of social and environmental health problems associated with louse infestations. The burden of crab lice infestation is largely unknown. Anecdotal evidence suggests that infestations diminished significantly in the 1980s, but no epidemiological studies have been performed in any large population group. More recently, Meinking 1999 sugges- ted that the levels of infestation have recovered.

9.4. Implications for public health

In general, low-grade morbidity is the principal effect of louse infestations on public health. Constant infestation affects general well-being through disturbed sleep, diminis- hed concentration and itching that results in excoriation. Body lice have a greater impact on infested individuals whose skin is not only excoriated, but is also thickened and dis- coloured over time through constant exposure to louse bites. Other pathological effects seen in some people with longer-term infestations include lymphadenopathy and impe- tigo due to S. aureus and Group A S. pyogenes Taplin Meinking, 1988, with a poten- tial reduction of their immune status rendering them more susceptible to other infec- tions. Body lice are primary vectors for: classical typhus, caused by Rickettsia prowazekii; trench fever, caused by B. quintana; and louse-borne relapsing fever LBRF, caused by Borrelia recurrentis . They are also secondary vectors for murine typhus, caused by Rickettsia moo- seri . Endemics of these diseases were still found throughout Europe and parts of North America in the early 20th century, resulting in considerable mortality and morbidity during and immediately following the two world wars Soper et al., 1945, 1947; Jackson Spach, 1996. For centuries, these diseases followed warfare, social disruptions and natural disasters. Surprisingly, no typhus outbreak was identified after the conflicts in the Balkans the region in Europe where typhus had most recently been endemic in the 1990s or after the 1991 Gulf War, when large numbers of prisoners of war became lousy in temporary camps. Typhus disappeared from high- and middle-income countries with the recession of body louse infestations during the late 20th century. The current endemic zones are primarily limited to a few tropical regions, mostly in upland areas of Ethiopia, parts of Somalia and southern Sudan, Rwanda and Burundi, and to parts of the high Andes and Himalayas, where the combination of poverty and colder climate makes laundering or complete changes of clothing impractical or impossible. Small outbreaks occur in other regions, and it is suspected that some occurrences are underreported or under-diagnosed Gratz, Human body lice 292 have remained primarily an infestation of children. In communities where reasonably effective methods of treatment are available, adults are normally only affected by head lice through contact with infested children in their care. Crab or pubic lice mostly affect sexually active adults, although they may be passed to children and others by close non- sexual physical contact. Few studies have investigated the epidemiology of this louse. One study, however, showed that they were more common on females between the ages of 15 and 19 years and on males more than 20 years of age Fisher Morton, 1970. In high- and medium-income countries, body lice are more common in urban environ- ments; that is because the majority of people prevented from laundering or changing clo- thing, due to poverty, congregate in urban environments. In the past, the prevalence of head lice Mellanby, 1941, 1943, and of infestations with lice lousiness in general Lindsay, 1993, was also greatest in urban industrial slums and communities that were in close proximity. However, in the United Kingdom, increased mobility of populations during the latter half of the 20th century led to a more even spread of infestations, with only small differences between rural and urban areas and between different regional communities Downs, Harvey Kennedy, 1999; Smith et al., 2003.

9.3. Louse infestation in Europe and North America

As a result of improved hygiene and economic advances, body lice declined steadily throughout the 20th century in all high- and medium-income countries. In North America, some researchers believe that in homeless populations crab lice may be more prevalent that body lice Meinking, 1999, but in Europe body lice are still common in the vulnerable homeless Raoult Roux, 1999; Foucault et al., 2006. Control of infesta- tions in these groups is difficult, due to constant reinfestation through contact with others in similar circumstances. Body lice have been shown to move freely between the clothing of individuals in close proximity in shelters, and these lice can move onto bedding and remain viable until the bed is inhabited the next night, but not beyond Peacock, 1916; MacLeod Craufurd- Benson, 1941. Consequently, a residue of infestation that could expand into the wider community – given appropriate circumstances – remains in most countries. In some countries, as a result of increased unemployment, homelessness and reduced social wel- fare programmes, the prevalence of lice is believed to have increased during the 1990s Downs, Harvey Kennedy, 1999; Meinking, 1999; Raoult Roux, 1999; Willems, et al., 2005. During the late 20th century, localized increases also arose in the Balkans Valenciano et al., 1999; Kondaj, 2002 and other regions of conflict Raoult et al., 1998 – with the risk of infestation disseminating farther afield. Despite a range of interventions that use synthetic insecticides, head louse infestations in children have persisted Downs, Harvey Kennedy, 1999; Willems et al., 2005. The limited number of studies available indicate that insecticides have had a local impact on infestation rates at various times, but that this has not been sustained. Overall levels of infestation declined through the 20th century, although there are few recorded data to Public Health Significance of Urban Pests 295 Over time, body lice have developed a greater body volume than head lice and, in turn, take larger blood-meals Busvine, 1978. They can tolerate longer periods of starvation and in most cases, can withstand being removed from their host for about 36 hours, but do not normally survive 48 hours McLeod Craufurd-Benson, 1941. They live in the folds and seams of clothing and use the fibres of cloth as a substrate for laying their eggs. All human lice attach their eggs to hairs or fibres in an area where the temperature is appropriate for incubation of the embryos and the local humidity is high enough to pro- tect the eggs from desiccation. Body lice only visit the body surface to feed, so after remo- val of clothing it is rare that lice are found on the skin. While not feeding, body lice of all stages are found alongside the eggs and empty eggshells in the clothing seams. In all cases, lice require optimum surface body temperature and humidity. In febrile individuals, lice move away from the skin and, given the opportunity, will move to another person Lloyd, 1919. 9.7. Louse management 9.7.1. Inspection and detection