Risk factors for human lice and bartonellosis among the homeless, San Francisco, California, USA.

Homeless persons in San Francisco, California, USA,have been shown to have head and body lice infestations and Bartonella quintana infections. We surveyed a self selected population of homeless persons in San Francisco to assess infestations of head and body lice, risks of having body lice, and presence of B. quintana in lice. A total of 203 persons who reported itching were surveyed during 2008-2010 and 2012: 60 (30%) had body lice, 10 (4.9%)had head lice, and 6 (3.0%) had both. B. quintana was detected in 10 (15.9%) of 63 body lice pools and in 6 (37.5%)of 16 head lice pools. Variables significantly associated(p<0.05) with having body lice in this homeless population included male sex, African-American ethnicity, and sleeping outdoors. Our study findings suggest that specific segments of the homeless population would benefit from information on preventing body lice infestations and louse borne diseases.