Ectoparasitism and Vector-Borne Diseases in 930 Homeless People From Marseilles :

Ticks are currently considered to be second only to mosquitoes as vectors of human infectious diseases in the world. Each tick species has preferred environmental conditions and biotopes that determine the geographic distribution of the ticks and, consequently, the risk areas for tickborne diseases. This is particularly the case when ticks are vectors and reservoirs of the pathogens. Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 15 ixodid-borne bacterial pathogens have been described throughout the world, including 8 rickettsiae, 3 ehrlichiae, and 4 species of the Borrelia burgdorferi complex. This article reviews and illustrate various aspects of the biology of ticks and the tickborne bacterial diseases (rickettsioses, ehrlichioses, Lyme disease, relapsing fever borrelioses, tularemia, Q fever), particularly those regarded as emerging diseases. Methods are described for the detection and isolation of bacteria from ticks and advice is given on how tick bites may be prevented and how clinicians should deal with patients who have been bitten by ticks.

Homeless people in developed countries have specific problems predisposing them to infectious diseases. Respiratory infections and outbreaks of tuberculosis and other aerosol transmitted infections have been reported. Homeless intravenous drug users are at an increased risk of contracting HIV, and hepatitis B and C infections. Skin problems are the main reason the homeless seek medical attention, and these commonly include scabies, pediculosis, tinea infections, and impetigo. Many foot disorders are more prevalent in the homeless including ulcers, cellulitis, erysipelas, and gas gangrene. The louse transmitted bacteria Bartonella quintana has recently been found to cause clinical conditions in the homeless such as urban trench fever, bacillary angiomatosis, endocarditis, and chronic afebrile bacteraemia. Treatment of homeless people is complicated by financial constraints, self-neglect, and lack of adherence. Patients with serious and contagious illnesses should be hospitalised. Physicians should be aware of these specific issues to enhance care.

Infection with Bartonella quintana can cause trench fever, endocarditis, bacillary angiomatosis, and peliosis. An outbreak of bacteremia due to B. quintana has been reported among homeless people in Seattle, and the seroprevalence is high among homeless people in both the United States and Europe. Body lice are known to be the vectors of B. quintana. We studied all the homeless people who presented in 1997 to the emergency departments of the University Hospital, Marseilles, France. Blood was collected for microimmunofluorescence testing for antibodies against B. quintana and for culture of the bacterium. Body lice were collected and analyzed by the polymerase chain reaction and sequencing of a portion of the citrate synthase gene of B. quintana. In 10 of 71 homeless patients (14 percent), blood cultures were positive for B. quintana, and 21 of the patients (30 percent) had high titers of antibody against the organism. A total of 17 patients (24 percent) had evidence of recent infection (bacteremia or seroconversion). Tests of lice from 3 of the 15 patients from whom they were collected were positive for B. quintana. The homeless people with B. quintana bacteremia were more likely to have been exposed to lice (P=0.002), were more likely to have headaches (P=0.03) and severe leg pain (P<0.001), and had lower platelet counts (P=0.006) than the homeless people who were seronegative for B. quintana and did not have bacteremia; 8 of the 10 patients with bacteremia were afebrile. Five patients had chronic bacteremia, as indicated by positive blood cultures over a period of several weeks. In an outbreak of urban trench fever among homeless people in Marseilles, B. quintana infections were associated with body lice in patients with nonspecific symptoms or no symptoms.