Risk factors for Lyme disease in a small rural community in northern California.

A 1-year prospective study of risk factors for seropositivity to and contraction of Lyme disease among members of a small rural community (population, approximately 150) was conducted in northwestern California in 1988-1989. The initial rate of seropositivity for Borrelia burgdorferi for 119 current or former residents ranged from 15 to 20% among three laboratories, with statistically significant interlaboratory agreement. Questionnaires were completed by 93 current residents at entry and 80 residents a year later to evaluate the association of serologic status with 20 categorical and 47 continuous variables. Seropositive subjects had resided in the study area about 2 years longer, were bitten by unspecified biting flies more often, and were less likely to have engaged in hiking than seronegative subjects. One of 59 seronegative subjects seroconverted a year later (annual incidence = 1.7%). The cumulative frequency of seropositivity for Lyme disease in the study population was > or = 24%. Of 83 subjects examined physically, 13 were diagnosed as having definite and 18 as having probable Lyme disease. The seropositivity rate was significantly higher (38.7%) among individuals with definite/probable Lyme disease than in asymptomatic subjects (13.5%). Subjects who were seronegative or free of Lyme disease reported nearly as many tick bites as subjects who were seropositive or had a diagnosis of the disease. Age, time spent outdoors in the fall multiplied by a clothing index, and woodcutting were significantly associated with Lyme disease in logistic regression analyses.

Episcleritis, conjunctivitis, and keratitis as ocular manifestations of Lyme disease.

A 35-year-old woman presented with a bilateral palpebral follicular conjunctivitis. Subsequently, she developed a bilateral keratitis and, on a separate occasion, an episcleritis that was associated with a recrudescence of Lyme disease and poor compliance with the antibiotic regimen. Both the keratitis and episcleritis cleared completely after topical corticosteroid therapy and reinstitution of appropriate antibiotic treatment. This report emphasizes the importance of collaboration between internal medicine and ophthalmologic specialists during the long-term management of Lyme disease.

Lyme borreliosis in California. Acarological, clinical, and epidemiological studies.

The relative abundance of, and spirochetal-infection rates in, adult ixodid ticks from eight Lyme borreliosis clinical-case areas and two comparison areas were investigated in northern California from late fall to early spring, 1984-87. The western black-legged tick (Ixodes pacificus) was the most abundant species at seven of nine sites yielding specimens as determined with a tick drag method. The Pacific Coast tick (Dermacentor occidentalis) was the most abundant species at two sites, and lesser numbers of this tick and the American dog tick (D. variabilis) were obtained from seven and two sites, respectively. Abundance of I. pacificus adults varied in clinical-case areas as well as in the comparison areas, and was not correlated significantly with spirochetal infection rates in this tick. Overall, spirochetes were detected in 1.4 and 1.0% of the adult I. pacificus collected from clinical case (n = 857) and comparison sites (n = 383), respectively, and in 0.8% of adult D. occidentalis (n = 253) from one comparison area. An additional 244 D. occidentalis adults from all other sites were tested with negative results. Five spirochetal isolates recovered from I. pacificus adults were identified as Borrelia burgdorferi with specific monoclonal antibodies. Seven of 10 patients interviewed reportedly contracted their infections in summer, and six presented with a history of tick bite. Nine patients owned or occasionally harbored one or more dogs, and at least one of the dogs contracted Lyme borreliosis at the same site as its owner. Clinical manifestations of the disease in human patients included erythema migrans (100%), arthritis/arthralgia (60%), neurologic abnormalities (60%), and cardiac involvement (20%). Four of nine patients whose sera were assayed by indirect immunofluorescence contained significant antibody titers to B. burgdorferi.

Human synovial dendritic cells. Direct observation of transition to fibroblasts.

A subpopulation of human synovial cells develop a stellate morphology during in vitro culture. These cells, called stellate cells or dendritic cells, appear capable of collagenase production. In other tissues, particularly mouse spleen and human peripheral blood, cells with a similar shape express immune region associated (Ia) antigens, stimulate a primary mixed leukocyte reaction, and present antigen to lymphocytes. To characterize synovial dendritic cells, we observed changes in their morphology by time-lapse videomicroscopy. Parallel cultures of cells from the same specimens were observed periodically for HLA-DR surface antigens by immunofluorescence microscopy. During culture, synovial dendritic cells gradually lost their distinct morphologic appearance and became indistinguishable from fibroblasts. Moreover, fibroblasts occasionally assumed a dendritic morphology. When cells were examined at 24-48 h or later, we could not detect HLA-DR antigens on synovial dendritic cells, defined as cells with 4 or more stellate, branching projections. Cells with only 1-3 projections often had HLA-DR antigens. Because human synovial dendritic cells may lose their characteristic morphology upon culture and because they appear to lack Ia antigens in the unstimulated state, we suggest that synovial dendritic cells may be closely related to fibroblasts.

Lyme disease in northern California.

Lyme disease is a recently described clinical entity with cutaneous, neurologic, articular and cardiac manifestations. Since the original description of the disease in 1977, more than 500 cases have been reported. Although the vast majority of patients have been from the area near Lyme, Connecticut, we have seen four patients from northern California with various aspects of Lyme disease. This diagnosis should be considered in patients who have traveled to tick regions and who have a distinctive skin lesion (erythema chronicum migrans). Clinical and epidemiologic evidence suggests the disease is transmitted by a tick, lxodes dammini in the eastern United States, lxodes pacificus in the West and lxodes ricinus in Europe. The etiologic agent, a new spirochete, may have been recently discovered.