The Prevalence and Incidence of Clinical and Asymptomatic Lyme Borreliosis in a Population at Risk

Abstract

A past history of clinical Lyme borreliosis and the 6-month incidence of clinical and asymptomatic Lyme borreliosis was studied prospectively in a high-risk population. In the spring, blood samples were drawn from 950 Swiss orienteers, who also answered a questionnaire. IgG antiBorrelia burgdorferi antibodies were detected by ELISA. Positive IgG antibodies were seen in 248 (26.1%), in contrast to 3.9%-6.0% in two groups of controls (n = 101). Of the orienteers, 1.9%-3.1% had a past history of definite or probable clinical Lyme borreliosis. Six months later a second blood sample was obtained from 755 participants, 558 (73.9%) of whom were seronegative initially; 45 (8.1%) had seroconverted from negative to positive. Only 1 (2.2%) developed clinical Lyme borreliosis, Among all participants, the 6-month incidence of clinical Lyme borreliosis was 0.8% (6/755) but was much higher (8.1%) for asymptomatic seroconversion (45/558). In conclusion, positive Lyme serology was common in Swiss orienteers, but clinical disease occurred infrequently.Lyme disease, now often called Lyme borreliosis (LB), may affect the skin, heart, joints, and nervous system [1][2][3][4][5][6]. Neurologic, cardiologic, and rheumatologic manifestations such as meningoencephalitis, neuropathy, atrioventricular nodal block, myocarditis, and arthritis may follow in a few weeks to months after erythema migrans (EM). This skin lesion, although characteristic, is by no means an obligatory sign of LB; it was found in only 41%-61% of patients with the disease [7,8]. Arthritis typically is oligoarticular and recurrent but may become chronic and erosive; it predominantly involves the knee joints [3,9].LB is caused by the bite of ticks infected with the spirochete Borrelia burgdorferi [10,11]. The ticks that can transmit disease are part of the Ixodes ricinus complex. The discovery of the spirochete led to serology as an aid in establishing the diagnosis of LB, especially in the absence of EM [12]. In Europe the disorder seems to have a wide and constant distribution [13]. In contrast, in the United States LB may have been confined to three enzootic areas (northeast coast, midwest, California), but cases appear to be increasing and infection to be spreading to new areas. Recognition may also account for some of the apparent increase. LB has now been reported from 35 states. In Long Island, New York, the incidence ofLB was found to be considerably higher than previously recognized [14].Some patients showed inapparent seroconversion after infection. The estimated ratio of apparent to inapparent infection was 1:1 in a study in Great Island, Massachusetts [8].To assess the usefulness of Lyme serology as a diagnostic tool, it would be important to know not only the sensitivity and specificity of the test but also its predictive value. This would imply knowledge about the prevalence and incidence of clinical LB and the ratio of apparent to inapparent infections in populations where the test is applied.We studied past history of clinical LB and frequency of positiv...

Genetic and Phenotypic Analysis of Borrelia valaisiana sp. nov. (Borrelia Genomic Groups VS116 and M19)

“…These results must be confirmed by culture of B. vafaisiana from human tissue. If B. valaisiana is rather common and infectious, but exerts a low pathogenic potential, this species might well contribute to the frequent finding of asymptomatic seropositivity among residents in Switzerland (10) and The Netherlands (42), two countries where B. vafaisiana is known to occur in ticks (28,29).…”

Infection of Field-Collected Ixodes ricinus (Acari: Ixodidae) Larvae with Borrelia burgdorferi in Switzerland

“…Woodmice (Apodemus sylvaticus L.) and yellow-necked mice (Apodemus flavicolus Melchior) are the principal reservoirs of B. burgdorferi (Humair et al 1993). The incidence of Lyme borreliosis is 1.8 cases per 100,000 inhabitants (Chamot 1989, Fahrer et al 1990, Zhioua 1993.…”

Coinfections Acquired from Ixodes Ticks

“…In an LD vaccine trial in the United States, 30 (11%) of the 269 study participants who acquired LD had asymptomatic IgG seroconversion to B. burgdorferi (196). Several seroprevalence studies in Europe have demonstrated that Ͼ50% of B. burgdorferiseropositive persons do not recall having any symptoms of LD (64,74,139). Furthermore, levels of IgM and IgG antibodies to B. burgdorferi decline slowly after treatment, and these antibodies have been demonstrated to persist for months to years after clinical cure (65,94).…”