Tick-borne diseases--a growing risk

The clinical assessment, treatment, and prevention of lyme disease, human granulocytic anaplasmosis, and babesiosis: clinical practice guidelines by the Infectious Diseases Society of America

Evidence-based guidelines for the management of patients with Lyme disease, human granulocytic anaplasmosis (formerly known as human granulocytic ehrlichiosis), and babesiosis were prepared by an expert panel of the Infectious Diseases Society of America. These updated guidelines replace the previous treatment guidelines published in 2000 (Clin Infect Dis 2000; 31[Suppl 1]:1-14). The guidelines are intended for use by health care providers who care for patients who either have these infections or may be at risk for them. For each of these Ixodes tickborne infections, information is provided about prevention, epidemiology, clinical manifestations, diagnosis, and treatment. Tables list the doses and durations of antimicrobial therapy recommended for treatment and prevention of Lyme disease and provide a partial list of therapies to be avoided. A definition of post-Lyme disease syndrome is proposed.

Response of the tick Dermacentor variabilis (Acari: Ixodidae) to hemocoelic inoculation of Borrelia burgdorferi (Spirochetales)

When Borrelia burgdorferi B31 low passage strain spirochetes were directly injected into the hemocoel of Dermacentor variabilis (Say) females, the bacteria were cleared from the hemocoel within < 24 h. Viable spirochetes were not found in hemolymph, salivary gland, or ovary tissues by subculturing or by IFA. The hemocyte population increased approximately 6 times within the first 6 h after inoculation compared with the uninoculated controls. In contrast, the soluble total hemolymph protein content decreased inversely with the increase in hemocytes. Borreliacidal activity was demonstrated with cell-free hemolymph from D. variabilis. In vitro antimicrobial assays using hemolymph from borrelia-challenged and nonchallenged ticks resulted in 72% spirochete reductions compared with only 11.5%, respectively, within 1 h. Additional evidence of induced antimicrobial hemolymph protein activity was demonstrated by SDS-PAGE, which revealed upregulation of a lysozyme-like peptide (approximately 15 kDa) (22% increase) and the induction of a approximately 5.8 kDa peptide in the B. burgdorferi-challenged ticks. In contrast with the nonvector borne Bacillus subtilis, D. variabilis presented a rapid and robust response to challenge with cultured B. burgdorferi spirochetes and lead to their early elimination. The role of the tick immune system, including possible differences between vector and nonvector ticks, in determining the success of invasive bacteria is discussed.

Seroprevalence and seroconversion for tick-borne diseases in a high-risk population in the northeast United States

PURPOSE

To determine the prevalence of serologic reactivity, the 1-year incidence of seroconversion, and the frequency of multiple infections, and their associations with symptoms in a group of volunteers at high risk for tick-borne infections in New York state.

METHODS

We performed a seroepidemiologic study of Lyme borreliosis, 2 of the ehrlichioses, Rocky Mountain spotted fever, and babesiosis among 671 participants who lived or worked in a high-risk area (mainly in eastern Long Island, New York) for tick-borne diseases. Sera were collected in the winters of 1994 and 1995. Signs and symptoms of tick-borne disease were monitored monthly by mail and telephone. Lyme borreliosis serologies were done by enzyme-linked immunosorbent assay and Western blot. Rocky Mountain spotted fever serologies were initially screened using Dip-S-Ticks, followed by specific indirect immunofluorescence. Ehrlichiosis serologies were determined by epifluorescent microscopy, as were antibodies to Babesia microti.

RESULTS

Of the 671 participants, 88 (13%) had antibodies to > or = 1 tick-borne organisms, including 34 (5% of the total) with antibodies to Borrelia burgdorferi. Twenty-seven participants had evidence of exposure to B. burgdorferi at baseline. Seven participants (1%) seroconverted during the course of the study, 5 of whom were symptomatic for Lyme borreliosis. Antibodies to spotted fever group rickettsiae were seen in 28 participants (4%), 22 of whom were positive at baseline and 6 of whom seroconverted during the observation period. None of the seropositive patients had any symptoms or signs of infection. Twenty-four participants (3%) had serologic evidence of exposure to Ehrlichia (all but one to Ehrlichia equi); 5 (0.7%) seroconverted during the observation period, including 3 subjects who were asymptomatic. Antibodies to B. microti were seen in 7 participants (1%), including one asymptomatic seroconversion during the year of observation. There was evidence of possible dual infection in 5 patients.

CONCLUSION

In a high-risk population, there was evidence of exposure to 5 tick-borne pathogens; however, many infections were asymptomatic, and coinfections were rare.

Emerging and resurging vector-borne diseases

Over the last four decades, a number of arthropod-borne infections have been recognized for the first time. Some have become of considerable public health importance, such as dengue hemorrhagic fever (DHF), and others are spreading geographically and their incidence is increasing. There has been an important recrudescence of several long-known vector-borne diseases. Malaria, leishmaniasis, dengue, and plague have resurged in numerous foci, in some cases where they were thought to be under effective control. In most instances, the appearance of new diseases and syndromes and the resurgence of old can be associated with ecological changes that have favored increased vector densities. Dam construction, irrigation and other development projects, urbanization, and deforestation have all resulted in changes in vector population densities that appear to have enabled the emergence of new diseases and the resurgence of old diseases. Greatly increased human travel has spread infectious agents, introducing them into areas in which they had been hitherto absent. It is essential to understand the factors that caused increased vector densities and hence the transmission of disease to prevent the emergence and resurgence of more diseases, as well as to serve as a basis for effective control.

Does Lyme disease occur in the south?: a survey of emerging tick-borne infections in the region

Lyme disease is the most common arthropod-borne infection in the United States. However, the risk of infection varies widely by geographic region. In the South, Borrelia burgdorferi has been identified in ticks and small mammals, but transmission of the agent to humans has not been documented. The Lyme disease-like disorder reported from the region may have another etiology.