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Source:
TUFTS UNIVERSITY submitted to  |
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| PERPETUATION OF BORRELIA LONESTARI.
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| PROJECT DIRECTOR: Telford, S. R.
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PERFORMING ORGANIZATION
BIOMEDICAL SCIENCES
TUFTS UNIVERSITY
N. GRAFTON,MA 01536 |
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NON TECHNICAL SUMMARY:
Lyme disease has emerged rapidly within the last 25 years to become the most common vector-borne infection in the United States, and in much of Europe. Lyme disease-like illnesses, termed Masters Disease or Southern Tick-Associated Rash-Illness (STARI) is associated with bites of Lone Star ticks. The etiologic agent for Masters Disease remains undescribed. A new agent, Borrelia lonestari, infects Lone Star ticks. The hypothesis that Borrelia lonestari is the agent of Masters Disease cannot be readily tested inasmuch as experimental material (viable spirochetes for developing animal models or attempting in vitro cultivation) is scarce. The current hypothesis to be refuted is that the Lone Star tick spirochete is the etiologic agent of Masters disease.
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| OBJECTIVES:
Lyme disease-like illnesses of undocumented etiology have been confused with Lyme disease in sites where blacklegged ticks (Ixodes scapularis) are found. These infections are associated with the bites of Lone Star ticks (Amblyomma americanum) in Missouri and North Carolina. This syndrome, termed Masters disease or Southern Tick-Associated Rash-Illness (STARI), is characterized by an erythema migrans from which no evidence of Borrelia burgdorferi may be detected, accompanied by generally mild constitutional symptoms with no chronic sequelae. Reactivity to B. Burgdorferi antigens seems rare in sera from these patients. Interestingly, Lone Star ticks are, however, infected by a recently described spirochete, Borrelia lonestari, closely related to relapsing fever spirochetes but as yet uncultivated. The current hypothesis to be refuted is that the Lone Star tick spirochete is the etiologic agent of Masters disease. Kochs postulate, the microbiological standard by which an
etiologic agent is incriminated, traditionally require that (1) the agent always be associated with the illness in a manner constituent with pathology and clinical aspects of the illness; 2) that it does occur in healthy individuals; and (3) that the illness may be reproduces by exposure to the pure, in vitro cultivated agent. Because B. lonestari has not been successfully cultivated or its DNA detected in erythema migrans of Masters Disease patients, Kochs postulates remain unfulfilled. Attempts at cultivating B. lonestari are hindered by the low infection rate in Lone Star ticks, ranging from 0-5% in several reports. Furthermore, development of a convenient animal model is difficult inasmuch as the enzootic cycle remains undescribed. Although Lone Star ticks feed mainly on deer in all stages, raccoons, opossums, foxes, coyotes, and turkeys may also serve as hosts. To our knowledge, B. lonestari has not been detected in any vertebrate. Elucidation of the life cycle of B. lonestari
might help provide a more constant or reliable source for cultivation attempts. We propose to describe the enzootic cycle of B. lonestari, evaluate transmission risk of this spirochete to people exposed to bites of A. americanum; and develop methods of cultivating this agent. Towards this end, we shall explore the hypothesis that B. lonestari shares the major features of the biology of B. theileri. In particular, we seek to determine (1) whether B. lonestari is maintained by transovarial transmission (TOT); and (2) that white-tailed deer serve as reservoir of B. lonestari. Should we succeed in demonstrating TOT, we shall endeavor to generate a laboratory colony of Lone Star ticks with high rates of filial infection. Such a resource could be used to facilitate efforts to cultivate B. lonestari, or at least provide partially-purified tick-derived antigens for seroepidemiological studies designed to evaluate its public health burden. Examination of deer reservoir competence for B.
lonestari may provide facts that could serve as the basis for eventual recommendations of new intervention strategies designed to reduce the incidence of Masters Disease.
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| APPROACH:
Objective 1: Is Borrelia lonestari perpetuated by transovarial transmission (TOT)? Laboratory efforts as well as field survey of larvae will be done to demonstrate TOT. Female Lone Star ticks will be collected by dragging vegetation. Adult ticks will be assayed nondestructively by the hemolymph test. Female ticks that contain spirochetes will be places on specific pathogen free New Zeeland white rabbits and allowed to feed to repletion. The spent female will be dissected and smears made of individual organs to demonstrate infection by fluorescent antibody. Male ticks that prove to be infected will be carefully dissected, and their tissues gently ground in HBSS/FBS in a glass Ten-Broeck type homogenizer. The material will be checked by darkfield microscopy and used in attempts to artificially infect and induce TOT in uninfected female ticks. Three measures of the efficiency of transovarial transmission must be determined. The transovarial transmission rate (TOTR), the
filial infection rate (FIR) and the vertical transmission rate (VTR). The rabbit upon which putatively infected ticks have fed will be kept alive for 1 month and bled weekly for serum to determine the kinetics of the immune response to B. lonestari exposure. At 2 months, the rabbit will be killed, necropsied, and examined for evidence of infection. Should we succeed in demonstrating that B. lonestari may be vertically transmitted, we shall attempt to determine how many tick generations may inherit infection. Objective 2: Do deer serve as reservoirs of B. lonestari? Because deer serve as main hosts for all stages of Lone Star ticks, they are the most likely candidate as amplification (reservoir) hosts. We choose to directly examine the question by field observations, which served well for answering the same question about the agent of Lyme disease. Preliminary analysis of deer blood suggests that deer are naturally infected by B. lonestari. Evidence of reservoir competence will be
sought from deer during August and September, when larval Lone Star ticks are most abundant. Each deer will be skinned within 4 hours of their deaths. All detached ticks will be collected, sorted by species, stage, and engorgement status. Those larvae that are deemed to have fed enough to molt will be reserved; others will be pooled and analyzed by PCR for evidence of infection. Nymphs resulting from such larvae will be examined for evidence of infection. We shall similarly analyze deer ticks that are obtained from deer to determine whether there is any transfer of B. lonestari to other species of ticks. We shall also determine whether other hosts such as gray squirrels, rats, rabbits weasels, opossums, foxes, raccoons, and skunks, may serve as reservoirs. We shall place 50 traps each month, and examine these hosts for the diversity and density of ticks infesting them.
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CRIS NUMBER: 0203137
SUBFILE: CRIS
PROJECT NUMBER: MASV-HS2710
SPONSOR AGENCY: CSVM
PROJECT TYPE: STATE
PROJECT STATUS: TERMINATED
MULTI-STATE PROJECT NUMBER: (N/A)
START DATE: Feb 15, 2002
TERMINATION DATE: Feb 14, 2004
GRANT PROGRAM: (N/A)
GRANT PROGRAM AREA: (N/A)
CLASSIFICATION HEADINGS
KA722 - Zoonotic Diseases and Parasites Affecting Humans
S3120 - Spiders, mites, ticks, and other arthropods
F1110 - Parasitology
G4.2 - Reduce Number and Severity of Pest and Disease Outbreaks
RESEARCH EFFORT CATEGORIES
| BASIC |
50% |
| APPLIED |
50% |
| DEVELOPMENTAL |
(N/A)% |
KEYWORDS: lyme disease; amblyomma americanum; deer; opossums; turkeys; gray squirrel; wildlife; borrelia; spirochaeta; skin diseases; disease transmission; skunks; foxes; raccoons; rats; rabbits; carnivores; animal models; bacterial diseases (animals); zoonoses; external parasites; parasitology; etiology; ixodes scapularis
PROGRESS: TO
(N/A)
IMPACT: TO
(N/A)
PUBLICATION INFORMATION: TO
PROJECT CONTACT INFORMATION
| NAME: |
Barbara Donato |
| PHONE: |
508-839-7910 |
| FAX: |
(N/A) |
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