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5 Surveillance, Spectrum, and Burden of Tick-Borne Disease, and At-Risk Populations
Pages 61-96

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From page 61...
... For example, Ixodes ticks can simultaneously or sequentially infect their hosts with Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti. How often this occurs -- and what it means for the presentation and severity of tickborne diseases -- is not well understood.
From page 62...
... miyamotoi, a relapsing fever-like Borrelia. Whether Borrelia miyamotoi causes human infection is unknown, and the clinical manifestations, if it does, are likewise unknown.
From page 63...
... . Absent from this arsenal of personal protective measures is a human Lyme disease vaccine.
From page 64...
... . Early disseminated Lyme disease consists of multiple erythema migrans skin lesions in addition to possible cardiac and neurological manifestations, such as seventh cranial nerve palsy and meningitis.
From page 65...
... First, serology testing using Western blots during early Lyme disease and in patients with erythema migrans is not sensitive. Second, the overreading of weak bands on a Western blot by many commercial laboratories results in a high percentage of false-positive reports, although no studies have been done to document the percentage.
From page 66...
... To others, Lyme disease occurs focally, depends on exposure to infected ticks, and usually is linked to objective clinical manifestations. Positive laboratory tests are needed to support a diagnosis for symptoms other than EM, and the disease typically responds to antibiotic treatment.
From page 67...
... The acknowledgment that Lyme disease may be a complex and chronic illness requires a comprehensive, multidisciplinary and patientcentered perspective. Patients are not interested in whether their illness is caused by Borrelia burgdorferi or another genotype of Borrelia.
From page 68...
... The species diversity of Borrelia has important research implications, such as the appropriate number of the patients needed for studies, the geographic locations of study sites, and the appropriate power for meaningful statistical analysis. The structure of OspA and OspC, the major outer surface proteins of Borrelia burgdorferi, and epitopes -- the part of B
From page 69...
... Furthermore, diagnostic tests for Lyme disease will need to consider genotypic variants of B burgdorferi, as well as whether concomitant infection with other pathogens can lead to false-positive or false-negative results.
From page 70...
... burgdorferi phenotypes; • Using appropriate animal models, such as the C3H persistent in fection mouse model, to assess new approaches to diagnosis and treatment; • Developing better biological and clinical instruments to evaluate and measure the effectiveness of outcomes of treating its various manifestations; • Establishing standard operating procedures for developing criteria for acute and chronic Lyme disease; and • Gathering information and biological samples from patients at vari ous stages of their disease, and using technology to evaluate those samples. DISCUSSION SESSION One clinician participant noted that chronic fatigue syndrome is a clinical condition of prolonged and severe fatigue of at least 6 months' duration for which other causes have been excluded.
From page 71...
... He also noted that, in addition to the development of such technology, a disease phenotype needs to be developed that would unify the research as technology moves forward. THE INCREASING HEALTH BURDEN OF HUMAN BABESIOSIS: CLINICAL MANIFESTATIONS, COINFECTION, AND RESEARCH NEEDS Peter J
From page 72...
... duncani have been transmitted through transfusions of whole blood, packed red blood cells, and platelets (Ruebush et al., 1981; Gubernot et al., 2009)
From page 73...
... microti and Borrelia burgdorferi infection. About 50 B
From page 74...
... The health burden of disease includes both the number and severity of cases. Babesiosis is characterized by a wide range of disease severity, from asymptomatic to fatal.
From page 75...
... Clinical Manifestations • What are the long-term complications of babesiosis? • How does coinfection with babesiosis and other co-transmitted pathogens influence transmission in the reservoir host and disease in humans?
From page 76...
... HME and HGA often present with severe headache, myalgias, and a variety of other constitutional symptoms, such as nausea and vomiting. Rashes occur relatively infrequently, differentiating these illnesses from Rocky Mountain spotted fever and Lyme disease.
From page 77...
... Life-threatening complications reported among these patients include acute respiratory distress syndrome, disseminated intravascular coagulation, meningitis, meningoencephalitis, and renal failure. One way to analyze how often people are infected is to look at crosssectional seroprevalence studies.
From page 78...
... It is not clear to what degree disease severity can be attributed to the host or the pathogen. HGA patients have a mean white blood cell count of 3.7 × 103 per microliter, yet the average proportion of infected leukocytes in less than 1 percent.
From page 79...
... Instead, 73 percent of reported HME cases and 53 percent of reported HGA cases relied on a single serum antibody test result as the laboratory basis for the diagnosis. Information on the sensitivity and specificity of serologic tests is limited.
From page 80...
... In the United States, Rickettsia rickettsii, which causes Rocky Mountain spotted fever, is the primary agent for human rickettsial disease. Increasingly, other Rickettsia pathogens are being reported, including Rickettsia parkeri and Rickettsia phillipi; the latter causes 364D rickettsiosis.
From page 81...
... Furthermore, patients who recover may experience long-term health effects, including impaired hearing from neurologic damage; cognitive deficits; and gangrene of fingers and toes caused by damage to blood vessels. Rocky Mountain spotted fever is the most potentially fatal known rickettsial illness.
From page 82...
... Although people living anywhere in the continental United States are at risk for Rocky Mountain spotted fever, there is spatial clustering of cases in the South Central and Southeast regions. Five states -- Arkansas, Missouri, North Carolina, Oklahoma, and Tennessee -- account for more than 64 percent of reported cases (Openshaw, 2010)
From page 83...
... Risk factors for Rocky Mountain spotted fever include poverty and age. Although many individuals associate tick-borne diseases with higher socioeconomic status, because persons in this group engage more frequently in outdoor leisure activities, states with the highest incidence of Rocky Mountain spotted fever fall below the median socioeconomic status for the United States.
From page 84...
... The brown dog tick is of continued interest to public health officials because it has also been associated with urban outbreaks of tick-borne diseases. For example, in 2009, more than 1,000 suspected cases of Rocky Mountain spotted fever occurred in urban Mexicali, Mexico.
From page 85...
... One participant noted that the distribution map of Rocky Mountain spotted fever bears a remarkable resemblance to the distribution of Amblyomma americanum, the Lone Star tick, and asked whether there is any new information about the relationship of the Lone Star and R amblyommii to human disease.
From page 86...
... In light of this, he suggested that, in addition to other methods targeted toward underreporting, active surveillance methods are considered to strengthen and improve knowledge of incidence of tick-borne diseases. Another participant shifted the discussion from surveillance to research on disease mechanisms by noting that there is considerable research on acute infection, but less on chronic infection, such as that reported for babesiosis.
From page 87...
... For this system to be effective, physicians, patients, and, potentially, patient advocacy organizations would need to be able to identify classical and less common manifestations of the respective diseases. This ability was seen as especially important in cases of Lyme disease where the classic presenting signs and symptom of erythema migrans may be absent in up to 20 percent of infected individuals.
From page 88...
... Krause noted that in experiments in the Peromyscus leucopus mouse, the effect of coinfection can vary according to the timing with which these organisms are introduced (e.g., simultaneous infection by a single coinfected tick or sequential infection from a second tick bite)
From page 89...
... Relapses of either agent appear to be a very rare occurrence, and most subsequent presentations of disease are the result of new infections. McQuiston commented that there is also a lack of data in terms of Rickettsia infection, but most Rocky Mountain spotted fever infections are acute infections that either are self-limited, and fatal, or resolve with antibiotic treatment.
From page 90...
... In the United States, Lyme disease, babesiosis, and Rocky Mountain spotted fever (RMSF) all have important geographic predilections.
From page 91...
... Like exposure, many factors can affect one's risk of becoming infected with a pathogen and developing severe or fatal disease. Many risk factors are associated with behavioral and biological indicators of the exposed individual or of the tick environment.
From page 92...
... Determining risk factors for tick-borne disease requires sufficiently sophisticated tests to detect disease accurately, and the development and conduct of surveillance studies capable of multivariate analysis to delineate independent risk factors that may be thrown together or overshadowed in case-control studies. Furthermore, despite disparate indications, it is difficult to isolate risk factors for exposure from risk factors for infection, and for this reason, many case-control studies measure exposure rate based on the number of infections reported rather than recording the total number of actual tick exposures or tick bites, an outcome measure that may not always be appropriate.
From page 93...
... For the patients with relapsing illness, the percentage of infected red blood cells ranged from 2 to 75 percent, compared with 0.5 to 10 percent for the control group. The group with relapsing illness required 2–10 courses of antiBabesia antibiotic to clear infection while the control group required only a single course of antibiotic.
From page 94...
... . The spleen removes red blood cells that are infected or senescent, and macrophages and other immune factors present in the spleen may help to eliminate intraerythrocytic pathogens.
From page 95...
... One participant questioned whether it is possible for Babesia to be transmitted through national blood donation programs. Krause observed that, although the chance of acquiring babesiosis from a blood transfusion likely is very low, Babesia microti is the most common infectious agent transmitted through the blood supply in the United States (FDA, 2008)
From page 96...
... Clinicians clearly need new methods for diagnosing tick-borne diseases, given the genetic diversity among different strains of a pathogen (e.g., Borrelia burgdoferi) and the realization that new species may be responsible for a larger burden of disease than previously recognized (e.g., Rickettsia parkeri in spotted fever rickettsiosis)


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