The ascendancy of \u3ci\u3eAmblyomma americanum\u3c/i\u3e as a vector of pathogens affecting humans in the United States

Until the 1990s, Amblyomma americanum was regarded primarily as a nuisance species, but a tick of minor importance as a vector of zoonotic pathogens affecting humans. With the recent discoveries of Ehrlichia chaffeensis, Ehrlichia ewingii, and “Borrelia lonestari,” the public health relevance of lone star ticks is no longer in question. During the next 25 years, the number of cases of human disease caused by A. americanum-associated pathogens will probably increase. Based on current trajectories and historic precedents, the increase will be primarily driven by biological and environmental factors that alter the geographic distribution and intensity of transmission of zoonotic pathogens. Sociologic and demographic changes that influence the likelihood of highly susceptible humans coming into contact with infected lone star ticks, in addition to advances in diagnostic capabilities and national surveillance efforts, will also contribute to the anticipated increase in the number of recognized cases of disease

Variability in ornamentation of adult Dermacentor parumapertus Neumann (Acari: Ixodidae): implications for tick identification

Abstract The hard tick Dermacentor parumapertus is an ectoparasite commonly found on hares and rabbits and occurs over much of the western United States. These ticks are rarely encountered except by hunters or scientists collecting rabbits for study. Herein we describe 74 adult D. parumapertus ticks (21F, 53M) removed from 8 black-tailed jackrabbits, Lepus californicus, in central Utah, and 13 adult D. parumapertus (7F, 6M) found on 4 L. californicus in western Texas. The Utah ticks were barely ornamented. Females displayed only slight gray ornamentation near the posterior edge of the scutum and whitish-gray spots distally on the femur of legs II, III, and IV; males were completely devoid of any ornamentation. In contrast, Texas specimens were richly ornamented in white, closely resembling D. variabilis. Females were brightly marked with white (not gray) on the scutum and had white spots distally on all femurs. Males from Texas were variously ornamented along the posterolateral margins of the scutum and displayed white spots distally on all femurs. Documentation of this variability in ornamentation in D. parumapertus is important, particularly as white-marked specimens can easily be confused with D. variabilis and since both species have been reported from rabbit hosts

Fatal Rickettsia conorii subsp. israelensis Infection, Israel

Fatal Rickettsia conorii subsp. israelensis Infection, Israe

Mortality in Serologically Unconfirmed Mediterranean Spotted Fever [with Reply]

I read with interest the article by Paddock et al. [1], who described the detection of occult mortality due to Rocky Mountain spotted fever (RMSF) by demonstrating Rickettsia rickettsii antigens or DNA in blood and tissues. In Mediterranean countries, including Israel, spotted fever is caused by members of the R. conorii complex, which are antigenically related to R. rickettsii. ... To the Editor -- We appreciate the comments by Yagupsky, which underscore several of the salient features of spotted fever- group rickettsial infections that we emphasized in our report [2]. For patients, diagnosticians, and clinicians faced with the potentially tragic consequences of Rocky Mountain spotted fever or severe Mediterranean spotted fever (MSF), these points merit repeating. First, the nonspecific signs and symptoms early in the course of rickettsial infections mimic many other infectious and noninfectious syndromes. Second, the diagnostic challenges posed by these diseases are compounded by the lack of rapid and widely available confirmatory tests early in the course of the illnesses. Finally, spotted fevers have the potential to kill otherwise healthy persons in ^ week after onset of symptoms, emphasizing the need for early administration of appropriate therapy

Rickettsia parkeri in Argentina

Clinical reports of an eschar-associated rickettsiosis in the Paraná River Delta of Argentina prompted an evaluation of Amblyomma triste ticks in this region. When evaluated by PCR, 17 (7.6%) of 223 questing adult A. triste ticks, collected from 2 sites in the lower Paraná River Delta, contained DNA of Rickettsia parkeri

Complete Genome Sequence of \u3ci\u3eRickettsia parkeri\u3c/i\u3e Strain Black Gap

A unique genotype of Rickettsia parkeri, designated R. parkeri strain Black Gap, has thus far been associated exclusively with the North American tick, Dermacentor parumapertus. The compete genome consists of a single circular chromosome with 1,329,522 bp and a G+C content of 32.5%

Outcome of Diagnostic Tests Using Samples from Patients with Culture-Proven Human Monocytic Ehrlichiosis: Implications for Surveillance

We describe the concordance among results from various laboratory tests using samples derived from nine culture-proven cases of human monocytic ehrlichiosis (HME) caused by Ehrlichia chaffeensis. A class-specific indirect immunofluorescence assay for immunoglobulin M (IgM) and IgG, using E. chaffeensis antigen, identified 44 and 33% of the isolation-confirmed HME patients on the basis of samples obtained at initial clinical presentation, respectively; detection of morulae in blood smears was similarly insensitive (22% positive). PCR amplifications of ehrlichial DNA targeting the 16S rRNA gene, the variable-length PCR target gene, and the groESL operon were positive for whole blood specimens obtained from all patients at initial presentation. As most case definitions of HME require a serologic response with compatible illness for a categorization of even probable disease, PCR would have been required to confirm the diagnosis of HME in all nine of these patients without the submission of a convalescent-phase serum sample. These data suggest that many, if not most, cases of HME in patients who present early in the course of the disease may be missed and underscore the limitations of serologically based surveillance systems

Analysis of Risk Factors for Fatal Rocky Mountain Spotted Fever: Evidence for Superiority of Tetracyclines for Therapy

Epidemiologic and clinical characteristics of fatal and nonfatal cases of Rocky Mountain spotted fever (RMSF) were compared to identify risk factors for death caused by this disease. Confirmed and probable RMSF cases reported through US national surveillance for 1981- 1998 were analyzed. Among 6388 RMSF patients, 213 died (annual case-fatality rate, 3M; range, 4.9 % in 1982 to 1.1 % in 1996). Use of tetracycline-class antibiotics for treatment of RMSF increased significantly in the 1990s, compared with use in the 1980s. Older patients, patients treated with chloramphenicol only, patients for whom tetracycline antibiotics were not the primary therapy, and patients for whom treatment was delayed ≥5 days after the onset of symptoms were at higher risk for death. Although the case-fatality rate was lower in the 1990s than in the 1980s, risk factors for fatal RMSF were similar. Despite the availability of effective antibiotics, RMSF-related deaths continue to occur because of delayed diagnosis and failure to use appropriate therapy