Jerome Goddard

Rickettsia parkeri: A Newly Recognized Cause of Spotted Fever Rickettsiosis in the United States

Ticks, including many that bite humans, are hosts to several obligate intracellular bacteria in the spotted fever group (SFG) of the genus Rickettsia. Only Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, has been definitively associated with disease in humans in the United States. Herein we describe disease in a human caused by Rickettsia parkeri, an SFG rickettsia first identified >60 years ago in Gulf Coast ticks (Amblyomma maculatum) collected from the southern United States. Confirmation of the infection was accomplished using serological testing, immunohistochemical staining, cell culture isolation, and molecular methods. Application of specific laboratory assays to clinical specimens obtained from patients with febrile, eschar-associated illnesses following a tick bite may identify additional cases of R. parkeri rickettsiosis and possibly other novel SFG rickettsioses in the United States.

Bed Bugs (Cimex lectularius) and Clinical Consequences of Their Bites

CONTEXT Bed bug (Cimex lectularius) infestations are rapidly increasing worldwide. Health consequences include nuisance biting and cutaneous and systemic reactions. The potential for bed bugs to serve as disease vectors and optimal methods for bed bug pest control and eradication are unclear. OBJECTIVES To present current knowledge of the health and medical effects of bed bugs and to explore key issues in pest control and eradication efforts. DATA SOURCES A search of MEDLINE and EMBASE databases (1960-October 2008) for articles using the keywords bed bugs, Cimex lectularius, humans, parasitology, pathogenicity, and drug effects. For pest control, PubMed and Toxline searches (1960-October 2008) were performed using the keywords bed bugs, Cimex, control, prevention, and eradication. Manual searches of older journals, textbooks, pest control trade journals, and newspapers (1892-October 2008) were also performed. STUDY SELECTION Original accounts or investigations of bed bugs, clinical responses with sufficient detail of cause and effect between the bed bug bite and clinical response, and convincing evidence of substantiated presence of bed bug exposure. For pest control, documentation that an eradication measure quantitatively decreased bed bugs. DATA EXTRACTION A trained medical reference librarian assisted with the literature search. Two authors with expertise in the diagnosis, treatment, and eradication of bed bugs reviewed the clinical articles. One author evaluated the pest control articles. DATA SYNTHESIS Fifty-three articles met inclusion criteria and were summarized. Only 2 clinical trials concerning bed bugs were identified and tested the ability of pest control interventions to eradicate bed bugs. Although transmission of more than 40 human diseases has been attributed to bed bugs, there is little evidence that they are vectors of communicable disease. A variety of clinical reactions to bed bugs have been reported, including cutaneous and rarely systemic reactions. A wide range of empirical treatments, including antibiotics, antihistamines, topical and oral corticosteroids, and epinephrine, have been used for bite reactions with varying results. No evidence-based interventions to eradicate bed bugs or prevent bites were identified. CONCLUSIONS Treatment options for cutaneous and systemic reactions from bed bug bites have not been evaluated in clinical trials and there is no evidence that outcomes differ significantly from those receiving no treatment. Evidence for disease transmission by bed bugs is lacking. Pest control and eradication is challenging due to insecticide resistance, lack of effective products, and health concerns about spraying mattresses with pesticides.

Rickettsia parkeri Rickettsiosis and Its Clinical Distinction from Rocky Mountain Spotted Fever

BACKGROUND Rickettsia parkeri rickettsiosis, a recently identified spotted fever transmitted by the Gulf Coast tick (Amblyomma maculatum), was first described in 2004. We summarize the clinical and epidemiological features of 12 patients in the United States with confirmed or probable disease attributable to R. parkeri and comment on distinctions between R. parkeri rickettsiosis and other United States rickettsioses. METHODS Clinical specimens from patients in the United States who reside within the range of A. maculatum for whom an eschar or vesicular rash was described were evaluated by > or =1 laboratory assays at the Centers for Disease Control and Prevention (Atlanta, GA) to identify probable or confirmed infection with R. parkeri. RESULTS During 1998-2007, clinical samples from 12 patients with illnesses epidemiologically and clinically compatible with R. parkeri rickettsiosis were submitted for diagnostic evaluation. Using indirect immunofluorescence antibody assays, immunohistochemistry, polymerase chain reaction assays, and cell culture isolation, we identified 6 confirmed and 6 probable cases of infection with R. parkeri. The aggregate clinical characteristics of these patients revealed a disease similar to but less severe than classically described Rocky Mountain spotted fever. CONCLUSIONS Closer attention to the distinct clinical features of the various spotted fever syndromes that exist in the United States and other countries of the Western hemisphere, coupled with more frequent use of specific confirmatory assays, may unveil several unique diseases that have been identified collectively as Rocky Mountain spotted fever during the past century. Accurate assessments of these distinct infections will ultimately provide a more valid description of the currently recognized distribution, incidence, and case-fatality rate of Rocky Mountain spotted fever.

Gulf Coast Ticks (Amblyomma maculatum) and Rickettsia parkeri, United States

Geographic distribution of Rickettsia parkeri in its US tick vector, Amblyomma maculatum, was evaluated by PCR. R. parkeri was detected in ticks from Florida, Georgia, Kentucky, Mississippi, Oklahoma, and South Carolina, which suggests that A. maculatum may be responsible for additional cases of R. parkeri rickettsiosis throughout much of its US range.

Isolation of Rickettsia parkeri and Identification of a Novel Spotted Fever Group Rickettsia sp. from Gulf Coast Ticks (Amblyomma maculatum) in the United States

ABSTRACT Until recently, Amblyomma maculatum (the Gulf Coast tick) had garnered little attention compared to other species of human-biting ticks in the United States. A. maculatum is now recognized as the principal vector of Rickettsia parkeri, a pathogenic spotted fever group rickettsia (SFGR) that causes an eschar-associated illness in humans that resembles Rocky Mountain spotted fever. A novel SFGR, distinct from other recognized Rickettsia spp., has also been detected recently in A. maculatum specimens collected in several regions of the southeastern United States. In this study, 198 questing adult Gulf Coast ticks were collected at 4 locations in Florida and Mississippi; 28% of these ticks were infected with R. parkeri, and 2% of these were infected with a novel SFGR. Seventeen isolates of R. parkeri from individual specimens of A. maculatum were cultivated in Vero E6 cells; however, all attempts to isolate the novel SFGR were unsuccessful. Partial genetic characterization of the novel SFGR revealed identity with several recently described, incompletely characterized, and noncultivated SFGR, including “Candidatus Rickettsia andeanae” and Rickettsia sp. Argentina detected in several species of Neotropical ticks from Argentina and Peru. These findings suggest that each of these “novel” rickettsiae represent the same species. This study considerably expanded the number of low-passage, A. maculatum-derived isolates of R. parkeri and characterized a second, sympatric Rickettsia sp. found in Gulf Coast ticks.

Role of the lone star tick, Amblyomma americanum (L.), in human and animal diseases.

We reviewed scientific literature pertaining to known and putative disease agents associated with the lone star tick, Amblyomma americanum. Reports in the literature concerning the role of the lone star tick in the transmission of pathogens of human and animal diseases have sometimes been unclear and even contradictory. This overview has indicated that A. americanum is involved in the ecology of several disease agents of humans and other animals, and the role of this tick as a vector of these diseases ranges from incidental to significant. Probably the clearest relationship is that of Ehrlichia chaffeensis and A. americanum. Also, there is a definite association between A. americanum and tularemia, as well as between the lone star tick and Theileria cervi to white-tailed deer. Evidence of Babesia cervi (= odocoilei) being transmitted to deer by A. americanum is largely circumstantial at this time. The role of A. americanum in cases of southern tick-associated rash illness (STARI) is currently a subject of intensive investigations with important implications. The lone star tick has been historically reported to be a vector of Rocky Mountain spotted fever rickettsiae, but current opinions are to the contrary. Evidence incriminated A. americanum as the vector of Bullis fever in the 1940s, but the disease apparently has disappeared. Q fever virus has been found in unfed A. americanum, but the vector potential, if any, is poorly understood at this time. Typhus fever and toxoplasmosis have been studied in the lone star tick, and several non-pathogenic organisms have been recovered. Implications of these tick-disease relationships are discussed.

Experimental Infection of Lone Star Ticks, Amblyomma americanum (L.), with Rickettsia parkeri and Exposure of Guinea Pigs to the Agent

Abstract The maculatum agent, Rickettsia parkeri (a member of the spotted fever group rickettsiae), was inoculated into a colony of the lone star tick, Amblyomma americanum, and followed for two tick generations. In addition, guinea pigs were exposed to the agent by direct injection and by feeding infected ticks on them. Eighty (53%) of 150 nymphal A. americanum that were inoculated with suspensions of R. parkeri were positive by hemolymph test and fluorescent antibody test for rickettsial infection when examined as adults. One-month survival of R. parkeri-infected ticks was similar to that of control (noninfected) ticks. Transstadial and transovarial transmission of R. parkeri in the laboratory was demonstrated in A. americanum. When guinea pigs were exposed to the maculatum agent by either direct injection of Vero cell-grown R. parkeri, injection of homogenates of infected ticks, or by feeding of infected ticks, they developed mild fevers and occasional scrotal reactions. These data indicate that R. parkeri can remain viable in lone star ticks for two generations and suggest that guinea pigs may become infected, displaying mild clinical signs.

Psychological Effects of Bed Bug Attacks (Cimex lectularius L.)

BACKGROUND In some individuals, psychological sequelae resulting from bed bug biting events include nightmares, flashbacks, hypervigilance (to keep the bugs away), insomnia, anxiety, avoidance behaviors, and personal dysfunction. These symptoms are suggestive of posttraumatic stress disorder (PTSD). METHODS We used a previously published PTSD checklist to analyze online blogs and other Internet sites where bed bug postings occur to assess postings for evidence of emotional trauma. RESULTS One hundred thirty-five postings were read and analyzed, and 110 (81%) of those postings reported psychological effects from bed bug infestations. Scoring with the PTSD checklist revealed a range of 0-52 (mean 13.25; SD 9.38); one met the criteria (≥50) considered positive for PTSD. CONCLUSIONS Based upon our survey of online postings concerning such effects, an as-yet-to-be-determined proportion of individuals who experience bed bug bites develop moderate-to-severe negative emotional symptoms after infestations. These individuals should be identified in the course of their interactions with health professionals so that appropriate mental health care may be provided.

The Evolving Medical and Veterinary Importance of the Gulf Coast tick (Acari: Ixodidae)

ABSTRACT Amblyomma maculatum Koch (the Gulf Coast tick) is a three-host, ixodid tick that is distributed throughout much of the southeastern and south-central United States, as well as several countries throughout Central and South America. A considerable amount of scientific literature followed the original description of A. maculatum in 1844; nonetheless, the Gulf Coast tick was not recognized as a vector of any known pathogen of animals or humans for >150 years. It is now identified as the principal vector of Hepatozoon americanum, the agent responsible for American canine hepatozoonosis, and Rickettsia parkeri, the cause of an emerging, eschar-associated spotted fever group rickettsiosis identified throughout much of the Western Hemisphere. Coincident with these discoveries has been recognition that the geographical distribution of A. maculatum in the United States is far more extensive than described 70 yr ago, supporting the idea that range and abundance of certain tick species, particularly those with diverse host preferences, are not fixed in time or space, and may change over relatively short intervals. Renewed interest in the Gulf Coast tick reinforces the notion that the perceived importance of a particular tick species to human or animal health can be relatively fluid, and may shift dramatically with changes in the distribution and abundance of the arthropod, its vertebrate hosts, or the microbial agents that transit among these organisms.

A Ten-Year Study of Tick Biting in Mississippi: Implications for Human Disease Transmission

Abstract To determine exactly which tick species bite people in Mississippi, information was gathered on ticks involved in human biting cases for the ten-year period, January 1, 1990-December 31, 1999. Specimens were identified by the author and, in most cases, confirmed by personnel at the Institute of Arthropodology and Parasitology, Georgia Southern University. A total of 119 ticks were recovered from 73 humans during the study period. Seven tick species were represented; most common included the lone star tick, Amblyomma americanum, the gulf coast tick, A. maculatum, the American dog tick, Dermacentor variabilis, and the black-legged deer tick, Ixodes scapularis. Interestingly, no immature Ixodes scapularis were collected. There were several unusual records. Twelve larvae of Amblyomma tuberculatum, a species associated with the gopher tortoise, were removed from a patient. Two Dermacentor albipictus larvae were collected from an elderly woman with no travel history except her backyard. One Dermacentor sp. nymph, removed from a man in central MS, was not even a North American species. One adult female Dermacentor variabilis was involved in a clinical case of tick paralysis. These findings indicate that, although we know which tick species are common human biters, unusual/unreported tick-human interactions may be more common than we think.