Rickettsialpox in North Carolina: a case report

Suspected and Confirmed Vector-Borne Rickettsioses of North America Associated with Human Diseases

The identification of pathogenic rickettsial agents has expanded over the last two decades. In North America, the majority of human cases are caused by tick-borne rickettsioses but rickettsiae transmitted by lice, fleas, mites and other arthropods are also responsible for clinical disease. Symptoms are generally nonspecific or mimic other infectious diseases; therefore, diagnosis and treatment may be delayed. While infection with most rickettsioses is relatively mild, delayed diagnosis and treatment may lead to increased morbidity and mortality. This review will discuss the ecology, epidemiology and public health importance of suspected and confirmed vector-transmitted Rickettsia species of North America associated with human diseases.

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

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.

Selected Zoonoses

Human risks of acquiring a zoonotic disease from animals used in biomedical research have declined over the last decade because higher quality research animals have defined microbiologic profiles. Even with diminished risks, the potential for exposure to infectious agents still exists, especially from larger species such as nonhuman primates, which may be obtained from the wild, and from livestock, dogs, ferrets, and cats, which are generally not raised in barrier facilities and are not subject to the intensive health monitoring performed routinely on laboratory rodents and rabbits. Additionally, when laboratory animals are used as models for infectious disease studies, exposure to microbial pathogens presents a threat to human health. Also, with the recognition of emerging diseases, some of which are zoonotic, constant vigilance and surveillance of laboratory animals for zoonotic diseases are still required.

Syndromic classification of rickettsioses: an approach for clinical practice

Rickettsioses share common clinical manifestations, such as fever, malaise, exanthema, the presence or absence of an inoculation eschar, and lymphadenopathy. Some of these manifestations can be suggestive of certain species of Rickettsia infection. Nevertheless none of these manifestations are pathognomonic, and direct diagnostic methods to confirm the involved species are always required. A syndrome is a set of signs and symptoms that characterizes a disease with many etiologies or causes. This situation is applicable to rickettsioses, where different species can cause similar clinical presentations. We propose a syndromic classification for these diseases: exanthematic rickettsiosis syndrome with a low probability of inoculation eschar and rickettsiosis syndrome with a probability of inoculation eschar and their variants. In doing so, we take into account the clinical manifestations, the geographic origin, and the possible vector involved, in order to provide a guide for physicians of the most probable etiological agent.

Parasitic mites of medical and veterinary importance--is there a common research agenda?

There are an estimated 0.5-1 million mite species on earth. Among the many mites that are known to affect humans and animals, only a subset are parasitic but these can cause significant disease. We aim here to provide an overview of the most recent work in this field in order to identify common biological features of these parasites and to inform common strategies for future research. There is a critical need for diagnostic tools to allow for better surveillance and for drugs tailored specifically to the respective parasites. Multi-'omics' approaches represent a logical and timely strategy to identify the appropriate mite molecules. Recent advances in sequencing technology enable us to generate de novo genome sequence data, even from limited DNA resources. Consequently, the field of mite genomics has recently emerged and will now rapidly expand, which is a particular advantage for parasitic mites that cannot be cultured in vitro. Investigations of the microbiota associated with mites will elucidate the link between parasites and pathogens, and define the role of the mite in transmission and pathogenesis. The databases generated will provide the crucial knowledge essential to design novel diagnostic tools, control measures, prophylaxes, drugs and immunotherapies against the mites and associated secondary infections.

Detection of Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari in skin biopsy specimens using a multiplex real-time polymerase chain reaction assay

BACKGROUND

Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia akari are the most common causes of spotted fever group rickettsioses indigenous to the United States. Infected patients characteristically present with a maculopapular rash, often accompanied by an inoculation eschar. Skin biopsy specimens are often obtained from these lesions for diagnostic evaluation. However, a species-specific diagnosis is achieved infrequently from pathologic specimens because immunohistochemical stains do not differentiate among the causative agents of spotted fever group rickettsiae, and existing polymerase chain reaction (PCR) assays generally target large gene segments that may be difficult or impossible to obtain from formalin-fixed tissues.

METHODS

This work describes the development and evaluation of a multiplex real-time PCR assay for the detection of these 3 Rickettsia species from formalin-fixed, paraffin-embedded (FFPE) skin biopsy specimens.

RESULTS

The multiplex PCR assay was specific at discriminating each species from FFPE controls of unrelated bacterial, viral, protozoan, and fungal pathogens that cause skin lesions, as well as other closely related spotted fever group Rickettsia species.

CONCLUSIONS

This multiplex real-time PCR demonstrates greater sensitivity than nested PCR assays in FFPE tissues and provides an effective method to specifically identify cases of Rocky Mountain spotted fever, rickettsialpox, and R. parkeri rickettsiosis by using skin biopsy specimens.

Human rickettsialpox, southeastern Mexico

The detection of Rickettsia akari in 2 human patients increased the diversity of rickettsioses affecting the public health in the southeast of Mexico. Rickettsialpox should be considered in the differential diagnosis with other febrile illnesses for the correct diagnosis and accurate treatment of this potential threat to human health.

Rickettsialpox: report of three cases and a review

Rickettsialpox is a rare mite-borne rickettsiosis that is encountered in urban populations in the eastern United States and throughout the world. It is characterized clinically by an eschar, fever, and a papulovesicular eruption. Both of these cutaneous manifestations may be mimicked by infectious diseases that have been designated as bioterrorist agents by the United States Centers for Diseases Control and Prevention: the former by anthrax, and the latter by smallpox. It is thus important for clinicians to be familiar with rickettsialpox. We report 3 cases and review the epidemiology, clinical and laboratory findings, differential diagnosis, and management of this disease.

Rickettsialpox in New York City: a persistent urban zoonosis

Rickettsialpox, a spotted fever rickettsiosis, was first identified in New York City (NYC) in 1946. During the next five years, approximately 540 additional cases were identified in NYC. However, during the subsequent five decades, rickettsialpox received relatively little attention from clinicians and public health professionals, and reporting of the disease diminished markedly. During February 2001 through August 2002, 34 cases of rickettsialpox in NYC were confirmed at CDC from cutaneous biopsy specimens tested by using immunohistochemical (IHC) staining, PCR analysis, and isolation of Rickettsia akari in cell culture, as well as an indirect immunofluorescence assay of serum specimens. Samples were collected from patients with febrile illnesses accompanied by an eschar, a papulovesicular rash, or both. Patients originated predominantly from two boroughs (Manhattan and the Bronx). Only 8 (24%) of the cases were identified prior to the reports of bioterrorism-associated anthrax in the United States during October 2001, and lesions of several patients evaluated during and subsequent to this episode were suspected initially to be cutaneous anthrax. IHC staining of biopsy specimens of eschars and papular lesions were positive for spotted fever group rickettsiae for 32 patients. Of the eleven patients for whom paired serum samples were obtained, all demonstrated fourfold or greater increases in antibody titers reactive with R. akari. The 17-kDa protein gene sequence of R. akari was amplified from eschars of five patients. Four isolates of R. akari were obtained from cutaneous lesions. Possible factors responsible for the increase in clinical samples evaluated for rickettsialpox during this interval include renewed clinical interest in the disease, improved diagnostic methods, epizootiological influences, and factors associated with the recent specter of bioterrorism.