Lucas S. Blanton

Rickettsial infections in the tropics and in the traveler.

Purpose of review The purpose of this review is to describe recent advances in our understanding of the pathogenesis, epidemiology, and clinical features of rickettsial diseases with emphasis placed on those relating to travel and tropical medicine. Recent findings Rickettsioses are becoming increasingly recognized as causes of febrile illness in travelers and in those residing in the tropics. In South and Central America, infection with Rickettsia rickettsii continues to have severe consequences. Resurgence of Mediterranean spotted fever in Bulgaria highlights the threat of rickettsial infections when there is a lapse in vector and reservoir control. Similar to African tick-bite fever, Rickettsia parkeri is an emerging cause of eschar-associated infection in Brazil, Argentina, and Uruguay. Several reports of murine typhus requiring hospitalization demonstrate the risk of this infection to the traveler. The use of fluoroquinolones for milder spotted fevers may fall out of favor with evidence of deleterious effects in those treated with ciprofloxacin. Summary With globalization and increased access to travel, clinical awareness of rickettsial diseases is of increasing importance. Although the growing number of rickettsial species may be daunting to the clinician, recognition of the patterns of rickettsial disease will ensure prompt and effective therapy.

Amblyomma imitator ticks as vectors of Rickettsia rickettsii, Mexico.

Real-time PCR of Amblyomma imitator tick egg masses obtained in Nuevo Leon State, Mexico, identified a Rickettsia species. Sequence analyses of 17-kD common antigen and outer membrane protein A and B gene fragments showed to it to be R. rickettsii, which suggested a potential new vector for this bacterium.

Southern Tick-Associated Rash Illness : Erythema Migrans Is Not Always Lyme Disease

Southern tick-associated rash illness (STARI) is a rash occurring after a tick bite. It is a form of erythema migrans, an annular rash with central clearing that is almost identical with the erythema migrans seen in Lyme disease. The etiologic agent is not known but may be a Borrelia species. The tick vector is different in the two diseases. Serious systemic complications are not currently recognized with STARI but treatment with doxycycline is prudent. Differentiating STARI from Lyme disease is discussed.

Reemergence of Murine Typhus in Galveston, Texas, USA, 2013

Twelve patients with murine typhus were identified in Galveston, Texas, USA, in 2013. An isolate from 1 patient was confirmed to be Rickettsia typhi. Reemergence of murine typhus in Galveston emphasizes the importance of vector control and awareness of this disease by physicians and public health officials.

Flea-Borne Rickettsioses and Rickettsiae

Rickettsia typhi and Rickettsia felis are flea-borne rickettsiae that are distributed throughout the world. This mini-review outlines the ecology and epidemiology of flea-borne rickettsioses; highlights important clinical, diagnostic, and therapeutic considerations; and discusses areas of uncertainty regarding Rickettsia felis and other rickettsiae harbored by fleas.

Opossums and Cat Fleas: New Insights in the Ecology of Murine Typhus in Galveston, Texas

Murine typhus is an acute undifferentiated febrile illness caused by Rickettsia typhi The classic reservoir (Rattus spp.) and flea vector (Xenopsylla cheopis) were once culprits of murine typhus in the United States. Vector and rodent control efforts have drastically decreased the prevalence of disease, except in a few endemic foci where opossums and cat fleas play a role in transmission. Since 2012, there has been a reemergence of murine typhus in Galveston, TX. We hypothesize that opossums and cat fleas are involved in the transmission of R. typhi in Galveston. To explore this, we sought to find the seroprevalence of typhus group antibodies from opossums. We also sought to find the prevalence of R. typhi in fleas parasitizing these animals. We collected blood from 12 opossums and found that eight (66.7%) had the presence of anti-R. typhi antibodies. All opossums were infested with fleas; a total of 250 Ctenocephalides felis fleas were collected from these animals. Seven opossums (53.8%) were infested with fleas that had molecular evidence of R. typhi infection, while six (46.2%) were infested with fleas that contained Candidatus Rickettsia senegalensis, an organism closely related to R. felis The minimum flea infection rate for R. typhi was 7.0%. The minimum infection rate for Candidatus R. senegalensis was 6.1%. Our study demonstrates that fleas infected with R. typhi parasitize opossums in Galveston. It is therefore likely that opossums and their fleas play a role in the citys recent reemergence of murine typhus.

Rickettsiae and Ehrlichiae Within a City Park: Is the Urban Dweller at Risk?

Tick-borne diseases, such as spotted fever rickettsioses and ehrlichioses, are potentially severe and life-threatening infections. The incidences of these infections increase during warm weather months as ticks become active. Clinicians often consider outdoor activities in rural areas to be a risk factor for exposure to ticks and the pathogens they carry, but are those who live, work, and play within an urban environment excluded from this risk? In this study, we collected ticks from two urban parks in Little Rock, AR, to assess the presence of rickettsiae and ehrlichiae within an urban setting. A total of 273 ticks were collected during July, 2011. Amblyomma americanum was the predominant tick species, with 255 (93%) of those collected. The remaining 18 (7%) were Dermacentor variabilis. Ticks were separated and pooled into groups for further testing. Forty-two of the 43 (98%) A. americanum pools demonstrated molecular evidence for the presence of rickettsiae. None of the D. variabilis contained rickettsiae. Restriction enzyme fragment length polymorphism analysis and DNA sequencing revealed Rickettsia amblyommii to be the species present. One A. americanum pool from park A demonstrated the presence of Ehrlichia chaffeensis, the pathogen responsible for human monocytotropic ehrlichiosis. These results indicate that tick-borne pathogens are not limited to rural or suburban areas.

Malassezia pachydermatis fungemia in an adult with multibacillary leprosy

Malassezia pachydermatis is a relatively rare agent of bloodstream infections. We describe an unusual case of Malassezia fungemia in an adult patient hospitalized for Staphylococcus aureus bacteremia who was also found to have multibacillary leprosy. Treatment of the patient required extensive medical management but resulted in a good outcome.

Cerebral phaeohyphomycosis by Fonsecaea monophora: Report in a patient with AIDS and a ring enhancing lesion

Fungal infections are infrequent causes of brain abscesses. Fonsecaea monophora is a dematiaceous fungus that appears to be neurotropic. We report a case of Fonsecaea monophora infection in a patient with acquired immunodeficiency syndrome, and review previous reports of brain abscesses by this organism.

An Unusual Cutaneous Manifestation in a Patient with Murine Typhus.

Murine typhus is a flea-borne febrile illness caused by Rickettsia typhi. Although often accompanied by rash, an inoculation lesion has not been observed as it is with many tick- and mite-transmitted rickettsioses. We describe a patient with murine typhus and an unusual cutaneous manifestation at the site of rickettsial inoculation.