[An update on rickettsiosis]. / L'actualité des rickettsioses.

Rickettsiae are strictly intracellular bacteria belonging to the Rickettsiaceae family. They are transmitted by various arthropods species, which are either vectors or reservoirs for the bacteria. The specific association between Rickettsieae and the vector are extensively studied, moreover Rickettsieae associated diseases are part of a continuously evolving field. Nevertheless, some rickettsiosis, such as epidemic typhus, have been described since the 16th century. Emerging diseases related to these bacteria are being investigated as well as new species, the implication of which is not always clear in human pathology when they are discovered. Some of these diseases are benign, others may be potentially fatal. Clinicians must therefore be aware of them. These issues are reviewed.

Enfermedades producidas por Rickettsia / Rickettsioses

El género Rickettsia está constituido por diferentes especies de bacterias gramnegativas, parásitos intracelulares obligados, muchos de los cuales constituyen actualmente paradigmas de patógenos emergentes. A excepción de R. prowazekii, su ciclo vital se mantiene al infectar especies de hospedadores (en general mamíferos),y vectores (en general garrapatas y pulgas), siendo el ser humano un huésped accidental. La patogenia común a todas consiste en una vasculitis de pequeños vasos por infección directa de las células endoteliales, produciéndose una pléyade de focos de vasculitis multisistémica. Según la distribución de las rickettsiasse puede producir neumonitis intersticial, miopericarditis, lesiones vasculíticas cutáneas, meningitis linfocitaria, así como afectación hepática, renal y gastrointestinal. La clasificación más utilizada es la que divide a lasrickettsiosis en dos grupos: el de las fiebres manchadas, y el de las fiebres tíficas. En nuestro entorno las dos entidades más frecuentes de ambos grupos son la fiebre botonosa mediterránea (producida por R. conorii ) yel tifus murino (producido por R. typhi ), respectivamente. El presente capítulo revisa estas entidades, así como otras rickettsiosis de interés por emergentes (R. slovaca,R. africae, R. prowazekii, R. felis), o por su alta incidenciaen otras áreas (R. rickettsii, Orientia tsutsugamushi) (AU)

Species of the genus Rickettsia are small, obligate intracelular, gramnegative bacteria, many of which are considered nowadays a paradigm of emergent pathogens. With the exception of R. prowazekii, they are maintained in the natural environment through a cycle involving different hosts (mainly mammals), and arthropod vectors(in general ticks, and fleas); humans are affected only by incidental transmission due to arthropod bites.The common pathogenesis of these diseases lie on the predominantly infection of endotelial cells, that determines the development of multisistemic small vessel vasculitis, which may affect lungs (interstitial pneumonitis), heart (miopericarditis), skin (rash),central nervous system (meningoencephalitis), as well as liver, and kidneys. They are classified in two groups: spotted-fever group, and typhus group rickettsia. In Spain the most prevalent rickettsioses of both groups are mediterranean spotted fever (caused by R. conorii ), andmurine typhus (caused by R. typhi ), respectively. This review focuses mainly in these two diseases, and also in other rickettsioses of interest due to their recently emergence or reemergence (R. slovaca, R. africae, R. prowazekii, R. felis), or to their high incidence in other areas (R. rickettsii, Orientia tsutsugamushi) (AU)

Naming of Rickettsiae and rickettsial diseases.

Over the last 20 years, advances in molecular techniques have greatly facilitated the identification of the members of the Rickettsiales, and numerous new species and diseases have been described. In this paper, we review taxonomic rules and appropriate approaches to valid naming of rickettsial species and the diseases they cause.

Rickettsial diseases and their serological diagnosis.

Rickettsial diseases (typhus and spotted fever group rickettsioses, scrub typhus and Q fever) may pose a serious public health problem, namely when they are non-diagnosed or misdiagnosed. Although rickettsiae can be isolated from or detected in clinical specimens, serological tests still remain an indispensable tool in the diagnosis of rickettsial diseases. The complement fixation test widely used in the past is being replaced by other tests which make differentiation of immunoglobulin classes possible. Of these tests microimmunofluorescence is considered the test of choice followed by the latex agglutination, indirect hemagglutination, immunoperoxidase assay, and enzyme-linked immunosorbent assay. The last one is also suitable for seroepidemiological studies. Immunoblot analysis can be used to confirm the results of other tests. The use of the low-specific and low-sensitive Weil-Felix test should be reserved only for situations in which other serologic tests are not available.

Improved clinical approach to the diagnosis of canine ehrlichiosis.

Canine ehrlichiosis is being recognised with increasing frequency in many parts of the world. Based upon a detailed clinical and laboratory examination including a simple in vitro blood culture diagnostic test 373 cases have been classified into seven broad groups. These groups include acute, haemorrhagic, chronic, uraemic, subclinical, carrier state and those with babesiosis. While many of these groups overlap they will assist the clinician in diagnosis and allow the application of specific therapy before the disease progresses to a chronic irreversible stage.