Jorge Zavala-Castro

Rickettsia felis as emergent global threat for humans.

The reported incidences of human cases and infected vectors have increased during the past 5 years.

Detection of a typhus group Rickettsia in Amblyomma ticks in the state of Nuevo Leon, Mexico.

Abstract: The state of Nuevo Leon, Mexico has had outbreaks of typhus group rickettsiosis, most recently recognized in 1997. Evaluation of the sera of 345 patients with a dengue‐like illness revealed that 25.5% had antibodies reactive with typhus group rickettsiae and 16% had antibodies to Rickettsia parkeri. Rickettsiae were detected by PCR and shell‐vial isolations in the field‐collected Amblyomma ticks. Molecular characterization by DNA sequence analysis of the gltA, ompB, and 17‐kDa gene identified the organisms to be R. prowazekii.

Fatal Human Infection with Rickettsia rickettsii, Yucatán, Mexico

The first fatal Rickettsia rickettsii infection was diagnosed in the southwest of Mexico. The patient had fever, erythematous rash, abdominal pain, and severe central nervous system involvement with convulsive crisis. The diagnosis of R. rickettsii infection was established by immunohistochemistry and specific polymerase chain reaction.

Identification of Ctenocephalides felis Fleas as a Host of Rickettsia felis, the Agent of a Spotted Fever Rickettsiosis in Yucatán, Mexico

In search for the vector of the recently recognized spotted fever rickettsiosis of the Yucatán, ticks, fleas, and lice were collected from vegetation and dogs in localities where seropositive persons had been found. The arthropods were examined by polymerase chain reaction (PCR) using primers for the genus-specific 17-kDa protein gene followed by restriction fragment length polymorphism (RFLP) and DNA sequencing. Eleven (20%) of 54 pools of Ctenocephalides felis fleas contained DNA of Rickettsia felis. None of 219 Amblyomma cajennense, 474 Rhiphicephalus sanguineus, 258 Boophilus sp. ticks, and 33 Poliplax species lice contained DNA of Rickettsia. The identity of the rickettsial DNA was confirmed as R. felis by PCR/RFLP for the citrate synthase and outer membrane protein A genes and by DNA sequencing. The results indicate that the host of R. felis in Yucatán is C. felis and suggest that the spotted fever rickettsiosis that has infected >5% of the population of the Yucatán and can present as a dengue-like illness is likely to be caused by R. felis.

Severe human infection with Rickettsia felis associated with hepatitis in Yucatan, Mexico

Rickettsia felis infection usually is a mild-to-moderate illness characterized by general signs and symptoms. Generally, patients do not require hospitalization. However, we detected 2 severe infections with R. felis. Our findings support the importance of R. felis infection as a potentially severe illness in humans.

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.

Murine typhus in child, Yucatan, Mexico.

A case of murine typhus in Yucatan was diagnosed in a child with nonspecific signs and symptoms. The finding of Rickettsia typhi increases the number of Rickettsia species identified in Yucatan and shows that studies are needed to determine the prevalence and incidence of rickettsioses in Mexico.

Guías Latinoamericanas de la RIICER para el diagnóstico de las rickettsiosis transmitidas por garrapatas

Tick-borne rickettsioses are worldwide infectious diseases that are considered emerging and re-emerging. Until recently the only tick-borne rickettsiosis present in Latin America was Rickettsia rickettsii infection, but to date, with the incorporation of new tools as PCR and sequencing and the quick cellular close tube cultures (Shell-vial), new species has been involved as human pathogens. In these guidelines, we offer an update of the microbiological assays for diagnosing rickettsioses. Besides we have included a section in which the most important hard ticks involved in human rickettsioses in Latinoamerica are detailed.

` Candidatus Rickettsia asemboensis’ and Wolbachia spp. in Ctenocephalides felis and Pulex irritans fleas removed from dogs in Ecuador

BackgroundFlea-borne infections are distributed worldwide. Up to date there are no reports about microorganisms associated to fleas in Ecuador.MethodsSeventy-one Pulex irritans and 8 Ctenocephalides felis fleas were removed from dogs in two Ecuadorian areas (Pastaza and Chimborazo Provinces) in December 2012. DNA extracts were tested by polymerase chain reaction (PCR) assays targeting universal 16S rRNA, as well as screened for the presence of Rickettsia spp. (gltA, htrA, ompB, sca4 and ompA genes) and Bartonella spp. (rpoB, gltA and ITS genes).ResultsOur results showed the presence of `Candidatus Rickettsia asemboensis’ (highly similar to R. felis) in C. felis and Wolbachia spp. endosimbionts in P. irritans collected from animals in Ecuador. No fleas were found to be positive for any Bartonella species or Yersinia pestis.ConclusionsClinicians should be aware of the potential risk of this new Candidatus Rickettsia sp. and keep in mind other flea-borne infections since these flea species frequently bite humans.

Rickettsia felis in the Americas

Abstract:  The authors describe their work in the Americas in Rickettsia felis cases in humans and the presence of Rickettsia felis in vectors.