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Hemophagocytic lymphohistiocytosis is a rare complication in Rickettsia typhi infections. We report the case of a 2-year-old boy with sudden night-onset fever, pallor, neck adenopathy and erythematous macular rash on the thorax, thighs and buttocks. During admission, he developed hyponatremia, hypoalbuminemia, anemia, thrombocytopenia, leukopenia, neutropenia, liver damage, hemorrhages and persistent fever. No hematological improvement was observed after the initial management, neoplastic diseases were discarded by bone marrow aspiration and lymph node biopsy; hemophagocytic lymphohistiocytosis was diagnosed. By immunohistochemistry and indirect immunofluorescence, murine typhus was also diagnosed and doxycycline was started with transitory recovery. Later, the child developed kidney failure and distributive shock that evolved to cardiac arrest and death. This is the first case report in Mexico on a fatal murine typhus associated with hemophagocytic lymphohistiocytosis in which the etiology was evidenced by histopathology.

Rickettsia typhi y Rickettsia felis son patógenos transmitidos por pulgas‚ ambos se caracterizan por producir enfermedad febril aguda indiferenciada. En la última década, se han reportado nuevas especies, denominadas organismos similares a R. felis o “Rickettsia felis-like organisims” (RFLO) en distintos artrópodos, entre estas: R. asembonensis y Candidatus R. senegalensis En Colombia, específicamente en el departamento de Caldas se ha informado la presencia de R. felis en pulgas y en garrapatas de Villeta, Cundinamarca, sin embargo, no se han realizado estudios en otras áreas de Colombia por lo que nos planteamos como objetivo determinar la seroprevalencia de rickettsiosis transmitidas por pulgas en humanos e identificar especies de Rickettsia sp. en pulgas recolectadas sobre perros y gatos del departamento del Cauca. Se realizó un estudio de corte transversal para la recolección de muestras de humanos entre julio y noviembre de 2017, para detectar anticuerpos IgG contra R. felis y R. typhi por IFI. Adicionalmente se recolectaron pulgas de perros y gatos, fueron clasificadas taxonómicamente y organizadas en pooles, la identificación de genes rickettsiales se realizó por qPCR para el gen gltA, y por PCR convencional para ompB y 17KDa. A las muestras con al menos dos genes positivos, se les realizó la técnica PCR-RFLP para los productos de 17KDa se usó la enzima XbaI y para ompB se utilizó la enzima NlaIV. Los resultados fueron confirmados por secuenciación. Se colectaron 506 muestras de humanos, en las que se determinó una seroprevalencia de 60,5% (306/506) contra R. typhi y de 40% (22/80) contra R. felis. Se recolectaron 1284 pulgas, todas identificadas como Ctenocephalides felis; se organizaron en 245 pooles de los que el 58% (144/245) fueron positivos para gltA, y de estos el 96,5% (139/144) para ompB y 17KDa; la restricción se realizó a todos los productos positivos para el gen 17KDa, identificando el 100% de las muestras como R. felis-RFLO y para el gen ompB, identificando el 14,4% como R. felis, el 84,9% R. asembonensis y el 0,7% Candidatus R. senegalensis. Una muestra identificada para cada especie, fue confirmada por secuenciación. Este estudio muestra la seroprevalencia contra R. typhi y R. felis en el departamento del Cauca siendo evidencia de co-circulacion de estas dos especies; estos resultados coinciden con los reportados para otras zonas de Colombia, sin embargo, son altos comparados con los obtenidos en otras regiones del mundo, 2% para R. typhi en Grecia, 10,3% para el grupo de tifo en el amazonas peruano, 3,8–18% y 3,2–6,5% contra R. typhi y R. felis en España. Adicionalmente es el primer reporte de Candidatus Rickettsia senegalensis en pulgas C. felis recolectadas de perros en Colombia, obteniendo 99,8% de identidad con las secuencias de gltA y ompB reportadas en el Genbank. Esta especie había sido reportada en África, Asia, India, Estados Unidos y Chile y su capacidad zoonótica aún no está descrita Se determinó la seroprevalencia de rickettsiosis transmitidas por pulgas, en el departamento del Cauca y la alta circulación especies de R. felis o RFLO en las zonas priorizadas del departamento. Colciencias Rickettsia typhi and Rickettsia felis are pathogens transmitted by fleas, both are characterized for generating undifferentiated acute febrile illness. In the last decade, new species have been reported in different arthropods designated as "Rickettsia felis-like organisims" (RFLO), among them: R. asembonensis and Candidatus R. senegalensis. In Colombia, specifically in the department of Caldas, the presence of R. felis in fleas and in ticks from Villeta, Cundinamarca has been reported, however no studies have been conducted in other areas of Colombia. To determine the seroprevalence of rickettsiosis transmitted by fleas in humans and identify species of Rickettsia sp. in fleas collected from dogs and cats from the department of Cauca. A cross-sectional study was conducted for the collection of human samples between July and November of 2017 to detect IgG antibodies against R. felis and R. typhi by IFI. Additionally, fleas were collected from dogs and cats, taxonomically classified and organized into pools, rickettsial gene identification was performed by qPCR for the gltA gene, and by conventional PCR for ompB and 17KDa. Samples with at least two positive genes were analyzed by PCR-RFLP, for the ompB products the NlaIV enzyme was used. The results were confirmed by sequencing. 506 human samples were collected, in which a seroprevalence of 60,5% was detected against R. typhi and 40% against R. felis. 1284 fleas were collected, all identified as Ctenocephalides felis; they were organized in 245 pools from which 58% (144/245) were positive for gltA, and from them 96,5% (139/144) for ompB and 17KDa; the restriction was made to all the positive products for the ompB gene, identifying 14,4% as R. felis, 84,9% as R. asembonensis and 0,7% Candidatus R. senegalensis. A sample identified for each species was confirmed by sequencing. This study shows the seroprevalence against R. typhi and R. felis in the department of Cauca, this serves as evidence of co-circulation of these two species; additionally these results coincide with others studies from different areas of Colombia , however they are higher compared to those obtained in other regions of the world, 2% for R. typhi in Greece, 10,3% for the typhus group in the Peruvian Amazon, 3,8-18% and 3,2-6,5% against R. typhi and R. felis in Spain. Furthermore, this is the first report of Candidatus Rickettsia senegalensis in C. felis fleas collected from dogs in Colombia, obtaining 99,8% identity with the gltA and ompB sequences reported in Genbank. This species had been reported in Africa, Asia, India, the United States and Chile and its zoonotic capacity is not yet described. The seroprevalence of rickettsiosis transmitted by fleas was determined in the department of Cauca and the high circulation species of R. felis or RFLO in the prioritized areas of the department. Magíster en Ciencias Biológicas Maestría