Rhipicephalus sanguineus Complex in the Americas: Systematic, Genetic Diversity, and Geographic Insights.

The Rhipicephalus sanguineus group encompasses at least 12 validated species of Palearctic and Afrotropical hard ticks, which are relevant in veterinary medicine and public health. The taxonomy of R. sanguineus s.s., has been particularly intensely debated, due to its wide geographic distribution, morphological variants, parasite-host associations, and its capacity and vectorial competence for the transmission of several pathogens. By sequencing mitochondrial markers, it was possible to identify the existence of multiple lineages, among which the Tropical and the Temperate lineages stand out, particularly in America. However, the northern limit between these lineages is not clear due to the lack of extensive sampling across Mexico. For this reason, the aim of the present study was to determine the genetic diversity and structure of the R. sanguineus group in Mexico and to compare it with the populations reported in the Americas, in order to propose the northern limit of the R. sanguineus Tropical lineage and the potential regions of sympatry with R. sanguineus s.s. The findings of this study now confirm the presence of R. sanguineus s.s. in Mexico, showing a subtle genetic structure and high genetic diversity throughout its distribution in the Americas. In contrast, the Tropical lineage seems to be genetically less diverse in its overall distribution in the Americas. The genetic diversity of these two independent lineages could have important epidemiological implications in the transmission of tick pathogens.

Causes of erythrocytosis and its impact as a risk factor for thrombosis according to etiology: experience in a referral center in Mexico City.

BACKGROUND: Thrombotic events are well documented in primary erythrocytosis, but it is uncertain if secondary etiologies increase the risk of thrombosis. This study aimed to determine the causes of erythrocytosis and to identify its impact as a risk factor for thrombosis. METHODS: Data were obtained from patients with erythrocytosis between 2000 and 2017 at a referral hospital in Mexico City. Erythrocytosis was defined according to the 2016 WHO classification. Time to thrombosis, major bleeding, or death were compared among groups of patients defined by the etiology of erythrocytosis using a Cox regression model, adjusting for cardiovascular risk factors. RESULTS: In total, 330 patients with erythrocytosis were studied. The main etiologies of erythrocytosis were obstructive sleep apnea (OSA) in 29%, polycythemia vera (PV) in 18%, and chronic lung disease (CLD) in 9.4% of the patients. The incidence rate of thrombosis was significantly higher in patients with PV and CLD than that in patients with OSA (incidence rates of 4.51 and 6.24 vs. 1.46 cases per 100 person-years, P=0.009), as well as the mortality rate (mortality rates of 2.72 and 2.43 vs. 0.17 cases per 100 person-years, P =0.003). CONCLUSION: The risk of thrombosis in CLD with erythrocytosis was comparable to that in patients with PV. Further larger-scale studies are needed to confirm these findings and evaluate the benefits of preventive management of COPD with erythrocytosis similar to PV.

Clinical features of patients with Rocky Mountain spotted fever, dengue and chikungunya infection.

INTRODUCTION: Clinical distinction between arbovirus infections and those caused by rickettsia is crucial to initiate appropriate medical treatment. OBJECTIVE: To compare the differences between Rocky Mountain spotted fever (RMSF) and other vector-borne diseases (dengue and chikungunya) with similar clinical presentation, and to identify data that could aid rapid diagnosis of these diseases. METHODS: We evaluated sociodemographic, clinical and laboratory data of 399 patients from five hospitals and clinics of Sonora, Mexico, between 2004 and 2016, with laboratory-confirmed diagnosis of RMSF, dengue, or chikungunya. RESULTS: The RMSF group had the highest lethality (49/63 deaths, 77.8 %), followed by the chikungunya group (3/161, 1.9 %) and the dengue group (3/161, 1.9 %). Clinical differences included the presence of rash, edema, and pruritus; in addition, differences in multiple biomarkers such as platelets, hemoglobin, indirect bilirubin, and serum sodium levels were documented. CONCLUSION: Rash on the palms and soles, edema and absence of pruritus, together with high levels of direct bilirubin and severe thrombocytopenia could be useful indicators to differentiate patients at RMSF advanced stages from those with dengue and chikungunya.

INTRODUCCIÓN: La distinción clínica entre infecciones arbovirales y las provocadas por rickettsias es crucial para iniciar el tratamiento médico apropiado. OBJETIVO: Comparar las diferencias entre fiebre manchada de las montañas rocosas (FMMR) y otras enfermedades transmitidas por vector (dengue y chikungunya) con presentación clínica similar e identificar los datos que pudieran ayudar al diagnóstico rápido de esas enfermedades. MÉTODOS: Se evaluaron datos sociodemográficos, clínicos y de laboratorio de 399 pacientes de cinco hospitales y clínicas en Sonora, México, entre 2004 y 2016, con el diagnóstico confirmado por laboratorio de FMMR, dengue o chikungunya. RESULTADOS: El grupo con FMMR presentó la mayor letalidad (49/63 muertes, 77.8 %), seguido por el de chikungunya (3/161, 1.9 %) y el de dengue (3/161, 1.9 %). Las diferencias clínicas consistieron en la presencia de exantema, edema y prurito; además, se documentaron diferencias en múltiples biomarcadores como plaquetas, hemoglobina, bilirrubina indirecta y niveles de sodio sérico. CONCLUSIÓN: El exantema en palmas y plantas, edema y ausencia de prurito, aunados a niveles altos de bilirrubina directa y trombocitopenia severa pudieran ser indicadores útiles para diferenciar a pacientes con FMMR en etapas avanzadas de aquellos con dengue y chikungunya.

Enfermedad granulomatosa hepática.

Granulomas are circumscribed lesions mainly composed of mononuclear cells that arise in response to poorly degradable antigenic stimuli. They are found in 2-15 % of liver biopsies and the meaning of their finding can range from an incidental phenomenon to the manifestation of a systemic disease of infectious, autoimmune or neoplastic origin. Clinical presentation usually points at the underlying pathology; however, the list of associated conditions is extensive, and differs based on patient epidemiological history and baseline characteristics. The most useful element for their study is a thorough medical history, with an emphasis on recent trips, exposures and consumption of drugs or raw or exotic foods. Detailed histopathological analysis may help identify the etiology. For example, the presence of epithelioid granulomas with caseous necrosis indicates tuberculosis and, its absence, sarcoidosis; eosinophil abundance can be associated with drug reactions or parasitic infections; and the presence of foreign bodies can be the cause of granulomatous liver disease (GLD). In this article, we describe the basic clinical-pathological aspects of GLD, and provide a brief summary of the most common etiologies, with an emphasis on the Latin-American region.

Los granulomas son lesiones circunscritas compuestas principalmente por células mononucleares que surgen en respuesta a estímulos antigénicos pobremente degradables. Se encuentran en 2 a 15 % de las biopsias hepáticas; su hallazgo puede significar desde un fenómeno incidental, hasta la manifestación de una enfermedad sistémica de origen infeccioso, autoinmune o neoplásico. El cuadro clínico suele apuntar a la patología subyacente, sin embargo, la lista de condiciones asociadas es amplia y difiere con base en los antecedentes epidemiológicos y a las características basales del paciente. El elemento de mayor utilidad para su estudio es la historia clínica exhaustiva, con énfasis en viajes recientes, exposición de riesgo y consumo de fármacos o alimentos crudos o exóticos. El análisis histopatológico detallado puede auxiliar en la identificación de la etiología, por ejemplo, la presencia de granulomas epitelioides con necrosis caseosa indica tuberculosis y su ausencia, sarcoidosis; la abundancia de eosinófilos es señal de reacciones farmacológicas o infecciones parasitarias; la presencia de cuerpos extraños puede ser la causa de la enfermedad granulomatosa hepática. En este artículo describimos los aspectos clínico-patológicos básicos de esta enfermedad y proveemos un breve resumen de las etiologías más comunes, principalmente en la región de Latinoamérica.

Una serie de casos fatales de fiebre manchada de las Montañas Rocosas en Sonora, México / A fatal case series of Rocky Mountain spotted fever in Sonora, México

Resumen Introducción. La fiebre manchada de las Montañas Rocosas es una infección muy letal, particularmente si no se diagnostica y se trata oportunamente. Objetivo. Describir el perfil clínico de los casos fatales de pacientes con fiebre manchada de las Montañas Rocosas, hospitalizados en Sonora, México. Materiales y métodos. Se analizó una serie de 47 defunciones por fiebre manchada de las Montañas Rocosas en el periodo de 2013 a 2016. El diagnóstico se confirmó mediante reacción en cadena de la polimerasa (PCR) o la cuadruplicación de los títulos de inmunoglobulina G (IgG) en muestras de suero pareadas analizadas mediante inmunofluorescencia indirecta. Se compararon las características clínicas y de laboratorio, estratificando a los sujetos en dos grupos: pediátricos y adultos. Resultados. No hubo diferencias en las manifestaciones clínicas entre los grupos; el exantema petequial fue el signo más frecuente (96 %), seguido por cefalea (70 %) y mialgias (67 %). La muerte ocurrió en el 55 % de los sujetos a pesar de haber recibido doxiciclina antes del quinto día del inicio de los síntomas. Los marcadores de laboratorio más frecuentes fueron trombocitopenia, falla hepática e insuficiencia renal. Conclusión. La fiebre manchada de las Montañas Rocosas es una enfermedad muy letal, lo cual puede estar relacionado con la ausencia de sospecha del diagnóstico y el retraso en la administración de doxiciclina, pero también con características atribuibles a Rickettsia rickettsii que inciden en la variabilidad de los resultados adversos que se han observado en regiones donde la enfermedad es frecuente.

Abstract Introduction: Rocky Mountain spotted fever is a highly lethal infectious disease, particularly if specific treatment with doxycycline is given belatedly. Objective: To describe the clinical profile of fatal Rocky Mountain spotted fever cases in hospitalized patients in the state of Sonora, México. Materials and methods: We conducted a cross-sectional study on a series of 47 deaths caused by Rickettsia rickettsii from 2013 to 2016. The diagnosis of Rocky Mountain spotted fever was confirmed in a single blood sample by polymerase chain reaction (PCR) or by a four-fold increase in immunoglobulin G measured in paired samples analyzed by indirect immunofluorescence. Clinical and laboratory characteristics were compared stratifying subjects into two groups: pediatric and adult. Results: There were no differences in clinical characteristics between groups; petechial rash was the most frequent sign (96%), followed by headache (70%) and myalgia (67%). Although that doxycycline was administered before the fifth day from the onset of symptoms, death occurred in 55% of patients. In clinical laboratory, thrombocytopenia, and biomarkers of liver acute failure and acute kidney failure were the most frequent. Conclusion: Rocky Mountain spotted fever remains as one of the most lethal infectious diseases, which may be related not only to the lack of diagnostic suspicion and delayed administration of doxycycline, but to genotypic characteristics of Rickettsia rickettsii that may play a role in the variability of the fatality rate that has been reported in other geographical regions where the disease is endemic.