Navegando por Autor "Walker, David Hughes"
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Item Amblyomma imitator ticks as vectors of Rickettsia rickettsii, Mexico.(2010) Oliveira, Karla Andrade de; Pinter, Adriano; Medina Sanchez, Aaron; Boppana, Venkata D.; Wikel, Stephen Kenneth; Saito, Tais B.; Shelite, Thomas; Blanton, Lucas; Popov, Vsevolod; Teel, Pete D.; Walker, David Hughes; Galvão, Márcio Antônio Moreira; Mafra, Cláudio Lísias; Bouyer, Donald H.Rickettsia rickettsii is a gram-negative, obligate, intracellular bacterium and the cause of Rocky Mountain spotted fever (RMSF). In Mexico, its transmission has been attributed to Rhipicephalus sanguineus and Amblyomma cajennense ticks. Amblyomma imitator has close affi nity with A. cajennense and was formerly confused with this species. These ticks’ distributional range extends from southern Texas, southward through Mexico (where they are widely sympatric with A. cajennense ticks) into Central America (1). In this study, we isolated and characterized R. rickettsii from A. imitator from Mexico by using molecular methods.Item Caracterização de Rickettsia spp. circulante em foco silencioso de febre maculosa brasileira no Município de Caratinga, Minas Gerais, Brasil.(2006) Cardoso, Luciane Daniele; Freitas, Renata Nascimento de; Mafra, Cláudio Lísias; Neves, Cristiane Vilas Boas; Figueira, Fátima Cristina Bacellar; Labruna, Marcelo Bahia; Gennari, Solange Maria; Walker, David Hughes; Galvão, Márcio Antônio MoreiraThe present study was intended to characterize Rickettsia spp. circulating in arthropod vectors in Caratinga,Minas Gerais, Brazil, by PCR and to investigate the presence of antibodies against the spotted fever Rickettsiae group (SFRG) in dogs and horses. 2,610 arthropods were collected and taxonomically identified. DNA samples obtained from these vectors were submitted to PCR and cycle-sequenced. Ctenocephalides and Amblyomma cajennense showed sequences presenting 100.0% homology with R. felis. A sequence obtained from Rhipicephalus sanguineus showed 99.0% homology with R. felis, and a sequence from A. cajennense showed 97.0% homology with R. honei and R. rickettsii. Canine (73) and equine (18) serum samples were tested by indirect fluorescent antibody (IFA) using R. rickettsii antigen. Only three of the equine sera tested (17.0%) had positive antibody titers. Molecular detection of rickettsiae species potentially pathogenic to humans in arthropod vectors and the presence of seroreactivity to SFRG in horses show the risk of transmission of rickettsiosis in this area and the need to maintain continuous epidemiological surveillance for rickettsial diseases.Item Clinical and laboratorial evidence of Rickettsia felis infections in Latin America.(2004) Galvão, Márcio Antônio Moreira; Mafra, Cláudio Lísias; Chamone, Chequer Buffe; Calic, Simone Berger; Zavala Velazquez, Jorge Ernesto; Walker, David HughesAfter the discovery and initial characterization of Rickettsia felis in 1992 by Azad and cols, and the subsequent first description of a human case of infection in 1994, there have been two communications of human rickettsiosis cases caused by Rickettsia felis in Latin America. The first one was published in 2000 by Zavala-Velazquez and cols in Mexico. In 2001 Raoult and cols described the occurrence of two human cases of Rickettsia felis rickettsiosis in Brazil. In the present discussion these two articles were compared and after the description of the principal signs and symptoms, it was concluded that more studies are needed with descriptions of a greater number of patients to establish the true frequency of the clinical signs and symptoms present in Rickettsia felis rickettsiosis.Item Fatal spotted fever rickettsiosis, Minas Gerais, Brazil.(2003) Galvão, Márcio Antônio Moreira; Dumler, J. Stephen; Mafra, Cláudio Lísias; Calic, Simone Berger; Chamone, Chequer Buffe; Cesarino Filho, Gracco; Olano, Juan Pablo; Walker, David HughesThe emergence and reemergence of a serious infectious disease are often associated with a high case-fatality rate because of misdiagnosis and inappropriate or delayed treatment. The current reemergence of spotted fever rickettsiosis caused by Rickettsia rickettsii in Brazil has resulted in a high proportion of fatal cases. We describe two familial clusters of Brazilian spotted fever in the state of Minas Gerais, involving six children 9 months to 15 years of age; five died. Immunohistochemical investigation of tissues obtained at necropsy of a child in each location, Novo Cruzeiro and Coronel Fabriciano municipalities, established the diagnosis by demonstration of disseminated endothelial infection with spotted fever group rickettsiae. The diagnosis in the two fatal cases from Coronel Fabriciano and the surviving patient from Novo Cruzeiro was further supported by immunofluorescence serologic tests.Item Human ehrlichioses in Brazil : first suspect cases.(2004) Calic, Simone Berger; Galvão, Márcio Antônio Moreira; Bacellar, Fátima; Rocha, Christiane Maria Barcellos Magalhães da; Mafra, Cláudio Lísias; Leite, Romário Cerqueira; Walker, David HughesBrazilian spotted fever (BSF) rickettsiosis is the most common and recognized of the human rickettsioses in Brazil. It is difficult to establish the diagnosis of human rickettsiosis infection by routine microbiologic methods, creating a false idea that Rickettsia and Ehrlichia infections are rare and without importance. New tick-borne diseases, like Human Granulocytic Anaplasmosis (HGA) and Human Monocytic Ehrlichiosis (HME), have been described in many countries. These diseases can present symptoms similar to rickettsioses of the spotted fever group, and they are transmitted by ixodid ticks. The first two suspected cases of human ehrlichiosis in Brazil were first considered to be cases of BSF. The differential diagnosis was made at the Minas Gerais Rickettsiosis Public Health Laboratory. The clinical and laboratory findings, with positive serology for the HME agent, indicated suspected cases of human ehrlichioses in Brazil.Item Prevalence of antibodies to spotted fever group rickettsiae in humans and domestic animals in a brazilian spotted fever−endemic area in the state of São Paulo, Brazil : serologic evidence for infection by Rickettsia rickettsii and another spotted fever group rickettsia.(2004) Horta, Maurício Cláudio; Labruna, Marcelo Bahia; Sangioni, Luis Antônio; Vianna, Manoella Campostrini Barreto; Gennari, Solange Maria; Galvão, Márcio Antônio Moreira; Mafra, Cláudio Lísias; Vidotto, Odilon; Schumaker, Teresinha T. S.; Walker, David HughesIn serum samples obtained from all the healthy humans, horses, dogs, and donkeys present on three farms in the Pedreira Municipality, an endemic area for Brazilian spotted fever, an indirect immunofluorescence assay (IFA) detected antibodies against Rickettsia rickettsii in 17 (77.3%) horses, 5 (31.3%) dogs (titers ranging from 64 to 4,048), and none of 4 donkeys or 50 humans. Five canine and eight equine sera with high antibody titers to R. rickettsii were also tested by IFA against R. bellii, R. akari, and R. africae antigens. Sera from two horses and two dogs that showed similar high antibody titers against two rickettsial antigens were evaluated after cross-absorption. Sera from seven horses and two dogs contained antibodies specific for R. rickettsii, and one dog serum had antibodies against a Rickettsia species very closely related to R. africae. The latter may have been caused by infection with the recently identified COOPERI strain.Item Revisiting Brazilian spotted fever focus of Caratinga, Minas Gerais state, Brazil.(2006) Galvão, Márcio Antônio Moreira; Cardoso, Luciane Daniele; Mafra, Cláudio Lísias; Calic, Simone Berger; Walker, David HughesWe revisited a Brazilian spotted fever focal area in Minas Gerais state, Brazil, in 2002, and performed a serologic survey in dogs and cats. The results of this survey are compared with the survey made 10 years before. The possible efficacy of vector control measures adopted in this area and the role of dogs and horses as sentinels of infection by Rickettsia are discussed.Item Rickettsia felis in the Americas.(2006) Galvão, Márcio Antônio Moreira; Zavala Velazquez, Jorge Ernesto; Calic, Simone Berger; Walker, David HughesThe authors describe their work in the Americas in Rickettsia felis cases in humans and the presence of Rickettsia felis in vectors.Item Rickettsia in synanthropic and domestic animals and in their host from two areas of low endemicity for Brazilian spotted fever, in the eastern region of Minas Gerais state, Brazil.(2010) Milagres, Bruno Silva; Padilha, Amanda de Freitas; Gabriel G. Gomes; Montandon, Carlos Emmanuel; Pena, Dárlen Crísthiê Hermelinda; Bastos, Fernanda Aparecida Nieri; Silveira, Iara; Pacheco, Richard de Campos; Labruna, Marcelo Bahia; Bouyer, Donald H.; Freitas, Renata Nascimento de; Walker, David Hughes; Mafra, Cláudio Lísias; Galvão, Márcio Antônio MoreiraThe aim of this study was to understand the current epidemiology of rickettsial diseases in two rickettsialendemic regions in Brazil. In the municipalities of Pingo D’Agua and Santa Cruz do Escalvado, among serum samples obtained from horses and dogs, reactivity by immunofluorescent assay against spotted fever group rickettsiae was verified. In some serum samples from opossums ( Didelphis aurita ) captured in Santa Cruz do Escalvado, serologic response against rickettsiae was also verified. Polymerase chain reaction identified rickettsiae only in ticks and fleas obtained in Santa Cruz do Escalvado. Rickettsiae in samples had 100% sequence homology with Rickettsia felis . These results highlight the importance of marsupials in maintenance of the sylvatic cycle of rickettsial disease and potential integration with the domestic cycle. Our data also support the importance of horses and dogs as sentinels in monitoring circulation of rickettsiae in an urban area.Item Rickettsioses emergentes e reemergentes numa região endêmica do Estado de Minas Gerais, Brasil.(2002) Galvão, Márcio Antônio Moreira; Lamounier, Joel Alves; Bonomo, Élido; Tropia, Margarete S.; Rezende, Eliane Garcia; Calic, Simone Berger; Chamone, Chequer Buffe; Machado, Mirtes C.; Otoni, Márcia E. A.; Leite, Romário Cerqueira; Caram, Camila; Mafra, Cláudio Lísias; Walker, David HughesO trabalho descreve um inquérito sorológico para rickettsioses em escolares e cães de Novo Cruzeiro, Minas Gerais, Brasil, em 1998. Trezentos e trinta e um escolares pertenciam a uma área endêmica e 142 a uma área não endêmica do município. Trinta e nove (10,1%) soros foram reativos à Reação de Imunofluorescência Indireta (RIFI) para Rickettsia rickettsii no título de 1:64, sendo que dentre esses reativos, 35 eram de estudantes de escolas de área endêmica. Dentre os 73 cães analisados quanto à presença de anticorpos anti R. rickettsii, anti Ehrlichia chaffeensis e anti Ehrlichia canis à RIFI no título de 1:64, 3 (4,11%), 11 (15,07%) e 13 (17,81%) desses animais foram reativos respectivamente aos antígenos testados. Conclui-se que, a sororeatividade para R. rickettsii em indivíduos sadios sem história prévia de febre maculosa brasileira, uma doença marcante por sua alta letalidade, e a presença de sororeatividade para Ehrlichia com potencial patogênico para o homem em cães, nos leva a indagar sobre a transmissão ao homem de outras espécies da família Rickettsiae na área estudada.Item Rickettsiosis of the genus rickettsia in South America.(2003) Galvão, Márcio Antônio Moreira; Mafra, Cláudio Lísias; Moron, Cecília; Anaya, Elisabeth; Walker, David HughesIn South America, human cases of infection by the genus Rickettsia have been described in several countries in the last twenty years. The role of international organizations, such as the Centers for Disease Control and Prevention in Atlanta, Georgia, USA and the World Health Organization Collaborating Center for Tropical Diseases at the University of Texas Medical Branch at Galveston, Texas, USA, was very important in the last twenty years for the development of surveillance systems and for the increase in notification of rickettsial diseases by the countries of South America. We hope that the next goal will be prevention and control of rickettsial diseases in the countries of South America, as well as maintaining the programs developed during the last twenty years, so that a good health system and improved social conditions will be possible.Item Spotted fever group rickettsia in small rodents from areas of low endemicity for brazilian spotted fever in the eastern region of Minas Gerais state, Brazil.(2013) Milagres, Bruno Silva; Padilha, Amanda de Freitas; Montandon, Carlos Emmanuel; Freitas, Renata Nascimento de; Pacheco, Richard de Campos; Walker, David Hughes; Labruna, Marcelo Bahia; Mafra, Cláudio Lísias; Galvão, Márcio Antônio MoreiraWe investigated the humoral immune response against different species of Rickettsia in serum samples from small rodents collected in two areas of a silent focus for Brazilian spotted fever in the eastern region of Minas Gerais State, Brazil. Sera samples were analyzed by indirect immunofluorescence assay using antigens from Rickettsia species of the spotted fever, ancestral, and transition groups. Titers ³ 1:64 were considered positive. In Santa Cruz do Escalvado, 94% (30 of 32) of the samples collected from Rattus rattus, 22% (5 of 23) from Nectomys squamipes, and 80% (4 of 5) from Akodon sp., reacted by indirect immunofluorescence assay with Rickettsia antigens of the spotted fever group. In the municipality of Pingo D’A´ gua, 84% (26 of 31) of the samples collected from R. rattus, 86% (6 of 7) of the samples from Oryzomys subflavus, 86% (6 of 7) from N. squamipes, and 100% (1 of 1) from Bolomys sp. contained antibodies that reacted with rickettsial antigens of the spotted fever group. These results demonstrated the previous exposure of small rodents to spotted fever group Rickettsia, suggesting the participation of these animals in the natural history of these rickettsiae in this region.Item Spotted fever rickettsiosis in Coronel Fabriciano, Minas Gerais State.(2003) Galvão, Márcio Antônio Moreira; Calic, Simone Berger; Chamone, Chequer Buffe; Siqueira, Cláudio Lísias Mafra de; Cesarino Filho, Gracco; Olano, Juan Pablo; Walker, David HughesWe report cases of spotted fever rickettsiosis in Coronel Fabriciano Municipality of Minas Gerais State, Brazil. The cases occurred in May and June of 2000. During this period there were two deaths among children from an area named Pedreira in a periurban area of this municipality. In a boy who died with clinical manifestations of Brazilian spotted fever, a necropsy revealed the presence of a spotted fever group Rickettsia. The serological results confirm the difficulty in the differential diagnosis of patients with symptoms of rickettsial diseases.