RESUMEN
Epidemiological methods are needed to evaluate community exposure to Borrelia burgdorferi, the causative agent of Lyme disease (LD). For LD serodiagnosis, the Centers for Disease Control and Prevention (CDC) recommends a 2-test approach that involves enzyme immunoassay (EIA) testing and Western immunoblotting (WB) of EIA-equivocal and EIA-positive specimens. The specificity of this approach was evaluated among residents of a LD-endemic community and was compared with WB alone and with a simplified 2-test approach (WB of equivocal EIA only). Participants reporting no previous diagnosis of LD were recruited during a community-wide serosurvey on Block Island, Rhode Island. Of 80 eligible participants, 20 had received LD vaccine. Seven (35%) of 20 vaccinees and 22 (37%) of 60 nonvaccinees reported nonspecific symptoms compatible with LD in the previous year. In this highly LD-endemic community, the overall specificity of the CDC-recommended approach was highest (100%), followed by WB alone (98.7%), then the simplified approach (95%).
Asunto(s)
Enfermedad de Lyme/diagnóstico , Western Blotting , Humanos , Técnicas para Inmunoenzimas , Pruebas SerológicasRESUMEN
BACKGROUND: In the summer of 2000, an outbreak of primary pneumonic tularemia occurred on Martha's Vineyard, Massachusetts. The only previously reported outbreak of pneumonic tularemia in the United States also occurred on the island in 1978. METHODS: We conducted a case-control study of adults with pneumonic tularemia and investigated the environment to identify risk factors for primary pneumonic tularemia. Patients with confirmed cases were residents of or visitors to Martha's Vineyard who had symptoms suggestive of primary pneumonic tularemia, were ill between May 15 and October 31, 2000, and had a positive laboratory test for tularemia. Controls were adults who had spent at least 15 days on Martha's Vineyard between May 15 and September 28, 2000. RESULTS: We identified 15 patients with tularemia; 11 of these cases were primary pneumonic tularemia. Francisella tularensis type A was isolated from blood and lung tissue of the one man who died. Patients were more likely than controls to have used a lawn mower or brush cutter in the two weeks before the illness or before an interview, for controls (odds ratio, 9.2; 95 percent confidence interval, 1.6 to 68.0) and during the summer (odds ratio, undefined; 95 percent confidence interval, 1.8 to infinity). Lawn mowing and brush cutting remained significant risk factors after adjustment for other potentially confounding variables. Only one patient reported being exposed to a rabbit while cutting brush. Of 40 trapped animals, 1 striped skunk (Mephitis mephitis) and 1 Norway rat (Rattus norvegicus) were seropositive for antibodies against F. tularensis. CONCLUSIONS: Study of this outbreak of primary pneumonic tularemia implicates lawn mowing and brush cutting as risk factors for this infection.
Asunto(s)
Anticuerpos Antibacterianos/sangre , Brotes de Enfermedades , Francisella tularensis/inmunología , Neumonía Bacteriana/epidemiología , Tularemia/epidemiología , Adolescente , Adulto , Animales , Estudios de Casos y Controles , Femenino , Francisella tularensis/aislamiento & purificación , Humanos , Masculino , Massachusetts/epidemiología , Mephitidae/microbiología , Ratas/microbiología , Factores de RiesgoRESUMEN
Human louse-borne relapsing fever occurs in sporadic outbreaks in central and eastern Africa that are characterized by significant morbidity and mortality. Isolates of the causative agent, Borrelia recurrentis, were obtained from the blood of four patients during a recent epidemic of the disease in southern Sudan. The glpQ gene, encoding glycerophosphodiester phosphodiesterase, from these isolates was sequenced and compared with the glpQ sequences obtained from other relapsing-fever spirochetes. Previously we showed that GlpQ of Borrelia hermsii is an immunogenic protein with utility as a serological test antigen for discriminating tick-borne relapsing fever from Lyme disease. In the present work, we cloned and expressed the glpQ gene from B. recurrentis and used recombinant GlpQ in serological tests. Acute- and convalescent-phase serum samples obtained from 42 patients with louse-borne relapsing fever were tested with an indirect immunofluorescence assay (IFA) and an enzyme-linked immunosorbent assay (ELISA) that used whole cells of B. recurrentis and with immunoblotting to whole-cell lysates of the spirochete and Escherichia coli producing recombinant GlpQ. The geometric mean titers of the acute- and convalescent-phase serum samples measured by IFA were 1:83 and 1:575, respectively. The immunoblot analysis identified a high level of reactivity and seroconversion to GlpQ, and the assay was more sensitive than the whole-cell IFA and ELISA using purified, recombinant histidine-tagged GlpQ. Serum antibodies to GlpQ and other antigens persisted for 27 years in one patient. We conclude that assessment of anti-GlpQ antibodies will allow serological confirmation of louse-borne relapsing fever and determination of disease prevalence.
Asunto(s)
Proteínas Bacterianas/genética , Infecciones por Borrelia/diagnóstico , Borrelia/clasificación , Hidrolasas Diéster Fosfóricas/genética , Phthiraptera/microbiología , Secuencia de Aminoácidos , Animales , Proteínas Bacterianas/análisis , Borrelia/genética , Borrelia/aislamiento & purificación , Infecciones por Borrelia/sangre , Clonación Molecular , Convalecencia , Cartilla de ADN , ADN Bacteriano/genética , Etiopía , Técnica del Anticuerpo Fluorescente Indirecta , Humanos , Insectos Vectores , Hidrolasas Diéster Fosfóricas/análisis , Filogenia , Reacción en Cadena de la Polimerasa/métodos , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Pruebas SerológicasRESUMEN
To compare clinical features and assess risk factors for human granulocytic ehrlichiosis (HGE) and early Lyme disease, we enrolled patients in a case-control study during the 1996 and 1997 tick seasons. Clinical and demographic characteristics were assessed for patients with laboratory-confirmed cases of HGE or Lyme disease, and risk factors were compared with those of matched control subjects. We identified 83 persons with Lyme disease, 27 with HGE, and 11 with apparent coinfection. Unsuspected Ehrlichia infection was identified in 8 (13%) of 60 patients with Lyme disease. Patients with HGE were older and more likely to have fever, chills, or dyspnea than were those with Lyme disease only. Most patients with apparent coinfection did not have hematologic abnormalities. In the risk factor analysis, tickborne illness was independently associated with rural residence and camping. The clinical spectrum of HGE overlaps that of Lyme disease, and physicians in areas of endemicity should consider both diseases in treating patients with a compatible rash or febrile illness.
Asunto(s)
Ehrlichiosis/patología , Enfermedad de Lyme/patología , Adulto , Factores de Edad , Acampada , Estudios de Casos y Controles , Diagnóstico Diferencial , Ehrlichiosis/epidemiología , Femenino , Humanos , Modelos Logísticos , Enfermedad de Lyme/epidemiología , Masculino , Persona de Mediana Edad , Análisis Multivariante , Factores de Riesgo , Población Rural , Wisconsin/epidemiologíaRESUMEN
OBJECTIVE: To evaluate the incidence of Borrelia burgdorferi infection in humans with erythema migrans (EM) in 2 southeastern states. DESIGN: Prospective case series. SETTING: Family medicine practice at academic center. PATIENTS: Twenty-three patients with solitary EM lesions meeting Centers for Disease Control and Prevention (CDC) criteria for Lyme disease. INTERVENTIONS: Patients underwent clinical and serologic evaluation for evidence of B burgdorferi infection. All lesions underwent photography, biopsy, culture and histopathologic and polymerase chain reaction analysis for B burgdorferi infection. Patients were treated with doxycycline hyclate and followed up clinically and serologically. MAIN OUTCOME MEASURES: Disappearance of EM lesions and associated clinical symptoms in response to antibiotic therapy; short-term and follow-up serologic assays for diagnostic antibody; growth of spirochetes from tissue biopsy specimens in Barbour-Stoenner-Kelly II media; special histopathologic stains of tissue for spirochetes; and polymerase chain reaction assays of tissue biopsy specimens for established DNA sequences of B burgdorferi. RESULTS: The EM lesions ranged from 5 to 20 cm (average, 9.6 cm). Five patients (22%) had mild systemic symptoms. All lesions and associated symptoms resolved with antibiotic therapy. Overall, 7 patients (30%) had some evidence of B burgdorferi infection. Cultures from 1 patient (4%) yielded spirochetes, characterized as Borrelia garinii, a European strain not known to occur in the United States; 3 patients (13%) demonstrated spirochetallike forms on special histologic stains; 5 patients (22%) had positive polymerase chain reaction findings with primers for flagellin DNA sequences; and 2 patients (9%) were seropositive for B burgdorferi infection using recommended 2-step CDC methods. No late clinical sequelae were observed after treatment. CONCLUSIONS: The EM lesions we observed are consistent with early Lyme disease occurring elsewhere, but laboratory confirmation of B burgdorferi infection is lacking in at least 16 cases (70%) analyzed using available methods. Genetically variable strains of B burgdorferi, alternative Borrelia species, or novel, uncharacterized infectious agents may account for most of the observed EM lesions.
Asunto(s)
Eritema Crónico Migrans/diagnóstico , Enfermedad de Lyme/diagnóstico , Adulto , Anciano , Antibacterianos/uso terapéutico , Anticuerpos Antibacterianos/sangre , Biopsia , Borrelia/clasificación , Grupo Borrelia Burgdorferi/genética , Grupo Borrelia Burgdorferi/crecimiento & desarrollo , Grupo Borrelia Burgdorferi/inmunología , Colorantes , ADN Bacteriano/análisis , ADN Bacteriano/genética , Doxiciclina/uso terapéutico , Eritema Crónico Migrans/tratamiento farmacológico , Eritema Crónico Migrans/microbiología , Femenino , Flagelina/análisis , Flagelina/genética , Estudios de Seguimiento , Georgia , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Fotograbar , Reacción en Cadena de la Polimerasa , Estudios Prospectivos , South CarolinaRESUMEN
Lyme disease begins at the site of a tick bite, producing a primary infection with spread of the organism to secondary sites occurring early in the course of infection. A major outer surface protein expressed by the spirochete early in infection is outer surface protein C (OspC). In Borrelia burgdorferi sensu stricto, OspC is highly variable. Based on sequence divergence, alleles of ospC can be divided into 21 major groups. To assess whether strain differences defined by ospC group are linked to invasiveness and pathogenicity, we compared the frequency distributions of major ospC groups from ticks, from the primary erythema migrans skin lesion, and from secondary sites, principally from blood and spinal fluid. The frequency distribution of ospC groups from ticks is significantly different from that from primary sites, which in turn is significantly different from that from secondary sites. The major groups A, B, I, and K had higher frequencies in the primary sites than in ticks and were the only groups found in secondary sites. We define three categories of major ospC groups: one that is common in ticks but very rarely if ever causes human disease, a second that causes only local infection at the tick bite site, and a third that causes systemic disease. The finding that all systemic B. burgdorferi sensu stricto infections are associated with four ospC groups has importance in the diagnosis, treatment, and prevention of Lyme disease.
Asunto(s)
Antígenos Bacterianos , Proteínas de la Membrana Bacteriana Externa/genética , Grupo Borrelia Burgdorferi/genética , Borrelia burgdorferi , Enfermedad de Lyme/microbiología , Grupo Borrelia Burgdorferi/patogenicidad , Genes Bacterianos , Variación Genética , Humanos , Virulencia/genéticaRESUMEN
The Centers for Disease Control and Prevention (CDC) recommend a two-test approach for the serodiagnosis of Lyme disease (LD), with EIA testing followed by Western immunoblotting (WB) of EIA-equivocal and -positive specimens. This approach was compared with a simplified two-test approach (WB of EIA equivocals only) and WB alone for early LD. Case-patients with erythema migrans (EM) rash >/=5 cm were recruited from three primary-care practices in LD-endemic areas to provide acute- (S1) and convalescent-phase serum specimens (S2). The simplified approach had the highest sensitivity when either S1 or S2 samples were tested, nearly doubling when S2 were tested, while decreasing slightly for the other two approaches. Accordingly, the simplified approach had the lowest negative likelihood ratio for either S1 or S2. For early LD with EM, the simplified approach performed well and was less costly than the other testing approaches since less WB is required.
Asunto(s)
Enfermedad de Lyme/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Western Blotting , Niño , Preescolar , Femenino , Humanos , Técnicas para Inmunoenzimas , Masculino , Persona de Mediana Edad , Sensibilidad y Especificidad , Pruebas SerológicasRESUMEN
In July 1995, an outbreak of acute febrile illness affected 11 (48%) of 23 family members from Nebraska and Kansas who had vacationed at a Colorado cabin in June. Similar symptoms were identified among five (17%) of 30 additional persons from Nebraska, Kansas, Florida, and Texas who had vacationed at the same cabin. Symptoms suggested tick-borne relapsing fever (TBRF). Although no spirochetes were detected in available blood smears from five case-patients, Borrelia hermsii was cultured from the blood of one case-patient and two chipmunks trapped near the cabin. Case-patients were more likely than non-ill cabin visitors to have slept on the floor (odds ratio [OR] = 28.0, 95% confidence interval [CI] = 3.0-258) or in the top bunk bed (OR = 5.2, 95% CI = 1.1-25.1). Tick-borne relapsing fever should considered in the differential diagnosis of fever in patients who have stayed overnight in mountain cabins in the western United States.
Asunto(s)
Brotes de Enfermedades , Fiebre Recurrente/epidemiología , Adolescente , Adulto , Anciano , Animales , Bacteriemia/microbiología , Borrelia/aislamiento & purificación , Estudios de Casos y Controles , Niño , Preescolar , Colorado/epidemiología , Femenino , Florida , Vivienda , Humanos , Técnicas para Inmunoenzimas , Kansas , Masculino , Persona de Mediana Edad , Nebraska , Factores de Riesgo , Roedores , Texas , Garrapatas , ViajeRESUMEN
Reported cases of Lyme disease in Hunterdon County, New Jersey, increased almost 200% from 75 (67/100,000 population) in 1992 to 216 (193/100,000 population) in 1993. For evaluation of risk factors for Lyme disease and for determination of the cause of this increase, a case-control study was conducted, and the reporting practices of physicians' offices were evaluated. For cases reported in 1993, age and sex distribution, month of disease onset, and proportion of cases with erythema migrans rash were within expected limits. Analysis of age-matched case-control data showed that rural residence; clearing periresidential brush during spring and summer months; and the presence of rock walls, woods, deer, or a bird feeder on residential property were associated with incident Lyme disease. A review of physician reporting patterns suggested that the increase in reported cases in 1993 was due to improved reporting as well as to an increase in the numbers of patients diagnosed with Lyme disease. In addition, substantial underreporting of Lyme disease by physicians' offices was found.
Asunto(s)
Notificación de Enfermedades , Enfermedad de Lyme/epidemiología , Pautas de la Práctica en Medicina , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Niño , Preescolar , Femenino , Humanos , Incidencia , Lactante , Masculino , Persona de Mediana Edad , New Jersey/epidemiología , Estudios Prospectivos , Análisis de Regresión , Factores de Riesgo , Encuestas y CuestionariosRESUMEN
A seroprevalence and risk factor study of emerging tickborne infectious diseases (Lyme disease, ehrlichiosis, and babesiosis) was conducted among 230 residents of a semirural community in Sonoma County, California. Over 50% of residents reported finding a tick on themselves in the preceding 12 months. Samples from 51(23%) residents were seroreactive to antigens from one or more tickborne disease agents: 1.4% to Borrelia burgdorferi, 0.4% to Ehrlichia equi, 4.6% to Ehrlichia chaffeensis, and 17.8% to the Babesia-like piroplasm WA1. Only 14 (27%) of these seroreactive residents reported one or more symptoms compatible with these diseases. Seroreactivity was significantly associated with younger age (<16 years), longer residence in the community (11-20 years), and having had a physician's diagnosis of Lyme disease. In northern California, the risk of infection with these emerging tickborne diseases, particularly in children, may be greater than previously recognized.
Asunto(s)
Anticuerpos Antibacterianos/sangre , Anticuerpos Antiprotozoarios/sangre , Enfermedades por Picaduras de Garrapatas/epidemiología , Enfermedades por Picaduras de Garrapatas/inmunología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Animales , Babesia/inmunología , Grupo Borrelia Burgdorferi/inmunología , California/epidemiología , Niño , Preescolar , Ehrlichia/inmunología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Factores de Riesgo , Población Rural , Estudios Seroepidemiológicos , Encuestas y Cuestionarios , GarrapatasRESUMEN
Reports of Lyme disease from areas where the disease is not endemic have increased. Eighty-six human serum samples from Papua New Guinea (nonendemic for Lyme disease) were examined for the presence of IgG antibodies that recognize Borrelia burgdorferi antigens, using the currently recommended two-tiered system of analysis (sensitive ELISA with Western blot). The percentage of positive tests dropped from 50% to 10% when individual negative controls were included in the two-tiered analysis. Positive serum samples failed to inhibit the growth of B. burgdorferi in culture and did not yield positive reactions in the fluorescent treponemal antibody-absorption test. These characteristics, together with atypical Western blot antigen recognition patterns and the absence of known vectors, provide evidence that seropositive results for these persons are not the result of exposure to B. burgdorferi. Individual negative controls may minimize false-positive results for serologic tests for Lyme disease, and these tests must be interpreted in the context of clinical and epidemiologic data.
Asunto(s)
Anticuerpos Antibacterianos/análisis , Anticuerpos Antibacterianos/inmunología , Antígenos Bacterianos/inmunología , Grupo Borrelia Burgdorferi/inmunología , Reacciones Cruzadas/inmunología , Enfermedad de Lyme/epidemiología , Enfermedad de Lyme/inmunología , Western Blotting , Grupo Borrelia Burgdorferi/crecimiento & desarrollo , Ensayo de Inmunoadsorción Enzimática , Prueba de Absorción de Anticuerpos Fluorescentes de Treponema , Humanos , Inmunoglobulina G/análisis , Inmunoglobulina G/inmunología , Papúa Nueva Guinea/epidemiología , Estudios SeroepidemiológicosRESUMEN
A flea-borne rickettsia, previously referred to as ELB, has been implicated as a cause of human illness. Using sequence data obtained from a fragment of the citrate synthase gene, we compared ELB, Rickettsia australis, R. rickettsii, and R. akari with the louse-borne R. prowazekii. We tallied 24 base pair differences between ELB and R. prowazekii and 25 between R. rickettsii and R. prowazekii; there were 30 base pair differences between R. australis and R. prowazekii and 29 between R. akari and R. prowazekii. We observed 32 differences between Rickettsia typhi and ELB. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analyses of ELB, with typing sera against R. typhi indicate that ELB surface antigens are more closely related to the flea-borne R. typhi than to the mite-borne R. akari. On the basis of the results of citrate synthase gene sequence comparisons, as well as previous comparisons with 16S rRNA and 17-kDa-protein gene segments, we found that ELB is sufficiently genetically distinct from other rickettsiae to be designated a new species, Rickettsia felis.
Asunto(s)
Rickettsia/aislamiento & purificación , Siphonaptera/microbiología , Animales , Antígenos Bacterianos/análisis , Secuencia de Bases , Gatos , Datos de Secuencia Molecular , Peso Molecular , ARN Ribosómico 16S/genética , Rickettsia/inmunologíaRESUMEN
Chickens were used as a laboratory model to determine the conditions affecting the ability of birds to infect ticks with Lyme disease spirochetes. Chicks (Gallus gallus) were exposed to 12 nymphal Ixodes scapularis at one week or three weeks of age. Xenodiagnostic larval ticks fed these birds at weekly intervals thereafter. Chicks exposed to infected nymphs at one week of age infected 87% of larvae at three weeks of age, but only infected 3% of larvae at four weeks and 0% of larvae at five weeks. Chicks exposed to nymphs at three weeks of age infected only 12% of larvae at four weeks, and 0% thereafter. Thus, experimentally infected chicks can infect larval ticks, but only for a brief interval after exposure. Young chicks are more infectious than older chickens. The immune response of infected chicks was rapid and directed against diverse antigens.
Asunto(s)
Vectores Arácnidos/microbiología , Grupo Borrelia Burgdorferi/fisiología , Borrelia burgdorferi , Pollos/microbiología , Ixodes/microbiología , Enfermedad de Lyme/transmisión , Animales , Anticuerpos Antibacterianos/sangre , Antígenos Bacterianos/inmunología , Western Blotting , Grupo Borrelia Burgdorferi/inmunología , Ensayo de Inmunoadsorción Enzimática , Femenino , Ninfa/microbiologíaRESUMEN
A retrospective case-control study investigated 45 Missouri outpatients with annular rashes meeting a surveillance case definition for erythema migrans and with onset in 1990-1991. Risk factors included being male, living near a body of water, and hunting. Twenty patients (44%) associated their rash with the bite of a tick; of these, 5 described an adult Amblyomma americanum. A typical rash was described as expanding over time and measuring 8 cm in diameter at 4 days after onset. Mild constitutional symptoms were common but fever was uncommon. Serologic tests failed to incriminate Borrelia burgdorferi or selected other arthropodborne pathogens. Skin specimens from suspected erythema migrans lesions of 23 Missouri patients sampled prospectively in 1991-1993 were culture-negative for B. burgdorferi. Thus, tick bite-associated annular rashes in Missouri remain idiopathic. Possible causes include infection with a novel A. americanum-transmitted pathogen and an atypical toxic or immunologic reaction to tick-associated proteins.
Asunto(s)
Grupo Borrelia Burgdorferi/aislamiento & purificación , Enfermedad de Lyme/epidemiología , Enfermedad de Lyme/microbiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Animales , Anticuerpos Antibacterianos/sangre , Grupo Borrelia Burgdorferi/inmunología , Estudios de Casos y Controles , Niño , Preescolar , Eritema Crónico Migrans/diagnóstico , Eritema Crónico Migrans/epidemiología , Eritema Crónico Migrans/microbiología , Femenino , Humanos , Enfermedad de Lyme/diagnóstico , Masculino , Persona de Mediana Edad , Missouri/epidemiología , Oportunidad Relativa , Distribución Aleatoria , Factores de Riesgo , Factores SexualesRESUMEN
Studies using serologic and polymerase chain reaction-(PCR) facilitated analysis of field samples from southern Texas indicate the presence of Rickettsia typhi and ELB agent infected cat fleas, Ctenocephalides felis (Bouché), and the first observation of ELB infected vertebrates (opossums). The ELB agent is a recently described typhus-like rickettsia that is not distinguished from R. typhi or R. prowazekii by currently available serologic reagents. Restriction digests of PCR products from 399 fleas revealed an ELB agent infection rate of 3.8% and a R. typhi infection rate of 0.8%. Three of nine tested opossums (Didelphis virginiana) were shown to harbor ELB agent infections. No R. typhi infected rats, Rattus norvegicus, or rat-fleas, Xenopsylla cheopis Rothschild, were detected among surveyed samples. The persistence of this murine typhus disease focus appears to be better accounted for by the presence of infected cat fleas, opossums, and other non-rat hosts found in close association with human populations. Involvement of the ELB agent in the biology of murine typhus is suggested by its prevalence among suspected vectors and reservoir hosts.
Asunto(s)
Rickettsia/aislamiento & purificación , Tifus Endémico Transmitido por Pulgas/microbiología , Animales , Secuencia de Bases , Gatos , Cartilla de ADN/genética , Perros , Humanos , Ratones , Datos de Secuencia Molecular , Zarigüeyas , Reacción en Cadena de la Polimerasa , Ratas , Rickettsia/genética , Rickettsia/patogenicidad , Siphonaptera/microbiología , Texas/epidemiología , Tifus Endémico Transmitido por Pulgas/epidemiología , Tifus Endémico Transmitido por Pulgas/transmisiónRESUMEN
Identification of ELB agent-infected fleas and rodents within several foci of murine typhus in the United States has prompted a retrospective investigation for this agent among human murine typhus patients. This agent is a recently described rickettsia which is indistinguishable from Rickettsia typhi with currently available serologic reagents. Molecular analysis of the 17-kDa antigen gene and the citrate synthase gene has discriminated this bacterium from other typhus group and spotted fever group rickettsiae. Current sequencing of its 16S ribosomal DNA gene indicates a homology of 98.5% with R. typhi and 99.5% with R. rickettsii. Through a combination of restriction fragment length polymorphism and Southern hybridization analysis of rickettsia-specific PCR products, one of five tested patient blood samples was shown to be infected with ELB while R. typhi infections were confirmed in the remaining samples. This is the first reported observation of a human infection by the ELB agent and underscores the utility of PCR-facilitated diagnosis and discrimination of these closely related rickettsial infections.
Asunto(s)
Infecciones por Rickettsia/microbiología , Rickettsia/aislamiento & purificación , Tifus Endémico Transmitido por Pulgas/microbiología , Adulto , Anciano , Anciano de 80 o más Años , Animales , Antígenos Bacterianos/genética , Secuencia de Bases , Cartilla de ADN/genética , ADN Bacteriano/genética , ADN Ribosómico/genética , Diagnóstico Diferencial , Femenino , Humanos , Masculino , Ratones , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Rickettsia/clasificación , Rickettsia/genética , Infecciones por Rickettsia/diagnóstico , Especificidad de la Especie , Tifus Endémico Transmitido por Pulgas/diagnósticoRESUMEN
Cat fleas (Ctenocephalides felis) from eight commercial flea colonies from various regions of the USA were examined by selective PCR amplification, and subsequent restriction digest analysis and Southern hybridization of PCR products, for the presence of a rickettsia-like organism (ELB agent). These flea colonies were either started with fleas from one supplier (EL Labs), in which ELB agent was first identified, or were started with fleas from stray cats and dogs and later came into contact with ELB-infected fleas. Infection rates in the colonies ranged from 43% to 93%. The successful propagation of ELB agent in these colonies may be due to efficient trans-stadial and transovarial transmission. While ELB agent has recently been identified in blood from human murine typhus cases, attempts to infect mammalian cells and SCID mice with flea isolates were unsuccessful.
Asunto(s)
Rickettsia/aislamiento & purificación , Siphonaptera/microbiología , Animales , Antígenos Bacterianos/genética , Secuencia de Bases , Gatos , ADN Bacteriano/genética , ADN Bacteriano/aislamiento & purificación , Desoxirribonucleasas de Localización Especificada Tipo II , Perros , Femenino , Humanos , Masculino , Ratones , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Rickettsia/clasificación , Rickettsia/genética , SimbiosisRESUMEN
The mosquito midgut plays a central role in the development and subsequent transmission of malaria parasites. Using a rodent malaria parasite, Plasmodium berghei, and the mosquito vector Anopheles stephensi, we investigated the effect of anti-mosquito-midgut antibodies on the development of malaria parasites in the mosquito. In agreement with previous studies, we found that mosquitoes that ingested antimidgut antibodies along with infectious parasites had significantly fewer oocysts than mosquitoes in the control group. We also found that the antimidgut antibodies inhibit the development and/or translocation of the sporozoites. Together, these observations open an avenue for research toward the development of a vector-based malaria parasite transmission-blocking vaccine.
Asunto(s)
Anopheles/parasitología , Plasmodium berghei/inmunología , Animales , Anopheles/inmunología , Anticuerpos/inmunología , Insectos Vectores/inmunología , Insectos Vectores/parasitología , Intestinos/inmunología , Plasmodium berghei/crecimiento & desarrolloRESUMEN
The recent discovery of cat fleas (Ctenocephalides felis) infected with a typhuslike rickettsia (designated the ELB agent) raises the question of whether similar rickettsial infections exist in wild cat flea populations. We verified the presence of the ELB agent and Rickettsia typhi in urban and suburban areas of Los Angeles, Calif. Opossums trapped in close proximity to the residences of human murine typhus cases in Los Angeles county and other areas within the city of Los Angeles were tested for the presence of typhus group rickettsiae by the polymerase chain reaction (PCR). The presence of rickettsiae in the spleen tissues of three opossums (n = 9) and in 66 opossum fleas (n = 205) was determined by PCR and was verified by dot blot and Southern transfer hybridization. Further analysis of the amplified PCR products generated by a series of primer pairs derived from either the 17-kDa antigen gene or the citrate synthase gene revealed that both R. typhi and the ELB agent were present in the tested samples. Dual infection was not noted in the samples; however, the fleas were infected with either R. typhi or the ELB agent. The presence of the ELB agent in the cat flea population may have implications for public health. Whether this agent is responsible for the mild cases of human murine typhus in urban and suburban areas of Los Angeles or in other endemic foci remains to be determined.