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Biomedical subjects

W Burgdorfer

Publications and source records attributed to W Burgdorfer.

At least 19 recordsLinked to original sources
PubMed1979

Rocky mountain spotted fever in Connecticut: human cases, spotted-fever group rickettsiae in ticks, and antibodies in mammals.

Three parameters were used in 1976 and 1977 to assess the status of Rocky Mountain spotted fever (RMSF) in Connecticut--compilation and review of clinical data on suspected human cases for the 13-year period 1965--1977, examination of tick tissues for spotted fever-group rickettsiae by the hemolymph test and direct immunofluorescence, and analyses of mammalian sera for antibodies against Rickettsia rickettsii. There were six presumptive RMSF cases which probably originated in Connecticut. Four of these cases occurred in areas where the American dog tick, Dermacentor variabilis, abounds. A total of 2994 ticks were examined by the hemolymph test. Rickettsia-like organisms were observed in 67 (2.9%) of 2330 D. variabilis and two (0.6%) of 351 Ixodes sp. near scapularis. Fewer than one-half of these organisms stained positively with spotted fever-group conjugate. Microagglutination tests on 1093 mammalian sera indicated that eight (16%) of 49 raccoons, 14 (2.6%) of 549 white-tailed deer, eight (1.7%) of 470 white-footed mice, and one of two gray squirrels had agglutinins in titers greater than or equal to 1:8 against R. rickettsii. Spotted fever-group rickettsiae are present at low frequency in inland as well as coastal regions of Connecticut.

Adult↗
PubMed1979

Ultrastructure of Rickettsia rhipicephali, a new member of the spotted fever group rickettsiae in tissues of the host vector Rhipicephalus sanguineus.

Rickettsia rhipicephali is similar in ultrastructure to R. rickettsii while differing from other rickettsiae of the typhus group and of Q fever and others by its lack of a prominently reticulated cytoplasmic matrix and in the thickness of the inner osmophilic layer of the cell wall. In tissues of the tick vector Rhipicephalus sanguineus, R. rhipicephali had a mean length and width of 1.2 and 0.46 micrometer, respectively. It possessed a trilaminar cell wall with an adhering capsule-like layer. The trilaminar cell wall was approximately 12 to 18 nm thick; its inner osmophilic layer was thicker than that previously reported for other rickettsiae. The capsule-like layer varied from 7 to 18 nm thick. The plasma membrane was similar in structure, measurement, and appearance to that of other reported rickettsiae. The cytoplasm appeared to be composed of a finely granular, amorphous, ground substance and randomly dispersed ribosomes and lacked a reticular matrix or nuclear fibrils. In massively infected salivary glands and ovarial tissues of its tick vector, R. rhipicephali produced a low degree of histopathology which does not appear to affect the engorgement and egg-laying process of the ticks.

Animals↗
PubMed1979

[New aspects of the part of the vector played by Ixodes ricinus L. in Switzerland. Preliminary note (author's transl)].

The authors, after having recalled their recent work on Ixodes ricinus ecology, give the new results about the part played by this species in the transmission of different infectious agents in Switzerland. I. ricinus was already known to be the most important vector of the tick borne encephalitis virus, and of protozoans of the Babesia genus. In this article, we describe the existence in the hemolymphe of different I. ricinus populations, of a rickettsia species related to the RMST group (Rocky-Mountain Spotted Fever), of a trypanosome, which is close to T. theileri, and of an infectious larval form (L3) of Dipetalonema rugosicauda. An outline is suggested with the object of illustrating the functioning of a natural foci of tick encephalitis. The biological significance of the unusual presence of trypanosomes and of larval filariae in ticks is also discussed. The authors underline the fact that rickettsia, trypanosomes and filarial forms are observed for the first time in Swiss I. ricinus.

Animals↗
PubMed1979

Ixodes ricinus: vector of a hitherto undescribed spotted fever group agent in Switzerland.

A tick/rickettsial survey in various parts of Switzerland revealed the presence of a new, hitherto undescribed spotted fever group rickettsia ("Swiss agent") in up to 11.7% of I. ricinus collected off vegetation. Infection in ticks was found to be generalized with rickettsiae developing intracellularly and occasionally also intranuclearly. As a result of massive growth in ovarial tissues, including the germinative cells, the rate of transovarial and filial infection was 100%. The "Swiss agent" appears to be nonpathogenic for guinea pigs, domestic rabbits, and Swiss mice, but in male meadow voles (Microtus pennsylvanicus) it produces a microscopically detectable infection in the tunica vaginalis. The rickettsia grows well in tissue culture systems including chick embryo fibroblast, Vero, and vole tissue cells, when inoculated via yolk sac into 5-day-old hens' eggs, it kills 100% of the embryos after 5 to 7 days. Antigenic relatedness of the "Swiss agent" to rickettsiae of the spotted fever group was indicated by indirect and direct fluorescent antibody staining. Preliminary serologic typing by microimmunofluorescence and by microagglutination indicated that the "Swiss agent" differs from all prototype strains of spotted fever group rickettsiae studied so far.

Animals↗
PubMed1978

Detection of the Rocky Mountain spotted fever agent, Rickettsia rickettsii, in dead ticks, Dermacentor andersoni.

Rickettsia rickettsii remained viable and retained chromophilic properties for not more than 24 h after Dermacentor andersoni were killed by freezing. Antigenic reactivity was detected for at least 71 days by direct immunofluorescence. However, rickettsiae in ticks suffocated with mineral oil remained pathogenic for at least 14 days. Accordingly, ticks removed from a host by mineral oil or dying from desiccation in transit are still suitable for rickettsial examination.

Animals↗
PubMed1978

Distribution and prevalence of spotted fever group rickettsiae in ticks from South Carolina, with an epidemiological survey of persons bitten by infected ticks.

Live ticks removed from human hosts were tested for the presence of spotted fever group rickettsiae from 1974 through 1976. Spotted fever group rickettsiae were detected in Dermacentor variabilis, Amblyomma americanum, Amblyomma maculatum, and Ixodes scapularis. Persons from whom positive ticks were removed in 1974 and 1975 were questioned about ensuing illness. Eleven of 51 persons from whom rickettsia-positive D. variabilis were removed reported some unexplained combination of symptoms compatible with Rocky Mountain spotted fever. Persons with positive ticks other than D. variabilis reported no illness in the 2 weeks following exposure. D. variabilis from the Coastal Plain of South Carolina have a higher percentage of infection than those from the Piedmont region. Conversely, most reported human cases of spotted fever are from the Piedmont.

Arachnid Vectors↗
PubMed1977

A comparison of serologic methods for diagnosis of Rocky Mountain spotted fever.

Sera referred to the North Carolina Division of Health Services for rickettsial serology in 1974 were tested by complement fixation (CF), microimmunofluorescence (micro-IF), microagglutination (MA) and hemagglutination (HA) for antibodies against Rickettsia rickettsii. There was good agreement among micro-IF,MA and HA tests in detecting antibody responses to this agent, but the CF test was definitely less sensitive than the others, even in illnesses with classical clinical manifestations of Rocky Mountain spotted fever (RMSF). Some variables that seemed to influence the CF result were the slow rate of increase in antibody titers, timing of serum collection, early antibiotic treatment and possibly, the particular association of CF antibody response with the IgG immunoliobulin class. Greater use of these newer, but relatively untried, serodiagnostic procedures is recommended infuture studies of RMSF.

Agglutination Tests↗
PubMed1977

Changing patterns in the incidence of Rocky Mountain Spotted Fever on Long Island (1971-1976).

Clinical data from 124 Rocky Mountain Spotted Fever (RMSF) cases submitted by Long Island physicians and hospitals were compiled for the six-year period 1971-1976. This information was subsequently compared to two parameters: first, the geographic distribution of human cases and rickettsia-infected Dermacentor variabilis (Say), and, secondly, the human population dynamics in Long Island towns since 1950. Despite an overall decline in the rate of suburbanization and population growth, cases of RMSF have increased significantly not only in eastern towns where RMSF has been endemic, but also in well-established western towns where recent population increases have been negligible. Phenomena associated with suburbanization, primarily the association of domestic and sylvan animals and their exposure to infected vector populations, may be instrumental in explaining the increased transmission of RMSF.

Adolescent↗
PubMed1977

Tick-borne diseases in the United States: Rocky Mountain spotted fever and Colorado tick fever. A review.

The historical, clinical, ecological, and epidemiological features of Rocky Mountain spotted fever and Colorado tick fever, the two important tick-borne diseases in the United States, are reviewed. Rocky Mountain spotted fever, once considered a disease of the past, has again become a measurable public health problem. Its nationwide incidence has steadily increased since 1960 and has reached record proportions in 1976. The various factors responsible for this trend as well as for the mortality rates, which in spite of availability of effective antibiotics ranges from 5 to 10%, are discussed. Education of the public about ticks and their potential role as vectors of Rickettsia rickettsii and/or Colorado tick fever virus, and about the clinical manifestations of Rocky Mountain spotted fever, is considered the best means for preventing high incidence and mortality from these diseases.

Antibodies, Viral↗
PubMed1976

Rocky Mountain spotted fever in Mississippi: survey for spotted fever antibodies in dogs and for spotted fever group reckettsiae in dog ticks.

During epidemiologic studies of Rocky Mountain Spotted Fever in Mississippi in 1973, dogs were surveyed for antibodies tp spotted fever group antigens and for tick parasites infected with rickettsiae of the spotted fever group. Fifty-three (46%) of 116 serum samples had complement-fixing antibody titers greater than or equal to 1:8 as compared to only one (5%) of 21 samples from a group of dogs obtained from metropolitan Chicage. Fifty-two per cent of the dogs tested from Mississippi had microagglutinating antibodies titers greater than or equal to 1:8; 9% of dogs from Chicago had similar titers. Rickettsia rickettsii was demonstrated in only one (0.8%) of 129 Dermacentor variabilis removed from Mississippi dogs. Quite unexpectedly, 167 (18.9%) of 884 Rhipicephalus sanguineus taken from these dogs contained spotted fever group rickettsiae.

Agglutination Tests↗
PubMed1976

Microimmunofluorescence test for the serological study of rocky mountain spotted fever and typhus.

A microimmunofluorescence test was used to study antibody responses to various spotted fever group and typhus group rickettsiae during Rocky Mountain spotted fever (RMSF) and epidemic typhus (ET). Patients with RMSF reacted most strongly to Rickettsia rickettsii; those with ET reacted predominantly to R. prowazekii. The degree of cross-reaction to other rickettsial strains varied from patient to patient, but a particular pattern of cross-reaction was consistently observed in serial sera from the same patient. Fresh isolates from three Montana RMSF cases were indistinguishable from each other and from strain R of R. rickettsii used as a standard antigen in all tests. Immunoglobulin M (IgM) antibodies were usually present in high titer in early-convalescent-phase sera from RMSF, as well as ET, patients. After RMSF, IgM antibodies persisted for a few months and, in one instance, for as long as 10 months. IgM responses to laboratory-acquired infections were infrequent in persons previously vaccinated with antigens related to the infecting strain. Previous antigenic conditioning from infection or vaccination may have accounted partly for the apparent lack of IgM response in a few study participants.

Adult↗
PubMed1975

Clinical and epidemiologic features of Rocky Mountain spotted fever in Mississippi, 1933-1973.

During the period 1933-1973, 169 cases of Rocky Mountain spotted fever (RMSF) were either reported by physicians or detected in a retrospective survey of hospitals and practicing physicians in Mississippi. The epidemiologic characteristics of 119 cases and the clinical features of 75 serologically confirmed cases are summarized in this communication and compared with other published reviews of RMSF. Although the percentage of reported fatal cases decreased overall since 1950, 9 of 49 reported cases (18%) in Mississippi were fatal during the period 1969-1972. The yearly number of reported cases of RMSF in Mississippi increased fourfold from 1970-1973. In the past 40 years, only 5 cases of RMSF have been reported from the Mississippi delta, a flat agricultural region that includes over one fourth of the total population of the state.

Adolescent↗
PubMed1975

Rhipicephalus sanguineus: vector of a new spotted fever group rickettsia in the United States.

A rickettsia related to but distinct from the spotted fever agent, Rickettsia rickettsii, has been detected in 167 (18.9%) of 884 Rhipicephalus sanguineus taken off dogs in central and northern Mississippi. The organisms could readily be isolated in male meadow voles (Microtus pennsylvanicus), where it produced massive infections in the tissues of tunica vaginalis. It was practically nonpathogenic for male guinea pigs, although inoculation of these animals with infected tunica vaginalis of voles afforded in 30 of 38 instances solid immunity to challenge with virulent R. rickettsii. The Rhipicephalus rickettsia grew well in monolayers of chicken embryo fibroblast, Vero, mouse L, and HeLa cells. Cytopathogenic effects were minimal unless large concentrations of rickettsiae were used as inocula. It also could be established in embryonated hen eggs but only after injection of massive doses of L cell-propagated organisms. Serological tests (complement fixation, microagglutination and/or micro immunofluorescence) indicated that the newly described Rickettsia belongs to the spotted fever group but differs from R. rickettsii, R. akari, and R. conorii. Antigenic differences were also demonstrated by direct fluorescence microscopy as well as by vaccine potency and mouse-toxin neutralization tests.

Animals↗