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Biomedical subjects

A Spielman

Publications and source records attributed to A Spielman.

At least 37 records · Page 2Linked to original sources
PubMed1999

Characteristics of garden dormice that contribute to their capacity as reservoirs for lyme disease spirochetes.

To describe the contribution of garden dormice to the epizootiology of Lyme disease, we compared their reservoir capacity for these pathogens to that of other sympatric hosts. Garden dormice are trapped most abundantly during early spring and again during midsummer, when their offspring forage. They are closely associated with moist forests. Garden dormice serve as hosts to nymphal ticks far more frequently than do other small mammals. Spirochetal infection is most prevalent in dormice, and many more larval ticks acquire infection in the course of feeding on these than on other rodents in the study site. Mature dormice appear to contribute more infections to the vector population than juveniles do. Replete larval ticks generally detach while their dormouse hosts remain within their nests. The population of garden dormice contributes five- to sevenfold more infections to the vector population than the mouse population does. Their competence, nymphal feeding density, and preference for a tick-permissive habitat combine to favor garden dormice over other putative reservoir hosts of Lyme disease spirochetes.

Animals↗
PubMed1999

Southern extension of the range of human babesiosis in the eastern United States.

We sought evidence of babesiosis in three residents of New Jersey who were suspected of local acquisition of Babesia microti infection. We tested serial blood samples from these residents for B. microti antibodies and amplifiable DNA by using immunofluorescent antibody and PCR techniques. All three residents experienced symptoms suggestive of acute babesiosis. The sera of each of the patients reacted against babesial antigen at a titer fourfold or higher in sequentially collected blood samples. PCR-amplifiable DNA, characteristic of B. microti, was detected in their blood. These data suggest that human B. microti infections were acquired recently in New Jersey, extending the range of this piroplasmosis in the northeastern United States.

Adult↗
PubMed1999

Eastern equine encephalitis virus in birds: relative competence of European starlings (Sturnus vulgaris).

To determine whether eastern equine encephalitis (EEE) virus infection in starlings may be more fulminant than in various native candidate reservoir birds, we compared their respective intensities and durations of viremia. Viremias are more intense and longer lasting in starlings than in robins and other birds. Starlings frequently die as their viremia begins to wane; other birds generally survive. Various Aedes as well as Culiseta melanura mosquitoes can acquire EEE viral infection from infected starlings under laboratory conditions. The reservoir competence of a bird is described as the product of infectiousness (proportion of feeding mosquitoes that become infected) and the duration of infectious viremia. Although starlings are not originally native where EEE is enzootic, a starling can infect about three times as many mosquitoes as can a robin.

Aedes↗
PubMed1999

Differential perpetuation of malaria species among Amazonian Yanomami Amerindians.

To determine whether malaria perpetuates within isolated Amerindian villages in the Venezuelan Amazon, we surveyed malaria infection and disease among 1,311 Yanomami in three communities during a 16-month period. Plasmodium vivax was generally present in each of these small, isolated villages; asymptomatic infection was frequent, and clinical disease was most evident among children less than five years of age (odds ratio [OR] = 6.3, 95% confidence interval [CI] = 1.4-29.2) and among persons experiencing parasitemias > or = 1,000 parasites/mm3 of blood (OR = 45.0, 95% CI = 5.5-370.7). Plasmodium falciparum, in contrast, was less prevalent, except during an abrupt outbreak in which 72 infections resulted in symptoms in all age groups and at all levels of parasitemia, and occasionally were life-threatening. The observed endemic pattern of P. vivax infection may derive from the capacity of this pathogen to relapse, while the epidemic pattern of P. falciparum infection may reflect occasional introductions of strains carried by immigrants or residents of distant villages and the subsequent disappearance of this non-relapsing pathogen.

Adolescent↗
PubMed1999

Effect of chemotherapy on malaria transmission among Yanomami Amerindians: simulated consequences of placebo treatment.

To determine whether chemotherapy effectively reduces Plasmodium falciparum malaria transmission in isolated human populations, we followed two abrupt sequential outbreaks of malaria infection among Yanomami Amerindians and modeled the effect of chemotherapy and the consequences if no drug was available. A Macdonald-type mathematical model demonstrated that both outbreaks comprised a single epidemic event linked by an invisible outbreak in vector mosquitoes. The basic reproductive number, R0, from fitted values based on the treated epidemic was 2 during the initial phase of the epidemic, and waned as vector density decreased with the onset of the dry season. In the observed epidemic, 60 (45%) of 132 village residents were affected, and the treated outbreak ended after two months. Although the initial chemotherapy regimen was only marginally effective, the duration of human infectivity was reduced from an expected nine months to two weeks. In the absence of this intervention, the initial R0 value would have been 40, more than 60% of the population would have been infected, and more than 30% would have remained parasitemic until the next rainy season (about six months later). Another outbreak would then have ensued, and malaria probably would have remained endemic in this village. Our simulated placebo treatment permits us to conclude that even partially effective chemotherapeutic interventions, such as those in our study, interrupt serial transmission of P. falciparum among isolated human populations that are exposed to infection seasonally.

Animals↗
PubMed1999

Density-dependent preprandial mating by deer ticks.

To determine whether the prevalence of preprandial insemination in deer ticks reflects their local abundance, we sampled adult ticks by flagging vegetation at selected sites in eastern Massachusetts in a standardized manner. Resulting female ticks were dissected to determine whether they contained endospermatophores, and the frequency of insemination was compared to the number of questing ticks flagged at each site. The prevalence of insemination correlated closely with density of ticks. The frequency of insemination increased linearly during the Ist 2 months during the fall. The mean daily probability of insemination during this period was about 1% when, on average, about 4 ticks were flagged per minute. A predictive equation was derived via multiple regression expressing deer tick abundance as a function of collection date and insemination prevalence (P < 0.05). The frequency of preprandial mating, thereby, was correlated with the abundance of questing deer ticks. Insemination prevalence increased predictably as the season of adult activity progressed. We conclude that a season-specific analysis of the frequency of preprandial insemination provides a robust indicator of the abundance of deer ticks that is unaffected by short-term fluctuations in the weather.

Animals↗
PubMed1998

Persistent parasitemia after acute babesiosis.

BACKGROUND: Babesiosis, a zoonosis caused by the protozoan Babesia microti, is usually not treated when the symptoms are mild, because the parasitemia appears to be transient. However, the microscopical methods used to diagnose this infection are insensitive, and few infected people have been followed longitudinally. We compared the duration of parasitemia in people who had received specific antibabesial therapy with that in silently infected people who had not been treated. METHODS: Forty-six babesia-infected subjects were identified from 1991 through 1996 in a prospective, community-based study designed to detect episodes of illness and of seroconversion among the residents of southeastern Connecticut and Block Island, Rhode Island. Subjects with acute babesial illness were monitored every 3 months for up to 27 months by means of thin blood smears, Bab. microti polymerase-chain-reaction assays, serologic tests, and questionnaires. RESULTS: Babesial DNA persisted in the blood for a mean of 82 days in 24 infected subjects without specific symptoms who received no specific therapy. Babesial DNA persisted for 16 days in 22 acutely ill subjects who received clindamycin and quinine therapy (P=0.03), of whom 9 had side effects from the treatment. Among the subjects who did not receive specific therapy, symptoms of babesiosis persisted for a mean of 114 days in five subjects with babesial DNA present for 3 or more months and for only 15 days in seven others in whom the DNA was detectable for less than 3 months (P<0.05); one subject had recrudescent disease after two years. CONCLUSIONS: When left untreated, silent babesial infection may persist for months or even years. Although treatment with clindamycin and quinine reduces the duration of parasitemia, infection may still persist and recrudesce and side effects are common. Improved treatments are needed.

Animals↗
PubMed1998

The effects of photic driving on mood states.

The EEG photic driving response is a sensitive neurophysiological measure. It has been used to assess drug effects, forms of epilepsy, neurological status of Alzheimer's patients, and physiological arousal. Photic driving also impacts the psychological status of a person by producing increased visual imagery and decreased physiological and subjective arousal. In this study, ten volunteers underwent nocturnal polysomnography followed by six daytime testing sessions. The six sessions consisted of the alpha attenuation test, two visual analog scales for mood, the Stanford Sleepiness Scale, photic stimulation, and the multiple sleep latency test. These tests were administered 2 hours upon awakening and every 2 hours thereafter. The mean mood across the six daytime testing sessions was computed for all mood variables pre- and post-photic stimulation. Significant differences were found for the subjective moods "sleepy," "alert," and "effort." However, no significant differences were found for pre- and post-photic driving for "angry," "irritable," "hungry," "tense," "overall," "happy," "sexual," and "sad." Additionally, all participants reported increased visual imagery during photic driving, as measured by their responses to an imagery questionnaire.

Adult↗
PubMed1998

Cytokines in murine lyme carditis: Th1 cytokine expression follows expression of proinflammatory cytokines in a susceptible mouse strain.

The cardiac infiltrate seen in murine Lyme carditis is composed predominantly of macrophages, but small numbers of T cells are also present. To identify the cytokines present in cardiac lesions from susceptible mice, semiquantitative polymerase chain reaction was done on cardiac tissue from mice infected with Borrelia burgdorferi. The temporal expression of proinflammatory and T cell-derived cytokines was characterized in cardiac tissue at days 0, 3, 7, 14, 21, and 42 after infection with B. burgdorferi. Early in the course of infection, up-regulation of the proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha was detected. The Th1 cytokine interferon-gamma appeared after the expression of the proinflammatory cytokines and remained elevated throughout the study. Interleukin-4 was not detectable at any time in cardiac lesions. These data are the first to identify cytokines expressed at the lesional level in murine Lyme carditis and to demonstrate a Th1 pattern of cytokine expression in this lesion.

Animals↗
PubMed1998

Spatially explicit model of transposon-based genetic drive mechanisms for displacing fluctuating populations of anopheline vector mosquitoes.

To evaluate the prospect of transposon-based genetic drive mechanisms for replacing African vectors of malaria with nonvector anopheline mosquitoes, we developed a spatially explicit simulation model that determined the likelihood that released transgenic mosquitoes may proceed to fixation or extinction under diverse conditions. We compared the effect on fixation of long breeding seasons with relatively subtle population fluctuations to short breeding seasons with severe bottlenecks. Assuming 100% transposition efficiency among heterozygotes with fitness varying between 50 and 100% of that of wild-type mosquitoes, we simulated releases of 1, 10, 50, 90, and 99% of transposon-bearers in relation to wild mosquitoes as well as 1 and 10% releases that were repeated annually. We also evaluated diverse patterns of release including linear, marginal, focused, and scattered distribution. Random dispersal provided the most rapid fixation of transposons within populations. More massive releases allowed longer persistence of transposon-bearers but did not promote fixation, especially when breeding seasons were long. Relative fitness of transposon-bearers, however, proved more powerful than pattern or number of releases in determining whether a construct will become fixed or extinct. Even when fitness approaches that of the wild-type, fixation of a construct may require 150 generations or more.

Animals↗
PubMed1998

Effect of prior exposure to noninfected ticks on susceptibility of mice to Lyme disease spirochetes.

To determine whether prior exposure to Nearctic Ixodes vector ticks protects native reservoir mice from tick-borne infection by Lyme disease spirochetes, we compared their infectivities for white-footed mice and laboratory mice that had been repeatedly infested by noninfected deer ticks. Nymphal ticks readily engorged on tick-exposed laboratory mice, but their feeding success on white-footed mice progressively declined. Tick-borne spirochetes readily infected previously tick-infested mice. Thus, prior infestation by Nearctic ticks does not protect sympatric reservoir mice or Palearctic laboratory mice from infection by sympatric tick-borne spirochetes.

Animals↗
PubMed1998

Diversity of European Lyme disease spirochetes at the southern margin of their range.

We determined whether the genospecies diversity of Lyme disease spirochetes in vector ticks questing on a subtropical island is as broad as that in Central Europe. Although spirochetes infected < 1% of the ticks sampled on Madeira Island, these infections included all three genospecies implicated in human disease. Therefore, spirochetal diversity is as great at the southern margin as it is in the center of this pathogen's range.

Animals↗
PubMed1998

Failure of Ixodes ticks to inherit Borrelia afzelii infection.

To define conditions promoting inherited infection by Lyme disease spirochetes in Ixodes ticks, we variously infected ticks with Borrelia afzelii and examined their progenies by dark-field microscopy, immunofluorescence, PCR, and serial passage. No episode of inherited infection was evident, regardless of instar or gender infected or frequency of exposure. We suggest that these spirochetes rarely, if ever, are inherited by vector ticks.

Animals↗
PubMed1998

Diversity of Babesia infecting deer ticks (Ixodes dammini).

To determine whether the presence of nonpathogenic piroplasms may confound field estimates of risk of Babesia microti infection, we identified sporozoites infecting the salivary glands of deer ticks (Ixodes dammini) by parallel microscopy and polymerase chain reaction assays. Piroplasms were evident in 14.4% of adult ticks from sites in the northcentral and northeastern United States. Of these, 83.3% contained DNA characteristic of Ba. odocoilei. This cervid piroplasm was detected in all of the sites examined and generally was more prevalent than was Ba. microti. Because deer ticks transmit both Ba. odocoilei and Ba. microti, estimates of pathogen prevalence based solely on microscopy may overestimate the risk of human babesiosis.

Animals↗
PubMed1997

A subtropical case of human babesiosis.

This report constitutes the first well-documented case of symptomatic human babesiosis from a subtropical site, south of the 40th parallel. This paper describes the definitive identification of Babesia divergens infection in a splenectomized patient from the Canary Islands.

Adult↗
PubMed1997

Heterogeneity of Lyme disease spirochaetes within individual vector ticks.

To determine whether Lyme disease spirochaetes (Borrelia burgdorferi) within vector ticks (lxodes dammini) sampled from enzootic sites comprise single or mixed populations, we compared their reactivity to a polyclonal rabbit immune serum with that to a battery of monoclonal antibodies (mAb) against OspA, OspB and flagellin. More spirochaetes were recognized by the polyclonal antibody than with the mAbs. Spirochaetes from field-sampled ticks reacted poorly to mAbs against OspB. No such differences in reactivity to polyclonal or monoclonal antibodies were observed for the N40 strain of B. burgdorferi from BSK cultures and infected laboratory-reared vector ticks. We conclude that in nature each tick may be infected by an antigenically heterogeneous mixture of spirochaetes.

Animals↗
PubMed1997

Enema infusion technique inappropriate for evaluating viral competence of ticks.

To determine whether anal infusion of virus simulates the natural route of infection rather than intracoelomic injection, we compared the course of Venezuelan equine encephalitis (VEE) virus infection in Amblyomma cajennense (F.) ticks that had been exposed to virus by enema infusion with that in ticks fed on a viremic host or exposed by intracoelomic inoculation. Although virus was detected in virtually all ticks 14 d after exposure, orally exposed ticks contained significantly less virus (10(1.9) plaque-forming units [PFU] per tick) than did ticks infected by enema (10(4.1) PFU per tick) or intracoelomically (10(4.2) PFU per tick). At 42 d after virus exposure, only 1% of 512 orally exposed ticks contained virus, but most enema (77%, n = 43) or intracoelomically (79%, n = 29) exposed ticks were infected. Replication of VEE virus in A. cajennense ticks exposed to virus by enema infusion, therefore, appeared more similar to that of ticks inoculated intracoelomically than to those exposed orally. Thus, because enema infusion may bypass potential midgut infection and escape barriers, this procedure may not be appropriate for determining vector competence in ixodid ticks.

Animals↗