Effects of granular carbaryl application on sympatric populations of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) nymphs.

A single application of granular carbaryl approaching the lowest recommended rate to the shrub layer of a forested area in late spring significantly reduced the abundance of Ixodes scapularis Say nymphs throughout their peak activity period, but had little effect on Amblyomma americanum L. nymphs. Factors influencing the efficacy of the application are discussed. The possible explanations for the lack of efficacy of granular carbaryl against A. americanum, including behavior, formulation, and application rate, are discussed.

Biases associated with several sampling methods used to estimate abundance of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae).

Several tick sampling methods were evaluated for ixodes scapularis Say and Amblyomma americanum (I.) in oak-dominated mixed hard-wood, pitch pine-dominated, and mixed hardwood and pine forests in coastal New Jersey. Walking surveys were more efficient for collecting I. scapularis adults than dragging by a factor of > 2:1. In contrast, drag sampling yielded nearly twice as many A. americanum adults compared with walking surveys. I. scapularis subadults were rarely collected during walking surveys. A. americanum nymphs were collected from drags approximately 3:1 over walking surveys. Twice as many A. americanum larvae were obtained from drags compared with walking surveys. All developmental stages of A. americanum responded positively to carbon dioxide. Pitfall traps and leaf litter samples collected very few ticks. Tick distribution among habitats varied significantly with the sampling method chosen, and the relative ranking of sites with respect to tick abundance varied depending on the stage of tick sampled. Failure to recognize the biases in these commonly used sampling techniques can potentially lead to incorrect conclusions that can have significant adverse public health consequences.

Comparison of Ixodes scapularis (Acari: Ixodidae) populations and their habitats in established and emerging Lyme disease areas in New Jersey.

Hunterdon Country, New Jersey, experienced a significant increase in the number of Lyme disease cases during 1990-1995, accounting for 21.2% of all New Jersey cases. This study compares the relative abundance of Ixodes scapularis Say in similar habitats in Hunterdon County, an emerging Lyme disease area, and Monmouth County, where Lyme disease has been established for well over a decade. The extent to which differences in habitat physiognomy could explain differences in tick populations, and consequently Lyme disease case rates, is addressed. Ticks were surveyed and vegetation measurements made in 4 habitat types at 1 site in each county. I. scapularis was 7 times more abundant in Monmouth County than in the Hunterdon County site, and the distribution of all life stages among habitats differed significantly between sites. The greater numbers of subadult ticks at the Monmouth County site was attributed to greater shrub cover and litter depth which created more favorable microclimatic conditions for tick survival. However, the overall physiognomy of the different vegetation types at the sites studied in Monmouth and Hunterdon counties was remarkably similar and did not appear to explain differences in tick abundance. Until further research clarifies microscale differences between habitats, the differences in the case rates between the counties appear to be more likely the result of reporting artifact.

Suppression of subadult Ixodes scapularis (Acari: Ixodidae) following removal of leaf litter.

Removal of leaf litter in wooded areas of a forested residential community significantly reduced the abundance of questing blacklegged tick, Ixodes scapularis Say, nymphs throughout their peak activity period. Removal of leaf litter, using hand rakes and leaf blowers during the early spring (March) and early summer (June) resulted in reductions in nymphal tick density ranging from 72.7 to 100%. Subsequent sampling of the I. scapularis population during the summer revealed similar rates of suppression of larvae. Although leaf removal provides levels of suppression similar to more traditional methods, including chemical acaricides, it is labor intensive and not free of possible nontarget effects. The potential role of leaf litter removal in an integrated program to control I. scapularis is discussed.

Effects of selected meterological factors on diurnal questing of Ixodes scapularis and Amblyomma Americanum (Acari: Ixodidade).

The diurnal questing behavior of adult Ixodes scapularis Say and Amblyomma americanum (L.) were monitored in the field to determine whether ticks would be collected with greater frequency during certain times of the day and under certain ambient meteorological conditions. Temperature and relative humidity explained a significant amount of the total variation in tick collections. Although both species were collected during every period, I. scapularis adults tended to quest earlier and later in the day when temperatures were lower and relative humidity higher, whereas A. americanum were collected with greater frequency in late morning and early afternoon during periods of higher temperatures and lower humidity. Questing of I. scapularis adults was observed at temperatures as low as -0.6 degrees C, whereas no adult A. americanum were collected below 4.4 degrees C. The questing temperature threshold for I. scapularis adults observed in this study was below that reported previously. The implications of these temporal activity patterns on the assessment of disease transmission risk and sampling bias are also discussed.

Efficacy of granular deltamethrin against Ixodes scapularis and Amblyomma americanum (Acari: Ixodidade) nymphs.

A single barrier application of granular deltamethrin to the woodland edges of a forested residential community in late spring significantly reduced the abundance of Ixodes scapularis Say nymphs. The application also suppressed the population of Amblyomma americanum (L.) nymphs, which recently became established in the study area. The efficacy of deltamethrin is compared with other commonly used acaricides.

Effects of an application of granular carbaryl on nontarget forest floor arthropods.

We evaluated the effects of a single application of granular carbaryl made against nymphal Ixodes scapularis Say on the diversity and abundance of forest arthropods taken in pitfall traps in oak and mixed oak-pine forest sites for 12 wk after treatment in central New Jersey. Significant short-term changes in arthropod assemblages were detected immediately posttreatment. Effects were not distributed equally across taxa. Seasonal changes in numbers and diversity of forest arthropods in the study areas may have affected the impact of the acaricide in the treatment area. Comparison with control areas indicated that reductions in abundance of some arthropod taxa in the treatment area were detectable 12 wk after treatment.

Apoptosis: Molecular mechanisms, regulation and role in pathogenesis.

OBJECTIVE: To review the current state of knowledge of apoptosis, with an emphasis on identifying potential and established roles for apoptosis in the pathogenesis of infectious diseases. DATA SOURCES: MEDLINE and the University of British Columbia library system were searched using the search subject, "apoptosis", for the years 1992 to 1996. Further search terms (eg, "pathogenesis") were used to narrow the results. These review articles and reference books were used as the basis for locating original articles on particular studies. DATA SELECTION: Approximately 40 studies were reviewed, with the criterion for selection being the relevance to either the molecular mechanisms behind apoptosis or roles for apoptosis in the pathogenesis of infectious diseases. DATA EXTRACTION: Relevant information from each study was collated into categories specific to morphological and biochemical characterization, and the regulation and molecular mechanisms of apoptosis and its role in the pathogenesis of infectious diseases. DATA SYNTHESIS AND CONCLUSIONS: Apoptosis is characterized by distinct morphological and biochemical changes that distinguish it from cell necrosis. Different signal transduction events and transcription factors can promote or inhibit apoptosis, although where and how these tie into the cell death pathway is still poorly understood. Apoptosis has been implicated in the pathogenesis of infectious diseases in two distinct ways: first, multicellular organisms use apoptosis to combat viral infections; and second, pathogens can alter the normal process of apoptosis in host cells by abnormal upregulation or downregulation. Many diseases have been shown to implicate apoptosis in their pathogenesis, raising the possibility of novel treatments for some disorders by therapeutically altering the occurrence and course of apoptosis. Therefore, further study of apoptosis in both health and disease needs to be rigorously pursued.

Temporal sequence and kinetics of proinflammatory and anti-inflammatory cytokine secretion induced by toxic shock syndrome toxin 1 in human peripheral blood mononuclear cells.

The staphylococcal superantigen toxic shock syndrome toxin 1 (TSST-1) induces massive cytokine production, which is believed to be the key factor in the pathogenesis of TSS. The temporal sequence and kinetics of both proinflammatory and anti-inflammatory cytokines induced by TSST-1 in human peripheral blood mononuclear cells were investigated. A panel of loss-of-function single-amino-acid-substitution mutants of TSST-1, previously demonstrated to be defective in either major histocompatibility complex (MHC) class II binding (G31R) or T-cell receptor (TCR) interaction (H135A, S14N), was studied in parallel to further elucidate the mechanisms of cytokine secretion. Wild-type recombinant (WT r) TSST-1 induced a biphasic pattern of cytokine secretion: an early phase with rapid release of proinflammatory cytokines (especially gamma interferon, interleukin-2 [IL-2], and tumor necrosis factor alpha [TNF-alpha]) within 3 to 4 h poststimulation, and a later phase with more gradual production of both proinflammatory (IL-1beta, IL-12, and TNF-beta) and anti-inflammatory (IL-6, IL-10) cytokines within 16 to 72 h poststimulation. G31R, which is defective in MHC class II binding, induced a cytokine profile similar to that of WT rTSST-1, except that secretion of the early-phase proinflammatory cytokines was delayed and production of IL-1beta and IL-12 was markedly reduced. In contrast, mutant toxins defective in TCR interaction either demonstrated complete absence of any cytokine secretion during the entire observation period (H135A) or resulted in complete abolishment of IL-2 and other early-phase proinflammatory cytokines, while secretion of IL-10 appeared unaffected (S14N). Neither WT rTSST-1 nor the mutant toxins induced IL-4 or transforming growth factor beta. Our data indicate that effective TCR interaction is critical for the induction of the early-phase proinflammatory cytokine response, thus underscoring the importance of T-cell signaling in TSS.