The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform

Michael J. Yabsley - One of the best experts on this subject based on the ideXlab platform.

Holly Gaff - One of the best experts on this subject based on the ideXlab platform.

  • Assessing the underwater survival of two tick species, Amblyomma Americanum and Amblyomma maculatum.
    Ticks and tick-borne diseases, 2018
    Co-Authors: Lindsey Bidder, Kristine M. Asmussen, Sean E. Campbell, Katerina A. Goffigan, Holly Gaff
    Abstract:

    Abstract The hard (ixodid) ticks Amblyomma Americanum and Amblyomma maculatum are found throughout the southeastern United States. To study the effects of water inundation, which is an increasingly common phenomenon in many coastal areas, unfed adult A. Americanum and A. maculatum ticks were tested for survival by submergence in three water conditions: freshwater, brackish water, and saltwater. The results demonstrated a significant difference in survival between the two species in all three water conditions, with A. maculatum ticks surviving a shorter time underwater than A. Americanum ticks. There is also a significant difference in A. Americanum survival among the different water conditions, with the highest mortality in saltwater and the lowest in freshwater. Amblyomma Americanum ticks survived the longest in freshwater (70 d), followed by brackish water (64 d), and the shortest survival was in saltwater (46 d), while the longest any A. maculatum tick survived was 24 d in freshwater. These findings demonstrate that any short-term flooding events, e.g., less than a week, would not likely eliminate these species of ticks in the flooded area.

  • Prevalence of Ehrlichia chaffeensis and Ehrlichia ewingii in Amblyomma Americanum and Dermacentor variabilis collected from southeastern Virginia, 2010-2011.
    Ticks and tick-borne diseases, 2014
    Co-Authors: Chelsea L. Wright, Holly Gaff, Wayne L. Hynes
    Abstract:

    Amblyomma Americanum is the most commonly encountered tick species in southeastern Virginia, representing approximately 95% of the human-biting tick population in this area. Here we investigated the prevalence of Ehrlichia chaffeensis and Ehrlichia ewingii in questing Amblyomma Americanum and Dermacentor variabilis ticks collected from multiple sites in southeastern Virginia from 2010 to 2011. Although both Ehrlichia species were detected in Amblyomma Americanum, no evidence of either pathogen was found in Dermacentor variabilis. Prevalence of E. chaffeensis varied by location, ranging from 0 to 5.08% among Amblyomma Americanum populations. Ehrlichia ewingii prevalence was slightly higher, ranging from 0 to 8.20% among A. Americanum populations. We conclude that both pathogens are established in southeastern Virginia A. Americanum populations, and that although there are no apparent temporal trends in Ehrlichia prevalence, there is variation among locations, suggesting the potential for disease hotspots.

Glen R. Needham - One of the best experts on this subject based on the ideXlab platform.

  • Pathogenicity of the fungus Beauveria bassiana (Balsamo) to Amblyomma Americanum (L.) and Dermacentor variabilis (Say) ticks (Acari: Ixodidae)
    International Journal of Acarology, 2002
    Co-Authors: S. Gomathinayagam, K. R. Cradock, Glen R. Needham
    Abstract:

    Abstract Amblyomma Americanum (L.) and Dermacentor variabilis (Say) ticks (Acari: Ixodidae) were challenged with the fungus Beauveria bassiana (Balsamo) Vuillemin (Deuteromycetes: Hyphomycetales). After two weeks 100% mortality was seen in A. Americanum exposed to conidial concentrations of 3.04 x 107 and 3.04 x 108 respectively. None of the D. variabilis had been killed. After five weeks 100% mortality of D. variabilis was achieved at the same concentrations. B. bassiana has potential for inclusion in tick management programs

  • Palp-Splaying Behavior and a Specific Mouthpart Site Associated with Active Water Vapor Uptake in Amblyomma Americanum (Acari: Ixodidae)
    Journal of medical entomology, 1999
    Co-Authors: Marvin D. Sigal, Jay A. Yoder, Glen R. Needham
    Abstract:

    Ticks actively absorb water vapor from unsaturated air via their mouthparts. A wax technique was used to cover select areas of the mouthparts of the lone star tick, Amblyomma Americanum (L.), to examine whether a specific site is involved in uptake. Covering dorsal, ventral, and distal regions failed to inhibit uptake, whereas wax applied to the proximal region, specifically the hypostome-cheliceral junction, blocked water absorption. A novel occurrence of a palp-splaying behavior was observed during hydrating conditions (93% RH), while ticks were motionless, compared with those held at desiccating conditions (63% RH), which were more active and the palps were not splayed.

  • A secreted calreticulin protein in ixodid tick (Amblyomma Americanum) saliva
    Journal of Insect Physiology, 1995
    Co-Authors: Deborah C. Jaworski, Frank A. Simmen, William J. Lamoreaux, Lewis B. Coons, Mark T. Muller, Glen R. Needham
    Abstract:

    A complementary DNA clone from salivary glands of feeding female Amblyomma Americanum ticks has been characterized as encoding calreticulin. Calreticulin, a major endoplasmic reticulum (ER) calcium-binding protein, appears to be secreted in Amblyomma and Dermacentor saliva. Evidence is accummulating that calreticulin performs roles unrelated to calcium storage. Unlike most known calreticulins, tick-secreted calreticulin lacks the ER retention signal, KDEL. This is the first molecular cloning of a specific tick salivary gland protein. The finding of a secreted calreticulin in tick saliva suggests a role for calreticulin in blood feeding through host immunosuppression or antihemostasis.

Joseph Piesman - One of the best experts on this subject based on the ideXlab platform.

  • A borreliacidal factor in Amblyomma Americanum saliva is associated with phospholipase A2 activity
    Experimental parasitology, 2009
    Co-Authors: Nordin S. Zeidner, Joseph Piesman, Marc C. Dolan, Gabrielle Dietrich, Amy J. Ullmann, Cherilyn Sackal, Donald E. Champagne
    Abstract:

    Previous work in our laboratory described the in vitro killing of Borrelia burgdorferi when co-cultured with saliva from adult Amblyomma Americanum. Borreliacidal activity was not evident using Ixodes scapularis saliva. Mixing trypsin with saliva eliminated the borreliacidal activity of A. Americanum saliva, while incorporating a trypsin inhibitor restored all borreliacidal activity, indicating this factor was of protein or peptide origin. One-dimensional PAGE indicated at least 7 major protein differences between I. scapularis and A. Americanum saliva. To determine the borreliacidal factor, A. Americanum saliva was fractionated by gel filtration and subsequent killing of B. burgdorferi was associated with a single fraction. Two-dimensional gel analysis indicated protein and/or peptide(s) in borreliacidal fractions running between 38 and 64 kDa. Finally, admixing saliva with the phospholipase A2 inhibitor oleyloxyethyl phosphorylcholine completely eliminated the ability of A. Americanum saliva to kill B. burgdorferi. These studies indicate the borreliacidal activity found in A. Americanum saliva is likely due to phospholipase A2 enzymatic activity.

  • Borreliacidal activity of saliva of the tick Amblyomma Americanum.
    Medical and veterinary entomology, 2005
    Co-Authors: K. E. Ledin, Nordin S. Zeidner, José M. C. Ribeiro, Brad J. Biggerstaff, Marc C. Dolan, Gabrielle Dietrich, L. Vredevoe, Joseph Piesman
    Abstract:

    . Amblyomma Americanum (Linneaus) (Acari: Ixodidae), an important tick vector of human and animal disease, is not a competent vector of the bacterial agent of Lyme disease, Borrelia burgdorferi, although its range overlaps the geographical distribution of Lyme disease within the United States. A possible mechanism that could prevent acquisition of B. burgdorferi spirochetes from infected hosts is the toxic effect of A. Americanum saliva on B. burgdorferi. The data presented here indicate that after 24 and 48 h of exposure to A. Americanum saliva, significantly fewer B. burgdorferi were alive compared to treatment controls as assessed by spirochete motility under dark-field microscopy and resistance to the dead stain, propidium iodide. After 48 h, fewer than 13% of saliva-exposed B. burgdorferi were alive. In contrast, significantly more B. burgdorferi exposed to Ixodes scapularis (Acari: Ixodidae) saliva survived after 24 or 48 h compared to A. Americanum saliva or treatment controls.

  • DNA evidence of Borrelia lonestari in Amblyomma Americanum (Acari: Ixodidae) in southeast Missouri.
    Journal of medical entomology, 2003
    Co-Authors: Rendi Murphree Bacon, Joseph Piesman, Robert D. Gilmore, Miquel Quintana, Barbara J B Johnson
    Abstract:

    Amblyomma Americanum collected near Lake Wappapello, Missouri, tested positive for Borrelia lonestari using polymerase chain reaction and sequence analyses of B. lonestari 16S rRNA and flagellin (flaB) genes. Twelve pools containing a total of 214 nymph or adult ticks contained evidence of infection with B. lonestari (minimum prevalence 5.6%). These data suggest that persons in southeast Missouri are at risk for exposure to B. lonestari after A. Americanum tick bite, a possible cause of erythema migrans-like rash illness in this region. Derivation of the complete coding sequence for B. lonestari flaB is also reported.

  • Amblyomma Americanum a potential vector of human ehrlichiosis
    American Journal of Tropical Medicine and Hygiene, 1993
    Co-Authors: Burt E Anderson, Christine M. Happ, K G Sims, James G Olson, James E Childs, Joseph Piesman, Gary O Maupin, Barbara J B Johnson
    Abstract:

    Abstract Polymerase chain reaction primers specific for Ehrlichia chaffeensis were used to amplify DNA from extracts of pooled ticks. Amplification was performed on extracts from 140 pools (1,579 total ticks) consisting of three tick genera collected from five states. The characteristic 389-basepair product was observed after amplification of extracts from seven different pools of adult Amblyomma Americanum (117 pools, 1,462 ticks), but not from pools of nymphs. No specific product was observed after amplification of 20 pools (105 ticks) of Dermacentor variabilis and three pools of Ixodes scapularis (12 ticks). Ehrlichia chaffeensis was present in A. Americanum at a minimum frequency of ≥ 0.48%, suggesting that A. Americanum may be a vector of human ehrlichiosis.

Wayne L. Hynes - One of the best experts on this subject based on the ideXlab platform.

  • Factors affecting the microbiome of Ixodes scapularis and Amblyomma Americanum.
    PloS one, 2020
    Co-Authors: R. Jory Brinkerhoff, Chris Clark, Kelly Ocasio, David T. Gauthier, Wayne L. Hynes
    Abstract:

    The microbial community composition of disease vectors can impact pathogen establishment and transmission as well as on vector behavior and fitness. While data on vector microbiota are accumulating quickly, determinants of the variation in disease vector microbial communities are incompletely understood. We explored the microbiome of two human-biting tick species abundant in eastern North America (Amblyomma Americanum and Ixodes scapularis) to identify the relative contribution of tick species, tick life stage, tick sex, environmental context and vertical transmission to the richness, diversity, and species composition of the tick microbiome. We sampled 89 adult and nymphal Ixodes scapularis (N = 49) and Amblyomma Americanum (N = 40) from two field sites and characterized the microbiome of each individual using the v3-v4 hypervariable region of the 16S rRNA gene. We identified significant variation in microbial community composition due to tick species and life stage with lesser impact of sampling site. Compared to unfed nymphs and males, the microbiome of engorged adult female I. scapularis, as well as the egg masses they produced, were low in bacterial richness and diversity and were dominated by Rickettsia, suggesting strong vertical transmission of this genus. Likewise, microbiota of A. Americanum nymphs and males were more diverse than those of adult females. Among bacteria of public health importance, we detected several different Rickettsia sequence types, several of which were distinct from known species. Borrelia was relatively common in I. scapularis but did not show the same level of sequence variation as Rickettsia. Several bacterial genera were significantly over-represented in Borrelia-infected I. scapularis, suggesting a potential interaction of facilitative relationship between these taxa; no OTUs were under-represented in Borrelia-infected ticks. The systematic sampling we conducted for this study allowed us to partition the variation in tick microbial composition as a function of tick- and environmentally-related factors. Upon more complete understanding of the forces that shape the tick microbiome it will be possible to design targeted experimental studies to test the impacts of individual taxa and suites of microbes on vector-borne pathogen transmission and on vector biology.

  • Prevalence of Ehrlichia chaffeensis and Ehrlichia ewingii in Amblyomma Americanum and Dermacentor variabilis collected from southeastern Virginia, 2010-2011.
    Ticks and tick-borne diseases, 2014
    Co-Authors: Chelsea L. Wright, Holly Gaff, Wayne L. Hynes
    Abstract:

    Amblyomma Americanum is the most commonly encountered tick species in southeastern Virginia, representing approximately 95% of the human-biting tick population in this area. Here we investigated the prevalence of Ehrlichia chaffeensis and Ehrlichia ewingii in questing Amblyomma Americanum and Dermacentor variabilis ticks collected from multiple sites in southeastern Virginia from 2010 to 2011. Although both Ehrlichia species were detected in Amblyomma Americanum, no evidence of either pathogen was found in Dermacentor variabilis. Prevalence of E. chaffeensis varied by location, ranging from 0 to 5.08% among Amblyomma Americanum populations. Ehrlichia ewingii prevalence was slightly higher, ranging from 0 to 8.20% among A. Americanum populations. We conclude that both pathogens are established in southeastern Virginia A. Americanum populations, and that although there are no apparent temporal trends in Ehrlichia prevalence, there is variation among locations, suggesting the potential for disease hotspots.