Vitellogenesis in \u3ci\u3eHyalomma dromedarii\u3c/i\u3e (Acari: Ixodidae): A Model for Analysis of Endocrine Regulation in Ixodid Ticks

The egg yolk proteins, vitellins, and their hemolymph precursors, vitellogenins, were characterized in the ixodid tick Hyalomma dromedarii. Three vitellins were identified. The high molecular weight vitellins, VN A and VN B, were composed of seven homologous molecular weight subunit polypeptides, VN 1-7. VN A appears to be a dimeric form of VN B. VN C was composed of single polypeptide. Low levels of vitellogenin, were identified in western immunoblots utilizing antibody raised against purified vitellin. Adult protein and polypeptide profiles, including vitellin and vitellogenin, were characterized as a function of sex, tissue and reproductive development. Quantitative assessment of the vitellin and vitellogenin was accomplished by ELISA. By this method, a rise in the level of vitellogenin from 0.15 to 11.19 % of the hemolymph protein between the stages of fed virgin and repletion in females was observed. Similarly, fat body levels rose from 0.15 to 3.0% during these physiological stages. The level of ovarian vitellin rose rapidly from 0.39 to over 50% of the tissue protein during the four days after repletion. The level of vitellogenin in midgut, salivary gland and muscle, increased slowly during repletion, and never exceeded 1.1% of its respective tissue protein. Tissue specific synthesis of vitellogenin and vitellin was monitored in vitro. Continuous synthesis of vitellogenin was demonstrated with replete fat body tissue over an eight day culture period. Other tissues, including ovary, midgut, muscle and salivary gland, did not synthesize vitellin or vitellogenin in vitro. Stimulation of vitellogenin synthesis by various authentic hormones and tissue extracts was tested both in vitro and in vivo. Vitellogenin synthesis by cultured fed virgin fat body was stimulated 35 fold by treatment with synganglion extracts from replete females. Similar stimulation of vitellogenesis with synganglion extracts was observed in vivo. Although Juvenile hormone bis-epoxide and 20 hydroxyecdysone treatment did not affect vitellogenin synthesis in cultured fed virgin fat body, they did demonstrate stimulatory activity in vivo. Multihormonal regulation of vitellogenesis, involving a synganglion factor, a juvenoid and 20 hydroxyecdysone is considered

Francisella tularensis: an arthropod-borne pathogen

Arthropod transmission of tularemia occurs throughout the northern hemisphere. Few pathogens show the adaptability of Francisella tularensis to such a wide array of arthropod vectors. Nonetheless, arthropod transmission of F. tularensis was last actively investigated in the first half of the 20th century. This review will focus on arthropod transmission to humans with respect to vector species, modes of transmission, geographic differences and F. tularensis subspecies and clades

Wide Distribution of a High-Virulence Borrelia burgdorferi Clone in Europe and North America

We found substantial population differentiation and recent trans-Atlantic dispersal of a high-virulence B. burgdorferi clone

Virulence difference between the prototypic Schu S4 strain (A1a) and Francisella tularensisA1a, A1b, A2 and type B strains in a murine model of infection

BACKGROUND: The use of prototypic strains is common among laboratories studying infectious agents as it promotes consistency for data comparability among and between laboratories. Schu S(4) is the prototypic virulent strain of Francisella tularensis and has been used extensively as such over the past six decades. Studies have demonstrated virulence differences among the two clinically relevant subspecies of F. tularensis, tularensis (type A) and holarctica (type B) and more recently between type A subpopulations (A1a, A1b and A2). Schu S(4) belongs to the most virulent subspecies of F. tularensis, subspecies tularensis. METHODS: In this study, we investigated the relative virulence of Schu S(4) in comparison to A1a, A1b, A2 and type B strains using a temperature-based murine model of infection. Mice were inoculated intradermally and a hypothermic drop point was used as a surrogate for death. Survival curves and the length of temperature phases were compared for all infections. Bacterial burdens were also compared between the most virulent type A subpopulation, A1b, and Schu S(4) at drop point. RESULTS: Survival curve comparisons demonstrate that the Schu S(4) strain used in this study resembles the virulence of type B strains, and is significantly less virulent than all other type A (A1a, A1b and A2) strains tested. Additionally, when bacterial burdens were compared between mice infected with Schu S(4) or MA00-2987 (A1b) significantly higher burdens were present in the blood and spleen of mice infected with MA00-2987. CONCLUSIONS: The knowledge gained from using Schu S(4) as a prototypic virulent strain has unquestionably advanced the field of tularemia research. The findings of this study, however, indicate that careful consideration of F. tularensis strain selection must occur when the overall virulence of the strain used could impact the outcome and interpretation of results

Whole genome single nucleotide polymorphism based phylogeny of Francisella tularensis and its application to the development of a strain typing assay

<p>Abstract</p> <p>Background</p> <p>A low genetic diversity in <it>Francisella tularensis </it>has been documented. Current DNA based genotyping methods for typing <it>F. tularensis </it>offer a limited and varying degree of subspecies, clade and strain level discrimination power. Whole genome sequencing is the most accurate and reliable method to identify, type and determine phylogenetic relationships among strains of a species. However, lower cost typing schemes are necessary in order to enable typing of hundreds or even thousands of isolates.</p> <p>Results</p> <p>We have generated a high-resolution phylogenetic tree from 40 <it>Francisella </it>isolates, including 13 <it>F. tularensis </it>subspecies <it>holarctica </it>(type B) strains, 26 <it>F. tularensis </it>subsp. <it>tularensis </it>(type A) strains and a single <it>F. novicida </it>strain. The tree was generated from global multi-strain single nucleotide polymorphism (SNP) data collected using a set of six Affymetrix GeneChip^®resequencing arrays with the non-repetitive portion of LVS (type B) as the reference sequence complemented with unique sequences of SCHU S4 (type A). Global SNP based phylogenetic clustering was able to resolve all non-related strains. The phylogenetic tree was used to guide the selection of informative SNPs specific to major nodes in the tree for development of a genotyping assay for identification of <it>F. tularensis </it>subspecies and clades. We designed and validated an assay that uses these SNPs to accurately genotype 39 additional <it>F. tularensis </it>strains as type A (A1, A2, A1a or A1b) or type B (B1 or B2).</p> <p>Conclusion</p> <p>Whole-genome SNP based clustering was shown to accurately identify SNPs for differentiation of <it>F. tularensis </it>subspecies and clades, emphasizing the potential power and utility of this methodology for selecting SNPs for typing of <it>F. tularensis </it>to the strain level. Additionally, whole genome sequence based SNP information gained from a representative population of strains may be used to perform evolutionary or phylogenetic comparisons of strains, or selection of unique strains for whole-genome sequencing projects.</p

Persistence of Yersinia pestis in Soil Under Natural Conditions

As part of a fatal human plague case investigation, we showed that the plague bacterium, Yersinia pestis, can survive for at least 24 days in contaminated soil under natural conditions. These results have implications for defining plague foci, persistence, transmission, and bioremediation after a natural or intentional exposure to Y. pestis

Pneumonic Plague Cluster, Uganda, 2004

In a case cluster, pneumonic plague transmission was compatible with respiratory droplet rather than aerosol transmission

Laboratory Analysis of Tularemia in Wild-Trapped, Commercially Traded Prairie Dogs, Texas, 2002

Oropharyngeal tularemia was identified as the cause of a die-off in captured wild prairie dogs at a commercial exotic animal facility in Texas. From this point source, Francisella tularensis–infected prairie dogs were traced to animals distributed to the Czech Republic and to a Texas pet shop. F. tularensis culture isolates were recovered tissue specimens from 63 prairie dogs, including one each from the secondary distribution sites. Molecular and biochemical subtyping indicated that all isolates were F. tularensis subsp. holarctica (Type B). Microagglutination assays detected antibodies against F. tularensis, with titers as great as 1:4,096 in some live animals. All seropositive animals remained culture positive, suggesting that prairie dogs may act as chronic carriers of F. tularensis. These findings demonstrate the need for additional studies of tularemia in prairie dogs, given the seriousness of the resulting disease, the fact that prairie dogs are sold commercially as pets, and the risk for pet-to-human transmission

Wild Felids as Hosts for Human Plague, Western United States

Plague seroprevalence was estimated in populations of pumas and bobcats in the western United States. High levels of exposure in plague-endemic regions indicate the need to consider the ecology and pathobiology of plague in nondomestic felid hosts to better understand the role of these species in disease persistence and transmission