Attempted experimental infection of domestic goats with Ehrlichia chaffeensis

Although white-tailed deer (WTD; Odocoileus virginianus ) are considered the primary natural reservoir host for Ehrlichia chaffeensis, the causative agent of human monocytotropic ehrlichiosis, the potential role of other vertebrates as reservoir hosts has not been fully explored. Because domestic goats are naturally infected in areas where E. chaffeensis is endemic in deer, we evaluated the susceptibility of domestic goats to experimental infection with E. chaffeensis. A total of 12 goats were inoculated with E. chaffeensis (15B-WTD-GA or Ark strain)-infected DH82 cells by one of three routes: intravenously, subcutaneously, or intradermally. White-tailed deer simultaneously inoculated with the same dose, route, and inoculum served as positive controls; additional goats and WTD were included as negative controls. Evidence of E. chaffeensis infection was evaluated in all animals by indirect fluorescent antibody assay, PCR, and cell culture isolation techniques. All goats exposed to E. chaffeensis seroconverted by 14 days post-infection (DPI), and E. chaffeensis was isolated from one goat on 3 DPI; however, molecular or cell culture evidence of active infection was not detected in goats later than 3 DPI. White-tailed deer exhibited serologic and molecular evidence of E. chaffeensis infection throughout both trials, and E. chaffeensis was reisolated in cell culture from all infected WTD on numerous days post-infection. Our results suggest that despite the occurrence of natural infection in goats, this animal may not be susceptible to experimental infection and thus may not serve as a suitable model of E. chaffeensis reservoir host infection.     

Phylogenetic comparison of the S10 genes of recent isolates of bluetongue virus from the United States and French Martinique Island

The sequences of the S10 genes of 28 recent isolates (1994-2004) of bluetongue virus (BTV) from the United States (US) and French Martinique Island (2006) in the Caribbean Basin were compared in phylogenetic analyses to those of viruses previously isolated in the same regions. Although the analyses segregated the recent virus isolates from the two regions into distinct topotype clusters, the analyses also confirm that viruses from the US and the Caribbean Basin/Central America can share similar S10 genes despite the fact that distinct constellations of BTV serotypes occur in the two regions.     

Biological transmission of vesicular stomatitis virus (New Jersey serotype) by Simulium vittatum (Diptera: Simuliidae) to domestic swine (Sus scrofa)

The role of hematophagous arthropods in vesicular stomatitis virus (New Jersey serotype; VSV-NJ) transmission during epizootics has remained unclear for decades in part because it has never been shown that clinical or subclinical disease in a livestock host results from the bite of an infected insect. In this study, we investigated the ability of VSV-NJ-infected black flies (Simulium vittatum Zetterstedt) to transmit the virus to domestic swine, Sus scrofa L. Experimental evidence presented here clearly demonstrates that VSV-NJ was transmitted from black flies to the swine. Transmission was confirmed by seroconversion or by the presence of clinical vesicular stomatitis followed by seroconversion. Our results represent the first report of clinical vesicular stomatitis in a livestock host after virus transmission by an insect.     

First culture isolation of Borrelia lonestari, putative agent of southern tick-associated rash illness

Southern tick-associated rash illness (STARI) is a Lyme disease-like infection described in patients in the southeastern and south-central United States, where classic Lyme disease is relatively rare. STARI develops following the bite of a lone star tick (Amblyomma americanum) and is thought to be caused by infection with an "uncultivable" spirochete tentatively named Borrelia lonestari. In this study, wild lone star ticks collected from an area where B. lonestari is endemic were cocultured in an established embryonic tick cell line (ISE6). The cultures were examined by dark-field microscopy for evidence of infection, and spirochete identity and morphology were evaluated by flagellin B and 16S rRNA gene sequence, by reaction to Borrelia-wide and B. burgdorferi-specific monoclonal antibodies, and by electron microscopy. Live spirochetes were first visualized in primary culture of A. americanum ticks by dark-field microscopy 14 days after the cell culture was inoculated. The sequences of the flagellin B and 16S rRNA genes of cultured spirochetes were consistent with previously reported sequences of B. lonestari. The cultured spirochetes reacted with a Borrelia-wide flagellin antibody, but did not react with an OspA antibody specific to B. burgdorferi, by indirect fluorescent antibody testing. Electron microscopy demonstrated organisms that were free and associated with ISE6 cells, with characteristic Borrelia sp. morphology. This study describes the first successful isolation of B. lonestari in culture, providing a much needed source of organisms for the development of diagnostic assays and forming a basis for future studies investigating the role of the organism as a human disease agent.     

No role of interstitial adenosine in insulin-mediated vasodilation.

The mechanisms behind the vasodilatory effect of insulin are not fully understood, but nitric oxide plays an important role. We have investigated the possibility that insulin mediates vasodilatation in the human skeletal muscle via an increase in extracellular adenosine concentrations. In eight healthy subjects (H) and in four subjects with a complete, high (C5-C6/7) spinal cord injury (SCI) a hyperinsulinaemic (480 mU min-1 kg-1), isoglycaemic clamp was performed. SCI subjects were included as it has been proposed that adenosine and adenine nucleotides may be released from nerve endings in the skeletal muscle. Adenosine concentrations in the extracellular fluid (ECF) of skeletal muscle in the thigh were measured by means of the microdialysis technique. Leg blood flow (LBF) was measured by termodilution. In response to insulin infusion, LBF always increased (P < 0.05) (from 228 +/- 25 and 318 +/- 18 mL min-1 to 451 +/- 41 and 530 +/- 29 mL min-1, SCI and H, respectively [mean +/- SEM]). Concentrations of adenosine in the muscle ECF did not change with infusion of insulin and did not differ between groups (before: 147 +/- 55 [SCI] and 207 +/- 108 [H] nmol L-1; during: 160 +/- 36 [SCI] and 165 +/- 74 [H] nmol L-1). No significant correlation between concentrations of adenosine and corresponding LBF rates was achieved (LBF=[-0.0936. Adenosine] + 475. R=-0.092, P=0.22, number of samples=181, number of subjects=12). Conclusion: the mechanism by which insulin mediates an increase in skeletal muscle blood flow is not associated with adenosine in the ECF.