2 research outputs found
Powassan virus multiplication in Dermacentor andersoni ticks
All stages of Dermacentor andersoni (Stiles) ticks were infected by feeding on rabbits injected intravenously with large doses of Powassan virus 48 to 72 hours after the ticks became attached. Viremia titers at least 10²˙⁵ mouse LD₅₀ per ml were required to establish infection in 1 to 5% of ticks ingesting viremic blood. The "infection-threshold" of D. andersoni adults for Powassan virus was elevated when viremia was induced towards the end of engorgement. When each stage in the tick's life cycle was infected a viral-eclipse phase was demonstrated in gut cells. Other organs such as salivary glands, Gene's organ glands and accessory glands supported virus multiplication. This was demonstrated by infectivity titrations and observation of fluorescent foci when the tissues were stained with Powassan virus antiserum conjugated with fluorescein isothiocyanate (FITC). Transstadial transfer of Powassan virus was observed through ecdysis of larvae to nymphs and from nymphs to adults. This occurred both after feeding on hamsters (which produced a substantial viremia) and guineapigs (which did not become viremic). Virus-was detected only in larval gut and invaded nymphal salivary glands during the molt. Infection localized in gut and salivary glands of engorged nymphs and flat adults, and was not detected in adult female accessory and Gene's glands until repletion.
Adult males maintained high virus titers in salivary glands only. Transovarial transfer was not detected although infectivity was present on the surface of eggs laid by the mediation of an infected Gene's organ gland. Powassan virus was detected in salivary gland secretions but not in rectal excretions in adults or nymphs. Transmission of Powassan virus to hamsters, guinea-pigs, and rabbits was demonstrated by the bite of D. andersoni nymphs and adults which were infected by ingestion of blood by their antecedent larvae.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat
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Multicenter Comparison of Nucleic Acid Amplification Tests for the Diagnosis of Rectal and Oropharyngeal Chlamydia trachomatis and Neisseria gonorrhoeae Infections
Research using nucleic acid amplification tests (NAATs) have repeatedly found rectal and oropharyngeal infections with Chlamydia trachomatis and Neisseria gonorrhoeae to be common and potentially more difficult to treat than genital infections. Unfortunately, public health and patient care efforts have been hampered by the lack of FDA-cleared NAATs with claims for anorectal or oropharyngeal samples. At the time of the initiation of this study, no commercially available assays had these claims. We formed a novel partnership among academic institutions and diagnostic manufacturers to address this public health need. From May 2018 through August 2019, we recruited 1108 women, 1256 men, and 26 transgender persons each of whom provided 3 anal and 3 oropharyngeal swab specimens. The 3 anal swabs were pooled into a single transport tube as were the 3 oropharyngeal swabs. The performance of each of three study assays was estimated by comparison to the composite result and relative to one another. Percent positivity for chlamydia was 5.9 and 1.2% from anal and oropharyngeal specimens, respectively, compared to 4.2 and 4.1% for gonorrhea. Sensitivity for chlamydia detection ranged from 81.0 to 95.1% and 82.8 to 100% for anal and oropharyngeal specimens, respectively. Gonorrhea sensitivity ranged from 85.9 to 99.0% and 74.0 to 100% for anal and oropharyngeal samples, respectively. Specificity estimates were ≥ 98.9% for all assays, organisms, and sample types. Although there was heterogeneity between sensitivity estimates, these assays offer better ability to detect extragenital infections than culture and potential solutions for providing appropriate sexual health care for populations in which these infections are of concern