Browsing by Author "Cumbie, Alexandra N."
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- Dermacentor Variabilis and Its Associated Rickettsiae in Southeastern Virginia; The Potential Role of Pathogen Spillover From Local Sympatric Tick SpeciesCumbie, Alexandra N.; Gaff, Holly; Hynes, Wayne (American Society of Tropical Medicine and Hygiene, 2021-11-01)Hard-bodied ticks are the most medically important group of arthropods in the United States (US). Dermacentor variabilis, the American dog tick, is a common vector in the US with its geographic range expanding across the eastern and western portions of the country. This tick is the historical vector of Rickettsia rickettsii, the causative agent of Rocky Mountain Spotted Fever and has been reported to harbor other spotted fever group rickettsiae anecdotally. In Virginia, spotted fever group rickettsiosis cases range between 300-400 per year based on passive surveillance data which do not often identify the rickettsial agent to species. There are a variety of rickettsial species reported in Virginia which include R. rickettsii, R. amblyommatis, R. montanensis, and R. parkeri. Each rickettsia can be detected in multiple tick species, but are typically transmitted by a single vector; all of which are sympatric with D. variabilis. The purpose of this study was assess current D. variabilis populations in Virginia and their associated rickettsiae. From 2012 to 2018 as part of a long-term active surveillance project, adult D. variabilis were collected using standard flagging methods and their immatures were collected using small mammal trapping. The presence of rickettsiae was detected using real-time PCR and confirmed using Sanger sequencing. Dermacentor variabilis in Virginia were observed to harbor R. montanensis, R. parkeri, and R. amblyommatis, with the most common rickettsial species being R. montanensis. No samples had detectable levels of R. rickettsii infection. The occurrence of pathogen spillover among sympatric tick species appears to be common in D. variabilis under select pressures (i.e. when other tick species are dominant in the same area). Once that pressure is removed, R. montanensis, the common endosymbiont of D. variabilis, becomes the predominant rickettsia detected.
- The Distribution, Seasonal Abundance, and Environmental Factors Contributing to the Presence of the Asian Longhorned Tick (Haemaphysalis longicornis, Acari: Ixodidae) in Central Appalachian VirginiaCumbie, Alexandra N.; Whitlow, Amanda M.; Arneson, Alicia; Du, Zhiyuan; Eastwood, Gillian (Oxford University Press, 2022-05-30)Over the past decade, Haemaphysalis longicornis, the Asian longhorned tick, has undergone a geographic range expansion in the United States, from its historical range in east Asia. This tick has been characterized by its frequent parasitism of livestock, an ability to reproduce through parthenogenesis, and its ability to transmit a variety of vector-borne pathogens to livestock, wildlife, and human hosts in its native geographic range. Thus far in the United States, 17 states have reported H. longicornis populations, including 38 counties in Virginia. These numbers come from presence-absence reports provided to the U.S. Department of Agriculture, but little has been reported about this ticks' seasonality in Virginia or its habitat preferences. Our current study detected H. longicornis populations in seven of the nine surveyed counties in Virginia. Haemaphysalis longicornis were observed in multiple habitat types including mixed hardwood forests and pastures, with abundant H. longicornis populations detected at one particular pasture site in Wythe County. This study also attempted to investigate environmental conditions that may be of importance in predicting tick presence likelihood. While sample size limited the scope of these efforts, habitat type and climatic metrics were found to be important indicators of H. longicornis collection success and abundance for both the nymphal and larval life stages. This current study reports useful surveillance data for monitoring these tick populations as they become established in the western half of Virginia and provides insight into their current distribution and maintenance over a large study region.
- First Evidence of Powassan Virus (Flaviviridae) in Ixodes scapularis in Appalachian Virginia, USACumbie, Alexandra N.; Whitlow, Amanda M.; Eastwood, Gillian (American Society of Tropical Medicine and Hygiene, 2022-03-01)Here we report the first detection and confirmation of Powassan virus (POWV) (family: Flaviridae) in Ixodes scapularis ticks collected from Appalachian Virginia. Ixodes scapularis ticks were collected from vegetation across field sites in eight counties of western Virginia from June 2019 to April 2021. From these collections, one nymph and one adult male I. scapularis were determined to be positive for POWV using real-time RT-PCR and Sanger sequencing. Both positive ticks were collected from Floyd county, VA, at residential sites; the nymph in June 2020 and the adult male in April 2021. The presence of POWV in Virginia in its natural tick vector is crucial knowledge in beginning to understand the movement and transmission of this pathogen into new geographical areas and the risk it poses to medical and veterinary health.
- Pathogen Spillover to an Invasive Tick Species: First Detection of Bourbon Virus in Haemaphysalis longicornis in the United StatesCumbie, Alexandra N.; Trimble, Rebecca N.; Eastwood, Gillian (MDPI, 2022-04-10)Haemaphysalis longicornis (Neumann, 1901) (Acari: Ixodidae), the Asian longhorned tick, is an invasive tick species present in the USA since at least 2017 and has been detected in one-third of Virginia counties. While this species is associated with the transmission of multiple pathogens in its native geographical range of eastern Asia, little is known about its ability to acquire and transmit pathogens in the USA, specifically those that are transmissible to humans, although from an animal health perspective, it has already been shown to vector Theileria orientalis Ikeda strains. Emerging tick-borne viruses such as Bourbon virus (genus: Thogotovirus) are of concern, as these newly discovered pathogenic agents have caused fatal clinical cases, and little is known about their distribution or enzootic maintenance. This study examined H. longicornis collected within Virginia (from ten counties) for Bourbon and Heartland viruses using PCR methods. All ticks tested negative for Heartland virus via qRT-PCR (S segment target). Bourbon-virus-positive samples were confirmed on two different gene targets and with Sanger sequencing of the PB2 (segment 1) gene. Bourbon virus RNA was detected in one nymphal stage H. longicornis from Patrick County, one nymph from Staunton City, and one larval pool and one adult female tick from Wythe County, Virginia. An additional 100 Amblyomma americanum (Linnaeus 1758; lone star tick) collected at the same Patrick County site revealed one positive nymphal pool, suggesting that Bourbon virus may have spilled over from the native vector, potentially by co-feeding on a shared Bourbon-virus-infected vertebrate host. Blood tested from local harvested deer revealed a 11.1% antibody seroprevalence against Bourbon virus, exposure which further corroborates that this tick-borne virus is circulating in the southwest Virginia region. Through these results, it can be concluded that H. longicornis can carry Bourbon virus and that pathogen spillover may occur from native to invasive tick species.