Browsing by Author "Eastwood, Gillian"

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    Battle of the Viruses: Aripo Virus Induced Superinfection Exclusion of Mosquito-borne Viruses
    Carver, James A. (Virginia Tech, 2021-01-06)
    Flaviviruses are a single-stranded, positive sense, RNA virus that affect around 400 million people annually. Flaviviruses are transmitted by arthropod vectors, the most common vector being the mosquito. Currently, many mosquito control strategies are in use, these control strategies are diverse in both efficiency and cost. However, developing new vector control strategies is becoming increasingly important, due to climate changing affecting vector population distribution and the current limitations conventional control strategies face. Although many different control strategies exist, there is limited research pertaining to reducing viral infection in the vector. Reducing the transmission capabilities of vectors could help relieve the disease burden felt around the world. Aripo virus (ARPV), an insect-specific flavivirus, has ushered in opportunities to discover a novel approach to arbovirus control. The exclusionary effects of ARPV were explored as a means to eventually understanding superinfection exclusion (SIE) and utilizing it as a calculated defense against mosquito-borne disease. Aripo virus was evaluated for its SIE potential in vitro and experiments were performed to explore the possible mechanisms underlying SIE. Aripo virus showed significant exclusion against the flaviviruses tested, as well as an alphavirus. Additionally, West Nile virus was unable to adapt and overcome SIE barriers over 9 serial passages. Lastly, ARPV was superinfected with chimeric viruses to asses replication kinetics, and possible exclusionary bias was seen with non-structural genes. These data show ARPV is capable of reducing viral titer, as well as possible leads into understanding the underlying mechanism of SIE, a critical step in utilizing SIE as a strategy to combat vector-borne disease.
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    Comparative Transmission and Pathogenesis of La Crosse Virus (LACV) Lineages and Evidence for LACV Circulation in Virginia Wildlife
    Faw, Lindsey Rae (Virginia Tech, 2024-11-26)
    La Crosse virus (LACV) is a mosquito-borne arbovirus that is the main cause of pediatric encephalitis in the United States in children under 16. LACV is maintained in hardwood forests utilizing Aedes spp. mosquitoes, primarily Aedes triseriatus, and Sciuridae vertebrate host species, primarily the Eastern Chipmunk (Tamias striatus) or via transovarial transmission from mother mosquitoes to offspring. Historically, LACV comprised two genetically distinct lineages: lineage I in the Midwest and Appalachian regions and lineage II in the southern region. Lineage I LACV is a growing public health concern in Appalachia, where cases now outnumber those in the Midwest, which historically accounted for most LACV cases. The majority (53%) of LACV cases between 2003 and 2023 were reported from Appalachian states surrounding Virginia (North Carolina: 331, Tennessee: 213, West Virginia: 225, and Kentucky: 11), but Virginia only reported 25 cases. In chapter two, we explore the hypothesis that LACV is circulating in Virginia utilizing serosurveillance to indicate LACV circulation. Blood samples provided by wildlife rehabilitation centers throughout Virginia (n=527 comprising 9 vertebrate species) were screened for LACV antibodies using Plaque Reduction Neutralization tests (PRNTs). We identified an overall prevalence rate of 1.90% across five seropositive vertebrate species. In addition to known hosts of LACV, Eastern Gray Squirrel, Eastern Cottontail, and Groundhog, we identified the first reported seropositive Red Fox. We highlight that LACV is circulating in Virginia, although at a much lower rate than reported from other states, which may explain the reduced number of cases. In addition to lineage I and II LACV, a new lineage was identified in 2005 in the Northeast but has yet to cause human disease. In the face of an apparent entomological risk demonstrated by the continued isolation of lineage III from mosquitoes in this region, it is unclear why there is a lack of clinical cases. The prevailing hypotheses are (1) under-diagnosis in cases of human disease or lack of detection in humans, (2) reduced virulence in lineage III LACV, (3) low prevalence of lineage III in local mosquito and host animal populations, or (4) reduced vector competence in local mosquito populations. In chapter three, we explore the vector competence of Aedes albopictus and Aedes triseriatus from the range of lineage III (Connecticut) and from the historic LACV range (Virginia) to transmit LACV lineage III. Using oral feeding and intrathoracic inoculation, bodies, legs, saliva, and ovaries were harvested to indicate infection, dissemination, ability to transmit, and ability to vertically transmit, respectively. Although there were no apparent differences in horizontal or vertical transmission, we demonstrated that LACV lineage III can be transmitted both horizontally and vertically, highlighting the potential public health risk associated with lineage III. In chapter four, we explore the pathogenesis of lineage III. An immune-competent murine model, CD-1, and an immune-deficient murine model, IFNAR-/-, were used to determine the pathogenesis of lineage III. Interestingly, in the immune-deficient model, lineage III was able to cause significant morbidity and mortality, but not in the immune-competent model. LACV lineage I and II can overcome the host immune system through the interferon pathway, allowing viral replication. We hypothesize that lineage III cannot circumvent the interferon system as the other lineages can and, therefore, cannot replicate to cause clinical disease. Overall, although lineage III can be transmitted in vector mosquitoes, it may be unable to cause disease in humans because it cannot overcome the antiviral responses, but this needs to be explored further to determine the underlying mechanism. However, viruses can evolve quickly, and we still advocate for continued surveillance and investigation into lineage III LACV.
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    The Distribution, Seasonal Abundance, and Environmental Factors Contributing to the Presence of the Asian Longhorned Tick (Haemaphysalis longicornis, Acari: Ixodidae) in Central Appalachian Virginia
    Cumbie, 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.
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    Drugs and Biodiversity Loss: Narcotraffic-Linked Landscape Change in Guatemala
    Winter, Steven N.; Eastwood, Gillian; Barrios-Izás, Manuel A. (IntechOpen, 2022-10-13)
    Characteristic of the Anthropocene, human impacts have resulted in worldwide losses in forested land cover, which can directly and indirectly drive biodiversity loss. The global illicit drug trade is one source of deforestation directly implicated with habitat loss in Central America, typically for drug trafficking and livestock production for money laundering. Given reports of deforestation in Central America linked to narcotraffic, we explored vegetation changes within Guatemala’s highly biodiverse Maya Biosphere Reserve by examining trends suggestive of deforestation in a protected area. As such, we collected satellite-derived data in the form of enhanced vegetation index (EVI), as well as history of burned areas, published human-“footprint” data, official population density, and artificial light activity in Laguna del Tigre National Park from 2002 to 2020 for descriptive analysis. We found consistent reductions in EVI and trends of anomalous losses of vegetation despite a baseline accounting for variation within the park. Analyses revealed weak correlations (R2 ≤ 0.26) between EVI losses and official sources of anthropogenic data, which may be attributable to the data’s limited spatial and temporal resolution. Alarmingly, simple analyses identified vegetation losses within a protected area, thus emphasizing the need for additional monitoring and science-based, but interdisciplinary policies to protect this biodiversity hotspot.
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    Ecology and Climate Tolerance of Emerging Tick Disease Vectors in Central Appalachia/Southwestern Virginia
    Whitlow, Amanda Marie (Virginia Tech, 2021-06-29)
    Little is known about the tick populations found within the central Appalachian/southwestern region of Virginia. The main focus of this research was to better assess local tick communities in the central Appalachian-Southwestern region of Virginia, which was addressed by determining species diversity, habitat associations, seasonal phenology, pathogen prevalence, and ecological factors that influences tick presence and abundance. A field study was conducted from June 2019 - November 2020 across 8 counties and 3 habitat types. Forested habitats exhibited greater tick species diversity than pasture and urban habitats. Each tick species was observed to be associated with particular habitats. The presence of B. burgdorferi sensu stricto (causative agent of Lyme disease), the human variant of A. phagocytophilum (causative agent of human granulocytic anaplasmosis), and Powassan virus (the causative agent of Powassan encephalitis) were detected in collected field specimens, suggesting a significant threat to public health. The detection of Powassan virus RNA in local Ixodes scapularis ticks is the first evidence of this viral pathogen within the region. The overwintering abilities of ticks, whose populations are expanding or becoming more invasive, including Haemaphysalis longicornis, Amblyomma americanum, and Amblyomma maculatum, were examined through a combination of laboratory and field experiments. Amblyomma americanum and H. longicornis nymphal ticks had a lower supercooling temperature than adult ticks, suggesting their potential to overwinter better; A. maculatum nymphs had similar average supercooling temperatures as the other two species at nymphal stage. Via a field experiment, A. americanum, H. longicornis, and A. maculatum were subjected to natural elements of a Virginian winter in a two-factor design investigating elevation and potential insulation coverage. Elevation and insulation coverage were found to have no significant impact on the overwintering survival of H. longicornis and A. americanum. However, the life-stage of the tick was determined to be a significant factor that dictated the survival of ticks of these species. Overwintering survival of Amblyomma maculatum nymphs was influenced by insulation (proxied by leaf litter); which may be attributed to this tick's preference of drier climate. Low overwintering survival suggests that a tick may not be able to establish a permanent population within the area.
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    Environmental Determinants of Aedes albopictus Abundance at a Northern Limit of Its Range in the United States
    Kache, Pallavi A.; Eastwood, Gillian; Collins-Palmer, Kaitlin; Katz, Marly; Falco, Richard C.; Bajwa, Waheed I.; Armstrong, Philip M.; Andreadis, Theodore G.; Diuk-Wasser, Maria A. (2020-02)
    Aedes albopictus is a vector of arboviruses with high rates of morbidity and mortality. The northern limit of Ae. albopictus in the northeastern United States runs through New York state (NYS) and Connecticut. We present a landscape-level analysis of mosquito abundance measured by daily counts of Ae. albopictus from 338 trap sites in 12 counties during May-September 2017. During the study period, the mean number of Ae. albopictus caught per day of trapping across all sites was 3.21. We constructed four sets of negative binomial generalized linear models to evaluate how trapping methodology, land cover, as well as temperature and precipitation at multiple time intervals influenced Ae. albopictus abundance. Biogents-Sentinel (BGS) traps were 2.78 times as efficient as gravid traps and 1.49 times as efficient as CO2-baited CDC light traps. Greater proportions of low- and medium-intensity development and low proportions of deciduous cover around the trap site were positively associated with increased abundance, as were minimum winter temperature and March precipitation. The cumulative precipitation within a 28-day time window before the date of collection had a nonlinear relationship with abundance, such that greater cumulative precipitation was associated with increased abundance until approximately 70 mm, above which there was a decrease in abundance. We concluded that populations are established in Nassau, Suffolk, and New York City counties in NYS; north of these counties, the species is undergoing population invasion and establishment. We recommend that mosquito surveillance programs monitoring the northward invasion of Ae. albopictus place BGS traps at sites chosen with respect to land cover.
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    Evaluating the Prevalence of Tick-Borne Viruses Circulating in Virginia Using a One-Health Approach
    Garba, Ahmed Oladayo (Virginia Tech, 2023-07-03)
    Ticks are hematophagous ectoparasites capable of transmitting various pathogens, including bacteria, protozoa, and viruses, to vertebrates. In the United States, tick-borne pathogens are responsible for around 95% of arthropod-borne diseases. Lyme disease is the most common tick-borne illness. However, emerging tick-borne viruses such as Bourbon virus (BRBV), Powassan virus (POWV), and Heartland virus (HRTV) can cause more severe health problems, including death and neurological abnormalities. The reports of molecular detection of viral RNA in field-collected ticks and serological evidence in a pilot study of wildlife species suggest the presence of these emerging viruses in Virginia. The presence poses a serious health threat, but the extent of their presence or circulation in Virginia is unknown. The objectives of the research are (1) to determine the evidence of circulation of POWV, HRTV, and BRBV in Virginia through serological assessment of domestic and wild animals in Virginia and (2) estimate transmission parameters and the basic reproduction number underlying tick-borne virus distribution and prevalence via a mathematical model. Here, we discuss the known literature relevant to tick-borne virus emergence; we assessed the presence of specific neutralizing antibodies against POWV, HRTV, and BRBV in wildlife and livestock sera collected from different health planning regions in Virginia. We used a susceptible-infected-susceptible (SIS) ordinary differential equation model to estimate transmission parameters that best describe the disease dynamics of emerging tick-borne viruses in Virginia. In our study, wildlife sera were seropositive against POWV (18%), BRBV (8%), and HRTV (5%). A wide range of different wildlife species were shown to be exposed to each virus examined. Livestock are also exposed to tick-borne viruses, with seroprevalences of 1%, 1.2%, and 8% detected in cattle for POWV, BRBV, and HRTV, respectively. We estimated the transmission rate and basic reproduction number to be 1.57 and 0.645, respectively. In conclusion, there is a widespread circulation of tick-borne viruses in western and northern Virginia within diverse species of animal populations.
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    Exploring the ecology of Orthobunyaviruses in Virginia and their pathogenesis in murine and poultry models
    Lopez, Krisangel (Virginia Tech, 2025-01-07)
    Cache Valley virus (CVV) is a vector-borne, negative-sense RNA virus, in the genus orthobunyavirus. Cache Valley Virus is a widespread pathogen in North America, and since its first isolation in 1956, has been associated with multiple epizootics of CVV in ruminants, leading to spontaneous abortions and congenital malformations. As such, CVV is a virus of high economic relevance, but little is known about fundamental aspects of its biology. To address this gap of knowledge, I conducted a series of studies to better understand the pathogenesis and ecology of CVV. This work is divided into two facets; the first is the development of animal models to assess the pathogenesis of CVV in various host species, and the second is vector surveillance to better understand the ecology of orthobunyaviruses within the Commonwealth of Virginia. In the first two chapters, I address the lack of small animal models to study CVV. First, I developed a murine model and an in utero model that mimic the natural progression of disease observed in CVV infection. In the second chapter, I study the growth kinetics of CVV in avian cell lines and in commercial poultry species. In the last chapter, I explore the distribution and diversity of mosquitoes and arthropod-borne viruses in Virginia. Overall, these studies provide insight into CVV pathogenesis and in utero transmission, the role of domestic poultry in the maintenance and amplification of CVV, and lastly, evidence of mosquito species range expansion, and high viral diversity across the Commonwealth of Virginia.
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    First Evidence of Powassan Virus (Flaviviridae) in Ixodes scapularis in Appalachian Virginia, USA
    Cumbie, 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.
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    Genomic Epidemiology of Rift Valley Fever Virus Involved in the 2018 and 2022 Outbreaks in Livestock in Rwanda
    Nsengimana, Isidore; Juma, John; Roesel, Kristina; Gasana, Methode N.; Ndayisenga, Fabrice; Muvunyi, Claude M.; Hakizimana, Emmanuel; Hakizimana, Jean N.; Eastwood, Gillian; Chengula, Augustino A.; Bett, Bernard; Kasanga, Christopher J.; Oyola, Samuel O. (MDPI, 2024-07-17)
    Rift Valley fever (RVF), a mosquito-borne transboundary zoonosis, was first confirmed in Rwanda’s livestock in 2012 and since then sporadic cases have been reported almost every year. In 2018, the country experienced its first large outbreak, which was followed by a second one in 2022. To determine the circulating virus lineages and their ancestral origin, two genome sequences from the 2018 outbreak, and thirty-six, forty-one, and thirty-eight sequences of small (S), medium (M), and large (L) genome segments, respectively, from the 2022 outbreak were generated. All of the samples from the 2022 outbreak were collected from slaughterhouses. Both maximum likelihood and Bayesian-based phylogenetic analyses were performed. The findings showed that RVF viruses belonging to a single lineage, C, were circulating during the two outbreaks, and shared a recent common ancestor with RVF viruses isolated in Uganda between 2016 and 2019, and were also linked to the 2006/2007 largest East Africa RVF outbreak reported in Kenya, Tanzania, and Somalia. Alongside the wild-type viruses, genetic evidence of the RVFV Clone 13 vaccine strain was found in slaughterhouse animals, demonstrating a possible occupational risk of exposure with unknown outcome for people working in meat-related industry. These results provide additional evidence of the ongoing wide spread of RVFV lineage C in Africa and emphasize the need for an effective national and international One Health-based collaborative approach in responding to RVF emergencies.
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    Identification of Potential Vectors and Detection of Rift Valley Fever Virus in Mosquitoes Collected Before and During the 2022 Outbreak in Rwanda
    Nsengimana, Isidore; Hakizimana, Emmanuel; Mupfasoni, Jackie; Hakizimana, Jean Nepomuscene; Chengula, Augustino A.; Kasanga, Christopher J.; Eastwood, Gillian (MDPI, 2025-01-08)
    Rift Valley fever virus (RVFV) is an emerging mosquito-borne arbovirus of One Health importance that caused two large outbreaks in Rwanda in 2018 and 2022. Information on vector species with a role in RVFV eco-epidemiology in Rwanda is scarce. Here we sought to identify potential mosquito vectors of RVFV in Rwanda, their distribution and abundance, as well as their infection status. Since an outbreak of RVF occurred during the study period, data were obtained both during an interepidemic period and during the 2022 Rwanda RVF outbreak. Five districts of the eastern province of Rwanda were prospected using a combination of unbaited light traps and Biogents (BG Sentinel and Pro) traps baited with an artificial human scent during three periods, namely mid-August to mid-September 2021, December 2021, and April to May 2022. Trapped mosquitoes were morphologically identified and tested for viral evidence using both RT-PCR and virus isolation methods on a Vero cell line. A total of 14,815 adult mosquitoes belonging to five genera and at least 17 species were collected and tested as 765 monospecific pools. Culex quinquefasciatus was the most predominant species representing 72.7% of total counts. Of 527 mosquito pools collected before the 2022 outbreak, a single pool of Cx. quinquefasciatus showed evidence of RVFV RNA. Of 238 pools collected during the outbreak, RVFV was detected molecularly from five pools (two pools of Cx. quinquefasciatus, two pools of Anopheles ziemanni, and one pool of Anopheles gambiae sensu lato), and RVFV was isolated from the two pools of Cx. quinquefasciatus, from Kayonza and Rwamagana districts, respectively. Minimum infection rates (per 1000 mosquitoes) of 0.4 before the outbreak and 0.6–7 during the outbreak were noted. Maximum-likelihood phylogenetic analysis indicates that RVFV detected in these mosquitoes is closely related to viral strains that circulated in livestock in Rwanda and in Burundi during the same RVF outbreak in 2022. The findings reveal initial evidence for the incrimination of several mosquito species in the transmission of RVFV in Rwanda and highlight the need for more studies to understand the role of each species in supporting the spread and persistence of RVFV in the country.
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    The Influence of Southwestern Virginia Environmental Conditions on the Potential Ability of Haemaphysalis longicornis, Amblyomma americanum, and Amblyomma maculatum to Overwinter in the Region
    Whitlow, Amanda Marie; Schürch, Roger; Mullins, Donald E.; Eastwood, Gillian (MDPI, 2021-11-06)
    Ticks are susceptible to environmental conditions and, to ensure survival during winter conditions, they adopt a wide variety of physiological and behavioral adaptations including utilization of a suitable niche with insulation (e.g., leaf coverage). To investigate the potential overwintering survival of three tick populations emerging within Appalachian Virginia (Haemaphysalis longicornis, Amblyomma americanum, and Amblyomma maculatum), both a laboratory experiment assessing super-cooling points and a two-factor (elevation and insulation coverage) field experiment assessing overwintering survivability were conducted across a natural southwestern Virginian winter (2020–2021). Dermacentor variabilis adults were included in this study as an example of a well-established species in this region known to overwinter in these conditions. Our study indicated that A. americanum and H. longicornis wintering tolerance is based on life stage rather than external factors such as insulation (e.g., leaf litter) and elevation. Amblyomma maculatum was more likely to survive without insulation. The ability to withstand the extreme temperatures of new regions is a key factor determining the survivability of novel tick species and is useful in assessing the invasion potential of arthropod vectors.
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    La Crosse Virus Circulation in Virginia, Assessed via Serosurveillance in Wildlife Species
    Faw, Lindsey R.; Riley, Jennifer; Eastwood, Gillian (MDPI, 2023-06-30)
    Mosquito-borne La Crosse virus (LACV; family: Peribunyaviridae) is the leading cause of pediatric arboviral encephalitis in the United States, with clinical cases generally centered in the Midwest and Appalachian regions. Incidence of LACV cases in Appalachian states has increased, such that the region currently represents the majority of reported LACV cases in the USA. The amount of reported LACV cases from Virginia, however, is minimal compared to neighboring states such as North Carolina, West Virginia, and Tennessee, and non-Appalachian regions of Virginia are understudied. Here we examine the hypothesis that LACV is circulating widely in Virginia, despite a low clinical case report rate, and that the virus is circulating in areas not associated with LACV disease. In this study, we screened local mammalian wildlife in northwestern counties of Virginia using passive surveillance via patients submitted to wildlife rehabilitation centers. Blood sera (527 samples; 9 species, 8 genera) collected between October 2019 and December 2022 were screened for neutralizing antibodies against LACV, indicating prior exposure to the virus. We found an overall LACV seroprevalence of 1.90% among all wild mammals examined and reveal evidence of LACV exposure in several wild species not generally associated with LACV, including eastern cottontails and red foxes, along with established reservoirs, eastern gray squirrels, although there was no serological evidence in chipmunks. These data indicate the circulation of LACV in Virginia outside of Appalachian counties, however, at a lower rate than reported for endemic areas within the state and in other states.
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    La Crosse Virus Shows Strain-Specific Differences in Pathogenesis
    Wilson, Sarah N.; López, Krisangel; Coutermarsh-Ott, Sheryl; Auguste, Dawn I.; Porier, Danielle L.; Armstrong, Philip M.; Andreadis, Theodore G.; Eastwood, Gillian; Auguste, A. Jonathan (MDPI, 2021-03-29)
    La Crosse virus (LACV) is the leading cause of pediatric viral encephalitis in North America, and is an important public health pathogen. Historically, studies involving LACV pathogenesis have focused on lineage I strains, but no former work has explored the pathogenesis between or within lineages. Given the absence of LACV disease in endemic regions where a robust entomological risk exists, we hypothesize that some LACV strains are attenuated and demonstrate reduced neuroinvasiveness. Herein, we compared four viral strains representing all three lineages to determine differences in neurovirulence or neuroinvasiveness using three murine models. A representative strain from lineage I was shown to be the most lethal, causing >50% mortality in each of the three mouse studies. However, other strains only presented excessive mortality (>50%) within the suckling mouse neurovirulence model. Neurovirulence was comparable among strains, but viruses differed in their neuroinvasive capacities. Our studies also showed that viruses within lineage III vary in pathogenesis with contemporaneous strains, showing reduced neuroinvasiveness compared to an ancestral strain from the same U.S. state (i.e., Connecticut). These findings demonstrate that LACV strains differ markedly in pathogenesis, and that strain selection is important for assessing vaccine and therapeutic efficacies.
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    Local persistence of novel regional variants of La Crosse virus in the Northeast USA
    Eastwood, Gillian; Shepard, John J.; Misencik, Michael J.; Andreadis, Theodore G.; Armstrong, Philip M. (2020-11-11)
    Background La Crosse virus (LACV) (genus Orthobunyavirus, family Peribunyaviridae) is a mosquito-borne virus that causes pediatric encephalitis and accounts for 50–150 human cases annually in the USA. Human cases occur primarily in the Midwest and Appalachian regions whereas documented human cases occur very rarely in the northeastern USA. Methods Following detection of a LACV isolate from a field-collected mosquito in Connecticut during 2005, we evaluated the prevalence of LACV infection in local mosquito populations and genetically characterized virus isolates to determine whether the virus is maintained focally in this region. Results During 2018, we detected LACV in multiple species of mosquitoes, including those not previously associated with the virus. We also evaluated the phylogenetic relationship of LACV strains isolated from 2005–2018 in Connecticut and found that they formed a genetically homogeneous clade that was most similar to strains from New York State. Conclusion Our analysis argues for local isolation and long-term persistence of a genetically distinct lineage of LACV within this region. We highlight the need to determine more about the phenotypic behavior of these isolates, and whether this virus lineage poses a threat to public health.
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    Pathogen Spillover to an Invasive Tick Species: First Detection of Bourbon Virus in Haemaphysalis longicornis in the United States
    Cumbie, 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.
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    Phylogenetic characterization of Orthobunyaviruses isolated from Trinidad shows evidence of natural reassortment
    Foster, Jerome E.; Lopez, Krisangel; Eastwood, Gillian; Guzman, Hilda; Carrington, Christine V. F.; Tesh, Robert B.; Auguste, A. Jonathan (Springer, 2023-02)
    The genus Orthobunyavirus is a diverse group of viruses in the family Peribunyaviridae, recently classified into 20 serogroups, and 103 virus species. Although most viruses within these serogroups are phylogenetically distinct, the absence of complete genome sequences has left several viruses incompletely characterized. Here we report the complete genome sequences for 11 orthobunyaviruses isolated from Trinidad, French Guiana, Guatemala, and Panama that were serologically classified into six serogroups and 10 species. Phylogenetic analyses of these 11 newly derived sequences indicate that viruses belonging to the Patois, Capim, Guama, and Group C serocomplexes all have a close genetic origin. We show that three of the 11 orthobunyaviruses characterized (belonging to the Group C and Bunyamwera serogroups) have evidence of histories of natural reassortment through the M genome segment. Our data also suggests that two distinct lineages of Group C viruses concurrently circulate in Trinidad and are transmitted by the same mosquito vectors. This study also highlights the importance of complementing serological identification with nucleotide sequencing when characterizing orthobunyaviruses.
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    The potential health impact of ivermectin mass drug administration for malaria control on swine in Mozambique
    Assenga, Alphonce Alexander (Virginia Tech, 2023-01-23)
    BACKGROUND: Both endo- and ectoparasites pose a great challenge to the health of pigs worldwide, placing a significant burden on low-resource countries where veterinary care is minimal. As part of a larger clinical trial assessing the use of ivermectin (IVM) mass drug administration to humans and pigs for the control of malaria vectors in the Mopeia district in Mozambique, a longitudinal study to assess the impact of IVM administration on pig health was performed. METHODS: Beginning in March 2022, IVM was administered to pigs in the intervention area once a month for three consecutive months. Seventy pigs from the treatment group and 70 pigs from the control group were randomly selected for inclusion in the study. Fecal samples were collected monthly for three months and analyzed for the presence of strongyle eggs, strongyle eggs in the larval stage (strongyles – larval) and Ascaris suum using the modified McMaster test. Fecal samples were also collected two weeks after each dose of IVM was given to pigs in the treatment group for determination of a fecal egg reduction count. Juvenile pigs were measured twice a month for the first 3 months of the study, then once monthly for another three months. Visual exam for ectoparasites was performed on all pigs for the presence of ticks, lice or scabies at the same time points. RESULTS: Overall, 55% [95% CI: 48-62%] of pigs were positive for Ascaris suum, 95.2% [95% CI: 91-98%] were positive for strongyle eggs, and 72.5% [95% CI: 65.5-79%] were positive for strongyle – larval. A significant difference in the ivermectin treatment group was only seen one month after the second dose of ivermectin was administered: pigs in the treatment group had a 23.6% lower prevalence of strongyles (p = 0.003) and 18% lower prevalence of strongyles – larval (p = 0.03). Pigs in the treatment group also had lower EPG for Ascaris suum (diff = 102 EPG; p = 0.006), strongyles (diff = 642 EPG; p < 0.001), and strongyles - larval (diff = 217 EPG; p < 0.001). Analysis of covariance regression found no significant difference(P>0.05) in average daily weight gain (ADG) between the treatment and control groups. CONCLUSION: IVM delivered once monthly for three months has a small impact on pig health. To counteract the multiple health challenges pigs face in these settings, different dosing schedules along with education on husbandry issues related to nutrition and sanitation should be investigated in order to maximize impact on pig health.
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    Potentially zoonotic gastrointestinal nematodes co-infecting free ranging non-human primates in Kenyan urban centres
    Mbuthia, Peris; Murungi, Edwin; Owino, Vincent; Akinyi, Mercy; Eastwood, Gillian; Nyamota, Richard; Lekolool, Isaac; Jeneby, Maamun (2021-01)
    Background: Natural infections with soil-transmitted nematodes occur in non-human primates (NHPs) and have the potential to cross primate-species boundaries and cause diseases of significant public health concern. Despite the presence of NHPs in most urban centres in Kenya, comprehensive studies on their gastrointestinal parasites are scant. Objective: Conduct a cross-sectional survey to identify zoonotic nematodes in free-ranging NHPs found within four selected urban and peri-urban centres in Kenya. Methods: A total of 86 NHPs: 41 African green monkeys [AGMs] (Chlorocebus aethiops), 30 olive baboons (Papio anubis), 5 blue monkeys (Cercopithecus mitis stuhlmanni) and 10 red-tailed monkeys (Cercopithecus ascanius) were sampled once in situ and released back to their habitat. Microscopy was used to identify nematodes egg and larvae stages in the samples. Subsequently, PCR coupled with high-resolution melting (PCR-HRM) analysis and sequencing were used to identify nodule worms. Results: NHPs inhabiting densely populated urban environs in Kenya were found infected with a rich diversity of nematodes including three potentially zoonotic nematodes including Oesophagostomum stephanostomum, Oesophagostomum bifurcum and Trichostrongylus colubriformis and co-infections were common. Conclusion: Phylogenetic analysis showed that O. stephanostomum from red-tailed and blue monkeys have a close evolutionary relatedness to human isolates suggesting the zoonotic potential of this parasite. Moreover, we also report the first natural co-infection of O. bifurcum and O. stephanostomum in free-ranging AGMs.
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    Prevalence and Associated Risk Factors of African Animal Trypanosomiasis in Cattle in Lambwe, Kenya
    Okello, Ivy; Mafie, Eliakunda; Eastwood, Gillian; Nzalawahe, Jahashi; Mboera, Leonard E. G.; Onyoyo, Samuel (Hindawi, 2022-07-14)
    Background. African animal trypanosomiasis (AAT) affects livestock productivity in sub-Saharan Africa. This study aimed to determine cattle AAT’s prevalence and associated risk factors in Lambwe Valley, Kenya. Methods. In a cross-sectional survey, livestock owners were recruited from four villages of Lambwe in Homa Bay, Kenya. Blood samples were collected from the jugular veins of cattle, and buffy coat smears were examined under a microscope. Parasites were further detected using polymerase chain reaction (PCR). Using a semistructured questionnaire, livestock owners were interviewed on their knowledge of AAT and control practices. Chi-square and multilevel models were used for the analysis. Results. The overall prevalence was 15.63% (71/454). Trypanosoma vivax 10.31% and T. congolense Savannah 6.01% were the common species and subspecies. A total of 61 livestock keepers were involved in the study. Of these, 91.80% (56/61) knew AAT, and 90.16% (55/61) could describe the symptoms well and knew tsetse fly bite as transmission mode. Self-treatment (54.09%; 33/61) was common, with up to 50.00% of the farmers using drugs frequently. Isometamidium (72.13%; 44/61) and diminazene (54.09%; 33/61) were drugs frequently used. Although 16.39% (10/61) of the farmers claimed to use chemoprophylactic treatment, 6/10 did not use the right drugs. Animals (92.1%; 58/63) with clinical signs had positive infections. Villages closer to the national park recorded a higher prevalence. Infections were higher in cattle owned by those self-treating (27.23%; 58/213), those using drug treatment without vector control (27.62%; 50/181), those using single-drug therapy, and those practicing communal grazing (20.00%; 59/295). Clinical signs strongly associate with positive infections under multilevel modeling. Conclusion. Cattle trypanosomiasis is prevalent in the Lambwe region of Kenya. This is influenced by inappropriate control practices, communal grazing, and the proximity of farms to the national park. In addition, clinical signs of the disease have a strong association with infections.