Surveillance for Selected Pathogens and Parasites of Northern Bobwhite (Colinus virginianus) from Western Oklahoma, USA, 2018-20

The Northern Bobwhite (Colinus virginianus) has been undergoing a range-wide population decline. Potential causes for declines across its historic range have been investigated for decades and include habitat loss and fragmentation and a variety of parasitic and infectious diseases. Although there have been studies on bobwhite ecology in Oklahoma, USA, relatively little is known about parasites and pathogens in the region. We evaluated the health of free-ranging bobwhites from nine sites in western Oklahoma. From 2018 to 2020, 206 bobwhites were evaluated for gross and microscopic lesions and tested for selected pathogens. In general, bobwhites were in good nutritional condition with ample muscle mass and fat stores. No significant gross lesions were observed in any bobwhite and no significant histologic lesions were detected in a subset. There was no evidence of infection with or exposure to reticuloendotheliosis virus, West Nile virus, respiratory Mycoplasmataceae species, Pasteurella multocida, intestinal Eimeria spp., or oral Trichomonas spp. Several pathogens of potential concern were detected, including avian adenovirus (8.6%), Toxoplasma gondii (2.3%), and haemosporidians (a Haemoproteus sp. (1.5%), Leucocytozoon schoutedeni (1.5%), and Plasmodium homopolare haplotype 2 [lineage LAIRI01; 3.6%]). Physaloptera sp. (12%) and Sarcocystis sp. (1%) were detected in the breast muscle. Low intraspecific genetic diversity was noted for Physaloptera sp., and sequences were most similar to Physaloptera sequences from bobwhites and grasshoppers (Orthoptera) in Texas. Low intensities of chewing lice, chiggers, and ticks were observed. A subset of bobwhites had evidence of exposure to selected toxicants and heavy metals; a small number had low levels of iron, manganese, zinc, molybdenum, and copper, which were not considered diagnostically relevant. In general, bobwhites from western Oklahoma appeared to be in good health with a low diversity of pathogens detected, but future work is needed to understand potentially changing disease risks for this population.

Lymphoproliferative Disease Virus and Reticuloendotheliosis Virus Detection and Disease in Wild Turkeys (Meleagris gallopavo)

Lymphoproliferative disease virus (LPDV) and reticuloendotheliosis virus (REV) are oncogenic retroviruses that can cause disease in wild and domestic fowl. Lymphoproliferative disease virus infections are common and widespread in Wild Turkeys (Meleagris gallopavo) in the US and east-central Canada, while REV has been detected worldwide in numerous avian host species. We tested tissues (spleen, liver, and/or bone marrow, plus neoplastic tissue, if present) from 172 Wild Turkeys that underwent necropsy from December 2018 through October 2021 for both viruses using PCR. We evaluated demographic, geographic, temporal, and seasonal data by chi-square test of independence and logistic regression for turkeys infected with LPDV and/or REV. At least one of these retroviruses was detected in 80.8% (139/172) of Wild Turkeys from 15 US states, with significantly more turkeys being positive for LPDV (72.1%, 124/172) versus REV (43.6%, 75/172; P<0.001). Both viruses (coinfections) were detected in 34.9% (60/172) of turkeys. Among LPDV-infected turkeys (including coinfections), bone marrow had the highest detection rate (38/58, 65.5%), significantly higher than spleen (30/58, 51.7%) and liver (20/58, 34.5%; P<0.001). In REV-infected turkeys, bone marrow had the highest detection rate (24/58, 41.4%). All three tissues (spleen, liver, bone marrow) concurrently tested positive in most (15/25, 60%) REV-infected turkeys. These results suggest LPDV tissue tropism for bone marrow, whereas REV may have broader tissue tropism. Histopathology consistent with lymphoid proliferation and/or neoplasia characteristic of lymphoproliferative disease was evident in 29/172 (16.9%) turkeys assessed, including two REV-only-infected turkeys. Season was significantly associated with LPDV prevalence (highest in winter); year and season were both significantly associated with REV prevalence (highest in 2020 and winter). These data contribute to optimizing diagnostic strategies that may aid in pathogen monitoring and improve detections to increase our understanding of the potential impacts of these viruses on Wild Turkey populations.

Storage time and temperature of filter paper strips affect anti-West Nile virus antibody detection in 2 galliform species

The effects of filter paper strip (FPS) storage time and temperature on antibody detection are poorly understood despite widespread use in wildlife research. We collected sera and FPSs from 23 wild turkeys (Meleagris gallopavo) and 20 northern bobwhites (Colinus virginianus) experimentally infected with West Nile virus (WNV) to compare FPS storage methods with WNV plaque reduction neutralization test (PRNT) sensitivity. FPS storage methods included: immediate elution after drying, and storage at -20°C for 3 mo, -20°C for 6 mo, room temperature (RT) for 3 mo, and RT for 6 mo prior to elution. FPS eluates and sera were co-titrated to determine endpoint antibody titers, which were compared between FPS sera eluted immediately and sera, and among FPS eluates that underwent different storage conditions. Antibody titers were ~4-fold less in FPS sera eluted immediately versus sera, and dropped more frequently below PRNT detection threshold in northern bobwhites, which had ~10-fold lower serum antibody titers than wild turkeys. Antibody titers were lower in FPS samples stored at RT and for 6 mo. WNV serologic surveys may result in falsely low seroprevalence estimates if FPSs are stored at RT for ≥ 3 mo before elution.

Vector communities under global change may exacerbate and redistribute infectious disease risk

Vector-borne parasites may be transmitted by multiple vector species, resulting in an increased risk of transmission, potentially at larger spatial scales compared to any single vector species. Additionally, the different abilities of patchily distributed vector species to acquire and transmit parasites will lead to varying degrees of transmission risk. Investigation of how vector community composition and parasite transmission change over space due to variation in environmental conditions may help to explain current patterns in diseases but also informs our understanding of how patterns will change under climate and land-use change. We developed a novel statistical approach using a multi-year, spatially extensive case study involving a vector-borne virus affecting white-tailed deer transmitted by Culicoides midges. We characterized the structure of vector communities, established the ecological gradient controlling change in structure, and related the ecology and structure to the amount of disease reporting observed in host populations. We found that vector species largely occur and replace each other as groups, rather than individual species. Moreover, community structure is primarily controlled by temperature ranges, with certain communities being consistently associated with high levels of disease reporting. These communities are essentially composed of species previously undocumented as potential vectors, whereas communities containing putative vector species were largely associated with low levels, or even absence, of disease reporting. We contend that the application of metacommunity ecology to vector-borne infectious disease ecology can greatly aid the identification of transmission hotspots and an understanding of the ecological drivers of parasite transmission risk both now and in the future.

Multi-Year Comparison of Community- and Species-Level West Nile Virus Antibody Prevalence in Birds from Atlanta, Georgia and Chicago, Illinois, 2005-2016

West Nile virus (WNV) is prevalent in the United States but shows considerable variation in transmission intensity. The purpose of this study was to compare patterns of WNV seroprevalence in avian communities sampled in Atlanta, Georgia and Chicago, Illinois during a 12-year period (Atlanta 2010-2016; Chicago 2005-2012) to reveal regional patterns of zoonotic activity of WNV. WNV antibodies were measured in wild bird sera using ELISA and serum neutralization methods, and seroprevalence among species, year, and location of sampling within each city were compared using binomial-distributed generalized linear mixed-effects models. Seroprevalence was highest in year-round and summer-resident species compared with migrants regardless of region; species explained more variance in seroprevalence within each city. Northern cardinals were the species most likely to test positive for WNV in each city, whereas all other species, on average, tested positive for WNV in proportion to their sample size. Despite similar patterns of seroprevalence among species, overall seroprevalence was higher in Atlanta (13.7%) than in Chicago (5%). Location and year of sampling had minor effects, with location explaining more variation in Atlanta and year explaining more variation in Chicago. Our findings highlight the nature and magnitude of regional differences in WNV urban ecology.

North American Arboviruses and White-Tailed Deer (Odocoileus virginianus): Associated Diseases and Role in Transmission

Background: Arboviral disease is of increasing concern to human and animal health professionals as emerging and re-emerging arboviruses are more frequently recognized. Wildlife species are known to play a role in the transmission and maintenance of arboviruses and infections can result in morbidity and mortality in wildlife hosts. Materials and Methods: In this review, we detail existing evidence of white-tailed deer (Odocoileus virginianus) as an important host to a diverse collection of arboviruses and evaluate the utility of this species as a resource to better understand the epidemiology of related viral diseases. Results: Relevant veterinary and zoonotic viral pathogens endemic to North America include epizootic hemorrhagic disease virus, bluetongue virus, orthobunyaviruses, vesicular stomatitis virus, Eastern equine encephalitis virus, West Nile virus, and Powassan virus. Exotic viral pathogens that may infect white-tailed deer are also identified with an emphasis on zoonotic disease risks. The utility of this species is attributed to the high degree of contact with humans and domestic livestock and evidence of preferential feeding by various insect vectors. Conclusions: There is mounting evidence that white-tailed deer are a useful, widely available source of information regarding arboviral circulation, and that surveillance and monitoring of deer populations would be of value to the understanding of certain viral transmission dynamics, with implications for improving human and domestic animal health.

Cell surface glycan engineering reveals that matriglycan alone can recapitulate dystroglycan binding and function

α-Dystroglycan (α-DG) is uniquely modified on O-mannose sites by a repeating disaccharide (-Xylα1,3-GlcAβ1,3-)_n termed matriglycan, which is a receptor for laminin-G domain-containing proteins and employed by old-world arenaviruses for infection. Using chemoenzymatically synthesized matriglycans printed as a microarray, we demonstrate length-dependent binding to Laminin, Lassa virus GP1, and the clinically-important antibody IIH6. Utilizing an enzymatic engineering approach, an N-linked glycoprotein was converted into a IIH6-positive Laminin-binding glycoprotein. Engineering of the surface of cells deficient for either α-DG or O-mannosylation with matriglycans of sufficient length recovers infection with a Lassa-pseudovirus. Finally, free matriglycan in a dose and length dependent manner inhibits viral infection of wildtype cells. These results indicate that matriglycan alone is necessary and sufficient for IIH6 staining, Laminin and LASV GP1 binding, and Lassa-pseudovirus infection and support a model in which it is a tunable receptor for which increasing chain length enhances ligand-binding capacity.

Experimental Susceptibility of North American Raccoons (Procyon lotor) and Striped Skunks (Mephitis mephitis) to SARS-CoV-2

Recent spillback events of SARS-CoV-2 from humans to animals has raised concerns about it becoming endemic in wildlife. A sylvatic cycle of SARS-CoV-2 could present multiple opportunities for repeated spillback into human populations and other susceptible wildlife. Based on their taxonomy and natural history, two native North American wildlife species -the striped skunk (Mephitis mephitis) and the raccoon (Procyon lotor) -represent a high likelihood of susceptibility and ecological opportunity of becoming infected with SARS-CoV-2. Eight skunks and raccoons were each intranasally inoculated with one of two doses of the virus (103 PFU and 105 PFU) and housed in pairs. To evaluate direct transmission, a naïve animal was added to each inoculated pair 48 h post-inoculation. Four control animals of each species were handled like the experimental groups. At predetermined intervals, we collected nasal and rectal swabs to quantify virus shed via virus isolation and detect viral RNA via rRT-PCR and blood for serum neutralization. Lastly, animals were euthanized at staggered intervals to describe disease progression through histopathology and immunohistochemistry. No animals developed clinical disease. All intranasally inoculated animals seroconverted, suggesting both species are susceptible to SARS-CoV-2 infection. The highest titers in skunks and raccoons were 1:128 and 1:64, respectively. Low quantities of virus were isolated from 2/8 inoculated skunks for up to day 5 post-inoculation, however no virus was isolated from inoculated raccoons or direct contacts of either species. Neither species had gross lesions, but recovering mild chronic pneumonia consistent with viral insult was recorded histologically in 5/8 inoculated skunks. Unlike another SARS-CoV-2 infection trial in these species, we detected neutralizing antibodies in inoculated raccoons; thus, future wildlife serologic surveillance results must be interpreted with caution. Due to the inability to isolate virus from raccoons, the lack of evidence of direct transmission between both species, and low amount of virus shed by skunks, it seems unlikely for SARS-CoV-2 to become established in raccoon and skunk populations and for virus to spillback into humans. Continued outbreaks in non-domestic species, wild and captive, highlight that additional research on the susceptibility of SARS-CoV-2 in wildlife, especially musteloidea, and of conservation concern, is needed.

Experimental Infection of Domestic Piglets (Sus scrofa) with Rift Valley Fever Virus

Rift Valley fever phlebovirus (RVFV) is a mosquito-transmitted phlebovirus (Family: Phenuiviridae, Order: Bunyavirales) causing severe neonatal mortality and abortion primarily in domestic ruminants. The susceptibility of young domestic swine to RVFV and this species' role in geographic expansion and establishment of viral endemicity is unclear. Six commercially bred Landrace-cross piglets were inoculated subcutaneously with 105 plaque-forming units of RVFV ZH501 strain and two piglets received a sham inoculum. All animals were monitored for clinical signs, viremia, viral shedding, and antibody response for 14 days. Piglets did not develop evidence of clinical disease, become febrile, or experience decreased weight gain during the study period. A brief lymphopenia followed by progressive lymphocytosis was observed following inoculation in all piglets. Four piglets developed a brief viremia for 2 days post-inoculation and three of these had detectable virus in oronasal secretions three days post-inoculation. Primary inoculated piglets seroconverted and those that developed detectable viremias had the highest titers assessed by serum neutralization (1:64-1:256). Two viremic piglets had a lymphoplasmacytic encephalitis with glial nodules; RVFV was not detected by immunohistochemistry in these sections. While young piglets do not appear to readily develop clinical disease following RVFV infection, results suggest swine could be subclinically infected with RVFV.

Serologic Evidence of Arthropod-Borne Virus Infections in Wild and Captive Ruminants in Ontario, Canada

Arthropod-borne viruses (arboviruses) are globally widespread, and their transmission cycles typically involve numerous vertebrate species. Serologic testing of animal hosts can provide a routine surveillance approach to monitoring animal disease systems, can provide a surveillance alternative to arthropod testing and human case reports, and may augment knowledge of epizootiology. Wild and captive ruminants represent good candidate sentinels to track geographic distribution and prevalence of select arboviruses. They often are geographically widespread and abundant, inhabit areas shared by humans and domestic animals, and are readily fed on by various hematophagous arthropod vectors. Ontario, Canada, is home to high densities of coexisting humans, livestock, and wild cervids, as well as growing numbers of arthropod vectors because of the effects of climate change. We collected blood samples from 349 livestock (cattle/sheep) and 217 cervids (wild/farmed/zoo) in Ontario (2016-2019) to assess for antibodies to zoonotic and agriculturally important arboviruses. Livestock sera were tested for antibodies to bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV). Sera from cervids were tested for antibodies to BTV, EHDV, West Nile virus (WNV), eastern equine encephalitis virus (EEEV), Powassan virus (POWV), and heartland virus (HRTV). Fifteen (9.0%) cattle were seropositive for EHDV-serotype 2. Nine (4.2%) cervids were seropositive for arboviruses; three confirmed as WNV, three as EEEV, and one as POWV. All animals were seronegative for BTV and HRTV. These results reveal low seroprevalence of important agricultural, wildlife, and zoonotic pathogens and underline the need for continued surveillance in this and other regions in the face of changing environmental conditions.

An Embryonated Egg Transmission Model for Epizootic Hemorrhagic Disease Virus

Epizootic hemorrhagic disease virus (EHDV) is a vector-borne orbivirus of ruminants; in North America there are three serotypes (EHDV-1, -2, and -6) and these primarily affect white-tailed deer (Odocoilus virginianus). EHDV is vectored by biting midges, Culicoides spp. Embryonated chicken eggs (ECE) have recently been used as an experimental host to investigate the vector competence of Australian Culicoides spp. for bluetongue serotype virus 1 and 23. In this study, we evaluated the use of the ECE model to determine its applicability for evaluating vector competence related to transmission of North American EHDV serotypes. We demonstrated that all three North American EHDV serotypes were able to replicate in ECEs and be transmitted from infected ECEs to Culicoides sonorensis Wirth & Jones. In addition, we were able to complete the transmission cycle from infected C. sonorensis to uninfected ECEs for EHDV-1 and -2.

Terrestrial Bird Migration and West Nile Virus Circulation, United States

Host migration and emerging pathogens are strongly associated, especially with regard to zoonotic diseases. West Nile virus (WNV), a mosquitoborne pathogen capable of causing severe, sometimes fatal, neuroinvasive disease in humans, is maintained in highly mobile avian hosts. Using phylogeographic approaches, we investigated the relationship between WNV circulation in the United States and the flight paths of terrestrial birds. We demonstrated southward migration of WNV in the eastern flyway and northward migration in the central flyway, which is consistent with the looped flight paths of many terrestrial birds. We also identified 3 optimal locations for targeted WNV surveillance campaigns in the United States—Illinois, New York, and Texas. These results illustrate the value of multidisciplinary approaches to surveillance of infectious diseases, especially zoonotic diseases.

Larviciding Culex spp. (Diptera: Culicidae) Populations in Catch Basins and Its Impact on West Nile Virus Transmission in Urban Parks in Atlanta, GA

In urban environments, road-side catch basins are common larval habitats of Culex spp. (Diptera: Culicidae) mosquitoes and important targets of larval control in areas subject to West Nile virus (WNv) transmission. We quantified the impact of larviciding basins on Culex spp. populations and WNv infection prevalence by treating basins in and around urban parks in Atlanta, GA, using Mosquito Dunks and Bits (active ingredient, a.i., Bacillus thuringiensis subsp. isrealensis, Dunks-10.31%, Bits-2.86%) and Altosid 30-Day Briquets (a.i., S-methoprene 8.62%) in two separate seasons. Treatments were coupled with WNv surveillance using gravid traps and aspiration of adults resting in basins. Larviciding led to >90% reductions in Culex spp. larval and pupal collections (Dunks/Bits) and >90% pupal mortality (Briquets) in treated sites during treatment periods; however, we did not observe significant reductions in Culex spp. collections in gravid traps (general linear mixed-effects model [GLMM] result, P > 0.1) or in adults collected resting in basins (GLMM, P > 0.5). In addition, WNv infection prevalence in Culex spp. mosquitoes was similar between treated and untreated sites (GLMM, P > 0.05). Larval control remains important for controlling WNv in Atlanta; however, at the scale and frequency applied in our study, larval control alone may not lead to meaningful reductions in adult populations and WNv infection prevalence. A greater understanding of the annual dynamics of Culex spp. breeding and the importance of basins as Culex spp. larval habitats are needed to meaningfully affect WNv in cities such as Atlanta.

Heartland Virus Exposure in White-Tailed Deer in the Southeastern United States, 2001-2015

Heartland virus (HRTV) is a North American phlebovirus suspected to be transmitted by the lone star tick Amblyomma americanum. White-tailed deer (WTD) have been shown to develop HRTV-neutralizing antibodies following experimental infection. To further define the geographic distribution of HRTV through retrospective sampling of WTD, sera from the WTD herd health serum archive at the Southeastern Cooperative Wildlife Disease Study between 2001 and 2015 were analyzed using serum neutralization. Of 783 serum samples tested, 57 (7.3%) were positive for HRTV-neutralizing antibodies. Deer with moderate to heavy tick burdens were more likely seropositive. Seropositive samples were obtained from deer originating from states with documented human cases of HRTV-associated disease. Seropositive samples were identified from years before the recognition of the first human case in 2009. Overall, this study indicates that WTD in the southeastern United States have been exposed to HRTV as early as 2001 and that the presence of seropositive animals corresponds roughly with reported human HRTV-associated disease.

Evidence for West Nile virus spillover into the squirrel population in Atlanta, Georgia

BACKGROUND

In the United States, spillover of West Nile virus (WNV) into wild mammal populations has been reported since the introduction of the virus into the New World in 1999. Eastern gray squirrels (Sciurus carolinensis) exhibit a high seroprevalence for WNV in urban settings where high virus circulation and human spillover have been reported. In Atlanta, Georgia, human cases of WNV are uncommon despite high infection rates in birds and mosquitoes. In this study, we evaluated WNV exposure of eastern gray squirrels in a WNV hot spot in Atlanta.

MATERIALS AND METHODS

Gray squirrels were live-trapped in Grant Park, Atlanta, during July-October, 2012, and a census was conducted to estimate squirrel density in the study site. Sera from trapped animals were tested for circulating virus-by-virus isolation in cell culture and for WNV-specific antibodies by enzyme-linked immunosorbent assay and plaque reduction neutralization test. Mosquitoes were collected at the same location and tested for virus isolation.

RESULTS

Among the 69 collected squirrels, 25 (36.2%) tested positive for WNV antibodies, although none were viremic. Seroprevalence was lower in juveniles (18.8%) than in adults (37.5%), but this difference was not statistically significant. Gender and squirrel density had no effect on seroprevalence. Seasonality of squirrel seroprevalence and of mosquito infection were significantly associated, both peaking in August. No difference in squirrel exposure was detected across the collection sites.

CONCLUSIONS

We report a high degree of WNV exposure in squirrels in Grant Park that was correlated with seasonality of mosquito infection. The detection of antibodies in juveniles suggests that circulation of WNV in the surveyed population is ongoing. Eastern gray squirrels may be suitable indicators for virus amplification and for risk of human spillover on a local scale in urban settings.

Avian species diversity and transmission of West Nile virus in Atlanta, Georgia

Background

The dilution effect is the reduction in vector-borne pathogen transmission associated with the presence of diverse potential host species, some of which are incompetent. It is popularized as the notion that increased biodiversity leads to decreased rates of disease. West Nile virus (WNV) is an endemic mosquito-borne virus in the United States that is maintained in a zoonotic cycle involving various avian host species. In Atlanta, Georgia, substantial WNV presence in the vector and host species has not translated into a high number of human cases.

Methods

To determine whether a dilution effect was contributing to this reduced transmission, we characterized the host species community composition and performed WNV surveillance of hosts and vectors in urban Atlanta between 2010 and 2011. We tested the relationship between host diversity and both host seroprevalence and vector infection rates using a negative binomial generalized linear mixed model.

Results

Regardless of how we measured host diversity or whether we considered host seroprevalence and vector infection rates as predictor variables or outcome variables, we did not detect a dilution effect. Rather, we detected an amplification effect, in which increased host diversity resulted in increased seroprevalence or infection rates; this is the first empirical evidence for this effect in a mosquito-borne system.

Conclusions

We suggest that this effect may be driven by an over-abundance of moderately- to poorly-competent host species, such as northern cardinals and members of the Mimid family, which cause optimal hosts to become rarer and present primarily in species-rich areas. Our results support the notion that dilution or amplification effects depend more on the identities of the species comprising the host community than on the absolute diversity of hosts.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-1999-6) contains supplementary material, which is available to authorized users.

Supersuppression: Reservoir Competency and Timing of Mosquito Host Shifts Combine to Reduce Spillover of West Nile Virus

In the eastern United States, human cases of West Nile virus (WNV) result from spillover from urban epizootic transmission between passerine birds and Culex mosquitoes. In Atlanta, GA, substantial WNV presence in hosts and vectors has not resulted in the human disease burden observed in cities with similar infection pressure. Our study goal was to investigate extrinsic ecological conditions that potentially contribute to these reduced transmission rates. We conducted WNV surveillance among hosts and vectors in urban Atlanta and recorded an overall avian seroprevalence of nearly 30%, which was significantly higher among northern cardinals, blue jays, and members of the mimid family, and notably low among American robins. Examination of temporal Culex feeding patterns showed a marked feeding shift from American robins in the early season to northern cardinals in the late season. We therefore rule out American robins as superspreaders in the Atlanta area and suggest instead that northern cardinals and mimids act as WNV "supersuppressor" species, which slow WNV transmission by drawing many infectious bites during the critical virus amplification period, yet failing to amplify transmission due to low host competencies. Of particular interest, urban forest patches provide spillover protection by increasing the WNV amplification fraction on supersuppressor species.

Pathogenesis of Vesicular Stomatitis New Jersey Virus Infection in Deer Mice ( Peromyscus maniculatus) Transmitted by Black Flies ( Simulium vittatum)

The natural transmission of vesicular stomatitis New Jersey virus (VSNJV), an arthropod-borne virus, is not completely understood. Rodents may have a role as reservoir or amplifying hosts. In this study, juvenile and nestling deer mice ( Peromyscus maniculatus) were exposed to VSNJV-infected black fly ( Simulium vittatum) bites followed by a second exposure to naive black flies on the nestling mice. Severe neurological signs were observed in some juvenile mice by 6 to 8 days postinoculation (DPI); viremia was not detected in 25 juvenile deer mice following exposure to VSNJV-infected fly bites. Both juvenile and nestling mice had lesions and viral antigen in the central nervous system (CNS); in juveniles, their distribution suggested that the sensory pathway was the most likely route to the CNS. In contrast, a hematogenous route was probably involved in nestling mice, since all of these mice developed viremia and had widespread antigen distribution in the CNS and other tissues on 2 DPI. VSNJV was recovered from naive flies that fed on viremic nestling mice. This is the first report of viremia in a potential natural host following infection with VSNJV via insect bite and conversely of an insect becoming infected with VSNJV by feeding on a viremic host. These results, along with histopathology and immunohistochemistry, show that nestling mice have widespread dissemination of VSNJV following VSNJV-infected black fly bite and are a potential reservoir or amplifying host for VSNJV.

Experimental infection of Holstein cows and calves with EHDV‑7 and preliminary evaluation of different inoculation methods

Infection of cattle with epizootic haemorrhagic disease (EHD) virus (EHDV) is frequently subclinical, yet reports of disease have increased in recent years. In 2006, a widespread EHDV‑7 epidemic caused disease and economic loss in the Israeli dairy industry. In this study, the main objective was to infect cattle with EHDV‑7 and replicate disease observed in Israel during 2006. Two infection studies were performed. Experiment 1, 4 cows inoculated with intradermal (ID) and subcutaneous (SC) injections with an EHDV‑7 blood inoculum. Experiment 2, 6 calves inoculated using 1 of the following 3 methods (2 calves/method): (1) mammalian cell culture supernatant by ID and SC injection; (2) culture supernatant by ID, SC, and intravenous injection; and (3) bite transmission from Culicoides sonorensis. Further, during experiment 2, C. sonorensis were fed on 4 infected calves (18 days post-inoculation) and processed for virus isolation 10 days later in order to evaluate infectivity of low‑titer viraemia. Three cows had detectable viraemia and all 4 seroconverted. No clinical signs were observed. All 6 calves developed viraemia, peaking 7‑10 dpi and all calves seroconverted. No differences in virus kinetics were observed between the inoculation groups. Calves in group 2 had transiently elevated rectal temperatures but no other clinical abnormalities were observed. The 124 midge pools processed after feeding on calves with low‑titer viraemia were virus isolation negative. Detectable viraemia was more consistent in calves than adult cows. This study demonstrates US‑origin cattle are susceptible to EHDV‑7 infection by multiple inoculation methods; however, as reported in other studies, the disease was not replicated experimentally.

Effect of Temperature on Replication of Epizootic Hemorrhagic Disease Viruses in Culicoides sonorensis (Diptera: Ceratopogonidae)

Replication of arboviruses, including orbiviruses, within the vector has been shown to be temperature dependent. Cooler ambient temperatures slow virus replication in arthropod vectors, whereas viruses replicate faster and to higher titers at warmer ambient temperatures. Previous research with epizootic hemorrhagic disease virus (EHDV) serotype 1 demonstrated that higher temperatures were associated with shorter extrinsic incubation periods in Culicoides sonorensis Wirth & Jones, a confirmed vector of EHDV in North America. To further our understanding of the effect of temperature on replication of EHDV within the vector, C. sonorensis were experimentally infected with one of three EHDV strains representing three serotypes (1, 2, and 7). Midges were fed defibrinated white-tailed deer (Odocoileus virginianus) blood spiked with EHDV (≥10(6.5) TCID(50)/ml) through a parafilm membrane using an artificial feeding device and were then held at 20, 25, or 30°C. In addition to this in vitro method, a white-tailed deer experimentally infected with EHDV-7 was used to provide an infectious bloodmeal to determine if the results were comparable with those from the in vitro feeding method. Whole midges were processed for virus isolation and titration at regular intervals following feeding; midges with ≥10(2.7) TCID(50) were considered potentially competent to transmit virus. The virus recovery rates were high throughout the study and all three viruses replicated within C. sonorensis to high titer (≥ 10(2.7) TCID(50)/midge). Across all virus strains, the time to detection of potentially competent midges decreased with increasing temperature: 12-16 d postfeeding (dpf) at 20°C, 4-6 dpf at 25°C, and 2-4 dpf at 30°C. Significant differences in replication of the three viruses in C. sonorensis were observed, with EHDV-2 replicating to a high titer in a smaller proportion of midges and with lower peak titers. The findings are consistent with previous studies of related orbiviruses, showing that increasing temperature can shorten the apparent extrinsic incubation period for multiple EHDV strains (endemic and exotic) in C. sonorensis.

Genetic characterization of epizootic hemorrhagic disease virus strains isolated from cattle in Israel

Epizootic hemorrhagic disease virus (EHDV), a member of the genus Orbivirus not reported previously in Israel, was isolated from Israeli cattle during a 'bluetongue-like' disease outbreak in 2006. To ascertain the origin of this new virus, three isolates from the outbreak were fully sequenced and compared with available sequences. Whilst the L2 gene segment clustered with the Australian EHDV serotype 7 (EHDV-7) reference strain, most of the other segments were clustered with EHDV isolates of African/Middle East origin, specifically Bahrain, Nigeria and South Africa. The M6 gene had genetic relatedness to the Australian/Asian strains, but with the limited data available the significance of this relationship is unclear. Only one EHDV-7 L2 sequence was available, and as this gene encodes the serotype-specific epitope, the relationship of these EHDV-7 L2 genes to an Australian EHDV-7 reflects the serotype association, not necessarily the origin. The genetic data indicated that the strains affecting Israel in 2006 may have been related to similar outbreaks that occurred in North Africa in the same year. This finding also supports the hypothesis that EHDV entered Israel during 2006 and was not present there before this outbreak.

Long term impacts of combined sewer overflow remediation on water quality and population dynamics of Culex quinquefasciatus, the main urban West Nile virus vector in Atlanta, GA

BACKGROUND

Combined sewers are a significant source of urban water pollution due to periodic discharges into natural streams. Such events (called combined sewer overflows, or CSOs) contribute to the impairment of natural waterways and are associated with increased mosquito productivity and elevated risk of West Nile virus transmission.

OBJECTIVES

We investigated the impact of CSOs on water quality and immature mosquito productivity in the city of Atlanta, Georgia, one year before and four years after CSO facility remediation.

METHODS

Water quality (ammonia, phosphate, nitrate and dissolved oxygen concentrations), immature mosquitoes (larvae and pupae), water temperature and rainfall were quantified biweekly between June-October at two urban creeks during 2008-2012. A before-after control-intervention design tested the impact of remediation on mosquito productivity and water quality, whereas generalized linear mixed-effect models quantified the factors explaining the long term impacts of remediation on mosquito productivity.

RESULTS

Ammonia and phosphate concentrations and late immature (fourth-instar and pupae) mosquito populations were significantly higher in CSO than in non-CSO creeks, while dissolved oxygen concentrations were lower. Remediation significantly improved water quality estimates (particularly ammonia and dissolved oxygen) and reduced the number of overflows, mosquito productivity and the overall contribution of CSO-affected streams as sources of vectors of West Nile virus.

CONCLUSIONS

The quality of water in CSOs provided a suitable habitat for immature mosquitoes. Remediation of the CSO facility through the construction of a deep storage tunnel improved water quality indices and reduced the productivity of mosquito species that can serve as vectors of West Nile virus.

Gene duplication and phylogeography of North American members of the Hart Park serogroup of avian rhabdoviruses

Flanders virus (FLAV) and Hart Park virus (HPV) are rhabdoviruses that circulate in mosquito–bird cycles in the eastern and western United States, respectively, and constitute the only two North American representatives of the Hart Park serogroup. Previously, it was suggested that FLAV is unique among the rhabdoviruses in that it contains two pseudogenes located between the P and M genes, while the cognate sequence for HPV has been lacking. Herein, we demonstrate that FLAV and HPV do not contain pseudogenes in this region, but encode three small functional proteins designated as U1–U3 that apparently arose by gene duplication. To further investigate the U1–U3 region, we conducted the first large-scale evolutionary analysis of a member of the Hart Park serogroup by analyzing over 100 spatially and temporally distinct FLAV isolates. Our phylogeographic analysis demonstrates that although FLAV appears to be slowly evolving, phylogenetically divergent lineages co-circulate sympatrically.

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Flanders virus (FLAV) does not contain pseudogenes as previously reported.

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The FLAV U1–U3 proteins arose by gene duplication.

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The SH protein of FLAV is tentatively expressed by coupled translation.

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Distinct lineages of FLAV circulate sympatrically in the United States.

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Histone H4 and cyclophilin A are apparently incorporated into FLAV particles.

Limited spillover to humans from West Nile Virus viremic birds in Atlanta, Georgia

West Nile Virus (WNV) is a mosquito-borne pathogen that impacts the health of its passerine bird hosts as well as incidentally infected humans in the United States. Intensive enzootic activity among the hosts and vectors does not always lead to human outbreaks, as is the situation throughout much of the southeastern United States. In Georgia, substantial yearly evidence of WNV in the mosquito vectors and avian hosts since 2001 has only led to 324 human cases. Although virus has been consistently isolated from mosquitoes trapped in Atlanta, GA, little is known about viral activity among the passerine hosts. A possible reason for the suppression of WNV spillover to humans is that viremic birds are absent from high human-use areas of the city. To test this hypothesis, multiseason, multihabitat, longitudinal WNV surveillance for active WNV viremia was conducted within the avian host community of urban Atlanta by collection of blood samples from wild passerine birds in five urban microhabitats. WNV was isolated from the serum of six blood samples collected from 630 (0.95%) wild passerine birds in Atlanta during 2010-2012, a proportion similar to that found in the Chicago, IL, area in 2005, when over 200 human cases were reported. Most of the viremic birds were Northern Cardinals, suggesting they may be of particular importance to the WNV transmission cycle in Georgia. Results indicated active WNV transmission in all microhabitats of urban Atlanta, except in the old-growth forest patches. The number of viremic birds was highest in Zoo Atlanta, where 3.5% of samples were viremic. Although not significant, these observations may suggest a possible transmission reduction effect of urban old-growth forests and a potential role in WNV amplification for Zoo Atlanta. Overall, spillover to humans remains a rare occurrence in urban Atlanta settings despite active WNV transmission in the avian population.

Hemi-nested PCR and RFLP methodologies for identifying blood meals of the Chagas disease vector, Triatoma infestans

Trypanosoma cruzi, the etiologic agent of Chagas disease, is transmitted by hematophagous reduviid bugs within the subfamily Triatominae. These vectors take blood meals from a wide range of hosts, and their feeding behaviors have been used to investigate the ecology and epidemiology of T. cruzi. In this study we describe two PCR-based methodologies that amplify a fragment of the 16S mitochondrial rDNA, aimed to improve the identification of blood meal sources for Triatoma infestans: a.- Sequence analyses of two heminested PCRs that allow the identification of mammalian and avian species, and b.- restriction fragment length polymorphism (RFLP) analysis from the mammalian PCR to identify and differentiate multi-host blood meals. Findings from both methodologies indicate that host DNA could be detected and the host species identified in samples from laboratory reared and field collected triatomines. The implications of this study are two-fold. First, these methods can be used in areas where the fauna diversity and feeding behavior of the triatomines are unknown. Secondly, the RFLP method led to the identification of multi-host DNA from T. infestans gut contents, enhancing the information provided by this assay. These tools are important contributions for ecological and epidemiological studies of vector-borne diseases.

Anaplasma odocoilei sp. nov. (family Anaplasmataceae) from white-tailed deer (Odocoileus virginianus)

Recently, an undescribed Anaplasma sp. (also called Ehrlichia-like sp. or WTD agent) was isolated in ISE6 tick cells from captive white-tailed deer. The goal of the current study was to characterize this organism using a combination of experimental infection, morphologic, serologic, and molecular studies. Each of 6 experimentally inoculated white-tailed deer fawns (Odocoileus virginianus) became chronically infected (100+ days) with the Anaplasma sp. by inoculation of either infected whole blood or culture. None of the deer showed evidence of clinical disease, but 3 of the 6 deer evaluated had multiple episodes of transient thrombocytopenia. Light microscopy of Giemsa-stained, thin blood smears revealed tiny, dark, spherical structures in platelets of acutely infected deer. Anaplasma sp. was detected in platelets of inoculated deer by polymerase chain reaction, transmission electron microscopy, immunohistochemistry, and in situ hybridization. Five of 6 deer developed antibodies reactive to Anaplasma sp. antigen, as detected by indirect fluorescent antibody testing. Phylogenetic analyses of 16S rRNA, groESL, and gltA sequences confirmed the Anaplasma sp. is related to A. platys. Two attempts to transmit the Anaplasma sp. between deer by feeding Amblyomma americanum, a suspected tick vector, were unsuccessful. Based on its biologic, antigenic, and genetic characteristics, this organism is considered a novel species of Anaplasma, and the name Anaplasma odocoilei sp. nov. is proposed with UMUM76(T) (=CSUR-A1) as the type strain.

Vector competence of Culicoides sonorensis (Diptera: Ceratopogonidae) to epizootic hemorrhagic disease virus serotype 7

Background

Culicoides sonorensis (Diptera: Ceratopogonidae) is a vector of epizootic hemorrhagic disease virus (EHDV) serotypes 1 and 2 in North America, where these viruses are well-known pathogens of white-tailed deer (WTD) and other wild ruminants. Although historically rare, reports of clinical EHDV infection in cattle have increased in some parts of the world over the past decade. In 2006, an EHDV-7 epizootic in cattle resulted in economic loss for the Israeli dairy industry. White-tailed deer are susceptible to EHDV-7 infection and disease; however, this serotype is exotic to the US and the susceptibility of C. sonorensis to this cattle-virulent EHDV is not known. The objective of the study was to determine if C. sonorensis is susceptible to EHDV-7 infection and is a competent vector.

Methods

To evaluate the susceptibility of C. sonorensis, midges were fed on EHDV-7 infected WTD, held at 22 ± 1°C, and processed individually for virus isolation and titration on 4–16 days post feeding (dpf). Midges with a virus titer of ≥10^2.7 median tissue culture infective doses (TCID₅₀)/midge were considered potentially competent. To determine if infected C. sonorensis were capable of transmitting EHDV-7 to a host, a susceptible WTD was then fed on by a group of 14–16 dpf midges.

Results

From 4–16 dpf, 45% (156/350) of midges that fed on WTD with high titer viremia (>10⁷ TCID₅₀/ml) were virus isolation-positive, and starting from 10–16 dpf, 32% (35/109) of these virus isolation-positive midges were potentially competent (≥10^2.7 TCID₅₀/midge). Midges that fed on infected deer transmitted the virus to a susceptible WTD at 14–16 dpf. The WTD developed viremia and severe clinical disease.

Conclusion

This study demonstrates that C. sonorensis is susceptible to EHDV-7 infection and can transmit the virus to susceptible WTD, thus, C. sonorensis should be considered a potential vector of EHDV-7. Together with previous work, this study demonstrates that North America has a susceptible ruminant and vector host for this exotic, cattle-virulent strain of EHDV-7.

Host predilection and transmissibility of vesicular stomatitis New Jersey virus strains in domestic cattle (Bos taurus) and swine (Sus scrofa)

BACKGROUND

Epidemiologic data collected during epidemics in the western United States combined with limited experimental studies involving swine and cattle suggest that host predilection of epidemic vesicular stomatitis New Jersey virus (VSNJV) strains results in variations in clinical response, extent and duration of virus shedding and transmissibility following infection in different hosts. Laboratory challenge of livestock with heterologous VSNJV strains to investigate potential viral predilections for these hosts has not been thoroughly investigated. In separate trials, homologous VSNJV strains (NJ82COB and NJ82AZB), and heterologous strains (NJ06WYE and NJOSF [Ossabaw Island, sand fly]) were inoculated into cattle via infected black fly bite. NJ82AZB and NJ06WYE were similarly inoculated into swine.

RESULTS

Clinical scores among viruses infecting cattle were significantly different and indicated that infection with a homologous virus resulted in more severe clinical presentation and greater extent and duration of viral shedding. No differences in clinical severity or extent and duration of viral shedding were detected in swine.

CONCLUSIONS

Differences in clinical presentation and extent and duration of viral shedding may have direct impacts on viral spread during epidemics. Viral transmission via animal-to-animal contact and insect vectored transmission are likely to occur at higher rates when affected animals are presenting severe clinical signs and shedding high concentrations of virus. More virulent viral strains resulting in more severe disease in livestock hosts are expected to spread more rapidly and greater distances during epidemics than those causing mild or inapparent signs.

Domestic cattle as a non-conventional amplifying host of vesicular stomatitis New Jersey virus

The role of vertebrates as amplifying and maintenance hosts for vesicular stomatitis New Jersey virus (VSNJV) remains unclear. Livestock have been considered dead-end hosts because detectable viraemia is absent in VSNJV-infected animals. This study demonstrated two situations in which cattle can represent a source of VSNJV to Simulium vittatum Zetterstedt (Diptera: Simuliidae) by serving: (a) as a substrate for horizontal transmission among co-feeding black flies, and (b) as a source of infection to uninfected black flies feeding on sites where VSNJV-infected black flies have previously fed. Observed co-feeding transmission rates ranged from 0% to 67%. Uninfected flies physically separated from infected flies by a distance of up to 11 cm were able to acquire virus during feeding although the rate of transmission decreased as the distance between infected and uninfected flies increased. Acquisition of VSNJV by uninfected flies feeding on initial inoculation sites at 24 h, 48 h and 72 h post-infection, in both the presence and absence of vesicular lesions, was detected.

Apparent disappearance of Vesicular Stomatitis New Jersey Virus from Ossabaw Island, Georgia

Ossabaw Island, Georgia, is the only reported endemic focus of Vesicular Stomatitis New Jersey Virus (VSNJV) in the United States. Based on recent negative serologic results of white-tailed deer and feral swine and the failure to isolate VSNJV from Lutzomyia shannoni, it appears that VSNJV is no longer present at this site. This apparent disappearance does not appear to be related to a change in L. shannoni habitat, specifically to the density of tree holes in the maritime and mixed hardwood forests. We believe that the disappearance of VSNJV from Ossabaw Island is directly related to a reduction in the feral swine population and a subsequent increase in the utilization of white-tailed deer by the known vector, L. shannoni.

The risk of West Nile Virus infection is associated with combined sewer overflow streams in urban Atlanta, Georgia, USA

BACKGROUND

At present, the factors favoring transmission and amplification of West Nile Virus (WNV) within urban environments are poorly understood. In urban Atlanta, Georgia, the highly polluted waters of streams affected by combined sewer overflow (CSO) represent significant habitats for the WNV mosquito vector Culex quinquefasciatus. However, their contribution to the risk of WNV infection in humans and birds remains unclear.

OBJECTIVES

Our goals were to describe and quantify the spatial distribution of WNV infection in mosquitoes, humans, and corvids, such as blue jays and American crows that are particularly susceptible to WNV infection, and to assess the relationship between WNV infection and proximity to CSO-affected streams in the city of Atlanta, Georgia.

MATERIALS AND METHODS

We applied spatial statistics to human, corvid, and mosquito WNV surveillance data from 2001 through 2007. Multimodel analysis was used to estimate associations of WNV infection in Cx. quinquefasciatus, humans, and dead corvids with selected risk factors including distance to CSO streams and catch basins, land cover, median household income, and housing characteristics.

RESULTS

We found that WNV infection in mosquitoes, corvids, and humans was spatially clustered and statistically associated with CSO-affected streams. WNV infection in Cx. quinquefasciatus was significantly higher in CSO compared with non-CSO streams, and WNV infection rates among humans and corvids were significantly associated with proximity to CSO-affected streams, the extent of tree cover, and median household income.

CONCLUSIONS

Our study strongly suggests that CSO-affected streams are significant sources of Cx. quinquefasciatus mosquitoes that may facilitate WNV transmission to humans within urban environments. Our findings may have direct implications for the surveillance and control of WNV in other urban centers that continue to use CSO systems as a waste management practice.

Absence of Rickettsia rickettsii and occurrence of other spotted fever group rickettsiae in ticks from Tennessee

Rocky Mountain spotted fever (RMSF) is the most common tick-borne illness in Tennessee. Little is known about the occurrence of R. rickettsii, the causative agent, in ticks in Tennessee. To better understand the prevalence and distribution of rickettsial agents in ticks, we tested 1,265 Amblyomma, Dermacentor, and Ixodes adult and nymphal ticks. Additionally, we tested 231 Amblyomma americanum larvae. Ticks were collected from 49 counties from humans, wild animals, domestic canines, and flannel drags. Spotted fever group rickettsiae (SFGR) DNA was detected by polymerase chain reaction (PCR) in 32% of adult and nymphal ticks. A total minimum infection rate of 85.63 was found in larval pools tested. Three rickettsial species, Rickettsia montana, Rickettsia amblyommii, and Rickettsia cooleyi were identified by molecular analysis. Rickettsia rickettsii was not detected. This study suggests that some RMSF cases reported in Tennessee may be caused by cross-reactivity with other SFGR antigenically related to R. rickettsii.

Lesion development and replication kinetics during early infection in cattle inoculated with Vesicular stomatitis New Jersey virus via scarification and black fly (Simulium vittatum) bite

Vesicular stomatitis viruses are the causative agents of vesicular stomatitis, an economically important contagious disease of livestock that occurs in North, Central, and South America. Little is known regarding the early stages of infection in natural hosts. Twelve adult Holstein steers were inoculated with Vesicular stomatitis New Jersey virus (VSNJV) on the coronary bands (CB) of the feet via scarification (SC) or by VSNJV-infected black fly (Simulium vittatum) bite (FB). Three additional animals were inoculated on the neck skin using FB. Clinical disease and lesion development were assessed daily, and animals were euthanatized from 12 hours post inoculation (HPI) through 120 HPI. The animals inoculated in the neck failed to develop any clinical signs or gross lesions, and VSNJV was detected neither by in situ hybridization (ISH) nor by immunohistochemistry (IHC). Lesions on the CB were more severe in the animals infected by FB than by SC. In both groups, peak VSNJV replication occurred between 24 and 48 HPI in keratinocytes of the CB, as evidenced by ISH and IHC. There was evidence of viral replication limited to the first 24 HPI in the local draining lymph nodes, as seen through ISH. Successful infection via FB required logarithmically less virus than with the SC technique, suggesting that components in black fly saliva may facilitate VSNJV transmission and infection in cattle. The lack of lesion development in the neck with the same method of inoculation used in the CB suggests that specific characteristics of the CB epithelium may facilitate VSNJV infection.

Rickettsia parkeri in Amblyomma americanum ticks, Tennessee and Georgia, USA

To determine the geographic distribution of the newly recognized human pathogen Rickettsia parkeri, we looked for this organism in ticks from Tennessee and Georgia, USA. Using PCR and sequence analysis, we identified R. parkeri in 2 Amblyomma americanum ticks. This rickettsiosis may be underdiagnosed in the eastern United States.

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

Biting flies have been suggested as mechanical vectors of vesicular stomatitis New Jersey Virus (family Rhabdoviridae, genus Vesiculovirus, VSNJV) in livestock populations during epidemic outbreaks in the western United States. We conducted a proof-of-concept study to determine whether biting flies could mechanically transmit VSNJV to livestock by using a black fly, Simulium vittatum Zetterstedt (Diptera: Simuliidae), domestic swine, Sus scrofa L., model. Black flies mechanically transmitted VSNJV to a naive host after interrupted feeding on a vesicular lesion on a previously infected host. Transmission resulted in clinical disease in the naïve host. This is the first demonstration of mechanical transmission of VSNJV to livestock by insects.

Experimental transmission of vesicular stomatitis New Jersey virus from Simulium vittatum to cattle: clinical outcome is influenced by site of insect feeding

Vesicular stomatitis New Jersey virus (VSNJV) is an insect-transmitted Rhabdovirus causing vesicular disease in domestic livestock including cattle, horses, and pigs. Natural transmission during epidemics remains poorly understood, particularly in cattle, one of the most affected species during outbreaks. This study reports the first successful transmission of VSNJV to cattle by insect bite resulting in clinical disease. When infected black flies (Simulium vittatum Zetterstedt) fed at sites where VS lesions are usually observed (mouth, nostrils, and foot coronary band), infection occurred, characterized by local viral replication, vesicular lesions, and high neutralizing antibody titers (> 1: 256). Viral RNA was detected up to 9 d postinfection in tissues collected during necropsy from lesion sites and lymph nodes draining those sites. Interestingly, when flies were allowed to feed on flank or neck skin, viral replication was poor, lesions were not observed, and low levels of neutralizing antibodies (range, 1:8-1:32) developed. Viremia was never observed in any of the animals and infectious virus was not recovered from tissues on necropsies performed between 8 and 27 d postinfection. Demonstration that VSNJV transmission to cattle by infected black flies can result in clinical disease contributes to a better understanding of the epidemiology and potential prevention and control methods for this important disease.

Detection of All Eight Serotypes of Epizootic Hemorrhagic Disease Virus by Real-Time Reverse Transcription Polymerase Chain Reaction

Epizootic hemorrhagic disease virus (EHDV) has been associated with bluetongue-like disease in cattle. Although U.S. EHDV strains have not been experimentally proven to cause disease in cattle, there is serologic evidence of infection. Differentiation of Bluetongue virus (BTV) and EHDV is necessary because diagnosis of infection caused by these viruses is often confused. The previously developed nested reverse transcription polymerase chain reaction (nRT-PCR) test for indigenous EHDV disease is sensitive and specific, but it is prone to contamination problems. Additionally, the EHDV nRT-PCR only detects 7 of the 8 serotypes. To develop an improved diagnostic test, sequence analysis was performed on 2 conserved target genes; one is highly expressed in infected mammalian cells, whereas the other is highly expressed in infected insect cells. This information was used to develop a rapid EHDV real-time PCR that detects all 8 EHDV serotypes. The EHDV assay did not cross-react with BTV strains and performed similarly to the nRT-PCR tests with archived clinical samples. In addition, it is superior to the nRT-PCR, not only because it is a closed system with fewer cross-contamination problems, but also because it detects all 8 serotypes and is less labor and time intensive.

Tick-borne diseases in North Carolina: is "Rickettsia amblyommii" a possible cause of rickettsiosis reported as Rocky Mountain spotted fever?

Cases of Rocky Mountain spotted fever (RMSF) in North Carolina have escalated markedly since 2000. In 2005, we identified a county in the Piedmont region with high case numbers of RMSF. We collected ticks and examined them for bacterial pathogens using molecular methods to determine if a novel tick vector or spotted fever group rickettsiae (SFGR) might be emerging. Amblyomma americanum, the lone star tick, comprised 99.6% of 6,502 specimens collected in suburban landscapes. In contrast, Dermacentor variabilis, the American dog tick, a principal vector of Rickettsia rickettsii, comprised < 1% of the ticks collected. Eleven of 25 lone star tick pools tested were infected with "Rickettsia amblyommii," an informally named SFGR. Sera from patients from the same county who were presumptively diagnosed by local physicians with a tick-borne illness were tested by an indirect immunofluorescence antibody (IFA) assay to confirm clinical diagnoses. Three of six patients classified as probable RMSF cases demonstrated a fourfold or greater rise in IgG class antibody titers between paired acute and convalescent sera to "R. amblyommii" antigens, but not to R. rickettsii antigens. White-tailed deer, Odocoileus virginianus, are preferred hosts of lone star ticks. Blood samples collected from hunter-killed deer from the same county were tested by IFA test for antibodies to Ehrlichia chaffeensis and "R. amblyommii." Twenty-eight (87%) of 32 deer were positive for antibodies to E. chaffeensis, but only 1 (3%) of the deer exhibited antibodies to "R. amblyommii," suggesting that deer are not the source of "R. amblyommii" infection for lone star ticks. We propose that some cases of rickettsiosis reported as RMSF may have been caused by "R. amblyommii" transmitted through the bite of A. americanum.

Pathology and epidemiology of natural West Nile viral infection of raptors in Georgia

Carcasses from 346 raptors found between August 2001 and December 2004 were tested for West Nile virus (WNV) using virus isolation and immunohistochemistry; 40 were positive for WNV by one or both methods. Of these 40 birds, 35 had histologic lesions compatible with WNV infection, one had lesions possibly attributable to WNV, and four had no histologic evidence of WNV. The most common histologic lesions associated with WNV infection were myocardial inflammation, necrosis, and fibrosis; skeletal muscle degeneration, inflammation, and fibrosis; and lymphoplasmacytic encephalitis. Other lesions included hepatitis, lymphoid depletion in spleen and bursa, splenic and hepatic hemosiderosis, pancreatitis, and ganglioneuritis. Gross lesions included calvarial and leptomeningeal hemorrhage, myocardial pallor, and splenomegaly. Red-tailed hawks (Buteo jamaicensis) (10/56), sharp-shinned hawks (Accipiter striatus) (8/40), and Cooper's hawks (Accipiter cooperii) (10/103) were most commonly affected. Also affected were red-shouldered hawks (Buteo lineatus) (2/43), an osprey (Pandion haliaetus) (1/5), barred owls (Strix varia) (4/27), a great horned owl (Bubo virginianus) (1/18), and eastern screech owls (Megascops asio) (4/42). Although birds were examined throughout the year, positive cases occurred only during the summer and late fall (June-December). Yearly WNV mortality rates ranged from 7-15% over the four years of the study. This study indicates trends in infection rates of WNV in raptorial species over a significant time period and supports the available information regarding pathology of WNV infection in Strigiformes and Falconiformes. Although many species tested were positive for WNV infection, severity of lesions varied among species.

West Nile virus antibodies in avian species of Georgia, USA: 2000-2004

West Nile virus (WNV) was first isolated in the state of Georgia in the summer of 2001. As amplifying hosts of WNV, avian species play an important role in the distribution and epidemiology of the virus. The objective of this study was to identify avian species that are locally involved as potential amplifying hosts of WNV and can serve as indicators of WNV transmission over the physiographic and land use variation present in the southeastern United States. Avian serum samples (n=14,077) from 83 species of birds captured throughout Georgia during the summers of 2000-2004 were tested by a plaque reduction neutralization test for antibodies to WNV and St. Louis encephalitis virus. Over the 5-year period, WNV-neutralizing antibodies were detected in 869 (6.2%) samples. The WNV seroprevalence increased significantly throughout the study and was species dependent. The highest antibody prevalence rates were detected in rock pigeons (Columba livia), northern cardinals (Cardinalis cardinalis), common ground doves (Columbina passerina), grey catbirds (Deumetella carolinensis), and northern mockingbirds (Mimus polyglottos). Northern cardinals, in addition to having high geometric mean antibody titers and seroprevalence rates, were commonly found in all land use types and physiographic regions. Rock pigeons, common ground doves, grey catbirds, and northern mockingbirds, although also having high seroprevalence rates and high antibody titers against WNV, were more restricted in their distribution and therefore may be of more utility when attempting to assess exposure rates in specific habitat types. Of all species tested, northern cardinals represent the best potential avian indicator species for widespread serologic-based studies of WNV throughout Georgia due to their extensive range, ease of capture, and high antibody rates and titers. Due to the large geographic area covered by this species, their utility as a WNV sentinel species may include most of the eastern United States.

Experimental vesicular stomatitis virus infection in horses: effect of route of inoculation and virus serotype

Horses were inoculated with Vesicular stomatitis New Jersey and Indiana viruses by routes simulating contact and vector transmission. Clinical signs, lesions, antibody development, viral shedding and persistence, and viremia were monitored. Horses were infected with both viruses by all routes as confirmed by seroconversion. Salivation, primary lesions at inoculation sites, and secondary oral lesions were the most common clinical findings. Viral shedding was most often from the oral cavity, followed by the nasal cavity; titers were highest from oral cavity samples. Virus was rarely isolated from the conjunctival sac and never from feces or blood. Development of neutralizing antibody coincided with cessation of lesion development and detection of virus by isolation. Circulating virus-specific IgM, IgG, IgA, and neutralizing antibodies developed in most animals postinoculation (PI) days 6 to 12, depending on the route of inoculation. At postmortem (PI days 12 to 15), lesions were healing, were not vesicular, and did not contain detectable virus by isolation, reverse transcriptase polymerase chain reaction, or immunohistochemistry. Numerous infiltrating lymphocytes and plasma cells suggested that lesion resolution was partially due to local immunity. Detection of viral RNA from tonsil and lymph nodes of head at necropsy suggests that these tissues play a role in the pathogenesis of the disease; molecular techniques targeting these tissues may be useful for confirming infection in resolving stages of disease. The routes of inoculation used in this study reflect the diversity of transmission routes that may occur during outbreaks and can be used to further study contact and vector transmission, vaccine development, and clarify pathogenesis of the disease in horses.

Necropsy Findings and Arbovirus Surveillance in Mourning Doves from the Southeastern United States

Mourning doves (Zenaida macroura) are the most abundant and widespread native member of the columbid family, as well as a major migratory game species, in the United States. However, there is little information on mortality factors in mourning doves. Records of necropsy accessions at the Southeastern Cooperative Wildlife Disease Study (SCWDS) from 15 southeastern states, from 1971 through 2005, were reviewed. One hundred thirty-five mourning doves were submitted from nine states during the 35-yr period. Trichomonosis constituted 40% (n = 54) of all diagnoses and was the most frequent diagnosis. Toxicoses and avian pox constituted 18.5% (n = 25) and 14.8% (n = 20) of all diagnoses, respectively. Remaining diagnoses included trauma, suspected toxicosis, Ascaridia columbae infection, suspected tick paralysis, and undetermined. Adults were observed more frequently with trichomonosis (94.1%) and toxicoses (68%) as compared to juveniles, but a gender predisposition was not apparent for either disease. Age and gender predilections were not apparent for cases of avian pox. The majority of the trichomonosis and avian pox cases were observed in the spring-summer, whereas the majority of the toxicosis cases were observed in the winter-spring. Additionally, the Georgia Department of Human Resources-Division of Public Health and West Virginia Department of Health and Human Resources submitted 809 mourning doves to SCWDS from 2001 through 2005 for West Nile virus surveillance efforts. West Nile virus was isolated from 2.1% (n = 17) and eastern equine encephalitis virus (EEEV) was isolated from 0.2% (n = 2) of the submitted birds.

Evaluation of white-tailed deer (Odocoileus virginianus) as natural sentinels for Anaplasma phagocytophilum

Anaplasma phagocytophilum, the causative agent of human granulocytotropic anaplasmosis, can infect white-tailed deer (WTD; Odocoileus virginianus), and this species is a crucial host for adult Ixodes scapularis, the primary vector of A. phagocytophilum. The goal of this study was to determine the geographic distribution of A. phagocytophilum among WTD across a 19 state region and to evaluate the utility of WTD as natural sentinels. Serologic testing using the indirect fluorescent antibody (IFA) assay was conducted on WTD serum samples and molecular and xenodiagnostic tests were performed to confirm serologic results. The surveillance system was assessed through examination of vital attributes including WTD age and gender associations with serologic status, sample size adequacy for accurate infection status classification, and presence of the vector, I. scapularis. Six hundred thirty-three of 2,666 (24%) WTD in 17 states tested positive for antibodies (>or=128) when tested by IFA assay. Testing for p44 and/or 16S rRNA gene targets identified 73 (16%) PCR positive WTD among 458 animals tested, all of which originated from seropositive populations. Attempts to culture A. phagocytophilum from WTD were unsuccessful; however, xenodiagnostic mice inoculated with blood from 3 WTD became infected. Seroprevalence did not differ by deer age or gender; however, WTD<or=0.75 years old had a higher prevalence of PCR positivity. Using seroprevalence data, a sample size of 6-9 animals per population was projected to be adequate for identifying seropositive populations. The presence of I. scapularis was significantly associated with A. phagocytophilum antibodies in WTD. Collectively, the results of this study demonstrate that WTD would be suitable natural sentinels for this emerging zoonotic pathogen.

West Nile virus detection in the organs of naturally infected blue jays (Cyanocitta cristata)

Blue jays (Cyanocitta cristata) are an effective indicator species for West Nile virus (WNV) and may be regionally important in surveillance efforts. The sites of WNV replication and sensitivity of virus detection techniques are undefined for blue jays. The objectives of this study were to describe the gross and microscopic pathology associated with natural WNV infection in blue jays, as well as determine the most appropriate tissues to be used for virus isolation, reverse transcription-nested polymerase chain reaction, and immunohistochemistry (IHC) techniques. Blue jays were collected in Georgia, USA, between May and September 2001. Initial screening by virus isolation indicated that 36 of 59 blue jays chosen for evaluation were WNV positive. From this group, 20 positive and five negative birds were chosen to compare virus detection techniques. Six positive and five negative birds were selected for histopathology examination. Splenomegaly and poor body condition were the most consistent gross findings among positive birds. The most consistent histopathologic findings in the tissues of WNV-positive blue jays were mononuclear leukocytosis and epicarditis/myocarditis. Brain, heart, and lung had the highest viral titers, and WNV antigen was most often detected by IHC in heart, kidney, liver, and lung. Reverse transcription-nested polymerase chain reaction proved to be the most sensitive diagnostic test applied in this study irrespective of the tissue type. Brain tissue could be used effectively for both virus isolation and RT-nPCR, and this tissue is simple to remove and process. The success of IHC is highly dependent on tissue selection, and the use of multiple tissues including heart, kidney, liver, or lung is recommended.

Experimental infection of white-tailed deer with Anaplasma phagocytophilum, etiologic agent of human granulocytic anaplasmosis

Serologic and molecular evidence of Anaplasma phagocytophilum has been demonstrated in white-tailed deer (WTD; Odocoileus virginianus), and deer are an important host for the tick vector Ixodes scapularis. In this study, we describe experimental infection of WTD with A. phagocytophilum. We inoculated four WTD with a human isolate of A. phagocytophilum propagated in tick cells. Two additional deer served as negative controls. All inoculated deer developed antibodies (titers, > or =64) to A. phagocytophilum, as determined by an indirect fluorescent antibody test, between 14 and 24 days postinfection [p.i.]), and two deer maintained reciprocal titers of > or =64 through the end of the 66-day study. Although morulae were not observed in granulocytes and A. phagocytophilum was not reisolated via tick cell culture of blood, 16S reverse transcriptase nested PCR (RT-nPCR) results indicated that A. phagocytophilum circulated in peripheral blood of three deer through at least 17 days p.i. and was present in two deer at 38 days p.i. Femoral bone marrow from one deer was RT-nPCR positive for A. phagocytophilum at 66 days p.i. There was no indication of clinical disease. These data confirm that WTD are susceptible to infection with a human isolate of A. phagocytophilum and verify that WTD produce detectable antibodies upon exposure to the organism. Because adults are the predominant life stage of I. scapularis found on deer and because adult I. scapularis ticks do not transmit A. phagocytophilum transovarially, it is unlikely that WTD are a significant source of A. phagocytophilum for immature ticks even though deer have a high probability of natural infection. However, the susceptibility and immunologic response of WTD to A. phagocytophilum render them suitable candidates as natural sentinels for this zoonotic tick-borne organism.