Tick-Borne Pathogens in Questing Blacklegged Ticks (Acari: Ixodidae) From Pike County, Pennsylvania

Active surveillance was conducted by collecting questing ticks from vegetation through a 2-yr survey in Pike County, Pennsylvania. Over a thousand blacklegged ticks (Ixodes scapularis Say) and American dog ticks (Dermacentor variabilis Say) were collected. A single specimen of the following species was collected: lone star tick (Amblyomma americanum L.), rabbit tick (Haemaphysalis leporispalustris Packard), and an Asian longhorned tick (Haemaphysalis longicornis Neumann). This study represents the largest county-wide study in Pennsylvania, surveying 988 questing I. scapularis adult and nymphs. Molecular detection of five distinct tick-borne pathogens was screened through real-time PCR at a single tick resolution. Respectively, the overall 2-yr adult and nymph prevalence were highest with Borrelia burgdorferi (Spirochaetales: Spirochaetacceae) (45.99%, 18.94%), Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae) (12.29%, 7.95%) where the variant-ha (8.29%, 3.03%) was overall more prevalent than the variant-v1 (2.49%, 4.17%), Babesia microti (Piroplasmida: Babesiidae) (4.97%, 5.30%), Borrelia miyamotoi (Spirochaetales: Spirochaetaceae) (1.38%, 1.89%), and Powassan virus lineage II [POWV]/deer tick virus (DTV) (2.07%, 0.76%). Adult and nymph coinfection prevalence of B. burgdorferi and B. microti (3.03%, 4.97%) and adult coinfection of B. burgdorferi and A. phagocytophilum or A. phagocytophilum and B. microti were significantly higher than the independent infection rate expected naturally. This study highlights the urgency to conduct diverse surveillance studies with large sample sizes to better understand the human risk for tick-borne diseases within small geographical areas.

Powassan Virus Encephalitis

Powassan virus is an increasingly recognized cause of severe encephalitis that is transmitted by Ixodes ticks. Given the nonspecific clinical, laboratory, and imaging features of Powassan virus disease, providers should consider it in patients with compatible exposures and request appropriate testing.

Infection with Borrelia burgdorferi Increases the Replication and Dissemination of Coinfecting Powassan Virus in Ixodes scapularis Ticks

Powassan virus (POWV) is a tick-borne neuroinvasive flavivirus endemic to North America. It is generally transmitted by the tick, Ixodes scapularis. This species also transmits Borrelia burgdorferi, the causative agent of Lyme disease. Infection with B. burgdorferi can result in arthritis, carditis, and neuroborreliosis. These pathogens experience sylvatic overlap. To determine the risk of human exposure to coinfected ticks, the interactions between POWV and B. burgdorferi are assessed in laboratory-infected I. scapularis. Adult male and female I. scapularis ticks are orally inoculated with either both pathogens, POWV only, B. burgdorferi only, or uninfected media. After twenty-one days, the ticks are dissected, and RNA is extracted from their midguts and salivary glands. In infected midguts, the quantity of POWV in coinfected ticks was elevated compared to those with only POWV. In addition, the salivary glands of ticks with infected midguts had increased POWV dissemination to those with only POWV. RNA sequencing is performed to identify the potential mechanism for this pattern, which varies between the organs. Ixodes scapularis ticks are found to be capable of harboring both POWV and B. burgdorferi with a benefit to POWV replication and dissemination.

Horizontal and Vertical Transmission of Powassan Virus by the Invasive Asian Longhorned Tick, Haemaphysalis longicornis, Under Laboratory Conditions

The Asian longhorned tick, Haemaphysalis longicornis, is an ixodid tick native to East Asia that was first detected in North America outside a port of entry in 2017. This invasive species has since been detected in 17 states. As the invasive range of the tick continues to expand, the vector competence of H. longicornis for pathogens native to North America must be assessed. Here, we evaluate the vector competence of H. longicornis for Powassan virus (POWV) under laboratory conditions. POWV is a North American tick-borne flavivirus that is typically transmitted through the bite of Ixodes species ticks. The invasive range of H. longicornis is expected to overlap heavily with the geographic range of Ixodes scapularis and POWV cases, highlighting the potential for this invasive tick species to amplify POWV transmission in natural foci should the native tick vectors and H. longicornis share similar hosts. In these studies, adult female H. longicornis ticks were infected with POWV via anal pore microinjection. Viral RNA and infectious virions were detected in tick tissues via q-RT-PCR and focus-forming assay, respectively. POWV-injected female ticks were infested on mice, and virus was transmitted to mice during tick feeding, as shown by clinical signs of disease and seroconversion in the tick-exposed mice, as well as the detection of viral RNA in various mouse tissues. A POWV-injected female tick transmitted virus to her larval progeny, indicating that H. longicornis can vertically transmit POWV. These naturally-infected larval ticks were also able to transmit POWV to the mouse on which they fed and to the nymphal stage after molting, further demonstrating that H. longicornis can transmit POWV in the horizontal and transstadial modes. Larval and nymphal ticks were also orally infected with POWV while feeding on viremic mice. Additionally, this study provides the first report of POWV neuropathology based on a natural tick transmission model of POWV. Together, our results suggest that the invasive H. longicornis tick is a competent vector of POWV. These findings underline the growing danger this tick may pose to human health in the United States. Additional scholarship on the tick's biology, ecology, and pathogen transmission dynamics in nature will be important towards understanding the full public health impact of this invasive species.

Seroprevalence of Powassan Virus Infection in an Area Experiencing a Cluster of Disease Cases: Sussex County, New Jersey, 2019

In 2019, a geographically focal cluster of 3 Powassan virus neuroinvasive disease cases occurred in New Jersey. We conducted a serosurvey of 273 adult area residents and estimated that immunoglobulin M seroprevalence was 0.31% (95% confidence interval [CI], .04%-1.00%) and 23% (95% CI, 7%-100%) of infections result in neuroinvasive disease.

Powassan Viruses Spread Cell to Cell during Direct Isolation from Ixodes Ticks and Persistently Infect Human Brain Endothelial Cells and Pericytes

Powassan viruses (POWVs) are neurovirulent tick-borne flaviviruses emerging in the northeastern United States, with a 2% prevalence in Long Island (LI) deer ticks (Ixodes scapularis). POWVs are transmitted within as little as 15 min of a tick bite and enter the central nervous system (CNS) to cause encephalitis (10% of cases are fatal) and long-term neuronal damage. POWV-LI9 and POWV-LI41 present in LI Ixodes ticks were isolated by directly inoculating VeroE6 cells with tick homogenates and detecting POWV-infected cells by immunoperoxidase staining. Inoculated POWV-LI9 and LI41 were exclusively present in infected cell foci, indicative of cell to cell spread, despite growth in liquid culture without an overlay. Cloning and sequencing establish POWV-LI9 as a phylogenetically distinct lineage II POWV strain circulating in LI deer ticks. Primary human brain microvascular endothelial cells (hBMECs) and pericytes form a neurovascular complex that restricts entry into the CNS. We found that POWV-LI9 and -LI41 and lineage I POWV-LB productively infect hBMECs and pericytes and that POWVs were basolaterally transmitted from hBMECs to lower-chamber pericytes without permeabilizing polarized hBMECs. Synchronous POWV-LI9 infection of hBMECs and pericytes induced proinflammatory chemokines, interferon-β (IFN-β) and proteins of the IFN-stimulated gene family (ISGs), with delayed IFN-β secretion by infected pericytes. IFN inhibited POWV infection, but despite IFN secretion, a subset of POWV-infected hBMECs and pericytes remained persistently infected. These findings suggest a potential mechanism for POWVs (LI9/LI41 and LB) to infect hBMECs, spread basolaterally to pericytes, and enter the CNS. hBMEC and pericyte responses to POWV infection suggest a role for immunopathology in POWV neurovirulence and potential therapeutic targets for preventing POWV spread to neuronal compartments. IMPORTANCE We isolated POWVs from LI deer ticks (I. scapularis) directly in VeroE6 cells, and sequencing revealed POWV-LI9 as a distinct lineage II POWV strain. Remarkably, inoculation of VeroE6 cells with POWV-containing tick homogenates resulted in infected cell foci in liquid culture, consistent with cell-to-cell spread. POWV-LI9 and -LI41 and lineage I POWV-LB strains infected hBMECs and pericytes that comprise neurovascular complexes. POWVs were nonlytically transmitted basolaterally from infected hBMECs to lower-chamber pericytes, suggesting a mechanism for POWV transmission across the blood-brain barrier (BBB). POWV-LI9 elicited inflammatory responses from infected hBMEC and pericytes that may contribute to immune cell recruitment and neuropathogenesis. This study reveals a potential mechanism for POWVs to enter the CNS by infecting hBMECs and spreading basolaterally to abluminal pericytes. Our findings reveal that POWV-LI9 persists in cells that form a neurovascular complex spanning the BBB and suggest potential therapeutic targets for preventing POWV spread to neuronal compartments.

Potential geographic distribution of Ixodes cookei, the vector of Powassan virus

Ixodes cookei Packard, the groundhog tick or woodchuck tick, is the main known vector of Powassan virus (POWV) disease in North America and an ectoparasite that infests diverse small- and mid-size mammals for blood meals to complete its life stages. Since I. cookei spends much of its life cycle off the host and needs hosts for a blood meal in order to pass to the next life stage, it is susceptible to changes in environmental conditions. We used a maximum-entropy approach to ecological niche modeling that incorporates detailed model-selection routes to link occurrence data to climatic variables to assess the potential geographic distribution of I. cookei under current and likely future climate conditions. Our models identified suitable areas in the eastern United States, from Tennessee and North Carolina north to southern Canada, including Nova Scotia, New Brunswick, eastern Newfoundland and Labrador, southern Quebec, and Ontario; suitable areas were also in western states, including Washington and Oregon and restricted areas of northern Idaho, northwestern Montana, and adjacent British Columbia, in Canada. This study produces the first maps of the potential geographic distribution of I. cookei. Documented POWV cases overlapped with suitable areas in the northeastern states; however, the presence of this disease in areas classified by our models as not suitable by our models but with POWV cases (Minnesota and North Dakota) requires more study.

Powassan virus: What is the risk to the blood supply?

Powassan virus (POWV) is an emerging tick-borne arbovirus that is found widely in Canada, the Northeastern and Northcentral United States, and the Russian Far East. While still rare, there has been an increase in reported cases of POWV disease over the last decade; most (>90%) cases have been neuroinvasive and the associated fatality rate is high (>10%). Transfusion-associated risk of POWV remains uncertain; while no intervention is likely indicated, one probable case of transfusion-transmitted POWV in the context of an increase in the incidence of POWV and other tick-borne infections, merits vigilance.

Ecology of Powassan Virus in the United States

Zoonotic viruses threaten the lives of millions of people annually, exacerbated by climate change, human encroachment into wildlife habitats, and habitat destruction. The Powassan virus (POWV) is a rare tick-borne virus that can cause severe neurological damage and death, and the incidence of the associated disease (Powassan virus disease) is increasing in the eastern United States. The mechanisms by which POWV is maintained in nature and transmitted to humans are complex and only partly understood. This review provides an overview of what is known about the vector species, vector-host transmission dynamics, and environmental and human-driven factors that may be aiding the spread of both the vector and virus.

Vector competence of human-biting ticks Ixodes scapularis, Amblyomma americanum and Dermacentor variabilis for Powassan virus

Background

Powassan virus (POWV; genus Flavivirus) is the sole North American member of the tick-borne encephalitis sero-complex and an increasing public health threat in the USA. Maintained in nature by Ixodes spp. ticks, POWV has also been isolated from species of other hard tick genera, yet it is unclear if these species can serve as vectors. Dermacentor variabilis and Amblyomma americanum share geographic and ecologic overlap with Ixodes spp. ticks and POWV transmission foci, raising the possibility that POWV could become established in these tick species and leading to range expansion and increased human risk. Therefore, we assessed the competency of Ixodes scapularis, D. variabilis and A. americanum for POWV lineage II (POWV II).

Methods

Larvae from all three species were co-infested on POWV-infected Balb/c mice. The engorged larvae were allowed to molt to nymphs and screened for the presence of POWV II RNA by reverse transcription-qPCR. Eight infected nymphs from each species were allowed to individually feed on a naïve mouse. Mice were screened for the presence of POWV II RNA to determine infection status.

Results

The results demonstrated that larvae from all three tick species were able to efficiently acquire POWV II via feeding on viremic mice, maintain infection through molting and successively transmit POWV to naïve mice at the nymphal stage at comparable rates across all three species.

Conclusions

Our findings reveal that non-Ixodes tick species can serve as competent vectors for POWV and highlight the potential role of these species in the ecology and epidemiology of POWV. Future studies examining the possible implications of these findings on POWV epidemiology and the adaptability of POWV in these new vectors are warranted.

Graphical abstract

The liver X receptor agonist LXR 623 restricts flavivirus replication

The vector-borne flaviviruses (VBFVs) are well known for causing great misery and death in humans worldwide. The VBFVs include those transmitted by mosquitos, such as Zika virus (ZIKV), dengue virus; and those transmitted by ticks including the tick-borne flavivirus serocomplex and Powassan virus (POWV). Two of our recent reports showed that intracranial POWV infection in the reservoir host, Peromyscus leucopus, was restricted and caused no overt clinical disease. Several modes of analyses suggested activation of the LXR pathway. Activation of the LXR pathway leads to increased efflux of cholesterol from cells and consequent disturbances in membrane biogenesis. Because VBFV replication is dependent on membrane biogenesis, we evaluated the effect of an LXR agonist (LXR623) on POWV and ZIKV infection and observed that the compound impaired permissive replication of both viruses in a human neuroblastoma SK-N-SH cell line. The LXR agonist resulted in failure of the viruses to induce ER expansion and elaborate vesicle formation, suggesting that the efflux of cholesterol was part of the antiviral mechanism. We also observed that the LXR agonist contributed to the mechanism of virus suppression by increased expression of mRNAs encoding for the antiviral cytokines CXCL10, RANTES and IFN1β. In sharp contrast, a LXR antagonist (GSK2033) had no significant effect on VBFV replication. We conclude that LXR623 impairs flavivirus replication by stimulating cellular antiviral factors.

A Virus-Like Particle-Based Vaccine Candidate against the Tick-Borne Powassan Virus Induces Neutralizing Antibodies in a Mouse Model

Powassan virus (POWV) is a tick-borne flavivirus circulating in North America and the Russian Far East that can cause severe neuroinvasive diseases, including encephalitis, meningitis, and meningoencephalitis. The reported neuroinvasive case fatality is about 10%, and approximately 50% of the survivors from the neuroinfection exhibit long-lasting or permanent neurological sequelae. Currently, treatment of POWV infection is supportive, and no FDA-approved vaccines or specific therapeutics are available. A novel Powassan vaccine candidate was created using virus-like particle technology (POW-VLP) and assembled with the viral structural proteins pre-Membrane (prM) and Envelope (E). Western blot immunoassay demonstrated high antigenicity of POW-VLP structural proteins. Transmission electron microscopy indicated that the POW-VLP exhibited icosahedral morphology typical of flaviviruses. A dose-escalation study in a murine model was performed to test immunogenicity and safety. Serum antibody was tested by ELISA, demonstrating that POW-VLP afforded 100% seroconversion to the E protein. Reporter viral-particle neutralization assay demonstrated high levels of neutralizing antibodies in the serum of immunized mice. Hybridomas expressing monoclonal antibodies were produced following POW-VLP immunization. The POW-VLP vaccine candidate created in this study provides a strategy for inducing protective antibodies against Powassan neuroinvasive infection.

Powassan Virus Infection Likely Acquired Through Blood Transfusion Presenting as Encephalitis in a Kidney Transplant Recipient

A kidney transplant patient without known tick exposure developed encephalitis 3 weeks after transplantation. During the transplant hospitalization, the patient had received a blood transfusion from an asymptomatic donor later discovered to have been infected with Powassan virus. Here, we describe a probable instance of transfusion-transmitted Powassan virus infection.

A Fatal Case of Powassan Virus Encephalitis

Powassan virus (POWV) is a flavivirus of the tick-borne encephalitis serogroup that causes a rare and potentially life-threatening neuroinvasive disease. Viral transmission occurs during zoonotic spillover from mammals by the bite of an infected tick in endemic regions of North America. The number of reported POWV cases has recently increased in the United States. We report a fatal case of POWV meningoencephalomyelitis in Northern Wisconsin following a documented tick bite. Histologic examination of the brain demonstrated widespread intraparenchymal and perivascular lymphohistocytic infiltration, microglial nodule formation, and marked neuronal degeneration, most severely involving the substantia nigra, anterior horn of spinal cord and cerebellum. Although no viral inclusions were seen in routine light microscopy, electron microscopy identified multiple neurons containing cytoplasmic clusters of virus particles ∼50 nm in diameter. POWV infection was confirmed using immunohistochemical analysis and reverse transcription-polymerase chain reaction. This report demonstrates in detail regional central nervous system involvement and ultrastructural characteristics of Powassan viral particles by transmission electron microscopy, while highlighting the utility of evaluating fixed autopsy tissues in cases of unexplained meningoencephalomyelitis.

Unusual cause at an unusual time-Powassan virus rhombencephalitis

Powassan virus lineage II (POWV) is an emerging tick-borne neurotropic pathogen, transmitted to humans by the bite of infected Ixodes scapularis ticks. In the United States, the disease is most prevalent in the Northeast and the upper Midwest and occurs mostly during the spring and summer months when tick activity is the highest. Some patients infected with POWV develop severe encephalitis, with high mortality. We report the case of a 42-year-old healthy man who developed progressive diplopia and dysarthria in December following a deer hunting trip. Routine blood work was unrevealing and MRI was normal. Extensive work-up for infectious, autoimmune, and paraneoplastic causes was positive only for POWV. The patient was treated with supportive care and intravenous corticosteroids, with an excellent outcome. We present a rare clinical presentation of a potentially fatal emerging disease that responded favorably to corticosteroids.

Diagnostic Approach for Arboviral Infections in the United States

Domestic arthropod-borne viruses (arboviruses) are single-stranded RNA viruses, the most common of which include the mosquito-borne West Nile virus, St. Louis encephalitis virus, La Crosse virus, Jamestown Canyon virus, and eastern equine encephalitis virus, as well as the tick-borne Powassan virus. Previously considered rare infections, they have been detected with increasing frequency over the past 2 decades. Here, we present an overview of the domestic arboviruses listed above and describe the modalities employed to diagnose infection. Global arboviruses, including dengue virus, Zika virus, and chikungunya virus, have also been increasingly detected in the United States within the last 5 years but are not a focus of this minireview. Typical manifestations of arbovirus infection range from no symptoms, to meningitis or encephalitis, to death. Serologies are the standard means of diagnosis in the laboratory, since most viruses have a short period of replication, limiting the utility of molecular tests. The interpretation of serologies is confounded by antibody cross-reactivity with viruses belonging to the same serogroup and by long-lasting antibodies from prior infections. Next-generation assays have improved performance by increasing antigen purity, selecting optimal epitopes, and improving interpretive algorithms, but challenges remain. Due to cross-reactivity, a positive first-line serology test requires confirmation by either a plaque reduction neutralization test or detection of seroconversion or a 4-fold rise in virus-specific IgM or IgG antibody titers from acute- and convalescent-phase sera. The use of molecular diagnostics, such as reverse transcription PCR or unbiased metagenomic sequencing, is limited to the minority of patients who present with ongoing viremia or central nervous system replication. With the continued expansion of vector range, the diagnosis of domestic arboviruses will become an increasingly important task for generalists and specialists alike.

Powassan Virus Encephalitis Following Brief Attachment of Connecticut Deer Ticks

BACKGROUND

Powassan virus (POWV) is a tick-transmitted pathogen that may cause severe encephalitis; experimentally, it can be transmitted within just 15 minutes following a tick bite. The deer tick virus subtype of POWV (DTV) is transmitted by the deer tick and is the likely cause of the increase in the number of POWV cases reported in the United States. However, DTV has only been definitively documented in 6 patients by molecular analysis of the virus.

METHODS

Two patients from Connecticut with encephalitis, who had a recent deer tick bite, were evaluated by the relevant serologic tests to determine if they had been infected with POWV. Evaluation also included molecular testing of an adult deer tick that had been removed from one of the patients.

RESULTS

We documented neuroinvasive POWV infection in 2 children from Connecticut. Based on the results of testing the tick removed from case 2, this patient was infected by DTV, representing the 7th reported case and the first documented case of DTV infection in a child. Of note, the duration of the tick bites in both cases was very short.

CONCLUSIONS

We provide the first clinical and epidemiologic evidence that POWV/DTV can be rapidly transmitted to a human host, that is, within hours of tick attachment, which is distinctive when compared to other deer tick-transmitted infections such as Lyme disease.

The emergence of human Powassan virus infection in North America

Powassan virus (POWV) is a tickborne flavivirus discovered in Ontario, Canada in 1958 that causes long-term neurological sequelae in about half the reported cases and death in a little more than 10 % of cases. The incidence of POWV disease is rising in the United States but there is limited understanding of the scope and causes of recent changes in POWV epidemiology. We focus on quantifying the increase in human POWV disease incidence and infection prevalence in the United States. We also examine differences in the frequency of symptomatic cases and asymptomatic or mildly symptomatic cases, as well as limitations in national and state surveillance for POWV infection. We searched SCOPUS for all articles containing original POWV prevalence research, case studies, or literature reviews published in English. Case studies were supplemented by Morbidity and Mortality Weekly Report POWV data from the Centers for Disease Control and Prevention (CDC) and surveillance information from state health department websites. An increase in the number of POWV cases has been reported in the United States over the past 50 yr, and the geographic range of human POWV cases has expanded. The age distribution of symptomatic POWV cases has shifted, with significantly more individuals over 40 yr old being diagnosed after 1998. The emergence of POWV is due in large part to: (i) a change in transmission of POWV from a vector that rarely bites people (Ixodes cookei) to a new vector that often bites people (Ixodes scapularis) and has expanded its geographic range, (ii) enhanced surveillance efforts for arboviruses, and (iii) a greater awareness of POWV infection.

Suspected Neuro-invasive Powassan Virus Infection in a Pediatric Patient

Powassan virus lineage II (POWV), also known as deer tick virus, is an emerging tick-borne pathogen transmitted by Ixodes scapularis, the natural vector for the organisms that causes Lyme disease, babesiosis, and anaplasmosis. POWV is the only tick-borne flavivirus in North America known to cause disease in humans. We present a suspected pediatric case of POWV infection in northern Wisconsin.

Utilization of RNA in situ Hybridization to Understand the Cellular Localization of Powassan Virus RNA at the Tick-Virus-Host Interface

Skin is the interface between an attached, feeding tick and a host; consequently, it is the first line of defense against invading pathogenic microorganisms that are delivered to a vertebrate host together with tick saliva. Central to the successful transmission of a tick-borne pathogen are complex interactions between the host immune response and early tick-mediated immunomodulation, all of which initially occur at the skin interface. The focus of this work was to demonstrate the use of RNA in situ hybridization (RNA ISH) as a tool for understanding the cellular localization of viral RNA at the feeding site of Powassan virus (POWV)-infected Ixodes scapularis ticks. Intense positive staining for POWV RNA was frequently detected in dermal foci and occasionally detected in hypodermal foci after 24 h of POWV-infected tick feeding. Additionally, duplex chromogenic RNA ISH staining demonstrated co-localization of POWV RNA with Mus musculus F4/80 RNA, CD11c RNA, vimentin RNA, Krt14 RNA, and CD3ε RNA at the feeding site of POWV-infected ticks. In future studies, RNA ISH can be used to validate transcriptomic analyses conducted at the tick-virus-host cutaneous interface and will provide cellular resolution for specific gene signatures temporally expressed during infected tick feeding. Such a systems biology approach will help create a more refined understanding of the cellular and molecular interactions influencing virus transmission at the cutaneous interface.

Geographic distribution of Tick-borne encephalitis virus complex

A comprehensive understanding of the geographic distribution of the tick-borne encephalitis virus (TBEV) complex is necessary due to increasing transboundary movement and cross-reactivity of serological tests. This review was conducted to identify the geographic distribution of the TBEV complex, including TBE virus, Alkhurma haemorrhagic fever virus, Kyasanur forest disease virus, louping-ill virus, Omsk haemorrhagic fever virus, and Powassan virus. Published reports were identified using PubMed, EMBASE, and the Cochrane library. In addition to TBEV complex case-related studies, seroprevalence studies were also retrieved to assess the risk of TBEV complex infection. Among 1406 search results, 314 articles met the inclusion criteria. The following countries, which are known to TBEV epidemic region, had conducted national surveillance studies: Austria, China, Czech, Denmark, Estonia, Finland, Germany, Hungary, Italy, Latvia, Norway, Poland, Romania, Russia, Switzerland, Sweden, Slovenia, and Slovakia. There were also studies/reports on human TBEV infection from Belarus, Bulgaria, Croatia, France, Japan, Kyrgyzstan, Netherland, and Turkey. Seroprevalence studies were found in some areas far from the TBEV belt, specifically Malaysia, Comoros, Djibouti, and Kenya. Kyasanur forest disease virus was reported in southwestern India and Yunnan of China, the Powassan virus in the United States, Canada, and east Siberia, Alkhurma haemorrhagic fever virus in Saudi Arabia and east Egypt, and Louping-ill virus in the United Kingdom, Ireland, and east Siberia. In some areas, the distribution of the TBEV complex overlaps with that of other viruses, and caution is recommended during serologic diagnosis. The geographic distribution of the TBEV complex appears to be wide and overlap of the TBE virus complex with other viruses was observed in some areas. Knowledge of the geographical distribution of the TBEV complex could help avoid cross-reactivity during the serologic diagnosis of these viruses. Surveillance studies can implement effective control measures according to the distribution pattern of these viruses.

Co-infections in Persons with Early Lyme Disease, New York, USA

In certain regions of New York state, USA, Ixodes scapularis ticks can potentially transmit 4 pathogens in addition to Borrelia burgdorferi: Anaplasma phagocytophilum, Babesia microti, Borrelia miyamotoi, and the deer tick virus subtype of Powassan virus. In a prospective study, we systematically evaluated 52 adult patients with erythema migrans, the most common clinical manifestation of B. burgdorferi infection (Lyme disease), who had not received treatment for Lyme disease. We used serologic testing to evaluate these patients for evidence of co-infection with any of the 4 other tickborne pathogens. Evidence of co-infection was found for B. microti only; 4–6 patients were co-infected with Babesia microti. Nearly 90% of the patients evaluated had no evidence of co-infection. Our finding of B. microti co-infection documents the increasing clinical relevance of this emerging infection.

Seroprevalence of Borrelia burgdorferi, B. miyamotoi, and Powassan Virus in Residents Bitten by Ixodes Ticks, Maine, USA

We conducted a serosurvey of 230 persons in Maine, USA, who had been bitten by Ixodes scapularis or I. cookei ticks. We documented seropositivity for Borrelia burgdorferi (13.9%) and B. miyamotoi (2.6%), as well as a single equivocal result (0.4%) for Powassan encephalitis virus.

Polio-Like Manifestation of Powassan Virus Infection with Anterior Horn Cell Involvement, Canada

Evidence of spinal cord involvement in Powassan virus infection is largely limited to mouse models. We report a case of a polio-like illness caused by Powassan virus infection in a 62-year-old man in Canada. Magnetic resonance imaging showed T2 hyperintensities in the anterior horns of the cervical spinal cord.