Morphologic and molecular characterization of new Cyclospora species from Ethiopian monkeys: C. cercopitheci sp.n., C. colobi sp.n., and C. papionis sp.n

Human infections associated with wild birds

Introduction

Wild birds and especially migratory species can become long-distance vectors for a wide range of microorganisms. The objective of the current paper is to summarize available literature on pathogens causing human disease that have been associated with wild bird species.

Methods

A systematic literature search was performed to identify specific pathogens known to be associated with wild and migratory birds. The evidence for direct transmission of an avian borne pathogen to a human was assessed. Transmission to humans was classified as direct if there is published evidence for such transmission from the avian species to a person or indirect if the transmission requires a vector other than the avian species.

Results

Several wild and migratory birds serve as reservoirs and/or mechanical vectors (simply carrying a pathogen or dispersing infected arthropod vectors) for numerous infectious agents. An association with transmission from birds to humans was identified for 10 pathogens. Wild birds including migratory species may play a significant role in the epidemiology of influenza A virus, arboviruses such as West Nile virus and enteric bacterial pathogens. Nevertheless only one case of direct transmission from wild birds to humans was found.

Conclusion

The available evidence suggests wild birds play a limited role in human infectious diseases. Direct transmission of an infectious agent from wild birds to humans is rarely identified. Potential factors and mechanisms involved in the transmission of infectious agents from birds to humans need further elucidation.

Clinical and pathologic features of lineage 2 West Nile virus infections in birds of prey in Hungary

In the southeast of Hungary a sparrow hawk (Accipiter nisus) and several goshawk (Accipiter gentilis) fledglings succumbed to encephalitis manifesting as an acute neurological disease during the summers of 2004 and 2005. Both years the causative agent was identified as a lineage 2 West Nile virus. This is the first description of clinical, pathological and immunohistochemical findings of infection caused by a neuroinvasive, lineage 2 West Nile virus and the first evidence of its circulation in continental Europe.

Antigen-specific cytotoxic T lymphocytes protect against lethal West Nile virus encephalitis

Infection with West Nile virus (WNV) causes fatal encephalitis in immunocompromised animals. Previous studies in mice have established that T cell protection is required for clearance of WNV infection from tissues and preventing viral persistence. The current study assessed whether specific WNV peptide epitopes could elicit a cytotoxic T lymphocyte (CTL) response capable of protecting against virus infection. Hidden Markov model analysis was used to identify WNV-encoded peptides that bound the MHC class I proteins K(b) or D(b). Of the 35 peptides predicted to bind MHC class I molecules, one immunodominant CTL recognition peptide was identified in each of the envelope and non-structural protein 4B genes. Addition of these but not control peptides to CD8(+) T cells from WNV-infected mice induced IFN-gamma production. CTL clones that were generated ex vivo lysed peptide-pulsed or WNV-infected target cells in an antigen-specific manner. Finally, adoptive transfer of a mixture of envelope- and non-structural protein 4B-specific CTL to recipient mice protected against lethal WNV challenge. Based on this, we conclude that CTL responses against immundominant WNV epitopes confer protective immunity and thus should be targets for inclusion in new vaccines.

Detection of West Nile virus lineages 1 and 2 by real-time PCR

West Nile virus (WNV) is a Flavivirus attracting worldwide attention because it has spread rapidly across the Americas since its first appearance in New York City in 1999. Several PCR-based diagnostic methods have been developed for the detection of WNV. The focus of these assays has been WNV lineage 1 which can be found worldwide, while lineage 2 viruses were thought to be endemic only in some regions of Africa. However, both lineages may be imported from Africa to Europe by migrating birds. In order to determine the incidence of WNV in Germany, a real-time-based PCR assay was developed, targeting a conserved region of WNV lineages 1 and 2. This assay is a suitable tool for the diagnosis of WNV and for surveillance studies.

Bird Species Potentially Involved in Introduction, Amplification, And Spread of West Nile Virus in A Mediterranean Wetland, The Camargue (Southern France)

West Nile virus (WNV) is a mosquito-transmitted Flavivirus with a transmission cycle involving birds as amplifying hosts. Wild birds are also believed to carry WNV over large distances and are able to introduce it into new areas during migration and dispersal. In this paper, our objective is to provide lists of birds potentially involved in the introduction, the amplification and the spread of WNV in the Camargue, a Mediterranean wetland in the south of France where several WNV outbreaks have occurred since the 1960s. Bird species were classified according to the following ecological factors: migratory status and provenance area, used biotopes, abundance and period of presence in the Camargue. The obtained lists of bird species potentially involved in the introduction, amplification and spread of WNV should prove useful to determine target species on which further studies on WNV ecology in birds could be focused.

Molecular characterization of Cyclospora-like organism from dairy cattle

Cyclospora cayetanensis was identified as the cause of large outbreaks of diarrhea in many parts of the world, but its host range and reservoirs remains poorly defined. Recently, oocysts resembling the C. cayetanensis were detected in dairy cattle fecal specimens from China. The 18S rDNA from two of these Cyclospora-like oocyst specimens from dairy cattle was amplified and sequenced. Phylogenetic analysis indicated that these cattle-associated Cyclospora-like organisms are nearly identical to each other and belong to the group of primate-derived Cyclospora, which are the closest known relatives of C. cayetanensis; while these cyclosporans constitute a coherent clade within the diverse group of Eimeria species. Moreover, on the basis of our finding that ruminant- and avian-associated Eimeria species are different in MnlI sites, a new PCR-restriction fragment length polymorphism protocol with primers NesCycF and NesCycR was developed to distinguish the Cyclospora species from ruminant-associated Eimeria species.

West Nile virus: recent trends in diagnosis and vaccine development

West Nile virus (WNV) is a mosquito-borne flavivirus, native to Africa, Europe, and Western Asia. In many respects, WNV is an outstanding example of a zoonotic pathogen that has leaped geographical barriers and can cause severe disease in human and horse. Before the emergence of WNV in the USA, only few methods of diagnosis were available. Recently, many changes in the fields of WN diagnosis and prevention have happened. This paper will review all these new tools. After a description of the main concerns in WNV and West Nile (WN) disease in humans and animals, this review will present the main available tests for serology and virology detection, from gold standard tests to more recently developed methods. Finally, licensed vaccines and candidate vaccines developed in humans, horses and birds will also been described.

Remote sensing based identification of environmental risk factors associated with West Nile disease in horses in Camargue, France

Geographic information system and remote sensing technologies were used to identify landscape features associated with risk of West Nile virus transmission as defined by the presence of confirmed horse cases. SPOT-4 images of Camargue area were used to generate a map of landscape categories of epidemic foci and the geographic information system was employed to determine the proportion of landscape components surrounding 10 horse case sites and 17 control sites. The spatio-temporal analysis of the cases outbreak gave the best results for a spatial window of 9 km and a temporal window of 18 days. Two clusters were identified (relative risk=3.35), both in the wet area of Camargue, near the town "Les Saintes Maries de la Mer". The first one was 4 km radius, the second 9 km. The relationships between the presence of cases and proportions of landscape categories were analyzed using generalized linear model. The best model indicated that rice fields and dry bushes, wet "sansouire" and open water were the major components of the landscape that were associated with the presence of West Nile virus cases.

Immunopathology of flavivirus infections

With the recent emergence of the flavivirus, West Nile virus (WNV), in particular, the New York strain of Lineage I WNV in North America in 1999, there has been a significant increase in activity in neurotropic flavivirus research. These viruses cause encephalitis that can result in permanent neurological sequelae or death. Attempts to develop vaccines have made progress, but have been variably successful, despite considerable commercial underwriting. Thus, the discovery of ways and means to combat disease is no less urgent. As such, most recent work has been directed towards dissecting and understanding the pathogenesis of disease, as a way of informing possible approaches to abrogation or amelioration of illness. Whether inherent to flaviviruses or because humans are incidental, dead-end hosts, it is clear that these viruses interact with their human hosts in extremely complex ways. This occurs from the cellular level, at which infection must be established to produce disease, to its interaction with the adaptive immune response, which may result in its eradication, with or without immunopathological and consequent neurological sequelae. As human proximity to and contact with flavivirus insect vectors and amplifying hosts cannot practically be eliminated, our understanding of the pathogenesis of flavivirus-induced diseases, especially with regard to possible targets for treatment, is imperative.

Emergency Medicine and the Public's Health: Emerging Infectious Diseases

In recent years, multiple global forces have contributed to the emergence and widespread distribution of previously unknown disease entities. This article discusses Ebola virus, West Nile virus, and Hantavirus as representative emerging infectious diseases. Smallpox is discussed along with concerns about the safety of the smallpox vaccine, given the uncertain risk of bioterrorism and smallpox exposure. ED physicians must become familiar with the presentation, management, and public health impact of all of these entities, as well as understand the potential impact of other emerging infectious diseases.

Modeling movement of West Nile virus in the Western hemisphere

We modeled West Nile virus (WNV) movement rates and patterns based on a migratory bird agent (the Swainson's Thrush) and a resident bird agent (the House Sparrow), and compared the results of these models with actual movement data to investigate the likelihood that the pattern of WNV outbreaks observed in the New World was consistent with migrant bird-mediated spread, as reported from the Old World. We found that, contrary to Old World patterns, WNV activity in the Western Hemisphere does not seem consistent with movement by infected migrant birds. Instead WNV spread appears best explained by a non-directional movement, perhaps that of dispersing resident birds.

Antibodies to West Nile Virus in Feral Swine from Florida, Georgia, and Texas, USA

West Nile virus (WNV) exposure has not yet been reported in feral swine (Sus scrofa) despite the broad geographic range and population density of this species. The objectives of this study were to determine the prevalence of antibodies to WNV in feral pigs, and to evaluate serologic diagnostics as applied to this species. Feral pig serum from three states was evaluated for antibodies to WNV. The overall WNV seroprevalence rate for 222 samples collected in 2001-2004 was 22.5%. Seroprevalence rates in Florida, Georgia, and Texas were 17.2%, 26.3%, and 20.5%, respectively. The results of this study demonstrate that feral pigs could represent useful mammalian sentinels of WNV.

Viral infections in pigeons

This review provides a current update on the major viral diseases of the domestic pigeon (Columba livia domestica), based on scientific reports and clinical experience. Paramyxovirus 1, adenovirus, rotavirus, herpesvirus 1, poxvirus and circovirus infections are described according to common clinical signs and target tissues. Since pigeons are sometimes treated as if they were poultry, the review also summarises the common viral infections of poultry for which pigeons are considered resistant. It is hoped that the review will provide a useful reference for veterinarians and others and offer advice on the diagnosis, treatment and prevention of the major infectious diseases of pigeons.

Lineage 1 and 2 strains of encephalitic West Nile virus, central Europe

Two different West Nile virus (WNV) strains caused lethal encephalitis in a flock of geese and a goshawk in southeastern Hungary in 2003 and 2004, respectively. During the outbreak in geese, 14 confirmed human cases of WNV encephalitis and meningitis were reported in the same area. Sequencing of complete genomes of both WNV strains and phylogenetic analyses showed that the goose-derived strain exhibits closest genetic relationship to strains isolated in 1998 in Israel and to the strain that emerged in 1999 in the United States. WNV derived from the goshawk showed the highest identity to WNV strains of lineage 2 isolated in central Africa. The same strain reemerged in 2005 in the same location, which suggests that the virus may have overwintered in Europe. The emergence of an exotic WNV strain in Hungary emphasizes the role of migrating birds in introducing new viruses to Europe.

Potential arbovirus emergence and implications for the United Kingdom

Climate change can cause arthropodborne diseases to emerge.

Arboviruses have evolved a number of strategies to survive environmental challenges. This review examines the factors that may determine arbovirus emergence, provides examples of arboviruses that have emerged into new habitats, reviews the arbovirus situation in western Europe in detail, discusses potential arthropod vectors, and attempts to predict the risk for arbovirus emergence in the United Kingdom. We conclude that climate change is probably the most important requirement for the emergence of arthropodborne diseases such as dengue fever, yellow fever, Rift Valley fever, Japanese encephalitis, Crimean-Congo hemorrhagic fever, bluetongue, and African horse sickness in the United Kingdom. While other arboviruses, such as West Nile virus, Sindbis virus, Tahyna virus, and Louping ill virus, apparently circulate in the United Kingdom, they do not appear to present an imminent threat to humans or animals.

Factors Affecting the Geographic Distribution of West Nile Virus in Georgia, USA: 2002–2004

The distribution of West Nile virus (WNV) is dependent on the occurrence of both susceptible avian reservoir hosts and competent mosquito vectors. Both factors can be influenced by geographic variables such as land use/landcover, elevation, human population density, physiographic region, and temperature. The current study uses geographic information systems (GIS) and logistic regression analyses to model the distribution of WNV in the state of Georgia based on a wild bird indicator system, and to identify human and environmental predictor variables that are important in the determination of WNV distribution. A database for Georgia was constructed that included (1) location points of all the avian samples tested for WNV, (2) local land use classifications, including temperature, physiographic divisions, land use/landcover, and elevation, (3) human demographic data from the U.S. Census, and (4) statistics summarizing land cover, elevation, and climate within a 1-km-radius landscape around each sample point. Logistic regression analysis was carried out using the serostatus of avian collection sites as the dependent variable. Temperature, housing density, urban/suburban land use, and mountain physiographic region were important variables in predicting the distribution of WNV in the state of Georgia. While weak, the positive correlation between WNV-antibody positive sites and the urban/suburban environment was consistent throughout the study period. The risks associated with WNV endemicity appear to be increased in urban/ suburban areas and decreased in the mountainous region of the state. This information may be used in addressing regional public health needs and mosquito control programs.

Toscana virus in Spain

Toscana virus (TOSV, Phlebovirus, family Bunyaviridae) infection is one of the most prevalent arboviruses in Spain. Within the objectives of a multidisciplinary network, a study on the epidemiology of TOSV was conducted in Granada, in southern Spain. The overall seroprevalence rate was 24.9%, significantly increasing with age. TOSV was detected in 3 of 103 sandfly pools by viral culture or reverse transcription-polymerase chain reaction from a region of the L gene. Nucleotide sequence homology was 99%-100% in TOSV from vectors and patients and 80%-81% compared to the Italian strain ISS Phl.3. Sequencing of the N gene of TOSV isolates from patients and vectors indicated 87%-88% and 100% homology at the nucleotide and amino acid levels, respectively, compared to the Italian strain. These findings demonstrate the circulation of at least 2 different lineages of TOSV in the Mediterranean basin, the Italian lineage and the Spanish lineage.

Neutralizing monoclonal antibodies against Russian strain of the West Nile virus

We have developed a panel of 16 hybridomas secreting neutralizing monoclonal antibodies (Nt- MAbs) to Russian isolate (LEIV-Vlg99-27889-human) of the West Nile virus (WNV). Most of the Nt-Mabs were either IgG1 or IgG3 subtypes. Nine of the 16 neutralizing MAbs detected WNV protein E in Western blot. According to their Nt-activities, Western blot results and cross-reactivity, the MAbs were divided into four groups. Monoclonal antibodies from group I were able to neutralize WNV strains Vlg99-27889, Vlg00-27924, Hp-94, A-1640, A-72, Tur-2914, and Eg101. The Nt-activity of MAbs from groups II-IV towards these WNV strains was variable. Recombinant fragments E(1-180), E(1-321), and E(260-466) of protein E were used for preliminary mapping of domains recognized by Nt-MAbs. Only five Nt-MAbs were able to react with the recombinant polypeptides. The MAbs 9E2, 7G9, 11G3, and 7E6 from group Ia recognized Nt-epitope(s) between amino acids 321 and 466 of protein E and Nt-MAb 4F11 (group III) reacted with residues 1-180. This demonstrates that two discrete regions of protein E are involved in neutralization of WNV. Our data on immunochemical, biological activities of Nt-MAbs and mapping of Nt-epitopes using recombinant polypeptides suggest at least 13 different Nt-epitopes for WNV.

The epidemiology and early clinical features of West Nile virus infection

We studied early clinical features of the West Nile virus (WNV) infection. Case patients were Ohio residents who reported to the Ohio Department of Health from August 14 to December 31, 2002, with a positive serum or cerebrospinal fluid for anti-WNV IgM. Of 441 WNV cases, medical records of 224 (85.5%) hospitalized patients were available for review. Most frequent symptoms were fever at a temperature of 38.0 degrees C or higher (n = 155; 69.2%), headache (n = 114; 50.9%), and mental status changes (n = 113; 50.4%). At least one neurological symptom, one gastrointestinal symptom, and one respiratory symptom was present in 186 (83.0%), 119 (53.1%), and 46 (20.5%) patients, respectively. Using multivariate logistic regression and controlling for age, we found that the initial diagnosis of encephalitis (P = .001) or reporting abdominal pain (P < .001) was associated with death. Because initial symptoms of WNV infection are not specific, physicians should maintain a high index of suspicion during the epidemic season, particularly in elderly patients with compatible symptoms.

Detection of West Nile virus and Japanese encephalitis virus using real-time PCR with a probe common to both viruses

A diagnostic method to distinguish between West Nile virus (WNV) and Japanese encephalitis virus (JEV) based on fluorogenic real-time polymerase chain reaction (TaqMan) assays was developed. To detect WNV and JEV with a single probe, a probe was designed to correspond to sequences in the core protein region that are shared by both viruses. The specificity of this assay depended on the primer sets used, which were specific to the target virus sequences: the primer set for WNV could detect only WNV strains and the primer set for JEV could detect only JEV strains. The assays were tested by detection of viruses from experimentally infected animal tissues. The method described in this study will be useful for the simultaneous discrimination of WNV and JEV in areas where JEV is endemic, such as East Asia.

Experimental Transmission of West Nile Virus (Flaviviridae: Flavivirus) byCarios capensisTicks from North America

Seabird soft ticks, Carios capensis (Ixodida: Argasidae), originally collected from coastal Georgia, USA, were allowed to ingest a blood meal from pekin ducklings (Anas domesticus) infected with WNV. After 35 days of extrinsic incubation, the ticks transmitted virus to naive ducklings. WNV was detected via plaque assay and RTPCR in ticks and in tissues and serum of ducklings 7 days post infestation.

No evidence for bacteriophage WO orf7 correlation with Wolbachia-induced cytoplasmic incompatibility in the Culex pipiens complex (Culicidae: Diptera)

Gene flow between populations of Culex pipiens L. is relevant to observed differences in disease transmission, insecticide resistance, behavior, and physiology. Intracellular Wolbachia bacteria have been hypothesized to affect gene flow in insects. Specifically, Wolbachia cause a form of embryonic mortality known as cytoplasmic incompatibility (CI) in crosses between individuals with different Wolbachia types. Incompatibility in Culex is exceptional in that it represents the most complex CI pattern known, and yet Culex populations are not infected with divergent Wolbachia strains. This has led to the hypothesis that extrachromosomal factors such as phages or mobile genetic elements may be involved in determining CI phenotype. Recent molecular characterization of Culex laboratory strains has identified variation in the orf7 locus of the Wolbachia-associated bacteriophage WO. Here, crosses between eight Culex strains differing in their orf7 type were conducted to examine for the hypothesized involvement of bacteriophage WO in determining CI in Culex. Although crossing results show examples of compatibility, partial compatibility, and incompatibility, the results fail to show a correlation between the CI phenotypes and orf7 type. Specific examples include high egg hatch resulting in crosses between Culex strains that differ significantly in their orf7 type and low egg hatch resulting in crosses between Culex strains with similar orf7 types. Thus, the phage orf7 locus alone cannot predict CI type in the Culex strains examined in this study. However, rejection of the hypothesized role of WO phage in Culex CI will require the characterization of additional phage loci.

Epidemic West Nile virus encephalomyelitis: a temperature-dependent, spatial model of disease dynamics

Since first being detected in New York in 1999, West Nile virus (WNV) has spread throughout the United States and more than 20,000 cases of equine WNV encephalomyelitis have been reported. A spatial model of disease occurrence was developed, using data from an outbreak of serologically confirmed disease in an unvaccinated population of horses at 108 locations in northern Indiana between 3 August and 17 October 2002. Daily maximum temperature data were recorded at meteorological stations surrounding the study area. The distribution of the total number of degree-days elapsing between July 4 and the date of diagnosis of each case was best described by a normal distribution (mean=5243 degrees F, S.D.=1047). The days on which the average risk was >25, >50 and >75% were predicted (versus observed) to occur on August 23 (August 9), August 31 (September 2) and September 9 (September 9). The epidemic was predicted to occur 3 days earlier, or 4 days later, than observed if temperatures in the study area were uniformly increased, or decreased, by 5 degrees F, respectively. Maps indicated that WNV encephalomyelitis risk always remained greater in the northwest quadrant of the study area. Since WNV might exist at a hypoendemic level of infection, and occasionally re-emerge as a cause of epidemics in equine populations, by identifying factors that contributed to this epidemic, the potential impact of future epidemics can be reduced. Such studies rely on a GIS framework, availability of meteorological and possibly remotely sensed data and information on host and landscape factors. An early-warning system for WNV transmission in equine populations could be developed.

MOLECULAR CHARACTERIZATION OF ISOSPOROID COCCIDIA (ISOSPORA AND ATOXOPLASMA SPP.) IN PASSERINE BIRDS

Prevalence and disease caused by isosporoid coccidia in passerine birds are well recognized, but confusion about the life cycles of the parasites has led to taxonomic inconsistencies. In this study, we characterized segments of the chromosomal small and large-subunit ribosomal RNA (rRNA) genes of coccidial parasites from 23 species of passerine birds, as well as heat shock protein 70, apicoplast rRNA, and chromosomal 5.8s rRNA genes from a subgroup of these animals, and we correlated genetic data with morphologic findings for different parasite developmental stages, host phylogeny, and overall taxonomic relations within the phylum Apicomplexa. Our findings indicate that isosporoid coccidia of passerine birds are monophyletic but exhibit substantial diversity, with most avian species having one or several unique parasite lineages that underwent synchronous speciation with their hosts, interrupted by sporadic episodes of lateral transmission across species and families. Molecular analyses support a homoxenous life cycle, with sexual forms occurring chiefly in the intestines and asexual merozoites present systemically. Rarely, extraintestinal sexual stages can occur. The passerine coccidia are genetically most closely related to species of Eimeria rather than Isospora. We suggest that these parasites, whether identified from blood merozoite stages or fecal oocysts, be provisionally grouped as a homogeneous clade of individual species in a single taxon and formally named when reliable criteria allowing reclassification of related genera in the suborder Eimeriina are clarified.

Punctate exanthem of West Nile Virus infection: report of 3 cases

The West Nile Virus (WNV) has rapidly emerged as an important etiology of meningoencephalitis in North America since 1999. Diagnosis of this infection on clinical grounds is difficult, as many signs and symptoms of infection are nonspecific. Although cutaneous manifestations are common in WNV-infected patients, these have not been described in detail nor are clinical images widely available. We describe 3 patients with WNV infections, two ambulatory, one hospitalized, who developed punctate erythematous, macular, and papular eruptions, most pronounced on the extremities. Histopathologic findings in one case showed a sparse superficial perivascular lymphocytic infiltrate, a feature commonly seen in viral exanthems but not previously reported with WNV infection. A literature review provides support that this punctate exanthem is a common cutaneous presentation of WNV infection.

Ultrastructural study of West Nile virus pathogenesis in Culex pipiens quinquefasciatus (Diptera: Culicidae)

The ultrastructural features of West Nile virus (WNV) replication and dissemination in orally infected Culex pipiens quinquefasciatus Say were analyzed over a 25-d infection period. To investigate the effects of virus replication on membrane induction, cellular organization, and cell viability in midgut and salivary gland tissues, midguts were dissected on days 3, 7, 14, and 21, and salivary glands were collected on days 7, 14, 21, and 25 postinfection (d.p.i.) for examination by transmission electron microscopy (TEM). Whole mosquito heads were embedded for TEM analysis 14 d.p.i. to localize WNV particles and to investigate the effects of replication on nervous tissues of the brain. Membrane proliferation was induced by WNV in the midgut epithelium, midgut muscles, and salivary glands, although extensive endoplasmic reticulum swelling was a unique feature of salivary gland infection. TEM revealed WNV-induced pathology in salivary glands at 14, 21, and 25 d.p.i., and we hypothesize that long-term virus infection of this tissue results in severe cellular degeneration and apoptotic-like cell death. This finding indicates that the efficiency of WNV transmission may decrease with mosquito age postinfection.

Novel flavivirus or new lineage of West Nile virus, central Europe

Rabensburg virus, isolated from Culex pipiens mosquitoes in central Europe, represents a new lineage of West Nile virus or a novel flavivirus of the Japanese encephalitis virus group.

A flavivirus (strain 97-103) was isolated from Culex pipens mosquitoes in 1997 following floods in South Moravia, Czech Republic. The strain exhibited close antigenic relationship to West Nile virus (WNV) prototype strain Eg-101 in a cross-neutralization test. In this study, mouse pathogenicity characteristics and the complete nucleotide and putative amino acid sequences of isolate 97-103, named Rabensburg virus (RabV) after a nearby Austrian city, were determined. RabV shares only 75%–77% nucleotide identity and 89%–90% amino acid identity with representative strains of WNV lineages 1 and 2. Another RabV strain (99-222) was isolated in the same location 2 years later; it showed >99% nucleotide identity to strain 97-103. Phylogenetic analyses of RabV, WNV strains, and other members of the Japanese encephalitis virus (JEV) complex clearly demonstrated that RabV is either a new (third) lineage of WNV or a novel flavivirus of the JEV group.

Le virus West Nile : généralités et implications en transfusion sanguine

West Nile virus (WNV) is an arbovirus (genus Flavivirus, Family Flaviviridae, transmitted to humans by mosquito bite. In most cases (80%), human infection remains asymptomatic. Severe central nervous system complications (encephalitis and meningoencephalitis) are rare. In the Old World, the virus circulation has been demonstrated in Asia, Australia, Africa, Middle East and Europe. Several outbreaks in humans have been described. Following its introduction into North America in 1999, WN virus has been responsible of a large number of human cases in USA and Canada. For the first time, viral transmission by blood products was clearly demonstrated in USA in 2002. In France, the presence of virus has been reported in the Southeastern departments since 1962. In 2003, the occurrence of humans cases at specific geographical foci urged the French National Blood Agency (etablissement francais du sang) to take preventive measures for evaluating the virus transmission risks.

Cyclospora cayetanensis, a food- and waterborne coccidian parasite

Food- and waterborne coccidia including Cryptosporidium parvum, Cyclospora cayetanensis, Sarcocystis hominis and Sarcocystis suihominis, and Isospora belli are cyst-forming apicomplexan protozoa that cause intracellular infections, predominantly in the epithelial cells of the intestine. They are transmitted by oocysts from person-to-person by the fecal-oral route or via contaminated water or food. The most common symptom of infection is diarrhea, however, asymptomatic infections occur. Infections are associated with intestinal inflammation, with pathological lesions such as villus blunting, and abnormal function such as malabsorption. Mild-to-moderate, self-limiting diarrhea is common in healthy individuals ingesting infective stages of these organisms. However, patients with immune dysfunction can have severe intestinal injury and prolonged diarrhea. Diagnosis in many cases is made by a microscopic examination of the stool, and the use of appropriate staining techniques, but more recently molecular methods for detection are used increasingly. Effective antimicrobial treatment for prolonged infection in immunocompromised patients is available for most of these infections. These gastrointestinal coccidial pathogens have important similarities in epidemiology, disease pathogenesis, clinical manifestations, diagnosis, and treatment. Although there are many other cyst-forming coccidia of public health, veterinary and/or economic importance, discussion in this chapter will be limited to C. cayetanensis, as an important example of the group. Aspects of the biology, epidemiology, diagnosis, disease, treatment and control are considered. This parasite is considered to be an emerging pathogen. From 1990 to 2000, there were 11 foodborne outbreaks of cyclosporosis in North America that affected at least 3600 people. There are many outstanding questions regarding this parasite and under-reporting is common because general diagnostic methods for intestinal parasites are inadequate for detection of Cyclospora.

Experimental West Nile virus infection in blue jays (Cyanocitta cristata) and crows (Corvus brachyrhynchos)

Ten crows (Corvus brachyrhynchos) and three blue jays (Cyanocitta cristata), species indigenous to North America, were intravenously inoculated with 10(3) PFU of West Nile virus (WNV) strain NY99 for production of positive tissues for Canadian surveillance. Both species developed clinical signs 4 days postinoculation (dpi). Virus was detected in blood, cloacal and tracheal swabs, and in a number of organs by reverse transcriptase-polymerase chain reaction (RT-PCR) and virus isolation (titers reaching over 10(7) PFU/0.1 g). Virus appeared as early as 1 dpi in blood (10(2)-10(3) PFU/ml) and spleen (10(3)-10(4) PFU/0.1 g of tissue), whereas kidney, liver, intestine, gonads, heart, skeletal muscle, and lung tested positive for WNV in a later stage of the infection. Immunostaining (IHC) using heterologous rabbit anti-WNV polyclonal antiserum detected viral antigen in a wide range of organs, starting at 2 dpi. Detection of WNV antigen in the brain of blue jays and crows by IHC was laborious as only few cells, not present in all sections, would stain positive. Mononuclear cells appeared to be an important target for virus replication, contributing to virus spread throughout tissues during the infection. This conclusion was based on the positive IHC staining of these cells in organs before virus antigen detection in parenchymal cells and supported by virus isolation and RT-PCR-positive results in white blood cells. The inability of blue jays and crows to perch and fly may reflect weakness due to generalized infection and marked skeletal muscle involvement, although involvement of the central nervous system cannot be excluded.

Enhancing West Nile virus surveillance, United States

We provide a method for constructing a county-level West Nile virus risk map to serve as an early warning system for human cases. We also demonstrate that mosquito surveillance is a more accurate predictor of human risk than monitoring dead and infected wild birds.

Pre-West Nile virus outbreak: perceptions and practices to prevent mosquito bites and viral encephalitis in the United States

Mosquitoes can transmit over 100 of the viruses that can cause encephalitis, meningitis, and hemorrhagic disease in humans (Chin 2000; Gubler 1996; Monath 1989). While much is known about the ecology, epidemiology, and clinical manifestations of the arboviral encephalitides (Campbell et al. 2002; Centers for Disease Control and Prevention 1997; Gubler 1998; Hayes 1989; Hubálek and Halouzka 1999), little empirical research exists regarding the U.S. population's knowledge of mosquitoes and arboviral encephalitis, particularly prior to the U.S. outbreak of West Nile virus (WNV) in 1999. A nationally representative 55-item survey instrument was successfully administered to 1,500 adults in the United States and an additional 250 adults in six states in the Northeast (Connecticut, Delaware, New Jersey, New York, Pennsylvania, and Rhode Island) regarding mosquitoes and mosquito-borne viral encephalitis. A summary outcome measure for mosquito bite prevention was created. Analyses revealed that the following were statistically significant predictors of behaviors taken to prevent mosquito bites: being concerned about being bitten by mosquitoes, perceived effectiveness of staying indoors in late afternoon and early evening was protective, perceived effectiveness that mosquito repellent is not harmful to health, owning dogs and/or cats as pets, being married, and being > or = 18-44 years old. Being concerned about being bitten by mosquitoes was the most robust predictor of behavioral action to prevent mosquito bites (OR = 7.3; 95% CI = 4.3, 12.2). Observed misperceptions and inadequate knowledge regarding insect repellents suggest increased promotion of the safety and efficacy of DEET-containing insect repellents is warranted.

The potential for West Nile virus to establish outside of its natural range: a consideration of potential mosquito vectors in the United Kingdom

Outbreaks of West Nile virus (WNV) infection have occurred sporadically in Europe, apparently due to the migration of infected birds and the subsequent establishment of a transmission cycle involving culicine and anopheline mosquitoes. Both human and equine species become infected, but are considered as dead end hosts since they play an insignificant role in the maintenance of the cycle. Following the introduction of WNV into the United States in 1999 it is increasingly apparent that the virus has an extraordinary ability to infect a very broad range of arthropod species. Here we consider the potential for British mosquitoes to transmit WNV in the event that it is introduced into the UK.

Immune modulation by flaviviruses

Flaviviruses cause pleomorphic disease with significant morbidity and mortality worldwide. Interestingly, in contrast to most viruses, which subvert or avoid host immune systems, members of the neurotropic Japanese encephalitis serocomplex cause functional changes associated with increased efficacy of the immune response. These viruses induce increased cell surface expression of immune recognition molecules, including class I and II major histocompatibility complex (MHC) and various adhesion molecules. Increases are functional: infected cells are significantly more susceptible to both virus- and MHC-specific cytotoxic T cell lysis. Induced changes are modulated positively or negatively by Th1 and Th2 cytokines, as well as by cell cycle position and adherence status at infection. Infection also increases costimulatory molecule expression on Langerhans cells in the skin. Local interleukin-1 beta production causes accelerated migration of phenotypically altered Langerhans cells to local draining lymph nodes, where initiation of antiviral immune responses occur. The exact mechanism(s) of upregulation is unclear, but changes are associated with NF-kappa B activation and increased MHC and ICAM-1 gene transcription, independently of interferon (IFN) or other proinflammatory cytokines. Increased MHC and adhesion molecule expression may contribute to the pathogenesis of flavivirus encephalitis. Results from a murine model of flavivirus encephalitis developed in this laboratory suggest that fatal disease is immunopathological in nature, with IFN-gamma playing a crucial role. We hypothesize that these viruses may decoy the adaptive immune system into generating low-affinity T cells, which clear virus poorly, as part of their survival strategy. This may enable viral growth and immune escape in cycling cells, which do not significantly upregulate cell surface molecules.

Discrimination of West Nile virus and Japanese encephalitis virus strains using RT-PCR RFLP analysis

West Nile (WN) virus is a mosquito-borne flavivirus that induces lethal encephalitis in humans and horses. Since an outbreak of WN encephalitis in humans and horses occurred in New York City in late August 1999, the possibility exists that WN virus will invade regions that have close links with the United States, such as Japan. We developed a genetic diagnostic method that discriminates between strains of WN virus and Japanese encephalitis (JE) virus. The method involves RT-PCR restriction fragment length polymorphism (RFLP) analysis with a RT-PCR primer set, a nested PCR primer set, and a restriction enzyme. We detected WN and JE viruses in experimentally infected animal brain, spleen, and serum samples. Our method is useful in distinguishing WN viruses from the endemic background of JE viruses, and in discriminating the highly virulent WN strain, which was isolated in New York in 1999, from other WN virus strains.

Vaccines and animal models for arboviral encephalitides

Arthropod-borne viruses ("arboviruses") cause significant human illness ranging from mild, asymptomatic infection to fatal encephalitis or hemorrhagic fever. The most significant arboviruses causing human illness belong to genera in three viral families, Togaviridae, Flaviviridae, and Bunyaviridae. These viruses represent a significant public health threat to many parts of the world, and, as evidenced by the recent introduction of the West Nile virus (WNV) to the Western Hemisphere, they can no longer be considered specific to any one country or region of the world. Like most viral diseases, there are no specific therapies for the arboviral encephalitides; therefore, effective vaccines remain the front line of defense for these diseases. With this in mind, the development of new, more effective vaccines and the appropriate animal models in which to test them become paramount. In fact, for many important arboviruses (e.g. California serogroup and St. Louis encephalitis viruses), there are currently no approved vaccines available for human use. For others, such as the alphaviruses, human vaccines are available only as Investigational New Drugs, and thus are not in widespread use. On the other hand, safe and effective vaccines against tick-borne encephalitis virus (TBEV) and Japanese encephalitis virus (JEV) have been in use for decades. New challenges in vaccine development have been met with new technologies in vaccine research. Many of the newer vaccines are now being developed by recombinant DNA technology. For example, chimeric virus vaccines have been developed using infectious clone technology for many of the arboviruses including, WNV, JEV, and TBEV. Other successful approaches have involved the use of naked DNA encoding and subsequently expressing the desired protective epitopes. Naked DNA vaccines have been used for TBEV and JEV and are currently under development for use against WNV. The development of less expensive, more authentic animal models to evaluate new vaccines against arboviral diseases will become increasingly important as these new approaches in vaccine research are realized. This article reviews the current status of vaccines, both approved for use and those in developmental stages, against the major arboviral encephalitides causing human disease. In addition, research on animal models, both past and present, for these diseases are discussed.

Evolutionary relationship between Old World West Nile virus strains

Little is known about the genetic relationships between European and other Old-World strains of West Nile virus (WNV) and persistence of WNV North of Mediterranean. We characterized the complete genomes of three WNV strains from France (horse-2000), Tunisia (human-1997) and Kenya (mosquito-1998), and the envelope, NS3 and NS5 genes of the Koutango virus. Phylogenetic analyses including all available full-length sequences showed that: (1) Koutango virus is a distant variant of WNV; (2) the three characterized strains belong to lineage 1, clade 1a; (3) the Tunisian strain roots the lineage of viruses introduced in North America. We established that currently available partial envelope sequences do not generate reliable phylogenies. Accordingly, establishing a large WNV sequence database is pivotal for the understanding of spatial and temporal epidemiology of this virus. For rapid completion of that purpose, colinearized E-NS3-NS5 gene sequences were shown to constitute a valuable surrogate for complete sequences.

Spatial analysis of West Nile virus: rapid risk assessment of an introduced vector-borne zoonosis

The distribution of human risk for West Nile virus was determined by spatial analysis of the initial case distribution for the New York City area in 1999 using remote sensing and geographic information system technologies. Cluster analysis revealed the presence of a statistically significant grouping of cases, which also indicates the area of probable virus introduction. Within the cluster, habitat suitability for potentially infective adult mosquitoes was measured by the amount of vegetation cover using satellite imagery. Logistic regression analysis revealed satellite-derived vegetation abundance to be significantly and positively associated with the presence of human cases. The logistic model was used to estimate the spatial distribution of human risk for West Nile virus throughout New York City. Accuracy of the resulting risk map was cross-validated using virus-positive mosquito sample sites. These new epidemiological methods aid in rapid entry point identification and spatial prediction of human risk of infection for introduced vector-borne pathogens.

Chorioretinal lesions in nonfatal cases of West Nile virus infection

OBJECTIVE

West Nile virus (WNV) disease is a zoonotic infection with recent outbreaks in the United States. Recent reports have highlighted the intraocular findings associated with WNV disease. We describe the intraocular findings observed in two patients infected by the West Nile virus.

DESIGN

Observational case reports.

METHODS

During an outbreak of WNV disease in Southwest Ohio, two patients with an acute onset of a systemic febrile illness accompanied by myalgia, arthralgia, headache, and a maculopapular rash were referred for blurred vision. Complete ophthalmologic examination, fundus photographs, and fluorescein angiograms were obtained on both patients. Both patients underwent serologic testing for viruses and cultures for bacteria, viruses, and fungi.

RESULTS

Ophthalmologic examination in each patient revealed anterior segment and vitreous inflammatory cells and multiple partially atrophic and partially pigmented chorioretinal lesions clustered in the peripheral fundus. Fundus examination in case 2 also revealed mild disc edema in both eyes. Intracranial pressure as measured by lumbar puncture was borderline elevated. The chorioretinal lesions in both patients showed a striking similarity and appeared hypofluorescent centrally and hyperfluorescent around the edges on a fluorescein angiogram. Serologic testing for the WNV was positive in both patients, and tests for all other bacteria, fungi, and viruses were negative.

CONCLUSIONS

WNV usually causes mild symptoms, but it occasionally causes neurologic illness with fatal outcome or severe morbidity. We present the cases of two patients with serology-proven WNV disease who developed chorioretinal lesions with a targetlike appearance and iridocyclitis.

DNA vaccine for West Nile virus infection in fish crows (Corvus ossifragus)

A DNA vaccine for West Nile virus (WNV) was evaluated to determine whether its use could protect fish crows (Corvus ossifragus) from fatal WNV infection. Captured adult crows were given 0.5 mg of the DNA vaccine either orally or by intramuscular (IM) inoculation; control crows were inoculated or orally exposed to a placebo. After 6 weeks, crows were challenged subcutaneously with 105 plaque-forming units of WNV (New York 1999 strain). None of the placebo inoculated-placebo challenged birds died. While none of the 9 IM vaccine-inoculated birds died, 5 of 10 placebo-inoculated and 4 of 8 orally vaccinated birds died within 15 days after challenge. Peak viremia titers in birds with fatal WNV infection were substantially higher than those in birds that survived infection. Although oral administration of a single DNA vaccine dose failed to elicit an immune response or protect crows from WNV infection, IM administration of a single dose prevented death and was associated with reduced viremia.

PCR-restriction fragment length polymorphism method for detection of Cyclospora cayetanensis in environmental waters without microscopic confirmation

We developed an alternative nested-PCR-restriction fragment length polymorphism (RFLP) protocol for the detection of Cyclospora cayetanensis in environmental samples that obviates the need for microscopic examination. The RFLP method, with the restriction enzyme AluI, differentiates the amplified target sequence from C. cayetanensis from those that may cross-react. This new protocol was used to reexamine a subset (121 of 180) of surface water samples. Samples previously positive when the CYCF3E and CYCR4B primers (33) and RFLP with MnlI (20) were used were also PCR positive with the new primers; however, they were RFLP negative. We verified, by sequencing these amplicons, that while two were most likely other Cyclospora species, they were not C. cayetanensis. We can detect as few as one oocyst seeded into an autoclaved pellet flocculated from 10 liters of surface water. This new protocol should be of great use for environmental microbiologists and public health laboratories.

Targeting single-nucleotide polymorphisms in the 18S rRNA gene to differentiate Cyclospora species from Eimeria species by multiplex PCR

Cyclospora cayetanensis is a coccidian parasite that causes protracted diarrheal illness in humans. C. cayetanensis is the only species of this genus thus far associated with human illness, although Cyclospora species from other primates have been named. The current method to detect the parasite uses a nested PCR assay to amplify a 294-bp region of the small subunit rRNA gene, followed by restriction fragment length polymorphism (RFLP) or DNA sequence analysis. Since the amplicons generated from C. cayetanensis and Eimeria species are the same size, the latter step is required to distinguish between these different species. The current PCR-RFLP protocol, however, cannot distinguish between C. cayetanensis and these new isolates. The differential identification of such pathogenic and nonpathogenic parasites is essential in assessing the risks to human health from microorganisms that may be potential contaminants in food and water sources. Therefore, to expand the utility of PCR to detect and identify these parasites in a multiplex assay, a series of genus- and species-specific forward primers were designed that are able to distinguish sites of limited sequence heterogeneity in the target gene. The most effective of these unique primers were those that identified single-nucleotide polymorphisms (SNPs) at the 3' end of the primer. Under more stringent annealing and elongation conditions, these SNP primers were able to differentiate between C. cayetanensis, nonhuman primate species of Cyclospora, and Eimeria species. As a diagnostic tool, the SNP PCR protocol described here presents a more rapid and sensitive alternative to the currently available PCR-RFLP detection method. In addition, the specificity of these diagnostic primers removes the uncertainty that can be associated with analyses of foods or environmental sources suspected of harboring potential human parasitic pathogens.

Spreading disease: integro-differential equations old and new

We investigate an integro-differential equation for a disease spread by the dispersal of infectious individuals and compare this to Mollison's [Adv. Appl. Probab. 4 (1972) 233; D. Mollison, The rate of spatial propagation of simple epidemics, in: Proc. 6th Berkeley Symp. on Math. Statist. and Prob., vol. 3, University of California Press, Berkeley, 1972, p. 579; J. R. Statist. Soc. B 39 (3) (1977) 283] model of a disease spread by non-local contacts. For symmetric kernels with moment generating functions, spreading infectives leads to faster traveling waves for low rates of transmission, but to slower traveling waves for high rates of transmission. We approximate the shape of the traveling waves for the two models using both piecewise linearization and a regular-perturbation scheme.

Cyclospora cayetanensis infection in Lagos, Nigeria

Although reports of Cyclospora infection continue to increase globally, few cases have been reported from the African continent. We present 11 cases of cyclosporiasis detected from stool samples submitted to seven major hospital laboratories in Lagos, Nigeria between March 1999 and April 2000.