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

Globalization, land use, and the invasion of West Nile virus

Many invasive species that have been spread through the globalization of trade and travel are pathogens. A paradigmatic case is the introduction of West Nile virus (WNV) into North America in 1999. A decade of research on the ecology and evolution of WNV includes three findings that provide insight into the outcome of future pathogen introductions. First, WNV transmission in North America is highest in urbanized and agricultural habitats, in part because the hosts and vectors of WNV are abundant in human-modified areas. Second, after its introduction, the virus quickly adapted to infect local mosquito vectors more efficiently than the originally introduced strain. Third, highly focused feeding patterns of the mosquito vectors of WNV result in unexpected host species being important for transmission. This research provides a framework for predicting and preventing the emergence of foreign vector-borne pathogens.

Detection of West Nile virus genome and specific antibodies in Iranian encephalitis patients

West Nile virus (WNV) is a mosquito-borne flavivirus which circulates in birds, horses and humans. An estimated 80% of WNV infections are asymptomatic. Fewer than 1% of infected persons develop neuroinvasive disease, which typically presents as encephalitis, meningitis, or acute flaccid paralysis. This study was conducted from January 2008 to June 2009 in Isfahan, Iran. Patients attending the emergency department with fever and loss of consciousness were consecutively included. Cerebrospinal fluids (CSF) were initially analysed through bacteriology and biochemistry examinations, resulting in those with evidence of meningitis being excluded. Patients' CSF and serum were diagnosed by serological and molecular assays. A total of 632 patients with fever and loss of consciousness were tested by CSF analyses. Samples of the remaining patients (39·4%) were referred for WNV investigation. Three (1·2%) of the patients were positive for both serum and CSF by RT–PCR, and six (2·4%) were positive only for IgG antibodies. History of insect bite, and blood transfusion and transplantation were risk factors for being positive by RT–PCR (P=0·048) and being IgG positive (P=0·024), respectively. The results of this study showed that the prevalence of West Nile fever is low in patients with encephalitis.

Climatic controls on West Nile virus and Sindbis virus transmission and outbreaks in South Africa

The processes influencing the magnitude of West Nile virus (WNV) transmission from 1 year to the next require thorough investigation. The intensity of WNV transmission is related to the dynamics and interactions between the pathogen, vector, vertebrate hosts, and environment. Climatic variability is one process that can influence interannual disease transmission. South Africa has a long WNV and Sindbis virus (SINV) record where consistent climate and disease relationships can be identified. We relate climate conditions to historic mosquito infection rates. Next, we detect similar associations with reported human outbreaks dating back to 1941. Both concurrent summer precipitation and the change in summer precipitation from the previous to the current summer were strongly associated with WNV and SINV transmission and recorded human outbreaks. Each 100 mm interannual summer precipitation change increased WNV infection rates by 0.39 WNV-positive Culex univittatus/1000 tested Cx. univittatus. An improved understanding of biotic and abiotic disease transmission dynamics may help anticipate and mitigate future outbreaks.

Cyclospora papionis, Cryptosporidium hominis, and human-pathogenic Enterocytozoon bieneusi in captive baboons in Kenya

Cyclospora papionis, Cryptosporidium hominis, and Enterocytozoon bieneusi were detected in 42 (17.9%), 6 (2.6%), and 29 (12.3%) of 235 newly captured baboons in Kenya, respectively. Most C. hominis subtypes and E. bieneusi genotypes found have been detected in humans in the area, suggesting that cross-species transmission of cryptosporidiosis and microsporidiosis is possible.

Host genetic risk factors for West Nile virus infection and disease progression

West Nile virus (WNV), a category B pathogen endemic in parts of Africa, Asia and Europe, emerged in North America in 1999, and spread rapidly across the continental U.S. Outcomes of infection with WNV range from asymptomatic to severe neuroinvasive disease manifested as encephalitis, paralysis, and/or death. Neuroinvasive WNV disease occurs in less than one percent of cases, and although host genetic factors are thought to influence risk for symptomatic disease, the identity of these factors remains largely unknown. We tested 360 common haplotype tagging and/or functional SNPs in 86 genes that encode key regulators of immune function in 753 individuals infected with WNV including: 422 symptomatic WNV cases and 331 cases with asymptomatic infections. After applying a Bonferroni correction for multiple tests and controlling for population stratification, SNPs in IRF3 (OR 0.54, p = 0.035) and MX1, (OR 0.19, p = 0.014) were associated with symptomatic WNV infection and a single SNP in OAS1 (OR 9.79, p = 0.003) was associated with increased risk for West Nile encephalitis and paralysis (WNE/P). Together, these results suggest that genetic variation in the interferon response pathway is associated with both risk for symptomatic WNV infection and WNV disease progression.

A cross-protective mAb recognizes a novel epitope within the flavivirus NS1 protein

Despite a resurgence of flavivirus infections worldwide, no approved therapeutic agent exists for any member of the genus. While cross-reactive antibodies with therapeutic potential against flaviviruses have been generated, the majority of them are anti-E antibodies with the potential to cause antibody-dependent enhancement of flavivirus infection and disease. We described previously mAbs against the non-structural NS1 protein of the West Nile virus (WNV) that were protective in mice when administered pre- or post-infection of WNV. Here, we demonstrate that one of these mAbs (16NS1) cross-reacted with Japanese encephalitis virus (JEV) and exhibited protective activity against a lethal JEV infection. Overlapping peptide mapping analysis combined with site-specific mutations identified a novel epitope ¹¹⁶KAWGKSILFA¹²⁵ and critical amino acid residues (¹¹⁸W and ¹²²I) for 16NS1 mAb binding. These results may facilitate the development of a broadly therapeutic mAb that lacks enhancing potential and/or subunit-based vaccine against flaviviruses that target the NS1 protein.

Alterations in the Aedes aegypti transcriptome during infection with West Nile, dengue and yellow fever viruses

West Nile (WNV), dengue (DENV) and yellow fever (YFV) viruses are (re)emerging, mosquito-borne flaviviruses that cause human disease and mortality worldwide. Alterations in mosquito gene expression common and unique to individual flaviviral infections are poorly understood. Here, we present a microarray analysis of the Aedes aegypti transcriptome over time during infection with DENV, WNV or YFV. We identified 203 mosquito genes that were ≥5-fold differentially up-regulated (DUR) and 202 genes that were ≥10-fold differentially down-regulated (DDR) during infection with one of the three flaviviruses. Comparative analysis revealed that the expression profile of 20 DUR genes and 15 DDR genes was quite similar between the three flaviviruses on D1 of infection, indicating a potentially conserved transcriptomic signature of flaviviral infection. Bioinformatics analysis revealed changes in expression of genes from diverse cellular processes, including ion binding, transport, metabolic processes and peptidase activity. We also demonstrate that virally-regulated gene expression is tissue-specific. The overexpression of several virally down-regulated genes decreased WNV infection in mosquito cells and Aedes aegypti mosquitoes. Among these, a pupal cuticle protein was shown to bind WNV envelope protein, leading to inhibition of infection in vitro and the prevention of lethal WNV encephalitis in mice. This work provides an extensive list of targets for controlling flaviviral infection in mosquitoes that may also be used to develop broad preventative and therapeutic measures for multiple flaviviruses.

Dengue (DENV), West Nile (WNV) and Yellow Fever (YFV) viruses are responsible for severe human disease and mortality worldwide. There is no vaccine available for dengue or West Nile virus and no specific antiviral is available for any of these viral infections. These viruses are transmitted to humans through the bite of a mosquito vector. Understanding the effects of viral infection on gene expression in the mosquito is crucial to the development of effective antiviral treatments for mosquitoes and may enable researchers to interrupt the human-insect infection cycle. Here we investigate the alterations in gene expression across the entire Aedes aegypti genome during infection with DENV, YFV and WNV over time. We describe several genes that share a similar expression profile during infection with all three viruses. We also use a WNV mosquito cell, mosquito and mouse model to show that virally downregulated genes are inhibitory to infection when overexpressed and that viral regulation of mosquito genes is tissue-specific. Our results provide an extensive amount of data highlighting viral gene targets in the mosquito during infection. This data may also be used to develop broad-spectrum anti-flaviviral treatments in mosquitoes.

Third lineage of rodent eimerians: morphology, phylogeny and re-description of Eimeria myoxi (Apicomplexa: Eimeriidae) from Eliomys quercinus (Rodentia: Gliridae)

Coccidian oocysts from feces of 46 individuals of the garden dormouse, Eliomys quercinus (Rodentia: Gliridae), were morphologically and molecularly characterized. Both morphological and sequence data (18S rDNA and ORF 470) showed low variability, indicating that all samples represent a single species. By comparison with published morphological descriptions of coccidia from glirid rodents, we determined that the samples represent Eimeria myoxi. Molecular data suggest that this species does not fall within the 2 known rodent-specific groups but branches as a third independent lineage. However, its exact position in respect to other eimerian clusters could not be established due to the lack of phylogenetic information at this taxonomic level for the 18S rRNA and ORF 470 genes. Based on these results, we provide a re-description of Eimeria myoxi, which contains morphological and molecular characteristics sufficient for its further unequivocal identification.

Association between HLA class I and class II alleles and the outcome of West Nile virus infection: an exploratory study

Background

West Nile virus (WNV) infection is asymptomatic in most individuals, with a minority developing symptoms ranging from WNV fever to serious neuroinvasive disease. This study investigated the impact of host HLA on the outcome of WNV disease.

Methods

A cohort of 210 non-Hispanic mostly white WNV⁺ subjects from Canada and the U.S. were typed for HLA-A, B, C, DP, DQ, and DR. The study subjects were divided into three WNV infection outcome groups: asymptomatic (AS), symptomatic (S), and neuroinvasive disease (ND). Allele frequency distribution was compared pair-wise between the AS, S, and ND groups using χ2 and Fisher's exact tests and P values were corrected for multiple comparisons (Pc). Allele frequencies were compared between the groups and the North American population (NA) used as a control group. Logistic regression analysis was used to evaluate the potential synergistic effect of age and HLA allele phenotype on disease outcome.

Results

The alleles HLA-A*68, C*08 and DQB*05 were more frequently associated with severe outcomes (ND vs. AS, P_A*68 = 0.013/Pc = 0.26, P_C*08 = 0.0075/Pc = 0.064, and P_DQB1*05 = 0.029/Pc = 0.68), However the apparent DQB1*05 association was driven by age. The alleles HLA-B*40 and C*03 were more frequently associated with asymptomatic outcome (AS vs. S, P_B*40 = 0.021/Pc = 0.58 and AS vs. ND P_C*03 = 0.039/Pc = 0.64) and their frequencies were lower within WNV⁺ subjects with neuroinvasive disease than within the North American population (NA vs. S, P_B*40 = 0.029 and NA vs. ND, P_C*03 = 0.032).

Conclusions

Host HLA may be associated with the outcome of WNV disease; HLA-A*68 and C*08 might function as “susceptible” alleles, whereas HLA-B*40 and C*03 might function as “protective” alleles.

Presença de culicídeos em município de porte médio do Estado de São Paulo e risco de ocorrência de febre do Nilo Ocidental e outras arboviroses

INTRODUÇÃO: O objetivo deste estudo foi mensurar a diversidade de espécies de culicídeos, descrever sua abundância e variação sazonal em áreas urbanas e matas de São José do Rio Preto, SP, e discutir o risco de ocorrência de arboviroses. MÉTODOS: Coletas de larvas e de mosquitos adultos foram realizadas mensalmente, em 2006 e 2007, em área urbana e em quatro fragmentos de mata. No perímetro urbano, coletaram-se larvas nos sítios mais prováveis de oviposição para mosquitos do gênero Culex e nas matas foi realizada a coleta de mosquitos adultos, sendo que em duas utilizaram-se armadilhas CDC à noite e, em duas, aspirador de Nasci de dia. RESULTADOS: Na área urbana identificaram-se 34 espécies de culicídeos em um total de 8.683 exemplares; destes, 80,7% corresponderam ao Culex quinquefasciatus, 9,6% ao Culex grupo Coronator, 3,2% ao Aedes albopictus (3,2%) e 1,1% ao Ochlerotatus fluviatilis. A abundância de larvas de Cx. quinquefasciatus correlacionou-se negativamente com a chuva. Nas quatro matas, foram coletados 2.268 mosquitos distribuídos entre 10 gêneros, 46 espécies ou grupos. As mais abundantes foram Aedeomyia squamipennis, Culex. coronator, Culex (Mel.) seção Melanoconion, Culex declarator, Ochlerotatus scapularis, Anopheles triannulatus, Culex bidens/interfor e Culex habilitator/pseudojhantinosoma. CONCLUSÕES: A abundância de Cx. quinquefasciatus na área urbana e a presença de outros culicídeos nas áreas urbanas e de matas apontam para a possibilidade de transmissão do vírus do Nilo Ocidental e de outras arboviroses em São José do Rio Preto e outras cidades do Brasil, sendo fundamental o estabelecimento de medidas visando à vigilância destas arboviroses.

Retrospective diagnosis of West Nile virus infection in a patient with meningoencephalitis in Tuscany, Italy

We report a case of West Nile virus (WNV) infection in a symptomatic woman living in Tuscany in 2007. A retrospective analysis on cerebrospinal fluids drawn from people affected by neurological diseases with unknown etiology allowed the identification of a case of WNV infection before the WNV outbreak in the Northeast Italy in 2008. This emphasizes the importance of maintaining a high level of epidemiological surveillance all over the Italian territory.

Is West Nile virus a potential cause of central nervous system infection in Brazil?

Meningitis and encephalitis are complications of West Nile virus (WNV) infection. Although WNV is endemic in North America, the virus has recently been reported in Colombia and Argentina. Investigation of WNV in Brazil is important since this virus has never been studied previously in this country.

OBJECTIVE

To investigate the presence of WNV infection in viral encephalitis/meningitis cases of unknown etiology in the city of Rio de Janeiro, Brazil.

METHOD

Thirty-seven adults with viral meningitis/encephalitis had their serum and CSF tested for WNV antibodies using the ELISA method.

RESULTS

Only one case was WNV-positive, but this case was also positive for dengue. The plaque reduction neutralization test distinguished infections, and was negative for WNV.

CONCLUSION

WNV can be confused with dengue infection. Their symptoms and neurological picture are similar. We did not find WNV in any patients with encephalitis and meningitis in the city of Rio de Janeiro. Up to now, it has not been detected in Brazil.

Phylogeography and epidemiological history of West Nile virus genotype 1a in Europe and the Mediterranean basin

Aim of this study was to reconstruct the temporal and spatial phylodynamics of WNV-1a, the genotype to which the majority of European/Mediterranean viral strains belongs, by using sequences retrieved from public databases. WNV-1a isolates segregated into two major clades: the recent West Mediterranean sequences formed a single monophyletic group within clade A. Clade B included sequences from East Mediterranean and America. Phylogeographic analysis suggested that WNV-1a probably originated in sub-Saharan Africa in the early XXth century, and then spread northwards since the late 1970s, via two routes: one crossing Eastern Mediterranean and the other the Western Mediterranean countries. Our data suggest that the circulation of the virus in a given geographical area usually precedes the onset of the outbreak by one year or more, and underline the importance of the spatial-temporal phylodynamics reconstruction in clarifying the recent epidemiology and in setting up an efficient surveillance system for emerging/reemerging zoonosis.

Evidence of simultaneous circulation of West Nile and Usutu viruses in mosquitoes sampled in Emilia-Romagna region (Italy) in 2009

BACKGROUND

In recent years human diseases due to mosquito-borne viruses were increasingly reported in Emilia-Romagna region (Italy), from the chikungunya virus in 2007 to the West Nile virus (WNV) in 2008. An extensive entomological survey was performed in 2009 to establish the presence and distribution of mosquito arboviruses in this region, with particular reference to flaviviruses.

METHODOLOGY/PRINCIPAL FINDINGS

From May 6 to October 31, a total of 190,516 mosquitoes were sampled in georeferenced stations, grouped in 1,789 pools according date of collection, location, and species, and analyzed by reverse transcription polymerase chain reaction (RT-PCR) to detect the presence of RNA belong to Flavivirus genus. WNV was detected in 27 mosquito pools, producing sequences similar to those of birds and human strains obtained in 2008 outbreak, pointed out the probable virus overwintering. Isolation of WNV was achieved from one of these pools. Moreover 56 pools of mosquitoes tested positive for Usutu virus (USUV). Most PCR positive pools consisted of Culex pipiens, which also was the most analyzed mosquito species (81.4% of specimens); interestingly, USUV RNA was also found in two Aedes albopictus mosquito pools. Simultaneous circulation of WNV and USUV in the survey area was highlighted by occurrence of 8 mosquito WNV- and USUV-positive pools and by the overlaying of the viruses "hot spots", obtained by kernel density estimation (KDE) analysis. Land use of sampled stations pointed out a higher proportion of WNV-positive Cx. pipiens pool in rural environments respect the provenience of total sampled pool, while the USUV-positive pools were uniformly captured in the different environments.

CONCLUSIONS/SIGNIFICANCE

Obtained data highlighting the possible role of Cx. pipiens mosquito as the main vector for WNV and USUV in Northern Italy, and the possible involvement of Ae. albopictus mosquito in USUV cycle. The described mosquito-based surveillance could constitute the foundation for a public health alert system targeting mosquito borne arboviruses.

A C-type lectin collaborates with a CD45 phosphatase homolog to facilitate West Nile virus infection of mosquitoes

West Nile virus (WNV) is the most common arthropod-borne flavivirus in the United States; however, the vector ligand(s) that participate in infection are not known. We now show that an Aedes aegypti C-type lectin, mosGCTL-1, is induced by WNV, interacts with WNV in a calcium-dependent manner, and facilitates infection in vivo and in vitro. A mosquito homolog of human CD45 in A. aegypti, designated mosPTP-1, recruits mosGCTL-1 to enable viral attachment to cells and to enhance viral entry. In vivo experiments show that mosGCTL-1 and mosPTP-1 function as part of the same pathway and are critical for WNV infection of mosquitoes. A similar phenomenon was also observed in Culex quinquefasciatus, a natural vector of WNV, further demonstrating that these genes participate in WNV infection. During the mosquito blood-feeding process, WNV infection was blocked in vivo with mosGCTL-1 antibodies. A molecular understanding of flaviviral-arthropod interactions may lead to strategies to control viral dissemination in nature.

Epidemiology of Cyclospora cayetanensis: A review focusing in endemic areas

Cyclospora cayetanensis is an intestinal coccidian protozoon that has emerged as an important cause of endemic or epidemic diarrhoeal illness in children and adults worldwide. Humans appear to be the only natural hosts. However, the role of animals as natural reservoirs is uncertain but of increasing concern. Human-to-human spread of the parasite occurs indirectly via the environment through oocysts in contaminated water, food or soil. In endemic areas, risk factors associated with the infection include contaminated water or food, contact with soil or animals, type of sanitation and low socioeconomic status. Infections linked to soil contact provide reasons to believe that this route of spread may be more common than realised in disadvantaged community settings. C. cayetanensis is an important cause of traveller's diarrhoea and numerous large foodborne outbreaks associated with the globalisation of the food supply and importation of fruits and vegetables from developing countries have occurred. Waterborne outbreaks have also been reported. Implementation of measures to prevent or control the spread of Cyclospora oocysts in the environment is critical. In endemic areas, the most important steps to prevent infection are improving environmental sanitation and health education. Significant gaps remain in our understanding of the epidemiology of human cyclosporiasis that highlight the need for continued research in several aspects of C. cayetanensis.

Low West Nile virus circulation in wild birds in an area of recurring outbreaks in Southern France

West Nile virus (WNV) has a history of irregular but recurrent epizootics in countries of Mediterranean and of Central and Eastern Europe. We have investigated the temporal enzootic activity of WNV in free-ranging birds over a 3-year period in an area with sporadic occurrences of WNV outbreaks in Southern France. We conducted an intensive serologic survey on several wild bird populations (>4000 serum samples collected from 3300 birds) selected as potential indicators of the WNV circulation. WNV antibodies were detected by seroneutralization and/or plaque reduction neutralization in house sparrows, black-billed magpies, and scops owls, but these species appeared to be insufficient indicators of WNV circulation. Overall seroprevalence was low (<1%), including in birds that had been potentially exposed to the virus during recent outbreaks. However, the detection of a seroconversion in one bird, as well as the detection of seropositive birds in all years of our monitoring, including juveniles, indicate a constant annual circulation of WNV at a low level, including in years without any detectable emergence of WN fever in horses or humans.

Update on Cyclospora cayetanensis, a food-borne and waterborne parasite

The coccidian parasite Cyclospora cayetanensis is recognized as an emerging pathogen that causes protracted diarrhea in humans. The first cases of Cyclospora infection were reported in the late 1970s and were observed among expatriates and travelers in regions where infections are endemic. Since then, Cyclospora has been considered a cause of traveler's diarrhea. Epidemiological investigations were reported and examined in areas of endemicity even before the true identity of Cyclospora was elucidated. Cyclospora was fully characterized in the early 1990s, but it was not until the 1995 Cyclospora outbreak in the United States and Canada that it caught the attention of the public and physicians. The biology, clinical presentation, epidemiology, diagnosis, treatment, and control of cyclosporiasis are reviewed, with a focus on diagnostic assays currently being used for clinical and environmental samples. Challenges and limitations in working with Cyclospora are also discussed.

Characterization of West Nile virus isolates from Spain: new insights into the distinct West Nile virus eco-epidemiology in the Western Mediterranean

West Nile virus (WNV) is a mosquito-borne flavivirus which causes important morbidity and mortality in birds, horses and humans. In the Western Mediterranean region, WNV causes sporadic, self-limited outbreaks, with few or no human cases. Here we report the characterization of two recent Western Mediterranean WNV isolates, obtained in Spain in 2007 from two golden eagles. Complete genome sequence comparisons revealed high identity between these isolates and close relationship with other Western Mediterranean WNV strains isolated since 1996. Phylogenetic analysis within this group indicated that two distinct phylogenetic groups have emerged from earlier strains. Pathogenicity analysis in mice showed that the Spanish isolate is less pathogenic than other strains either from the Western Mediterranean (Morocco 2003) or from North America (NY'99). Changes in amino acid position NS3-249 (claimed as a virulence marker) did not influence the pathogenicity observed.

Imported West Nile virus encephalitis in an Israeli tourist

West Nile virus is an arbovirus that has caused large outbreaks of febrile illness, meningitis and encephalitis in Europe, North America and the Middle East. We describe the first laboratory-confirmed human case of West Nile virus infection in Australia, in a 58-year-old tourist who was almost certainly infected in Israel. The case is a reminder of the need to consider exotic pathogens in travellers and of the risk of introducing new pathogens into Australia.

In silico evidence for the species-specific conservation of mosquito retroposons: implications as a molecular biomarker

BACKGROUND

Mosquitoes are the transmissive vectors for several infectious pathogens that affect man. However, the control of mosquitoes through insecticide and pesticide spraying has proved difficult in the past. We hypothesized that, by virtue of their reported vertical inheritance among mosquitoes, group II introns - a class of small coding ribonucleic acids (scRNAs) - may form a potential species-specific biomarker. Structurally, introns are a six-moiety complex. Depending on the function of the protein encoded within the IV moiety, the highly mobile class of group II introns or retroposons is sub-divided into two: Restriction Endonuclease (REase)-like and Apurinic aPyramydinic Endonuclease (APE)-like. REase-like retroposons are thought to be the ancestors of APE retroposons. Our aim in this study was to find evidence for the highly species-specific conservation of the APE subclass of mosquito retroposons.

METHODS AND RESULTS

In silico targeted sequence alignments were conducted across a 1,779-organism genome database (1,518 bacterial, 59 archeal, 201 eukaryotic, and the human), using three mosquito retroposon sequence tags (RST) as BLASTN queries [AJ970181 and AJ90201 of Culex pipien origin and AJ970301 of Anoplese sinensis origin]. At a calibration of E = 10, A & D = 100, default filtration and a homology cut-off of >95% identity, no hits were found on any of the 1,518 bacterial genomes. Eleven (100%) and 15 (100%) hits obtained on the 201-eukaryote genome database were homologs (>95% score) of C.pipien quinquefasciatus JHB retroposons, but none of An. sinensis. Twenty and 221 low score (30-43% identity) spurious hits were found at flanking ends of genes and contigs in the human genome with the C.pipien and An. sinensis RSTs respectively. Functional and positional inference revealed these to be possible relatives of human genomic spliceosomes. We advance two models for the application of mosquito RST: as precursors for developing molecular biomarkers for mosquitoes, and as RST-specific monoclonal antibody (MAb)-DDT immunoconjugates to enhance targeted toxicity.

CONCLUSION

We offer evidence to support the species-specific conservation of mosquito retroposons among lower taxa. Our findings suggest that retroposons may therefore constitute a unique biomarker for mosquito species that may be exploited in molecular entomology. Mosquito RST-specific MAbs may possibly permit synthesis of DDT immunoconjugates that could be used to achieve species-tailored toxicity.

Climate change and infectious diseases in Europe

Concerted action is needed to address public health issues raised by climate change. In this Review we discuss infections acquired through various routes (arthropod vector, rodent, water, food, and air) in view of a changing climate in Europe. Based on an extensive review of published work and expert workshops, we present an assessment of the infectious disease challenges: incidence, prevalence, and distribution are projected to shift in a changing environment. Due to the high level of uncertainty on the rate of climate change and its impact on infectious diseases, we propose to mount a proactive public health response by building an integrated network for environmental and epidemiological data. This network would have the capacity to connect epidemic intelligence and infectious disease surveillance with meteorological, entomological, water quality, remote sensing, and other data, for multivariate analyses and predictions. Insights from these analyses could then guide adaptation strategies and protect population health from impending threats related to climate change.

Genetic variation in OAS1 is a risk factor for initial infection with West Nile virus in man

West Nile virus (WNV) is a re-emerging pathogen that can cause fatal encephalitis. In mice, susceptibility to WNV has been reported to result from a single point mutation in oas1b, which encodes 2'-5' oligoadenylate synthetase 1b, a member of the type I interferon-regulated OAS gene family involved in viral RNA degradation. In man, the human ortholog of oas1b appears to be OAS1. The 'A' allele at SNP rs10774671 of OAS1 has previously been shown to alter splicing of OAS1 and to be associated with reduced OAS activity in PBMCs. Here we show that the frequency of this hypofunctional allele is increased in both symptomatic and asymptomatic WNV seroconverters (Caucasians from five US centers; total n = 501; OR = 1.6 [95% CI 1.2-2.0], P = 0.0002 in a recessive genetic model). We then directly tested the effect of this SNP on viral replication in a novel ex vivo model of WNV infection in primary human lymphoid tissue. Virus accumulation varied markedly among donors, and was highest for individuals homozygous for the 'A' allele (P<0.0001). Together, these data identify OAS1 SNP rs10774671 as a host genetic risk factor for initial infection with WNV in humans.

Impact of climate change and other factors on emerging arbovirus diseases

While some skeptics remain unconvinced that global climate change is a reality, there is no doubt that during the past 50 years or so, patterns of emerging arbovirus diseases have changed significantly. Can this be attributed to climate change? Climate is a major factor in determining: (1) the geographic and temporal distribution of arthropods; (2) characteristics of arthropod life cycles; (3) dispersal patterns of associated arboviruses; (4) the evolution of arboviruses; and (5) the efficiency with which they are transmitted from arthropods to vertebrate hosts. Thus, under the influence of increasing temperatures and rainfall through warming of the oceans, and alteration of the natural cycles that stabilise climate, one is inevitably drawn to the conclusion that arboviruses will continue to emerge in new regions. For example, we cannot ignore the unexpected but successful establishment of chikungunya fever in northern Italy, the sudden appearance of West Nile virus in North America, the increasing frequency of Rift Valley fever epidemics in the Arabian Peninsula, and very recently, the emergence of Bluetongue virus in northern Europe. In this brief review we ask the question, are these diseases emerging because of climate change or do other factors play an equal or even more important role in their emergence?

Vector competence of Australian mosquito species for a North American strain of West Nile virus

Since the establishment of West Nile virus (WNV) into the United States, concern has arisen that this virus may also pose a serious threat to Australian biosecurity. The vector competence of 19 Australian mosquito species for a North American strain of WNV was evaluated. Mosquitoes collected from Cairns, Brisbane, and Sydney were exposed to blood containing 10(4.0+/-0.3) cell culture infectious dose(50)/mosquito WNV that was isolated from a crow during the 1999 New York outbreak. Mosquitoes were tested 12-15 days later to determine their infection, dissemination, and transmission rates. A number of Culex spp. demonstrated a high vector competence for this virus, with some populations of Culex annulirostris, the primary Australian Kunjin virus vector, displaying transmission rates up to 84%. Similarly, Cx. quinquefasciatus and Cx. gelidus were highly competent, with infection and transmission rates of >80% and >50%, respectively. Common Aedes spp., including Aedes notoscriptus, Ae. vigilax, and Ae. procax, were moderately susceptible, and some Verrallina spp. and Coquillettidia spp. were relatively refractory to infection. Thus, Australia possesses a number of competent mosquito species that could facilitate local transmission of WNV, should it be introduced.

Equine West Nile virus disease occurrence and the Normalized Difference Vegetation Index

The association between the Normalized Difference Vegetation Index (NDVI) and periods of above- or below-average reported cases of equine West Nile virus encephalomyelitis, reported in Texas between 2002 and 2004, was investigated. A time-series of case reports, using a biweekly window, was constructed. Because of the disparity in number of cases reported (1698, 672 and 101 in 2002, 2003 and 2004, respectively), data were standardized by calculating the number of cases reported during each biweekly period as a ratio of the annual average number of cases reported. The mean NDVI (0.439) in Texas in biweekly periods in which cases were reported was significantly higher (P<0.001) than the mean NDVI (0.396) in periods in which cases were not reported. The best-fitting model of standardized case ratios included the mean NDVI in the preceding 4-week period. This association was further investigated in the two ecological regions of Texas in which most cases were reported during the study period--Prairies and Lakes, and the Panhandle Plains. Standardized case ratios in the Prairies and Lakes ecoregion were best predicted by NDVI estimated 19-20 weeks previously, whereas standardized case ratios in the Panhandle Plains region were most strongly associated with NDVI estimated 1-4 weeks previously, indicating that the temporal lag between appropriate environmental conditions and resulting increased risk of WNV transmission can vary in different regions. The associations identified could be useful in an early-warning system of increased disease risk.

Review of companion animal viral diseases and immunoprophylaxis

In this article we review important established, newly emergent and potential viral diseases of cats, dogs and rabbits. Topics covered include virus epidemiology, disease pathogenesis, existing and prospective immunoprophylaxis against the viruses. For some feline viruses, notably the immunodeficiency virus, leukaemia virus and peritonitis virus, available vaccines are poorly efficacious but there are good prospects for this. A further challenge for the industry is likely to be due to viruses jumping species and the emergence of more virulent variants of established viruses resulting from mutations as has been the case for the canine parvovirus, coronaviruses and feline calicivirus.

Cyclosporiasis: an emerging public health concern around the world and in Africa

BACKGROUND

Cyclosporiasis is an emerging gastro-enteric disease caused by the coccidia protozoan Cyclospora cayetanensis. It is associated with diarrhoea among children in developing countries, in the Americas where C. cayetanensis is endemic, traveller's diarrhoea and/or food and waterborne outbreaks in the developed countries.

OBJECTIVES

The aim of this review is to highlight cyclosporiasis and its relevance to public health in East Africa and Africa at large.

METHODS

All literature on Cyclospora, C. cayetanensis, cyclosporiasis in Africa, and endemic cyclosporiasis was searched from libraries, colleagues and internet but only literature on its history, clinical presentation, epidemiology in endemic settings, and occurrence in Africa were scrutinised.

RESULTS

In Sub Saharan Africa, cyclosporiasis has been reported in at least 3 countries, including Tanzania, in East Africa, occurring in both immunocompromised and immunocompetent patients. Zoonotic species of Cyclospora have also been identified in East African primates, indicating likely endemicity of this little reported disease in the region. This can be attributed to lack of awareness in the public and medical profession concerning the disease, and therefore not routinely checked at the health centres. Cyclosporiasis is characterized by intermittent diarrhoea, and secondary conditions or sequelae such as reactive arthritis syndrome (Reiter's syndrome), have been associated with progression of the disease. Its management is based on antibiotics, an unusual scenario for a protozoa.

CONCLUSIONS

Although many aspects of this disease and its transmission remain an enigma, the situation has been rapidly changing since the disease first came to medical attention in the 1970s.

Importance of bird-to-bird transmission for the establishment of West Nile virus

West Nile virus (WNV) is principally considered to be maintained in a mosquito-bird transmission cycle. Under experimental conditions, several other transmission routes have been observed, but the significance of these additional routes in nature is unknown. Here, we derive an expression for the basic reproduction number (R0) for WNV including all putative routes of transmission between birds and mosquitoes to gauge the relative importance of these routes for the establishment of WNV. Parameters were estimated from published experimental results. Sensitivity analysis reveals that R0 is sensitive to transmission between birds via close contact, but not to mosquito-to-mosquito transmission. In seasons or in areas where the mosquito-to-bird ratio is low, bird-to-bird transmission may be crucial in determining whether WNV can establish or not. We explain the use of R0 as a flexible tool to measure the risk of establishment of vector-borne diseases.

Serologic survey of potential vertebrate hosts for West Nile virus in Poland

A survey for antibodies to West Nile virus (WNV; genus ,Flavivirus) was carried out by plaque-re-duction neutralization microtesting in 78 horses, 20 domestic chickens, and 97 wild birds belonging to 10 species from different areas in Poland. Specific antibodies were detected in five juvenile (hatching-year) birds collected in 2006: three white storks (Ciconia ciconia) in a wildlife rehabilitation center (5.4% of all examined storks; the antibody titers in each bird were 1:320, 1:160, and 1:20), one free-living mute swan (Cygnus olor; the titer was 1:20), and one hooded crow (Corvus corone cornix; the titer 1:20) in a wildlife rehabilitation center; thus the overall seropositivity to WNV was 5.2% among all the birds sampled. These data do not rule out the presence of WNV activity in Poland with 100% certainty, but they indicate a significant trace that demands verification. In addition, one black-headed gull (Larus ridibundus) had neutralizing antibodies for the Usutu Flavivirus, the first case recorded in Poland.

West Nile virus antibodies in permanent resident and overwintering migrant birds in south-central Kansas

We conducted serological studies, using epitope-blocking ELISAs directed at West Nile virus (WNV) and flavivirus antibodies, of wild birds in south-central Kansas, the first for this state, in the winters of 2003-04 through 2005-06. Overwintering migratory species (primarily the American tree sparrow and dark-eyed junco) consistently showed significantly lower seropositivity than permanent residents (primarily the northern cardinal). The cardinal showed annual variation in seropositivity between winters. Of 35 birds that were serial sampled within a single winter, one cardinal may have seroconverted between late December and mid-February, providing a preliminary suggestion of continued enzootic transmission, chronic infection, or bird-bird transfer as overwintering mechanisms. Breeding population size of the cardinal did not change after the introduction of WNV to Kansas. Of eighteen birds that were serial sampled between winters, none seroconverted. Among overwintering migrants, the Harris' Sparrow showed the highest seropositivity, possibly related to its migration route through the central Great Plains, an area of recent high WNV activity. The finding that permanent resident birds exhibit higher seropositivity than migrant birds suggests that resident birds contribute to the initiation of annual infection cycles,although this conclusion is speculative in the absence of data on viral titers and the length of viremia.

KEYWORDS

West Nile Virus-flavivirus-birds-epitope-blocking ELISA-winter.

The relative contribution of antibody and CD8+ T cells to vaccine immunity against West Nile encephalitis virus

West Nile virus (WNV) is a mosquito borne, neurotropic flavivirus that causes a severe central nervous system (CNS) infection in humans and animals. Although commercial vaccines are available for horses, none is currently approved for human use. In this study, we evaluated the efficacy and mechanism of immune protection of two candidate WNV vaccines in mice. A formalin-inactivated WNV vaccine induced higher levels of specific and neutralizing antibodies compared to a DNA plasmid vaccine that produces virus-like particles. Accordingly, partial and almost complete protection against a highly stringent lethal intracranial WNV challenge were observed in mice 60 days after single dose immunization with the DNA plasmid and inactivated virus vaccines, respectively. In mice immunized with a single dose of DNA plasmid or inactivated vaccine, antigen-specific CD8(+) T cells were induced and contributed to protective immunity as acquired or genetic deficiencies of CD8(+) T cells lowered the survival rates. In contrast, in boosted animals, WNV-specific antibody titers were higher, survival rates after challenge were greater, and an absence of CD8(+) T cells did not appreciably affect mortality. Overall, our experiments suggest that in mice, both inactivated WNV and DNA plasmid vaccines are protective after two doses, and the specific contribution of antibody and CD8(+) T cells to vaccine immunity against WNV is modulated by the prime-boost strategy.

A neural network-based method for risk factor analysis of West Nile virus

There is a lack of knowledge about which risk factors are more important in West Nile virus (WNV) transmission and risk magnitude. A better understanding of the risk factors is of great help in developing effective new technologies and appropriate prevention strategies for WNV infection. A contribution analysis of all risk factors in WNV infection would identify those major risk factors. Based on the identified major risk factors, measures to control WNV proliferation could be directed toward those significant risk factors, thus improving the effectiveness and efficiency in developing WNV control and prevention strategies. Neural networks have many generally accepted advantages over conventional analytical techniques, for instance, ability to automatically learn the relationship between the inputs and outputs from training data, powerful generalization ability, and capability of handling nonlinear interactions. In this article, a neural network model was developed for analysis of risk factors in WNV infection. To reveal the relative contribution of the input variables, the neural network was trained using an algorithm called structural learning with forgetting. During the learning, weak neural connections are forced to fade away while a skeletal network with strong connections emerges. The significant risk factors can be identified by analyzing this skeletal network. The proposed approach is tested with the dead bird surveillance data in Ontario, Canada. The results demonstrate the effectiveness of the proposed approach.

West Nile virus past infections in the general population of Southern Spain

OBJECTIVE

To analyze the prevalence of past and recent infections by West Nile virus (WNV) and the risk factors associated with WNV exposure in a representative population from southern Spain.

METHODS

Sample size was established for an estimated prevalence of past WNV infections of 5 +/- 2.5% in 504 subjects. A pre-stratification was performed according to age distribution and place of residence. After random telephone solicitation and acquisition of informed consent, a serum sample was collected and an epidemiologic survey performed on all participating subjects. Samples were tested with ELISA-IgG and MAC-ELISA to detect specific IgG and IgM antibodies; results were confirmed by the plaque reduction neutralization test (PRNT). Multivariate analysis using a forward stepwise logistic regression model was performed to assess potential risk factors associated with WNV exposure.

RESULTS

Prevalence of past WNV infections confirmed by PRNT in the 504 participants was 0.6%, affecting mainly older persons (mean age 65 +/- 23 vs. 34 +/- 22 years; P = 0.018), those living in rural areas (5.4% vs. 0% in urban areas; P = 0.01), and individuals with risk professions (prevalence 2.8% vs. 0%; P = 0.048). None of the five recent infections detected by MAC-ELISA was confirmed by PRNT.

CONCLUSIONS

These results strongly suggest past circulation and exposure of the human population to WNV in southern Spain.

Pathogenic flaviviruses

Haemorrhagic disease, encephalitis, biphasic fever, flaccid paralysis, and jaundice are typical manifestations of diseases in human beings after infections by mosquito-borne or tick-borne flaviviruses such as yellow fever, dengue, West Nile, St Louis encephalitis, Japanese encephalitis, tick-borne encephalitis, Kyasanur Forest disease, and Omsk haemorrhagic fever. Although the characteristics of these viruses are well defined, they are still unpredictable with increases in disease severity, unusual clinical manifestations, unexpected methods of transmission, long-term persistence, and the discovery of new species. This Seminar will compare the epidemiological and clinical features of the medically important flaviviruses, consider the effect of human activity on their evolution and dispersal, and draw attention to new findings and some of the unanswered questions, unresolved issues, and controversies that remain.

Phylogenetic relationships among Eimeria spp. (Apicomplexa, Eimeriidae) infecting rabbits: evolutionary significance of biological and morphological features

Monophyly of all 11 valid Eimeria species from rabbits (Oryctolagus cuniculus Linnaeus, 1758) was revealed based on nuclear 18S rDNA sequence data. This finding implies that these species, which vary considerably in terms of their morphology and biology, diversified on a single host or several closely related species. Phylogenetic analysis divided rabbit Eimeria species into 2 sister lineages, corresponding to the presence/absence of the oocyst residuum. Other morphological or biological traits (oocyst shape and size, presence/absence of oocyst inner structures, pathogenicity, infection site, pre-patent and patent periods, sporulation time, and number of asexual generations) do not explicitly correlate with the phylogeny of rabbit coccidia.