Imported Chikungunya Infection, Italy

Localization of nitric oxide-producing hemocytes in Aedes and Culex mosquitoes infected with bacteria

Mosquitoes are significant vectors of various pathogens. Unlike vertebrates, insects rely solely on innate immunity. Hemocytes play a crucial role in the cellular part of the innate immune system. The gaseous radical nitric oxide (NO) produced by hemocytes acts against pathogens and also functions as a versatile transmitter in both the immune and nervous systems, utilizing cyclic guanosine monophosphate (cGMP) as a second messenger. This study conducted a parallel comparison of NO synthase (NOS) expression and NO production in hemocytes during Escherichia coli K12 infection in four vector species: Aedes aegypti, Aedes albopictus, Culex pipiens molestus, and Culex pipiens quinquefasciatus. Increased NOS expression by NADPH diaphorase (NADPHd) staining and NO production by immunofluorescence against the by-product L-citrulline were observed in infected mosquito hemocytes distributed throughout the abdomens. NADPHd activity and citrulline labeling were particularly found in periostial hemocytes near the heart, but also on the ventral nerve chord (VNC). Pericardial cells of Ae. aegypti and Cx. p. molestus showed increased citrulline immunofluorescence, suggesting their involvement in the immune response. Oenocytes displayed strong NADPHd and citrulline labeling independent of infection status. This comparative study, consistent with findings in other species, suggests a widespread phenomenon of NO's role in hemocyte responses during E. coli infection. Found differences within and between genera highlight the importance of species-specific investigations.

Reporting delays of chikungunya cases during the 2017 outbreak in Lazio region, Italy

BACKGROUND

Emerging arboviral diseases in Europe pose a challenge due to difficulties in detecting and diagnosing cases during the initial circulation of the pathogen. Early outbreak detection enables public health authorities to take effective actions to reduce disease transmission. Quantification of the reporting delays of cases is vital to plan and assess surveillance and control strategies. Here, we provide estimates of reporting delays during an emerging arboviral outbreak and indications on how delays may have impacted onward transmission.

METHODOLOGY/PRINCIPAL FINDINGS

Using descriptive statistics and Kaplan-Meyer curves we analyzed case reporting delays (the period between the date of symptom onset and the date of notification to the public health authorities) during the 2017 Italian chikungunya outbreak. We further investigated the effect of outbreak detection on reporting delays by means of a Cox proportional hazard model. We estimated that the overall median reporting delay was 15.5 days, but this was reduced to 8 days after the notification of the first case. Cases with symptom onset after outbreak detection had about a 3.5 times higher reporting rate, however only 3.6% were notified within 24h from symptom onset. Remarkably, we found that 45.9% of identified cases developed symptoms before the detection of the outbreak.

CONCLUSIONS/SIGNIFICANCE

These results suggest that efforts should be undertaken to improve the early detection and identification of arboviral cases, as well as the management of vector species to mitigate the impact of long reporting delays.

The alphavirus nonstructural protein 2 NTPase induces a host translational shut-off through phosphorylation of eEF2 via cAMP-PKA-eEF2K signaling

Chikungunya virus (CHIKV) is a reemerging alphavirus. Since 2005, it has infected millions of people during outbreaks in Africa, Asia, and South/Central America. CHIKV replication depends on host cell factors at many levels and is expected to have a profound effect on cellular physiology. To obtain more insight into host responses to infection, stable isotope labeling with amino acids in cell culture and liquid chromatography-tandem mass spectrometry were used to assess temporal changes in the cellular phosphoproteome during CHIKV infection. Among the ~3,000 unique phosphorylation sites analyzed, the largest change in phosphorylation status was measured on residue T56 of eukaryotic elongation factor 2 (eEF2), which showed a >50-fold increase at 8 and 12 h p.i. Infection with other alphaviruses (Semliki Forest, Sindbis and Venezuelan equine encephalitis virus (VEEV)) triggered a similarly strong eEF2 phosphorylation. Expression of a truncated form of CHIKV or VEEV nsP2, containing only the N-terminal and NTPase/helicase domains (nsP2-NTD-Hel), sufficed to induce eEF2 phosphorylation, which could be prevented by mutating key residues in the Walker A and B motifs of the NTPase domain. Alphavirus infection or expression of nsP2-NTD-Hel resulted in decreased cellular ATP levels and increased cAMP levels. This did not occur when catalytically inactive NTPase mutants were expressed. The wild-type nsP2-NTD-Hel inhibited cellular translation independent of the C-terminal nsP2 domain, which was previously implicated in directing the virus-induced host shut-off for Old World alphaviruses. We hypothesize that the alphavirus NTPase activates a cellular adenylyl cyclase resulting in increased cAMP levels, thus activating PKA and subsequently eukaryotic elongation factor 2 kinase. This in turn triggers eEF2 phosphorylation and translational inhibition. We conclude that the nsP2-driven increase of cAMP levels contributes to the alphavirus-induced shut-off of cellular protein synthesis that is shared between Old and New World alphaviruses. MS Data are available via ProteomeXchange with identifier PXD009381.

The recorded economic costs of alien invasive species in Italy

Whilst the ecological impacts of invasion by alien species have been well documented, little is known of the economic costs incurred. The impacts of invasive alien species on the economy can be wide-ranging, from management costs, to loss of crops, to infrastructure damage. However, details on these cost estimates are still lacking, particularly at national and regional scales. In this study, we use data from the first global assessment of economic costs of invasive alien species (InvaCost), where published economic cost data were systematically gathered from scientific and grey literature. We aimed to describe the economic cost of invasions in Italy, one of the most invaded countries in Europe, with an estimate of more than 3,000 alien species. The overall economic cost of invasions to Italy between 1990 and 2020 was estimated at US$ 819.76 million (EUR€ 704.78 million). This cost was highest within terrestrial habitats, with considerably fewer costs being exclusively associated with aquatic habitats and management methods, highlighting a bias within current literature. There was also a clear indication of informational gaps, with only 15 recorded species with costs. Further, we observed a tendency towards particular taxonomic groups, with insect species accounting for the majority of cost estimates in Italy. Globally, invasion rates are not slowing down and the associated economic impact is thus expected to increase. Therefore, the evaluation and reporting of economic costs need to be improved across taxa, in order to mitigate and efficiently manage the impact of invasions on economies.

New methodologies for the estimation of population vulnerability to diseases: a case study of Lassa fever and Ebola in Nigeria and Sierra Leone

Public health practitioners require measures to evaluate how vulnerable populations are to diseases, especially for zoonoses (i.e. diseases transmitted from animals to humans) given their pandemic potential. These measures would be valuable to support strategic and operational decision making and allocation of resources. Although vulnerability is well defined for natural hazards, for public health threats the concept remains undetermined. Here, we develop new methodologies to: (i) quantify the impact of zoonotic diseases and the capacity of countries to cope with these diseases, and (ii) combine these two measures (impact and capacity) into one overall vulnerability indicator. The adaptive capacity is calculated from estimations of disease mortality, although the method can be adapted for diseases with no or low mortality but high morbidity. As an example, we focused on the vulnerability of Nigeria and Sierra Leone to Lassa Fever and Ebola. We develop a simple analytical form that can be used to estimate vulnerability scores for different spatial units of interest, e.g. countries or regions. We show how some populations can be highly vulnerable despite low impact threats. We finally outline future research to more comprehensively inform vulnerability with the incorporation of relevant factors depicting local heterogeneities (e.g. bio-physical and socio-economic factors). This article is part of the theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control'. This theme issue is linked with the earlier issue 'Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes'.

A new multiplex RT-qPCR method for the simultaneous detection and discrimination of Zika and chikungunya viruses

OBJECTIVE

The re-emergence and spread of tropical viruses to new areas has raised a wave of concern worldwide. In order to treat patients at an early stage and prevent the diffusion of an outbreak, early diagnosis, and therefore fast and adequate detection, is needed. To this end, a multiplex reverse transcription real-time polymerase chain reaction TaqMan method was designed to detect Zika (ZIKV) and chikungunya (CHIKV) viruses simultaneously.

METHODS

Two methods targeting different genome segments were selected from the literature for each virus. These were adapted for high genome coverage and combined in a four-plex assay that was thoroughly validated in-house. The SCREENED tool was used to evaluate the sequence coverage of the method.

RESULTS

The full validation approach showed that the new four-plex method allows the specific and sensitive identification and discrimination of ZIKV and CHIKV in routine samples. The combination of two targets per virus allowing almost 100% coverage of about 500 genomes is shown for the first time.

CONCLUSIONS

PCR is a reliable user-friendly technique that can be applied in remote areas. Such multiplex methods enable early and efficient diagnosis, leading to rapid treatment and effective confinement in outbreak cases. They may also serve as an aid for surveillance, and the full validation permits easy method-transfer allowing worldwide harmonization.

Establishment and Comparison of Pathogenicity and Related Neurotropism in Two Age Groups of Immune Competent Mice, C57BL/6J Using an Indian Isolate of Chikungunya Virus (CHIKV)

Chikungunya (CHIK) is a febrile arboviral illness caused by chikungunya virus (CHIKV) and has been identified in more than 60 countries across the globe. A major public health concern, the infection occurs as an acute febrile phase and a chronic arthralgic phase. The disease manifests differently in different age groups that can range from asymptomatic infection in the younger age group to a prolonged chronic phase in the elderly population. The present study was undertaken to evaluate strain-specific pathogenesis of ECSA genotype of CHIKV strains derived from clinical isolates in adult C57BL/6J mice model. The strain that was pathogenic and developed distinct acute and post-acute phase of CHIK infection was further evaluated for dose-dependent pathogenesis. Upon arriving on the optimal dose to induce clinical symptoms in the mice, the disease progression was evaluated across the acute and the post-acute phase of infection for a period of 15 days post-infection in two age groups of mice, namely eight weeks old and 20 weeks old mice groups. Biochemical, hematological, and virology attributes were measured and correlated to morbidity and linked neurotropism and limb thickness in the two age groups. Our results show that CHIKV exhibit strain-specific pathogenesis in C57BL/6J mice. Distinct dissimilarities were observed between the two age groups in terms of pathogenesis, viral clearance and host response to CHIKV infection.

Vector competence of Aedes bromeliae and Aedes vitattus mosquito populations from Kenya for chikungunya virus

Background

Kenya has experienced outbreaks of chikungunya in the past years with the most recent outbreak occurring in Mandera in the northern region in May 2016 and in Mombasa in the coastal region from November 2017 to February 2018. Despite the outbreaks in Kenya, studies on vector competence have only been conducted on Aedes aegypti. However, the role played by other mosquito species in transmission and maintenance of the virus in endemic areas remains unclear. This study sought to determine the possible role of rural Aedes bromeliae and Aedes vittatus in the transmission of chikungunya virus, focusing on Kilifi and West Pokot regions of Kenya.

Methods

Four day old female mosquitoes were orally fed on chikungunya virus-infected blood at a dilution of 1:1 of the viral isolate and blood (10^6.4 plaque-forming units [PFU]/ml) using artificial membrane feeder (Hemotek system) for 45 minutes. The engorged mosquitoes were picked and incubated at 29–30°C ambient temperature and 70–80% humidity in the insectary. At days 5, 7 and 10 post-infection, the mosquitoes were carefully dissected to separate the legs and wings from the body and their proboscis individually inserted in the capillary tube containing minimum essential media (MEM) to collect salivary expectorate. The resultant homogenates and the salivary expectorates were tested by plaque assay to determine virus infection, dissemination and transmission potential of the mosquitoes.

Results

A total of 515 female mosquitoes (311 Ae. bromeliae and 204 Ae. vittatus) were exposed to the East/Central/South Africa (ECSA) lineage of chikungunya virus. Aedes vittatus showed high susceptibility to the virus ranging between 75–90% and moderate dissemination and transmission rates ranging from 35–50%. Aedes bromeliae had moderate susceptibility ranging between 26–40% with moderate dissemination and transmission rates ranging from 27–55%.

Conclusion

This study demonstrates that both Ae. vittatus and Ae. bromeliae populations from West Pokot and Kilifi counties in Kenya are competent vectors of chikungunya virus. Based on these results, the two areas are at risk of virus transmission in the event of an outbreak. This study underscores the need to institute vector competence studies for populations of potential vector species as a means of evaluating risk of transmission of the emerging and re-emerging arboviruses in diverse regions of Kenya.

Kenya experienced its first chikungunya outbreak in 2004/2005 along the coastal area, followed by sporadic outbreaks in Mandera in 2016, and subsequently in Mombasa city in late 2017 and early 2018. Despite the rising risk of transmission of the virus in the country based on evidence of outbreaks in Kenya, vector competence studies have only been limited to Ae. aegypti, while the role played by other Aedes species largely remain unknown. This study demonstrated the ability of Ae. bromeliae and Ae. vittatus to transmit chikungunya virus under controlled laboratory conditions. Vector competence remains the most important approach in disease risk assessment that provides knowledge to the public health sector in developing vector control guideline.

The Role of Culex pipiens L. (Diptera: Culicidae) in Virus Transmission in Europe

Over the past three decades, a range of mosquito-borne viruses that threaten public and veterinary health have emerged or re-emerged in Europe. Mosquito surveillance activities have highlighted the Culex pipiens species complex as being critical for the maintenance of a number of these viruses. This species complex contains morphologically similar forms that exhibit variation in phenotypes that can influence the probability of virus transmission. Critical amongst these is the choice of host on which to feed, with different forms showing different feeding preferences. This influences the ability of the mosquito to vector viruses and facilitate transmission of viruses to humans and domestic animals. Biases towards blood-feeding on avian or mammalian hosts have been demonstrated for different Cx. pipiens ecoforms and emerging evidence of hybrid populations across Europe adds another level of complexity to virus transmission. A range of molecular methods based on DNA have been developed to enable discrimination between morphologically indistinguishable forms, although this remains an active area of research. This review provides a comprehensive overview of developments in the understanding of the ecology, behaviour and genetics of Cx. pipiens in Europe, and how this influences arbovirus transmission.

Antibody-mediated enhancement aggravates chikungunya virus infection and disease severity

The arthropod-transmitted chikungunya virus (CHIKV) causes a flu-like disease that is characterized by incapacitating arthralgia. The re-emergence of CHIKV and the continual risk of new epidemics have reignited research in CHIKV pathogenesis. Virus-specific antibodies have been shown to control virus clearance, but antibodies present at sub-neutralizing concentrations can also augment virus infection that exacerbates disease severity. To explore this occurrence, CHIKV infection was investigated in the presence of CHIKV-specific antibodies in both primary human cells and a murine macrophage cell line, RAW264.7. Enhanced attachment of CHIKV to the primary human monocytes and B cells was observed while increased viral replication was detected in RAW264.7 cells. Blocking of specific Fc receptors (FcγRs) led to the abrogation of these observations. Furthermore, experimental infection in adult mice showed that animals had higher viral RNA loads and endured more severe joint inflammation in the presence of sub-neutralizing concentrations of CHIKV-specific antibodies. In addition, CHIKV infection in 11 days old mice under enhancing condition resulted in higher muscles viral RNA load detected and death. These observations provide the first evidence of antibody-mediated enhancement in CHIKV infection and pathogenesis and could also be relevant for other important arboviruses such as Zika virus.

Vector competence of populations of Aedes aegypti from three distinct cities in Kenya for chikungunya virus

BACKGROUND

In April, 2004, chikungunya virus (CHIKV) re-emerged in Kenya and eventually spread to the islands in the Indian Ocean basin, South-East Asia, and the Americas. The virus, which is often associated with high levels of viremia in humans, is mostly transmitted by the urban vector, Aedes aegypti. The expansion of CHIKV presents a public health challenge both locally and internationally. In this study, we investigated the ability of Ae. aegypti mosquitoes from three distinct cities in Kenya; Mombasa (outbreak prone), Kisumu, and Nairobi (no documented outbreak) to transmit CHIKV.

METHODOLOGY/PRINCIPAL FINDINGS

Aedes aegypti mosquito populations were exposed to different doses of CHIKV (105.6-7.5 plaque-forming units[PFU]/ml) in an infectious blood meal. Transmission was ascertained by collecting and testing saliva samples from individual mosquitoes at 5, 7, 9, and 14 days post exposure. Infection and dissemination were estimated by testing body and legs, respectively, for individual mosquitoes at selected days post exposure. Tissue culture assays were used to determine the presence of infectious viral particles in the body, leg, and saliva samples. The number of days post exposure had no effect on infection, dissemination, or transmission rates, but these rates increased with an increase in exposure dose in all three populations. Although the rates were highest in Ae. aegypti from Mombasa at titers ≥106.9 PFU/ml, the differences observed were not statistically significant (χ2 ≤ 1.04, DF = 1, P ≥ 0.31). Overall, about 71% of the infected mosquitoes developed a disseminated infection, of which 21% successfully transmitted the virus into a capillary tube, giving an estimated transmission rate of about 10% for mosquitoes that ingested ≥106.9 PFU/ml of CHIKV. All three populations of Ae. aegypti were infectious as early as 5-7 days post exposure. On average, viral dissemination only occurred when body titers were ≥104 PFU/ml in all populations.

CONCLUSIONS/SIGNIFICANCE

Populations of Ae. aegypti from Mombasa, Nairobi, and Kisumu were all competent laboratory vectors of CHIKV. Viremia of the infectious blood meal was an important factor in Ae. aegypti susceptibility and transmission of CHIKV. In addition to viremia levels, temperature and feeding behavior of Ae. aegypti may also contribute to the observed disease patterns.

First case of imported chikungunya infection in Croatia, 2016

In recent years, several European countries reported cases of imported chikungunya infection. We present the first imported clinically manifested chikungunya fever in Croatia. A 27-year-old woman returned to Croatia on 21 March 2016, after she stayed in Costa Rica for two months where she had noticed a mosquito bite on her left forearm. Five days after the mosquito bite she developed severe arthralgias, fever and erythematous papular rash. In next few days symptoms gradually subsided. After ten days she felt better, but arthralgias re-appeared accompanied with morning stiffness. Two weeks after the onset of the disease she visited the infectious diseases outpatient department. The physical examination revealed rash on the trunk, extremities, palms and soles. Laboratory findings showed slightly elevated liver transaminases. Serological tests performed on day 20 after disease onset showed a high titer of chikungunya virus (CHIKV) IgM and IgG antibodies which indicated CHIKV infection. CHIKV-RNA was not detected. Serology to dengue and Zika virus was negative. The patient was treated with nonsteroid anti-inflammatory drugs and paracetamol. Her symptoms ameliorated, however, three months later she still complaint of arthralgias. The presented case highlights the need for inclusion of CHIKV in the differential diagnosis of arthralgia in all travelers returning from countries with documented CHIKV transmission.

A large-scale stochastic spatiotemporal model for Aedes albopictus-borne chikungunya epidemiology

Chikungunya is a viral disease transmitted to humans primarily via the bites of infected Aedes mosquitoes. The virus caused a major epidemic in the Indian Ocean in 2004, affecting millions of inhabitants, while cases have also been observed in Europe since 2007. We developed a stochastic spatiotemporal model of Aedes albopictus-borne chikungunya transmission based on our recently developed environmentally-driven vector population dynamics model. We designed an integrated modelling framework incorporating large-scale gridded climate datasets to investigate disease outbreaks on Reunion Island and in Italy. We performed Bayesian parameter inference on the surveillance data, and investigated the validity and applicability of the underlying biological assumptions. The model successfully represents the outbreak and measures of containment in Italy, suggesting wider applicability in Europe. In its current configuration, the model implies two different viral strains, thus two different outbreaks, for the two-stage Reunion Island epidemic. Characterisation of the posterior distributions indicates a possible relationship between the second larger outbreak on Reunion Island and the Italian outbreak. The model suggests that vector control measures, with different modes of operation, are most effective when applied in combination: adult vector intervention has a high impact but is short-lived, larval intervention has a low impact but is long-lasting, and quarantining infected territories, if applied strictly, is effective in preventing large epidemics. We present a novel approach in analysing chikungunya outbreaks globally using a single environmentally-driven mathematical model. Our study represents a significant step towards developing a globally applicable Ae. albopictus-borne chikungunya transmission model, and introduces a guideline for extending such models to other vector-borne diseases.

Global expansion of chikungunya virus: mapping the 64-year history

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that is emerging as a global threat because of the highly debilitating nature of the associated disease and unprecedented magnitude of its spread. Chikungunya originated in Africa and has since spread across the entire globe causing large numbers of epidemics that have infected millions of people in Asia, the Indian subcontinent, Europe, the Americas, and Pacific Islands. Phylogenetic analysis has identified four different genotypes of CHIKV: Asian, West African, East/Central/South African (ECSA), and Indian Ocean Lineage (IOL). In the absence of well-designed epidemiological studies, the aim of this review article was to summarize the global epidemiology of CHIKV and to provide baseline data for future research on the treatment, prevention, and control of this life-threatening disease.

First mass development of Aedes albopictus (Diptera: Culicidae)-its surveillance and control in Germany

The Asian tiger mosquito Aedes albopictus has undergone a dramatic expansion of its range in the last few decades. Since its first detection in 2007 in Germany at the motorway A5 coming from Italy via Switzerland to Germany, it has been continuously introduced by vehicles, most probably from Italy. After a hint from an alert gardener in an allotment garden area in Freiburg, Southwest Germany, in 2015, a surveillance programme was started focusing on the garden area and adjacent areas as well as most of the cemeteries as potential infestation areas. The surveillance programme confirmed a high infestation of the allotment garden. The container index (CI) exceeded almost 30% in August 2015. In lethal gravid Aedes traps (GATs) and BG-Sentinel traps, 4038 adults were caught. It could be proven that the Aedes population is more or less still spatially restricted to the allotment garden area which is adjacent to a train station where trucks from Novara, Italy, arrive loaded on trains. Outside the garden area, only a few breeding sites with developmental stages and adults were found within a radius of approximately 600 m from the highly infested garden area. It is most likely that Ae. albopictus females are constantly introduced as 'blind passengers' to Freiburg via trucks from Italy to Freiburg, Germany. After the first detection of the mass development of Ae. albopictus immediate and comprehensive control measures were initiated to reduce or even eliminate the Aedes population. Citizen awareness, especially of the gardeners, was increased by providing thorough information about the biology and control of Ae. albopictus. Beside environmental management, tablets based on Bacillus thuringiensis israelensis (Bti) were applied. The success of the control activities by the gardeners is reflected by the data gained during monthly inspection of the garden plots. The number of gardens without any container increased from 17% in July to 22% in August and 35% in September, 2015, resulting in a successful reduction of the Ae. albopictus population. The study underlines the importance of a comprehensive surveillance programme to assess the population density of Ae. albopictus as a basis for integrated control activities.

Molecular Mimicry between Chikungunya Virus and Host Components: A Possible Mechanism for the Arthritic Manifestations

Background

Chikungunya virus (CHIKV), a reemerging pathogen causes a self limited illness characterized by fever, headache, myalgia and arthralgia. However, 10–20% affected individuals develop persistent arthralgia which contributes to considerable morbidity. The exact molecular mechanisms underlying these manifestations are not well understood. The present study investigated the possible occurrence of molecular mimicry between CHIKV E1 glycoprotein and host human components.

Methodology

Bioinformatic tools were used to identify peptides of CHIKV E1 exhibiting similarity to host components. Two peptides (A&B) were identified using several bioinformatic tools, synthesised and used to validate the results obtained in silico. An ELISA was designed to assess the immunoreactivity of serum samples from CHIKV patients to these peptides. Further, experiments were conducted in a C57BL/6J experimental mouse model to investigate if peptide A and peptide B were indeed capable of inducing pathology.

Findings

The serum samples showed reactivity of varying degrees, indicating that these peptides are indeed being recognized by the host immune system during CHIKV infection. Further, these peptides when injected into C57BL/6J mice were able to induce significant inflammation in the muscles of C57BL/6J mice, similar to that observed in animals that were injected with CHIKV alone. Additionally, animals that were primed initially with CHIKV followed by a subsequent injection of the CHIKV peptides exhibited enhanced inflammatory pathology in the skeletal muscles as compared to animals that were injected with peptides or virus alone. Collectively these observations validate the hypothesis that molecular mimicry between CHIKV E1 protein and host proteins does contribute to pathology in CHIKV infection.

The outcome of Chikungunya virus infection is usually benign but persistent arthritis has been reported in 10–20% of patients after Chikungunya fever. However, some reports have suggested that similarity between host proteins and viral proteins (molecular mimicry) leads to immune mediated damage. However, this has not been proved conclusively. Therefore, this study was undertaken to identify if molecular mimicry exists between CHIKV and host components. Using various bioinformatics tools we identified common sequences and structural homology between glycoprotein of the virus and two human host tissue proteins- HLA-B27 molecule and a domain of complement C3. Two peptides having homology to these human tissue components were synthesized. These peptides were recognized by antibodies present in serum of CHIKV patients. Experiments were conducted to investigate if the peptides were capable of inducing pathology in an experimental C57BL/6J mouse model. Both the peptides on their own were able to induce significant inflammation in the muscles of C57BL/6J mice similar to that observed in animals that were injected with CHIKV alone. Additionally, animals that were injected initially with CHIKV followed by a subsequent injection of the two CHIKV peptides exhibited increased pathology as compared to animals that were injected with peptides or virus alone.

Seroprevalence of Common Viral Diseases: A Hospital Based Study from Amritsar, India

INTRODUCTION

There is a paucity of published data on epidemiology of the viral infections in Punjab, India. The Viral Research and Diagnostic Laboratory (VRDL) located at Government Medical College (GMC), Amritsar conducts the initial diagnosis of common viruses circulating in the region.

AIM

To report the seroprevalence of various viral diseases in Amritsar and neighboring districts of Punjab along with the demographic and geographical data of the patients.

MATERIALS AND METHODS

Whole blood sera samples from a total of 5781 patients suspected of various viral diseases (chikungunya, dengue, hepatitis A, hepatitis B, hepatitis C, hepatitis E, herpes simplex-1 or herpes simplex-2) were received at VRDL, GMC, Amritsar from January 2015 to April 2016 and a cross sectional study was conducted. The diagnosis was based on serological assays.

RESULTS

Out of total 5781 suspected cases, 1790 were diagnosed with antibodies for atleast one of the tested viral diseases. Dengue virus was the highest occurring viral disease (56.77%). Male patients infected with viruses outnumbered female cases, except for hepatitis E and herpes simplex-1. The 21-40 years age group appeared to be the most susceptible age group for nearly all studied viral infections. Among the total nine reported outbreak investigations, largest encompassed 1335 dengue cases from Amritsar district.

CONCLUSION

VRDL established in GMC, Amritsar has become instrumental in detection of emerging and re-emerging viral diseases including outbreak investigation of communicable diseases. Timely action with the help of adequate information and capacity to diagnose the viruses might help in saving numerous lives.

γδ T Cells Play a Protective Role in Chikungunya Virus-Induced Disease

Chikungunya virus (CHIKV) is an alphavirus responsible for causing epidemic outbreaks of polyarthralgia in humans. Because CHIKV is initially introduced via the skin, where γδ T cells are prevalent, we evaluated the response of these cells to CHIKV infection. CHIKV infection led to a significant increase in γδ T cells in the infected foot and draining lymph node that was associated with the production of proinflammatory cytokines and chemokines in C57BL/6J mice. γδ T cell(-/-) mice demonstrated exacerbated CHIKV disease characterized by less weight gain and greater foot swelling than occurred in wild-type mice, as well as a transient increase in monocytes and altered cytokine/chemokine expression in the foot. Histologically, γδ T cell(-/-) mice had increased inflammation-mediated oxidative damage in the ipsilateral foot and ankle joint compared to wild-type mice which was independent of differences in CHIKV replication. These results suggest that γδ T cells play a protective role in limiting the CHIKV-induced inflammatory response and subsequent tissue and joint damage.

IMPORTANCE

Recent epidemics, including the 2004 to 2007 outbreak and the spread of CHIKV to naive populations in the Caribbean and Central and South America with resultant cases imported into the United States, have highlighted the capacity of CHIKV to cause explosive epidemics where the virus can spread to millions of people and rapidly move into new areas. These studies identified γδ T cells as important to both recruitment of key inflammatory cell populations and dampening the tissue injury due to oxidative stress. Given the importance of these cells in the early response to CHIKV, this information may inform the development of CHIKV vaccines and therapeutics.

Serological Evidence of Chikungunya Virus among Acute Febrile Patients in Southern Mozambique

Background

In the last two decades, chikungunya virus (CHIKV) has rapidly expanded to several geographical areas, causing frequent outbreaks in sub-Saharan Africa, South East Asia, South America, and Europe. Therefore, the disease remains heavily neglected in Mozambique, and no recent study has been conducted.

Methods

Between January and September 2013, acute febrile patients with no other evident cause of fever and attending a health center in a suburban area of Maputo city, Mozambique, were consecutively invited to participate. Paired acute and convalescent serum samples were requested from each participant. Convalescent samples were initially screened for anti-CHIKV IgG using a commercial indirect immunofluorescence test, and if positive, the corresponding acute sample was screened using the same test.

Results

Four hundred patients were enrolled. The median age of study participants was 26 years (IQR: 21–33 years) and 57.5% (224/391) were female. Paired blood samples were obtained from 209 patients, of which 26.4% (55/208) were presented anti-CHIKV IgG antibodies in the convalescent sample. Seroconversion or a four-fold titer rise was confirmed in 9 (4.3%) patients.

Conclusion

The results of this study strongly suggest that CHIKV is circulating in southern Mozambique. We recommend that CHIKV should be considered in the differential diagnosis of acute febrile illness in Mozambique and that systematic surveillance for CHIKV should be implemented.

Chikungunya virus (CHIKV) is an emerging arbovirus that remains heavily neglected in Mozambique, and no recent study has been conducted. Between January and September 2013, four hundred acute febrile patients with no other evident cause of fever and attending a health center in a suburban area of Maputo city, Mozambique, were consecutively invited to participate. Paired acute and convalescent serum samples were drawn from each participant. Convalescent samples were initially screened for anti-CHIKV IgG, and if positive the corresponding acute sample was screened using the same test. Of the 209 patients from which paired samples was obtained, 26.4% (55/208) presented anti-CHIKV IgG antibodies in the convalescent sample. Seroconversion or a four-fold titer rise was confirmed in 9 (4.3%) patients. Overall our findings demonstrate that CHIKV is circulating in southern Mozambique and suggest that CHIKV should be considered in the differential diagnosis of acute febrile illness.

Antiviral Phosphorodiamidate Morpholino Oligomers are Protective against Chikungunya Virus Infection on Cell-based and Murine Models

Chikungunya virus (CHIKV) infection in human is associated with debilitating and persistent arthralgia and arthritis. Currently, there is no specific vaccine or effective antiviral available. Anti-CHIKV Phosphorodiamidate Morpholino Oligomer (CPMO) was evaluated for its antiviral efficacy and cytotoxcity in human cells and neonate murine model. Two CPMOs were designed to block translation initiation of a highly conserved sequence in CHIKV non-structural and structural polyprotein, respectively. Pre-treatment of HeLa cells with CPMO1 significantly suppressed CHIKV titre, CHIKV E2 protein expression and prevented CHIKV-induced CPE. CPMO1 activity was also CHIKV-specific as shown by the lack of cross-reactivity against SINV or DENV replication. When administered prophylactically in neonate mice, 15 μg/g CPMO1v conferred 100% survival against CHIKV disease. In parallel, these mice demonstrated significant reduction in viremia and viral load in various tissues. Immunohistological examination of skeletal muscles and liver of CPMO1v-treated mice also showed healthy tissue morphology, in contrast to evident manifestation of CHIKV pathogenesis in PBS- or scrambled sCPMO1v-treated groups. Taken together, our findings highlight for the first time that CPMO1v has strong protective effect against CHIKV infection. This warrants future development of morpholino as an alternative antiviral agent to address CHIKV infection in clinical applications.

Independent Emergence of the Cosmopolitan Asian Chikungunya Virus, Philippines 2012

Outbreaks involving the Asian genotype Chikungunya virus (CHIKV) caused over one million infections in the Americas recently. The outbreak was preceded by a major nationwide outbreak in the Philippines. We examined the phylogenetic and phylogeographic relationships of representative CHIKV isolates obtained from the 2012 Philippines outbreak with other CHIKV isolates collected globally. Asian CHIKV isolated from the Philippines, China, Micronesia and Caribbean regions were found closely related, herein denoted as Cosmopolitan Asian CHIKV (CACV). Three adaptive amino acid substitutions in nsP3 (D483N), E1 (P397L) and E3 (Q19R) were identified among CACV. Acquisition of the nsP3-483N mutation in Compostela Valley followed by E1-397L/E3-19R in Laguna preceded the nationwide spread in the Philippines. The China isolates possessed two of the amino acid substitutions, nsP3-D483N and E1-P397L whereas the Micronesian and Caribbean CHIKV inherited all the three amino acid substitutions. The unique amino acid substitutions observed among the isolates suggest multiple independent virus dissemination events. The possible biological importance of the specific genetic signatures associated with the rapid global of the virus is not known and warrant future in-depth study and epidemiological follow-up. Molecular evidence, however, supports the Philippines outbreak as the possible origin of the CACV.

Protective and Pathogenic Responses to Chikungunya Virus Infection

Chikungunya virus (CHIKV) is an arbovirus responsible for causing epidemic outbreaks of human disease characterized by painful and often debilitating arthralgia. Recently CHIKV has moved into the Caribbean and the Americas resulting in massive outbreaks in naïve human populations. Given the importance of CHIKV as an emerging disease, a significant amount of effort has gone into interpreting the virus-host interactions that contribute to protection or virus-induced pathology following CHIKV infection, with the long term goal of using this information to develop new therapies or safe and effective anti-CHIKV vaccines. This work has made it clear that numerous distinct host responses are involved in the response to CHIKV infection, where some aspects of the host innate and adaptive immune response protect from or limit virus-induced disease, while other pathways actually exacerbate the virus-induced disease process. This review will discuss mechanisms that have been identified as playing a role in the host response to CHIKV infection and illustrate the importance of carefully evaluating these responses to determine whether they play a protective or pathologic role during CHIKV infection.

Single-Stranded RNA Viruses

In this chapter, we describe 73 zoonotic viruses that were isolated in Northern Eurasia and that belong to the different families of viruses with a single-stranded RNA (ssRNA) genome. The family includes viruses with a segmented negative-sense ssRNA genome (families Bunyaviridae and Orthomyxoviridae) and viruses with a positive-sense ssRNA genome (families Togaviridae and Flaviviridae). Among them are viruses associated with sporadic cases or outbreaks of human disease, such as hemorrhagic fever with renal syndrome (viruses of the genus Hantavirus), Crimean–Congo hemorrhagic fever (CCHFV, Nairovirus), California encephalitis (INKV, TAHV, and KHATV; Orthobunyavirus), sandfly fever (SFCV and SFNV, Phlebovirus), Tick-borne encephalitis (TBEV, Flavivirus), Omsk hemorrhagic fever (OHFV, Flavivirus), West Nile fever (WNV, Flavivirus), Sindbis fever (SINV, Alphavirus) Chikungunya fever (CHIKV, Alphavirus) and others. Other viruses described in the chapter can cause epizootics in wild or domestic animals: Geta virus (GETV, Alphavirus), Influenza A virus (Influenzavirus A), Bhanja virus (BHAV, Phlebovirus) and more. The chapter also discusses both ecological peculiarities that promote the circulation of these viruses in natural foci and factors influencing the occurrence of epidemic and epizootic outbreaks

Detection of rickettsial DNA in ticks and wild boars in Kyoto City, Japan

The tick is a well-known vector for arthropod-borne pathogens, such as tick-borne encephalitis, Lyme disease, Japanese spotted fever and severe fever with thrombocytopenia syndrome. It is therefore important to know the tick population and distribution in our environment and wild animals in order to prevent tick-borne diseases. Here, we report the results of tick surveillance from May to September 2011 at 14 geographical points and in 5 wild boars in Kyoto City, Kyoto prefecture, Japan. We collected 3,198 ticks comprising 5 tick species, Haemaphysalis (H.) longicornis, H. flava, H. kitaokai, Amblyomma testudinarium and Dermacentor taiwanensis. Interestingly, the proportion of tick species varied according to geographical region within the city. The ticks collected in the city were reported as potential vectors of pathogens, such as rickettsiosis. We detected rickettsial DNA by PCR in 71.1% of 201 ticks investigated. The ticks that carried rickettsiae were distributed across the whole the city. The sequences of PCR-amplified DNA fragments were determined and showed similarities to spotted fever group rickettsiae. Although their pathogenicity for animals including humans is still unclear, it is important to stay alert and pay attention to tick-borne diseases in order to ensure the safety of the citizens of the city as well as that of visitors.

Comparative host feeding patterns of the Asian tiger mosquito, Aedes albopictus, in urban and suburban Northeastern USA and implications for disease transmission

Background

Aedes albopictus is an invasive species which continues expanding its geographic range and involvement in mosquito-borne diseases such as chikungunya and dengue. Host selection patterns by invasive mosquitoes are critically important because they increase endemic disease transmission and drive outbreaks of exotic pathogens. Traditionally, Ae. albopictus has been characterized as an opportunistic feeder, primarily feeding on mammalian hosts but occasionally acquiring blood from avian sources as well. However, limited information is available on their feeding patterns in temperate regions of their expanded range. Because of the increasing expansion and abundance of Ae. albopictus and the escalating diagnoses of exotic pathogens in travelers returning from endemic areas, we investigated the host feeding patterns of this species in newly invaded areas to further shed light on its role in disease ecology and assess the public health threat of an exotic arbovirus outbreak.

Methodology/Principal Findings

We identified the vertebrate source of 165 blood meals in Ae. albopictus collected between 2008 and 2011 from urban and suburban areas in northeastern USA. We used a network of Biogents Sentinel traps, which enhance Ae. albopictus capture counts, to conduct our collections of blooded mosquitoes. We also analyzed blooded Culex mosquitoes collected alongside Ae. albopictus in order to examine the composition of the community of blood sources. We found no evidence of bias since as expected Culex blood meals were predominantly from birds (n = 149, 93.7%) with only a small proportion feeding on mammals (n = 10, 6.3%). In contrast, Aedes albopictus fed exclusively on mammalian hosts with over 90% of their blood meals derived from humans (n = 96, 58.2%) and domesticated pets (n = 38, 23.0% cats; and n = 24, 14.6% dogs). Aedes albopictus fed from humans significantly more often in suburban than in urban areas (χ², p = 0.004) and cat-derived blood meals were greater in urban habitats (χ², p = 0.022). Avian-derived blood meals were not detected in any of the Ae. albopictus tested.

Conclusions/Significance

The high mammalian affinity of Ae. albopictus suggests that this species will be an efficient vector of mammal- and human-driven zoonoses such as La Crosse, dengue, and chikungunya viruses. The lack of blood meals obtained from birds by Ae. albopictus suggest that this species may have limited exposure to endemic avian zoonoses such as St. Louis encephalitis and West Nile virus, which already circulate in the USA. However, growing populations of Ae. albopictus in major metropolitan urban and suburban centers, make a large autochthonous outbreak of an arbovirus such as chikungunya or dengue viruses a clear and present danger. Given the difficulties of Ae. albopictus suppression, we recommend that public health practitioners and policy makers install proactive measures for the imminent mitigation of an exotic pathogen outbreak.

Aedes albopictus is one of the most invasive and aggressive disease vectors in the world. The range of this species is currently still expanding, particularly into highly dense human population centers in temperate areas in the USA and Europe, raising the public health threat of emerging and re-emerging diseases such as chikungunya and dengue. The prominence of Ae. albopictus as a major vector was exposed during the global pandemic of chikungunya virus, primarily because of a virus adaptation which enhanced the transmission efficiency by this mosquito species and also because of the first locally-transmitted cases of chikungunya virus in temperate Europe. Blood feeding patterns by mosquitoes are a critical component of virus proliferation and determine the degree and intensity of disease epidemics, particularly in newly invaded areas. We examined the blood meal sources of invasive Ae. albopictus in the northernmost boundary of their range in temperate North America and found that the species fed exclusively on mammalian hosts, with over 90% of their blood meals derived from humans and their associated pets (cats and dogs). The high mammalian affinity of Ae. albopictus suggests that this species may be an efficient vector of mammal-driven zoonoses and human-driven anthroponoses such as dengue and chikungunya viruses in this region.

Incubation periods of mosquito-borne viral infections: a systematic review

Mosquito-borne viruses are a major public health threat, but their incubation periods are typically uncited, non-specific, and not based on data. We systematically review the published literature on six mosquito-borne viruses selected for their public health importance: chikungunya, dengue, Japanese encephalitis, Rift Valley fever, West Nile, and yellow fever viruses. For each, we identify the literature's consensus on the incubation period, evaluate the evidence for this consensus, and provide detailed estimates of the incubation period and distribution based on published experimental and observational data. We abstract original data as doubly interval-censored observations. Assuming a log-normal distribution, we estimate the median incubation period, dispersion, 25th and 75th percentiles by maximum likelihood. We include bootstrapped 95% confidence intervals for each estimate. For West Nile and yellow fever viruses, we also estimate the 5th and 95th percentiles of their incubation periods.

Dendritic cell immunoreceptor regulates Chikungunya virus pathogenesis in mice

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus responsible for recent epidemic outbreaks of debilitating disease in humans. Alphaviruses are known to interact with members of the C-type lectin receptor family of pattern recognition proteins, and given that the dendritic cell immunoreceptor (DCIR) is known to act as a negative regulator of the host inflammatory response and has previously been associated with rheumatoid arthritis, we evaluated DCIR's role in response to CHIKV infection. Although we observed an increase in the proportion of dendritic cells at the site of CHIKV infection at 24 to 36 h postinfection, these cells showed decreased cell surface DCIR, suggestive of DCIR triggering and internalization. In vitro, bone marrow-derived dendritic cells from DCIR-deficient (DCIR(-/-)) mice exhibited altered cytokine expression following exposure to CHIKV. DCIR(-/-) mice exhibited more severe disease signs than wild-type C57BL6/J mice following CHIKV infection, including a more rapid and more severe onset of virus-induced edema and enhanced weight loss. Histological examination revealed that DCIR-deficient animals exhibited increased inflammation and damage in both the fascia of the inoculated foot and the ankle joint, and DCIR deficiency skewed the CHIKV-induced cytokine response at the site of infection at multiple times postinfection. Early differences in virus-induced disease between C57BL6/J and DCIR(-/-) mice were independent of viral replication, while extended viral replication correlated with enhanced foot swelling and tissue inflammation and damage in DCIR(-/-) compared to C57BL6/J mice at 6 to 7 days postinfection. These results suggest that DCIR plays a protective role in limiting the CHIKV-induced inflammatory response and subsequent tissue and joint damage.

Effectiveness of ultra-low volume nighttime applications of an adulticide against diurnal Aedes albopictus, a critical vector of dengue and chikungunya viruses

Aedes albopictus, the Asian tiger mosquito, continues expanding its geographic range and involvement in mosquito-borne diseases such as chikungunya and dengue. Vector control programs rarely attempt to suppress this diurnal species with an ultra-low volume (ULV) adulticide because for maximum efficacy applications are conducted at night. During 2009-2011 we performed experimental nighttime applications of a novel adulticide (DUET®) against field populations of Ae. albopictus within an urban site composed of approximately 1,000 parcels (home and yard) in northeastern USA. Dual applications at mid label rate of the adulticide spaced one or two days apart accomplished significantly higher control (85.0 ± 5.4% average reduction) than single full rate applications (73.0 ± 5.4%). Our results demonstrate that nighttime ULV adulticiding is effective in reducing Ae. albopictus abundance and highlight its potential for use as part of integrated pest management programs and during disease epidemics when reducing human illness is of paramount importance.

The "auto-dissemination" approach: a novel concept to fight Aedes albopictus in urban areas

BACKGROUND

The main constraint to the fight against container-breeding mosquito vectors of human arboviruses is the difficulty in targeting the multiplicity of larval sources, mostly represented by small man-made water containers. The aim of this work is to assess the feasibility of the "auto-dissemination" approach, already tested for Aedes aegypti, as a possible alternative to traditional, inefficient control tools, against Ae. albopictus in urban areas. The approach is based on the possibility that wild adult females, exposed to artificial resting sites contaminated with pyriproxyfen, can disseminate this juvenile hormone analogue to larval habitats, thus interfering with adult emergence.

METHODOLOGY

We carried out four field experiments in two areas of Rome that are typically highly infested with Ae. albopictus, i.e. the main cemetery and a small green area within a highly urbanised neighbourhood. In each area we used 10 pyriproxyfen "dissemination" stations, 10 "sentinel" sites and 10 covered, control sites. The sentinel and control sites each contained 25 Ae. albopictus larvae. These were monitored for development and adult emergence.

PRINCIPAL FINDINGS

When a 5% pyriproxyfen powder was used to contaminate the dissemination sites, we observed significantly higher mortality at the pupal stage in the sentinel sites (50-70%) than in the controls (<2%), showing that pyriproxyfen was transferred by mosquitoes into sentinel sites and that it had a lethal effect.

CONCLUSIONS

The results support the potential feasibility of the auto-dissemination approach to control Ae. albopictus in urban areas. Further studies will be carried out to optimize the method and provide an effective tool to reduce the biting nuisance caused by this aggressive species and the transmission risk of diseases such as Dengue and Chikungunya. These arboviruses pose an increasing threat in Europe as Ae. albopictus expands its range.

Surveillance for West Nile, dengue, and chikungunya virus infections, Veneto Region, Italy, 2010

In 2010, in Veneto Region, Italy, surveillance of summer fevers was conducted to promptly identify autochthonous cases of West Nile fever and increase detection of imported dengue and chikungunya in travelers. Surveillance highlighted the need to modify case definitions, train physicians, and when a case is identified, implement vector control measures.

Impact of Chikungunya virus on Aedes albopictus females and possibility of vertical transmission using the actors of the 2007 outbreak in Italy

We investigated the impact of CHIKV strains on some Aedes albopictus (Skuse) reproductive parameters and the possibility of vertical transmission. Two strains were collected in the area where the epidemic occurred in 2007, one isolated from mosquitoes, the other one isolated from a viraemic patient. Different types of blood meals, either infected or non-infected, were offered to Ae. albopictus females, that were then analyzed at increasing time post infection. The virus titre, measured by two RT-PCR methods in the blood meals, influenced the rate of infection and the rate of dissemination of CHIKV in Ae. albopictus body. We found individual variability with respect to the infection/dissemination rates and their latency both considering the female's body and appendages. The hatching rate was significantly lower for the eggs laid by the infected females than for the control eggs, while the mortality during the larval development (from first instar larva to adult emergence) was similar among the progeny of infected and non-infected female groups. Our findings seem to support the hypothesis that the vertical transmission is a rare event under our conditions, and that a certain time period is required in order to get the ovarioles infected. Field observations conducted during the Spring 2008 showed no evidence of the presence of infected overwintering progeny produced by Ae. albopictus females infected during the 2007 outbreak.

Chikungunya: a re-emerging virus

In the past decade, chikungunya--a virus transmitted by Aedes spp mosquitoes--has re-emerged in Africa, southern and southeastern Asia, and the Indian Ocean Islands as the cause of large outbreaks of human disease. The disease is characterised by fever, headache, myalgia, rash, and both acute and persistent arthralgia. The disease can cause severe morbidity and, since 2005, fatality. The virus is endemic to tropical regions, but the spread of Aedes albopictus into Europe and the Americas coupled with high viraemia in infected travellers returning from endemic areas increases the risk that this virus could establish itself in new endemic regions. This Seminar focuses on the re-emergence of this disease, the clinical manifestations, pathogenesis of virus-induced arthralgia, diagnostic techniques, and various treatment modalities.

Expecting the unexpected: nucleic acid-based diagnosis and discovery of emerging viruses

Extrapolation from recent disease history suggests that changes in the global environment, including virus, vector and human behavior, will continue to influence the spectrum of viruses to which humans are exposed. In this article, these environmental changes will be enumerated, and their potential impact on target-focused, nucleic acid-based diagnostic tests will be considered, followed by a presentation of some emerging technological responses.

Transmission potential of chikungunya virus and control measures: the case of Italy

During summer 2007 Italy has experienced an epidemic caused by Chikungunya virus – the first large outbreak documented in a temperate climate country – with approximately 161 laboratory confirmed cases concentrated in two bordering villages in North–Eastern Italy comprising 3,968 inhabitants. The seroprevalence was recently estimated to be 10.2%. In this work we provide estimates of the transmission potential of the virus and we assess the efficacy of the measures undertaken by public health authorities to control the epidemic spread. To such aim, we developed a model describing the temporal dynamics of the competent vector, known as Aedes albopictus, explicitly depending on climatic factors, coupled to an epidemic transmission model describing the spread of the epidemic in both humans and mosquitoes. The cumulative number of notified cases predicted by the model was 185 on average (95% CI 117–278), in good agreement with observed data. The probability of observing a major outbreak after the introduction of an infective human case was estimated to be in the range of 32%–76%. We found that the basic reproduction number was in the range of 1.8–6 but it could have been even larger, depending on the density of mosquitoes, which in turn depends on seasonal meteorological effects, besides other local abiotic factors. These results confirm the increasing risk of tropical vector–borne diseases in temperate climate countries, as a consequence of globalization. However, our results show that an epidemic can be controlled by performing a timely intervention, even if the transmission potential of Chikungunya virus is sensibly high.

West Nile Virus in the New World: trends in the spread and proliferation of West Nile Virus in the Western Hemisphere

The observed patterns and variations in the ecology, epidemiology, distribution and prevalence of the West Nile Virus (WNV) in different areas of the Western Hemisphere make this pathogen of particular importance as a model for understanding the potential risk factors associated with emerging pathogens worldwide, particularly those involving zoonotic pathogens whose epidemiology involves the potential for vertical transmission in arthropod vector species, and horizontal and vertical transmission within and among vertebrate host species. Record numbers of human WNV cases were recorded in Canada during 2007, with >50% more cases than documented in any previous year. Although overall numbers of human infections recorded in the United States were not exceptionally high during 2007 relative to epidemic levels reported in 2002 and 2003, the state of Oklahoma reported that the highest-ever number of human WNV cases and the numbers of human cases recorded in Canada were 50% higher than previous record levels recorded in 2003. The record and near-record numbers of human WNV infections recorded in several regions of North America during 2007 have important implications for the future management and surveillance of WNV vectors and reservoirs in North America. The spatiotemporal distribution of WNV infections in humans and animals recorded during 2007 in North America and South America have important implications for the surveillance and management of public health threats from WNV in the Western Hemisphere. Serological surveys conducted in areas of intense WNV transmission in the United States have reported low prevalence of antibodies to WNV in human s populations, indicating that additional epidemic outbreaks of human disease from WNV can be expected in the future.

Persistent arthralgia induced by Chikungunya virus infection is associated with interleukin-6 and granulocyte macrophage colony-stimulating factor

Background. Chikungunya virus (CHIKV) infection induces arthralgia. The involvement of inflammatory cytokines and chemokines has been suggested, but very little is known about their secretion profile in CHIKV-infected patients.

Methods. A case-control longitudinal study was performed that involved 30 adult patients with laboratory-confirmed Chikungunya fever. Their profiles of clinical disease, viral load, and immune mediators were investigated.

Results. When patients were segregated into high viral load and low viral load groups during the acute phase, those with high viremia had lymphopenia, lower levels of monocytes, neutrophilia, and signs of inflammation. The high viral load group was also characterized by a higher production of pro-inflammatory cytokines, such as interferon-α and interleukin (IL)–6, during the acute phase. As the disease progressed to the chronic phase, IL-17 became detectable. However, persistent arthralgia was associated with higher levels of IL-6 and granulocyte macrophage colony-stimulating factor, whereas patients who recovered fully had high levels of Eotaxin and hepatocyte growth factor.

Conclusions. The level of CHIKV viremia during the acute phase determined specific patterns of pro-inflammatory cytokines, which were associated with disease severity. At the chronic phase, levels of IL-6, and granulocyte macrophage colony-stimulating factor found to be associated with persistent arthralgia provide a possible explanation for the etiology of arthralgia that plagues numerous CHIKV-infected patients.

Chikungunya fever in the United States: a fifteen year review of cases

BACKGROUND

Chikungunya virus (CHIKV) represents a threat to the United States, because humans amplify CHIKV and vectors that transmit CHIKV are present.

METHODS

We described the epidemiology of laboratory-confirmed chikungunya fever (CHIK) cases in the United States in 1995-2009 and compared states with CHIKV vectors with states with returning viremic CHIK cases. For 2006-2009, we evaluated reporting of CHIK cases to ArboNET, the arboviral surveillance system.

RESULTS

In 1995-2009, 109 CHIK cases were identified in the United States; all adult travelers. Sixty-two subjects (57%) had recently visited India, and 13 (12%) had CHIKV viremia. Of the 26 jurisdictions with CHIK cases, 22 (85%) reported the presence of CHIKV vectors. Twelve viremic travelers returned to 6 states with CHIKV vectors. Of the 106 cases identified in 2006-2009, only 27 (25%) were reported to ArboNET, with a median of 122 days (range, 44-273 days) between illness onset and reporting.

CONCLUSIONS

No locally acquired CHIK cases were identified. However, several viremic travelers returned to states with CHIKV vectors and presented a risk for local transmission. Incomplete and delayed reporting made ArboNET less useful. To minimize the risk of CHIKV spread in the United States, healthcare providers and public health officials should be educated about recognition, diagnosis, and reporting of CHIK cases.

Comparative pathogenesis of epidemic and enzootic Chikungunya viruses in a pregnant Rhesus macaque model

Since 2004, an East African genotype of Chikungunya virus (CHIKV) has emerged, causing significant epidemics of an arthralgic syndrome. In addition, this virus has been associated for the first time with neonatal transmission and neurological complications. In the current study, pregnant Rhesus macaques were inoculated with an enzootic or epidemic strain of CHIKV to compare pathogenesis and transplacental transmission potential. Viremias were similar for both strains and peaked at 2-3 days post-inoculation (dpi). Viral RNA was detected at necropsy at 21 dpi in maternal lymphoid, joint-associated, and spinal cord tissues. The absence of detectable viral RNA and the lack of germinal center development in fetuses indicated that transplacental transmission did not occur. Neutralizing antibodies were detected in all dams and fetuses. Our study establishes a non-human primate model for evaluating vaccines and antiviral therapies and indicates that Rhesus macaques could serve as a competent enzootic reservoir.

piggybac- and PhiC31-mediated genetic transformation of the Asian tiger mosquito, Aedes albopictus (Skuse)

BACKGROUND

The Asian tiger mosquito, Aedes albopictus (Skuse), is a vector of several arboviruses including dengue and chikungunya. This highly invasive species originating from Southeast Asia has travelled the world in the last 30 years and is now established in Europe, North and South America, Africa, the Middle East and the Caribbean. In the absence of vaccine or antiviral drugs, efficient mosquito control strategies are crucial. Conventional control methods have so far failed to control Ae. albopictus adequately.

METHODOLOGY/PRINCIPAL FINDINGS

Germline transformation of Aedes albopictus was achieved by micro-injection of embryos with a piggyBac-based transgene carrying a 3xP3-ECFP marker and an attP site, combined with piggyBac transposase mRNA and piggyBac helper plasmid. Five independent transgenic lines were established, corresponding to an estimated transformation efficiency of 2-3%. Three lines were re-injected with a second-phase plasmid carrying an attB site and a 3xP3-DsRed2 marker, combined with PhiC31 integrase mRNA. Successful site-specific integration was observed in all three lines with an estimated transformation efficiency of 2-6%.

CONCLUSIONS/SIGNIFICANCE

Both piggybac- and site-specific PhiC31-mediated germline transformation of Aedes albopictus were successfully achieved. This is the first report of Ae. albopictus germline transformation and engineering, a key step towards studying and controlling this species using novel molecular techniques and genetic control strategies.

Endocytosis of chikungunya virus into mammalian cells: role of clathrin and early endosomal compartments

BACKGROUND

The replicative cycle of chikungunya virus (CHIKV), an alphavirus that recently re-emerged in India and in Indian Ocean area, remains mostly unknown. The aim of the present study was to investigate the intracellular trafficking pathway(s) hijacked by CHIKV to enter mammalian cells.

METHODOLOGY/PRINCIPAL FINDINGS

Entry pathways were investigated using a variety of pharmacological inhibitors or overexpression of dominant negative forms of proteins perturbating cellular endocytosis. We found that CHIKV infection of HEK293T mammalian cells is independent of clathrin heavy chain and- dependent of functional Eps15, and requires integrity of Rab5-, but not Rab7-positive endosomal compartment. Cytoskeleton integrity is crucial as cytochalasin D and nocodazole significantly reduced infection of the cells. Finally, both methyl beta-cyclodextrin and lysomotropic agents impaired CHIKV infection, supporting that a cholesterol-, pH-dependent step is required to achieve productive infection. Interestingly, differential sensitivity to lysomotropic agents was observed between the prototypal 37997 African strain of CHIKV and the LR-OPY1 virus isolated from the recent outbreak in Reunion Island.

CONCLUSIONS

Together our data indicate that CHIKV entry in its target cells is essentially mediated by clathrin-independent, Eps15-dependent endocytosis. Despite that this property is shared by the prototypal 37997 African strain of CHIKV and the LR-OPY1 virus isolated from the recent outbreak in La Réunion Island, differential sensitivity to lysomotropic agents may support that the LR-OPY1 strain has acquired specific entry mechanisms.

Suppressing Aedes albopictus, an emerging vector of dengue and chikungunya viruses, by a novel combination of a monomolecular film and an insect-growth regulator

The Asian tiger mosquito Aedes albopictus (Skuse) is rapidly increasing its global range and importance in transmission of chikungunya and dengue viruses. We tested pellet formulations of a monomolecular film (Agnique) and (S)-methoprene (Altosid) under laboratory and field conditions. In the laboratory, Agnique provided 80% control for 20 days, whereas Altosid, in combination with Agnique, provided 80% control for > 60 days. During field trials, the 1:1 pellet ratio of combined products provided > 95% control for at least 32 days and 50% control for at least 50 days. Altosid remained effective after a 107-day laboratory-induced drought, suggesting that the product serves as a means of control during drought conditions and against spring broods in temperate regions. Agnique and Altosid, when used in tandem for cryptic, difficult-to-treat locations, can provide long-term control of Ae. albopictus larvae and pupae. The possible additive or synergistic effects of the combined products deserve further investigation.

An outbreak of chikungunya in southern Thailand from 2008 to 2009 caused by African strains with A226V mutation

OBJECTIVES

To elucidate clinical and molecular characteristics of chikungunya fever (CHIK fever) from the 2008-2009 outbreak caused by chikungunya virus (CHIKV) in southern Thailand.

METHODS

Three hundred and eighty-one sera from 332 patients with acute febrile illness were tested for anti-CHIKV IgM antibody by ELISA. A molecular analysis of these sera was performed using a semi-nested reverse transcriptase polymerase chain reaction (RT-PCR), followed by direct sequencing and phylogenetic analysis.

RESULTS

One hundred and seventy-nine patients were diagnosed with CHIK fever by molecular analysis and/or anti-CHIKV IgM antibody detection. Patients diagnosed with CHIK fever were significantly older than controls (mean age 38.8±19 vs. 28.7±18 years, p<0.0001) and presented with arthralgia more often than controls. One hundred percent of the sera were positive by RT-PCR, whereas only 10% were positive in serological tests for anti-CHIKV IgM antibody by ELISA if the serum was obtained during the first 4 days of fever. In contrast, CHIKV-specific IgM antibody by ELISA was found in 100% of patients, whereas 15% of patients were positive by RT-PCR if the serum was obtained more than 9 days after the onset of fever. RT-PCR for CHIKV should be performed if the patients present within the first 4 days of fever. Patients presenting after at least 9 days of fever should be tested for IgM antibody. Based on phylogenetic analysis, the CHIKV strains isolated belong to African genotypes harboring the E1 A226V mutation, indicating a single origin of the 2004-2009 CHIKV outbreaks.

CONCLUSIONS

The novel CHIKV mutation could potentially modify the epidemiological presentation of CHIK fever. Early diagnosis of CHIK fever is essential for preventing further massive outbreaks.

The arrival, establishment and spread of exotic diseases: patterns and predictions

The impact of human activities on the principles and processes governing the arrival, establishment and spread of exotic pathogens is illustrated by vector-borne diseases such as malaria, dengue, chikungunya, West Nile, bluetongue and Crimean-Congo haemorrhagic fevers. Competent vectors, which are commonly already present in the areas, provide opportunities for infection by exotic pathogens that are introduced by travel and trade. At the same time, the correct combination of environmental conditions (both abiotic and biotic) makes many far-flung parts of the world latently and predictably, but differentially, permissive to persistent transmission cycles. Socioeconomic factors and nutritional status determine human exposure to disease and resistance to infection, respectively, so that disease incidence can vary independently of biological cycles.

Chikungunya virus: possible impact on transfusion medicine

In recent years, large chikungunya virus (CHIKV) outbreaks originating in Kenya have spread to islands of the Indian Ocean and parts of India, Southeast Asia, and Europe. Concern of transfusion transmission has been heightened for this mosquito-borne arbovirus because of high population infection incidence during outbreaks and the high-titer viremia lasting approximately 6 days. The virus has not circulated in the Americas; however, the abundant presence of competent mosquito vectors suggests large outbreaks are possible should the virus be introduced and autochthonous transmission occur. Chikungunya virus produces a fever-arthralgia syndrome resulting in considerable morbidity and some mortality, particularly among older age groups and/or those with pre-existing conditions. Estimated transfusion risks range as high as 150 per 10 000 donations during outbreaks. Possible measures to prevent possible CHIKV transfusion transmission include deferral of symptomatic donors, discontinuing blood collections in affected areas, and CHIKV nucleic acid screening of donations. Even a relatively small outbreak in Italy resulted in considerable adverse impact on blood collections and economic consequence. Assays suitable for testing donations for CHIKV RNA are not yet available, and given the highly geographically and temporally sporadic nature of CHIKV outbreaks, there may be considerable reluctance to develop and implement them.