Kdr genotyping and the first report of V410L and V1016I kdr mutations in voltage-gated sodium channel gene in Aedes aegypti (Diptera: Culicidae) from Iran

BACKGROUND

Aedes aegypti is the main vector of arboviral diseases worldwide. The species invaded and became established in southern Iran in 2020. Insecticide-based interventions are primarily used for its control. With insecticide resistance widespread, knowledge of resistance mechanisms is vital for informed deployment of insecticidal interventions, but information from Iranian Ae. aegypti is lacking.

METHODS

Fifty-six Ae. aegypti specimens were collected from the port city of Bandar Lengeh in Hormozgan Province in the South of Iran in 2020 and screened for kdr mutations. The most common kdr mutations in Latin America and Asia (V410L, S989P, V1016G/I and F1534C), especially when present in combinations, are highly predictive of DDT and pyrethroid resistance were detected. Phylogenetic analyses based on the diversity of S989P and V1016G/I mutations were undertaken to assess the phylogeography of these kdr mutations.

RESULTS

Genotyping all four kdr positions of V410L, S989P, V1016G/I and F1534C revealed that only 16 out of the 56 (28.57%) specimens were homozygous wild type for all kdr mutation sites. Six haplotypes including VSVF (0.537), VSVC (0.107), LSVF (0.016), LSIF (0.071), VPGC (0.257) and LPGC (0.011) were detected in this study. For the first time, 11 specimens harbouring the V410L mutation, and 8 samples with V1016I mutation were found. V410L and V1016I were coincided in 8 specimens. Also, six specimens contained 1016G/I double mutation which was not reported before.

CONCLUSIONS

The relatively high frequency of these kdr mutations in Iranian Ae. aegypti indicates a population exhibiting substantial resistance to pyrethroid insecticides, which are used widely in control operations and household formulations. The detection of the 410L/1016I kdr mutant haplotype in Iranian Ae. aegypti suggests possible convergence of invasive populations from West Africa or Latin America. However, as Iran has very limited maritime/air connections with those African countries, a Latin American origin for the invasive Ae. aegypti in Iran is more plausible.

Medically Significant Vector-Borne Viral Diseases in Iran

Vector-borne viral diseases (VBVDs) continue to pose a considerable public health risk to animals and humans globally. Vectors have integral roles in autochthonous circulation and dissemination of VBVDs worldwide. The interplay of agricultural activities, population expansion, urbanization, host/pathogen evolution, and climate change, all contribute to the continual flux in shaping the epidemiology of VBVDs. In recent decades, VBVDs, once endemic to particular countries, have expanded into new regions such as Iran and its neighbors, increasing the risk of outbreaks and other public health concerns. Both Iran and its neighboring countries are known to host a number of VBVDs that are endemic to these countries or newly circulating. The proximity of Iran to countries hosting regional diseases, along with increased global socioeconomic activities, e.g., international trade and travel, potentially increases the risk for introduction of new VBVDs into Iran. In this review, we examined the epidemiology of numerous VBVDs circulating in Iran, such as Chikungunya virus, Dengue virus, Sindbis virus, West Nile virus, Crimean-Congo hemorrhagic fever virus, Sandfly-borne phleboviruses, and Hantavirus, in relation to their vectors, specifically mosquitoes, ticks, sandflies, and rodents. In addition, we discussed the interplay of factors, e.g., urbanization and climate change on VBVD dissemination patterns and the consequent public health risks in Iran, highlighting the importance of a One Health approach to further surveil and to evolve mitigation strategies.

An Overview of Indian Biomedical Research on the Chikungunya Virus with Particular Reference to Its Vaccine, an Unmet Medical Need

Chikungunya virus (CHIKV) is an infectious agent spread by mosquitos, that has engendered endemic or epidemic outbreaks of Chikungunya fever (CHIKF) in Africa, South-East Asia, America, and a few European countries. Like most tropical infections, CHIKV is frequently misdiagnosed, underreported, and underestimated; it primarily affects areas with limited resources, like developing nations. Due to its high transmission rate and lack of a preventive vaccine or effective treatments, this virus poses a serious threat to humanity. After a 32-year hiatus, CHIKV reemerged as the most significant epidemic ever reported, in India in 2006. Since then, CHIKV-related research was begun in India, and up to now, more than 800 peer-reviewed research papers have been published by Indian researchers and medical practitioners. This review gives an overview of the outbreak history and CHIKV-related research in India, to favor novel high-quality research works intending to promote effective treatment and preventive strategies, including vaccine development, against CHIKV infection.

The First Genomic Characterization of the Chikungunya Virus in Saudi Arabia

BACKGROUND

Chikungunya is an arboviral infection caused by the Chikungunya virus (CHIKV) transmitted to humans by mosquitoes of Aedes spp. CHIKV has been confined to African countries and South-East Asia up to 2004, but since then, the pathogen has become more global, and its high morbidity rate has become more visible. Saudi Arabia is not an endemic region of CHIKV, and the virus's origin is not yet fully understood. This study aimed to characterize the genome of CHIKV from samples detected in Jeddah in 2018.

METHOD

Twenty-two sets of primers were designed to amplify near-full length genome of CHIKV. RT-PCR was conducted from clinical samples. Two samples were used for studying near complete genome sequence while the remaining samples were used to study the E1 gene. Different bioinformatics tools were utilized.

RESULTS

Phylogenetic analysis showed that the CHIKV strains clustered with strains isolated from Kenya during 2017-2018 and belonged to ECSA genotype. E1: L136F, K211E and I317V mutations were identified in our strains. Also, E2: M74I, A76T, and V264A mutations were documented. Additionally, the capsid N79S substitution was also detected.

CONCLUSION

The genome of CHIKV was analyzed for the first time in Saudi Arabia to better understand the origin of the CHIKV and its genetic diversity, which showed high similarity with IE-a subclade of CHIKV strains detected in Mombasa (Kenya) indicating its possible origin.

Molecular analysis of knockdown resistance (kdr) mutations in the voltage-gated sodium channel gene of Aedes aegypti populations from Saudi Arabia

Background

The Aedes aegypti mosquito is the primary vector for dengue, chikungunya, yellow fever and Zika viruses worldwide. The first record of Ae. aegypti in southwestern Saudi Arabia was in 1956. However, the first outbreak and cases of dengue fever were reported in 1994, and cases have increased in recent years. Vector control for Ae. aegypti mainly uses pyrethroid insecticides in outdoor and indoor space spraying. The constant use of pyrethroids has exerted intense selection pressure for developing target-site mutations in the voltage-gated sodium channel (vgsc) gene in Ae. Aegypti against pyrethroids—mutations that have led to knockdown resistance (kdr).

Methods

Aedes aegypti field populations from five regions (Jazan, Sahil, Makkah, Jeddah and Madinah) of southwestern Saudi Arabia were genotyped for known kdr mutations in domains IIS6 and IIIS6 of the vgsc gene using polymerase chain reaction (PCR) amplification and sequencing. We estimated the frequency of kdr mutations and genotypes from Saudi Arabia as well as from other countries, Thailand, Myanmar (Southeast Asia) and Uganda (East Africa). We constructed haplotype networks to infer the evolutionary relationships of these gene regions.

Results

The three known kdr mutations, S989P, V1016G (IIS6) and F1534C (IIIS6), were detected in all five regions of Saudi Arabia. Interestingly, the triple homozygous wild genotype was reported for the first time in two individuals from the highlands of the Jazan region and one from the Al-Quoz, Sahil region. Overall, nine genotypes comprising four haplotypes were observed in southwestern Saudi Arabia. The median-joining haplotype networks of eight populations from Saudi Arabia, Southeast Asia and East Africa for both the IIS6 and IIIS6 domains revealed that haplotype diversity was highest in Uganda and in the Jazan and Sahil regions of Saudi Arabia, whereas haplotype diversity was low in the Jeddah, Makkah and Madinah regions. Median-joining haplotype networks of both domains indicated selection acting on the kdr-mutation containing haplotypes in Saudi Arabia.

Conclusions

The presence of wild type haplotypes without any of the three kdr mutations, i.e. that are fully susceptible, in Saudi Arabia indicates that further consideration should be given to insecticide resistance management strategies that could restore pyrethroid sensitivity to the populations of Ae. aegypti in Saudi Arabia as part of an integrative vector control strategy.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05525-y.

Epidemiological Evidence of Mosquito-Borne Viruses among Persons and Vectors in Iran: A Study from North to South

•

The overall seroprevalence of DENV, WNV and CHIKV in Iran were 5.9%, 18.8% and 1.8% between 2017 and 2018.

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No proof of viral RNAs was presence in vectors.

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Gilan and Hormozgan were high risk regions and the elderlies were at higher risk of infection by WNV and CHIKV.

Detection of chikungunya virus in the Southern region, Saudi Arabia

Background and aim

Despite the fact that the chikungunya viral infection is a neglected disease, complications such as hemorrhagic fever, arthritis, and lymphopenia remain a health concern. The aim of this study was to determine the prevalence of the chikungunya virus in the Southern Region, Saudi Arabia. Enzyme immunoassay and polymerase chain reaction have been compared between samples.

Materials and methods

Forty samples from two southern hospitals in Saudi Arabia were collected between December 2019 and February 2020 and screened for chikungunya virus IgG antibodies and for viral RNA. Selection criteria were based on hematological parameters and rheumatological profiles such as rheumatoid factor, c-reactive protein, anti-nuclear antibody, and anti-cyclic citrullinated peptide (anti-CCP) of out-patients.

Results

One confirmed case of chikungunya virus was detected using the ELISA test. However, no viral RNA was detected in any of the samples. This suggests that the virus is cleared rapidly in patients.

Conclusion

Chikungunya is a neglected viral disease in Saudi Arabia. Future work should focus on detailed investigation of this viral infection and its vectors.

Lack of Zika Virus and Other Recognized Flaviviruses among the Mosquito Vectors during and Post the Hajj Mass Gathering

Makkah city, Kingdom of Saudi Arabia (KSA), contains many of the world’s mosquito vectors of parasitic and arboviral disease and is the site of the Hajj mass gathering. As such there is a risk of exportation and globalization of vector-borne viruses, including the re-emerging Zika virus (ZIKV). There was international concern regarding the introduction of ZIKV to KSA and potential international spread of the virus following the 2016 Hajj which took place few days after the Rio summer Olympics at the height of the ZIKV pandemic. We aimed to detect flaviviruses, including ZIKV, circulating among mosquito hosts in the city of Makkah during and post the 2016 Hajj pilgrimage. Mosquitos (adults and larvae) were sampled from 15 sites in Makkah city during and post the 2016 Hajj and identified to species by morphological keys. Mosquitos were pooled according to date of collection, location, and species. A Pan-Flaviviruses RT-PCR assay that enables identification of 51 flaviviruses species and three tentative species was used to detect flavivirus RNA directly from mosquito homogenates. Between the 10 September and 6 October 2016, 9412 female mosquitos were collected. Of these, 81.3% were Aedes aegypti, 18.6% were Culex species, and 0.1% were Anopheles species. Of the total 493 mosquito pools generated, 242 (49%) were positive by the Pan-Flaviviruses primer set. Sequence analysis revealed that none of the mosquitos carried a pathogenic flavivirus, including ZIKV, but were infected with a novel insect-specific flavivirus. We found no pathogenic flaviviruses circulating in Makkah city during and post the 2016 Hajj and no evidence of introduction of ZIKV through the pilgrimage. Enhanced vector-borne diseases surveillance, prevention, and control are crucial in KSA especially during international mass gatherings such as the annual Hajj to prevent outbreaks and the spread of viruses with epidemic and pandemic potentials.

Systematic analysis of disease-specific immunological signatures in patients with febrile illness from Saudi Arabia

Objectives

Little is known about the prevalence of febrile illness in the Arabian region as clinical, laboratory and immunological profiling remains largely uncharacterised.

Methods

A total of 2018 febrile patients from Jazan, Saudi Arabia, were recruited between 2014 and 2017. Patients were screened for dengue and chikungunya virus, Plasmodium, Brucella, Neisseria meningitidis, group A streptococcus and Leptospira. Clinical history and biochemical parameters from blood tests were collected. Patient sera of selected disease-confirmed infections were quantified for immune mediators by multiplex microbead-based immunoassays.

Results

Approximately 20% of febrile patients were tested positive for one of the pathogens, and they presented overlapping clinical and laboratory parameters. Nonetheless, eight disease-specific immune mediators were identified as potential biomarkers for dengue (MIP-1α, MCP-1), malaria (TNF-α), streptococcal and meningococcal (eotaxin, GRO-α, RANTES, SDF-1α and PIGF-1) infections, with high specificity and sensitivity profiles. Notably, based on the conditional inference model, six of these mediators (MIP-1α, TNF-α, GRO-α, RANTES, SDF-1α and PIGF-1) were revealed to be 68.4% accurate in diagnosing different febrile infections, including those of unknown diseases.

Conclusions

This study is the first extensive characterisation of the clinical analysis and immune biomarkers of several clinically important febrile infections in Saudi Arabia. Importantly, an immune signature with robust accuracy, specificity and sensitivity in differentiating several febrile infections was identified, providing useful insights into patient disease management in the Arabian Peninsula.

Detection of arboviruses in mosquitoes: Evidence of circulation of chikungunya virus in Iran

Mosquitoes are vectors of viruses affecting animal and human health. In Iran, the prevalence of mosquito-borne viruses remains poorly investigated. Once infected, mosquito females remain infected for all their life making virus detections possible at early steps before infections are reported in vertebrate hosts. In this study, we used a recently developed high-throughput chip based on the BioMark Dynamic arrays system capable of detecting 37 arboviruses in a single experiment. A total of 1,212 mosquitoes collected in Mazandaran, North-Khorasan, and Fars provinces of Iran were analyzed. Eighteen species were identified, belonging to five genera; the most prevalent species were Anopheles maculipennis s.l. (42.41%), Culex pipiens (19.39%), An. superpictus (11.72%), and Cx. tritaeniorhynchus (10.64%). We detected chikungunya virus (CHIKV) of the Asian genotype in six mosquito pools collected in North Khorasan and Mazandaran provinces. To our knowledge, this is the first report of mosquitoes infected with CHIKV in Iran. Our high-throughput screening method can be proposed as a novel epidemiological surveillance tool to identify circulating arboviruses and to support preparedness to an epidemic in animals and humans.

Imported cases of Chikungunya virus in Iran

Background

Chikungunya virus (CHIKV) is a widespread mosquito-borne virus representing a serious challenge to public health. The largest outbreak in the Middle-East was recorded in 2016–2017 in Pakistan. Sistan and Baluchistan Province of Iran shares a wide border with Pakistan; accordingly, introduction of CHIKV from Pakistan to Iran seems to be probable. The current study is aimed at investigating CHIKV infection in Sistan and Baluchistan Province.

Methods

Between April 2017 and June 2018, a total of 159 serum samples of CHIK suspected cases from 10 cities of Sistan and Baluchistan Province were tested by molecular and serological assays. Samples obtained up to 4 days after onset of illness were tested by real time PCR (n = 8). Samples collected 5–10 days after disease onset were subjected to ELISA, as well as real time PCR tests (n = 72). Samples obtained after the 10th day of disease onset were tested by only ELISA (n = 79). Phylogenetic analysis of real time PCR positive samples was carried out by sequencing of a 1014-bp region of Envelope 1 gene (E1 gene). Chi-square and independent t tests were used to evaluate the association between variables and CHIKV infection.

Results

In total, 40 (25.1%) out of 159 samples tested positive either by real time PCR or ELISA tests.Out of 151 samples serologically analyzed, 19 (12.6%) and 28 (18.6%) cases were positive for anti-CHIKV IgM and anti-CHIKV IgG antibodies, respectively. Of 80 samples tested by real time PCR, CHIKV RNA was detected in 11 (13.7%) sera, all of them had recent travel history to Pakistan. Additionally, phylogenetic analysis of 5 samples indicated their similarity with recent isolates of Pakistan outbreak 2016–2017 belonging to Indian Ocean sub-lineage of ECSA genotype. A significant correlation between abroad travel history and CHIKV infection was observed (P < 0.001). The most common clinical symptoms included fever, arthralgia/arthritis, myalgia, headache, and chill.

Conclusions

These results present substantial evidence of CHIKV introduction to Iran from Pakistan and emphasize the need for the enhancement of surveillance system and preventive measures.

Mosquito biodiversity and mosquito-borne viruses in the United Arab Emirates

Background

In the last 50 years, the United Arab Emirates (UAE) has experienced rapid population growth and urbanization. Urbanization is known to influence biodiversity, and there appears to be a link between the emergence of arboviruses and urban growth. Very little is known about the UAE mosquito species richness and dominant vectors. We performed a mosquito survey comparing peri-urban sites in Dubai and Al Ain to a protected, natural site in Fujairah emirate. We measured mosquito biodiversity and species composition, and screened mosquito pools for common arboviruses to measure arbovirus activity in the region.

Results

We report ten species of mosquitoes from the UAE, with highest species diversity in the natural site, a protected wadi near the eastern coast. The predominant mosquito was Culex perexiguus, and was associated with peri-urban habitats. The site with lowest mosquito species diversity but relatively high species richness was the peri-urban site of Al Ain Zoo, where we identified Bagaza virus and Barkedji virus, two flaviviruses, in pools of Cx. perexiguus.

Conclusions

Decreased mosquito biodiversity was associated with increased levels of urbanization. The predominance of two species at peri-urban sites was related to the availability of their larval habitats. Arboviruses were associated with the presence of a single predominant mosquito species, Cx. perexiguus.

Seroprevalence of Zika virus among asymptomatic pregnant mothers and their newborns in the Najran region of southwest Saudi Arabia

BACKGROUND

Zika virus (ZIKV) is a teratogenic flavivirus that can cause microcephaly. Its main vector, Aedes aegypti, has been previ.ously identified in Saudi Arabia, but no ZIKV infection has yet been reported. Nevertheless, the country is at risk from ZIKV because it receives many travelers throughout the year, including pilgrims from ZIKV-endemic countries.

OBJECTIVES

Screen asymptomatic pregnant mothers and their newborns attending a major hospital in the Najran region for subclinical or past infections with ZIKV, using ELISA and RT-PCR.

DESIGN

Cross-sectional.

SETTING

Najran Maternity and Children Hospital (NMCH).

SUBJECTS AND METHODS

All pregnant women admitted to NMCH in labor between November 2016 and July 2017 were included in the study. Clinical and demographic data were collected by pre-validated physician-administered questionnaires. Paired umbilical and maternal serum samples were collected and frozen at -60°C, using ELISA to measure anti-ZIKA IgG and IgM antibodies and RT-PCR to further investigate positive samples.

MAIN OUTCOME MEASURES

Maternal and newborn serum anti-ZIKV IgM and IgG and ZIKV RT-PCR.

SAMPLE SIZE

410 mother-newborn pairs.

RESULTS

The median gestational age was 38.5 weeks (range 33-42). Most (n=342, 83.41%) of the women were from Najran city. All of the newborns had normal growth parameters with no congenital malformations. None of the mothers had symptoms suggestive of ZIKV infection; 3 (0.7%) exhibited a low-grade fever (38°C), but did not test positive for anti-ZIKV antibodies. Thirty-five (8.53%) of mothers had travelled inside Saudi Arabia, but none outside the country. Twenty-four (5.85%) mothers tested positive for anti-ZIKV IgM and 52 (12.68%) tested positive for anti-ZIKV IgG, but all infant samples were negative. All seropositive ZIKV IgM were also ZIKV IgG positive, but RT-PCR test.ing of all seropositive samples was negative.

CONCLUSION

Although previous (resolved) ZIKV infection and cross-reactivity of the ELISA method with other flaviviruses cannot be ex.cluded, the study found no confirmed cases of acute ZIKV infection. However, given the presence of the vector in Saudi Arabia, the presence of presumptive positive serology and the ongoing risk of ZIKV entry via a regular influx of travelers from endemic areas, we propose that continuous surveillance be conducted for ZIKV as well for other flaviviruses. Larger-scale nationwide studies are strongly recommended to gain a broader view of the potential threat from ZIKV in the country.

LIMITATIONS

Small sample size, unavailability of plaque reduction neutralization tests to confirm serology results, and RT-PCR was only conducted on ELISA-positive serum samples, due to resource constraints.

CONFLICT OF INTEREST

None.

Mother-to-child transmission of Chikungunya virus: A systematic review and meta-analysis

BACKGROUND

Chikungunya virus (CHIKV) is an emerging arboviral infection with a global distribution and may cause fetal and neonatal infections after maternal CHIKV-infections during gestation.

METHODOLOGY

We performed a systematic review to evaluate the risk for: a) mother-to-child transmission (MTCT), b) antepartum fetal deaths (APFD), c) symptomatic neonatal disease, and d) neonatal deaths from maternal CHIKV-infections during gestation. We also recorded the neonatal clinical manifestations after such maternal infections (qualitative data synthesis). We searched PubMed (last search 3/2017) for articles, of any study design, with any of the above outcomes. We calculated the overall risk of MTCT, APFDs and risk of symptomatic neonatal disease by simple pooling. For endpoints with ≥5 events in more than one study, we also synthesized the data by random-effect-model (REM) meta-analysis.

PRINCIPAL FINDINGS

Among 563 identified articles, 13 articles from 8 cohorts were included in the quantitative data synthesis and 33 articles in the qualitative data synthesis. Most cohorts reported data only on symptomatic rather than on all neonatal infections. By extrapolation also of these data, the overall pooled-MTCT-risk across cohorts was at least 15.5% (206/1331), (12.6% by REMs). The pooled APFD-risk was 1.7% (20/1203); while the risk of CHIKV-confirmed-APFDs was 0.3% (3/1203). Overall, the pooled-risk of symptomatic neonatal disease was 15.3% (203/1331), (11.9% by REMs). The pooled risk of symptomatic disease was 50.0% (23/46) among intrapartum vs 0% (0/712) among antepartum/peripartum maternal infections. Infected newborns, from maternal infections during gestation were either asymptomatic or presented within their first week of life, but not at birth, with fever, irritability, hyperalgesia, diffuse limb edema, rashes and occasionally sepsis-like illness and meningoencephalitis. The pooled-risk of neonatal death was 0.6% (5/832) among maternal infections and 2.8% (5/182) among neonatal infections; long-term neurodevelopmental delays occurred in 50% of symptomatic neonatal infections.

CONCLUSIONS/SIGNIFICANCE

Published cohorts with data on the risk to the fetus and/or newborn from maternal CHIKV-infections during gestation were sparse compared to the number of recently reported CHIKV-infection outbreaks worldwide; however perinatal infections do occur, at high rates during intrapartum period, and can be related to neonatal death and long-term disabilities.

Dengue Hemorrhagic Fever Virus in Saudi Arabia: A Review

Dengue fever is a global disease with a spectrum of clinical manifestation ranging from mild febrile disease to a severe disease in the form of dengue hemorrhagic fever and dengue shock syndrome. Dengue virus is one viral hemorrhagic fever that exists in the Kingdom of Saudi Arabia in addition to Alkhurma (Alkhurma) Hemorrhagic Fever, Chikungunya virus, Crimean-Congo Hemorrhagic Fever, and Rift Valley Fever. The disease is limited to the Western and South-western regions of Saudi Arabia, where Aedes aegypti exists. The majority of the cases in Saudi Arabia had mild disease and is related to serotypes 1-3 but not 4. The prospect for Dengue virus control relies on vector control, health education, and possibly vaccine use. Despite extensive collaborative efforts between multiple governmental sectors, including Ministry of Health, Ministry of Municipalities and Rural Affairs, and Ministry of Water, dengue remains a major public health concern in the regions affected.

Urban Chikungunya in the Middle East and North Africa: A systematic review

Background

The epidemiology of Chikungunya virus (CHIKV) in the Middle East and North Africa (MENA) is not well characterized despite increasing recognition of its expanding infection and disease burden in recent years.

Methodology / Principal findings

Following Cochrane Collaboration guidelines and reporting our findings following PRISMA guidelines, we systematically reviewed records describing the human prevalence and incidence, CHIKV prevalence/infection rates in vectors, outbreaks, and reported cases for CHIKV across the MENA region. We identified 29 human seroprevalence measures, one human incidence study, one study reporting CHIKV infection rates in Aedes, and nine outbreaks and case reports/series reported in the MENA from 1970–2015. Overall, anti-CHIKV antibody or reports of autochthonous transmission were identified from 10 of 23 countries in the MENA region (Djibouti, Egypt, Iraq, Iran, Kuwait, Pakistan, Saudi Arabia, Somalia, Sudan, and Yemen), with seroprevalence measures among general populations (median 1.0%, range 0–43%) and acute febrile illness populations (median 9.8%, range 0–30%). Sudan reported the highest number of studies (n = 11) and the highest seroprevalence among general populations (median 12%, range 0–43%) and undifferentiated acute febrile illness populations (median 18%, range 10–23%). CHIKV outbreaks were reported from Djibouti, Pakistan, Sudan, and Yemen.

Conclusions / Significance

Seroprevalence studies and outbreak reports suggest endemic transmission of urban cycle CHIKV in at least the Red Sea region and Pakistan. However, indications of seroprevalence despite a low quantity of CHIKV epidemiologic research from the region suggests that CHIKV transmission is currently underrecognized.

Chikungunya virus (CHIKV) is an alphavirus whose principal vectors are the Aedes aegypti and Aedes albopictus mosquitoes. Though long endemic to Asia and Africa, detection of CHIKV has recently been reported throughout the Western Hemisphere, including much of South America and the Caribbean. In the Middle East and North Africa (MENA), the epidemiology of CHIKV remains poorly characterized despite recent reports of outbreaks and novel transmission in the Arabian Peninsula. To better understand existing data describing the epidemiology of urban CHIKV in the MENA region, we conducted a systematic review of human prevalence studies and incidence studies; CHIKV detections, prevalence, and infection rates in Aedes; and reported CHIKV outbreaks, case series, and case reports from the region. A total of 29 seroprevalence studies were identified through our search, with anti-CHIKV antibodies and/or outbreaks detected in Djibouti, Egypt, Iraq, Iran, Kuwait, Pakistan, Saudi Arabia, Somalia, Sudan, and Yemen. Sudan reported the highest number of studies (n = 11) and the highest seroprevalence among all studies. The epidemiology of urban CHIKV in other MENA countries is less well characterized, suggesting underascertainment of cases and the need for further research.

Alkhurma hemorrhagic fever virus

Alkhurma hemorrhagic fever virus (AHFV) was first isolated in Jeddah, Saudi Arabia, in the 1990s from the blood of a butcher. Subsequently, the virus was recognized in many patients in Saudi Arabia and rarely from Egypt and Djibouti. In this review, we summarize the current literature on AHFV globally with special focus on Saudi Arabia.

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.

Chikungunya virus: an update on the biology and pathogenesis of this emerging pathogen

Re-emergence of chikungunya virus, a mosquito-transmitted pathogen, is of serious public health concern. In the past 15 years, after decades of infrequent, sporadic outbreaks, the virus has caused major epidemic outbreaks in Africa, Asia, the Indian Ocean, and more recently the Caribbean and the Americas. Chikungunya virus is mainly transmitted by Aedes aegypti mosquitoes in tropical and subtropical regions, but the potential exists for further spread because of genetic adaptation of the virus to Aedes albopictus, a species that thrives in temperate regions. Chikungunya virus represents a substantial health burden to affected populations, with symptoms that include severe joint and muscle pain, rashes, and fever, as well as prolonged periods of disability in some patients. The inflammatory response coincides with raised levels of immune mediators and infiltration of immune cells into infected joints and surrounding tissues. Animal models have provided insights into disease pathology and immune responses. Although host innate and adaptive responses have a role in viral clearance and protection, they can also contribute to virus-induced immune pathology. Understanding the mechanisms of host immune responses is essential for the development of treatments and vaccines. Inhibitory compounds targeting key inflammatory pathways, as well as attenuated virus vaccines, have shown some success in animal models, including an attenuated vaccine strain based on an isolate from La Reunion incorporating an internal ribosome entry sequence that prevents the virus from infecting mosquitoes and a vaccine based on virus-like particles expressing envelope proteins. However, immune correlates of protection, as well as the safety of prophylactic and therapeutic candidates, are important to consider for their application in chikungunya infections. In this Review, we provide an update on chikungunya virus with regard to its epidemiology, molecular virology, virus-host interactions, immunological responses, animal models, and potential antiviral therapies and vaccines.

Updates on chikungunya epidemiology, clinical disease, and diagnostics

Chikungunya virus (CHIKV) is an Aedes-borne alphavirus, historically found in Africa and Asia, where it caused sporadic outbreaks. In 2004, CHIKV reemerged in East Africa and spread globally to cause epidemics, including, for the first time, autochthonous transmission in Europe, the Middle East, and Oceania. The epidemic strains were of the East/Central/South African genotype. Strains of the Asian genotype of CHIKV continued to cause outbreaks in Asia and spread to Oceania and, in 2013, to the Americas. Acute disease, mainly comprising fever, rash, and arthralgia, was previously regarded as self-limiting; however, there is growing evidence of severe but rare manifestations, such as neurological disease. Furthermore, CHIKV appears to cause a significant burden of long-term morbidity due to persistent arthralgia. Diagnostic assays have advanced greatly in recent years, although there remains a need for simple, accurate, and affordable tests for the developing countries where CHIKV is most prevalent. This review focuses on recent important work on the epidemiology, clinical disease and diagnostics of CHIKV.

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.