Mass scale screening of common arboviral infections by an affordable, cost effective RT-PCR method

Distribution and mitochondrial CO1-based genetic diversity of Aedes aegypti L (Culicidae: Diptera) in Saudi Arabia

Mosquitoes (Diptera: Culicidae) act as vectors for various pathogens and parasites that affect millions of people worldwide. Aedes aegypti (Linnaeus, 1762) is one of the devastating pests of humans, acting as a key vector of dengue viruses. Therefore, correct identification of this serious pest to determine its distribution is paramount in its management. Morphological identification is usually based on the maturity and quality of the specimens. This can still yield ambiguous results in distinguishing Ae. aegypti species due to limited taxonomic expertise and the presence of cryptic species. In this research, mitochondrial CO1 gene-based identification was adopted to analyze 7 samples, each containing 7 specimens of Ae. aegypti from various localities of Saudi Arabia: Jeddah (A1), Makkah (A2), Al Madinah Al Munawwarah (A4), Jazan (A5), Qunfudah (A6), Yanbu (A8), and Najran (A10). DNA barcoding and maximum likelihood (ML) tree analysis revealed that all 49 species belong to Ae. aegypti and showed high similarity with specimens of this species worldwide.

Differential genotypic signatures of Toll-like receptor polymorphisms among dengue-chikungunya mono- and co-infected Eastern Indian patients

Dengue (DENV) and chikungunya (CHIKV) viral infections trigger high patient morbidity and mortality. Mono-/co-infection of these viruses activates innate immune response, triggering Toll-like receptor (TLR) pathways. The present study investigated the differential role of TLR3, 7 and 8 single-nucleotide polymorphisms (SNPs) between mono- and co-infected Eastern Indian patients. Interaction of TLR polymorphic variants with signal peptidase complex (SPC18) was explored which might affect immune signalling against DENV/CHIKV infections. Out of 550 febrile symptomatic patients, 128 DENV-CHIKV co-infected samples were genotyped for eight SNPs of TLR3 (rs3775290-chr4:186083063), TLR7 (rs179008-chrX:12885540, rs5741880-chrX:12869297, rs179010-chrX:12884766, rs3853839-chrX:12889539) and TLR8 (rs5744080-chrX:12919685, rs3764879-chrX:12906578, rs3764880-chrX:12906707) by PCR-RFLP along with 157 healthy individuals. Statistical analysis established genotypic association of TLR SNPs with DENV-CHIKV co-infection, and difference between mono- and co-infected patients and their role in determining high viral load (HVL) during competitive viral replication among co-infected patients. In silico protein-protein docking evaluated interactive effect of TLR variants with SPC18. The findings revealed patients with CC genotypes of TLR7 and 8 SNPs were significantly susceptible towards co-infection, whereas specific genotypes of TLR7 and 8 imparted protection against co-infection. Differential analysis between mono-/co-infected patients revealed distinct genotypic distribution of TLR3, 7 and 8 SNPs. Co-infected patients with TT-rs179010 exhibited DENV-HVL, whereas CHIKV-HVL was detected among patients with other genotypes. Molecular docking of TLR7-rs179008 Q variant and TLR8-rs3764880 V variant with SPC18 generated better free binding energy. This study underlined the importance of TLR7 and 8 SNPs towards mono-/co-infection of DENV/CHIKV, with certain genotypes associated with co-infection susceptibility. Moreover, it suggested a probable role of specific genotypes of TLR7 and 8 polymorphisms imparting high dengue/chikungunya viral load among co-infected patients.

Emergence of West Nile virus in West Bengal, India: a new report

Background

The ICMR virus unit in Kolkata functions as an Appex Referral Laboratory for the detection of dengue (DENV) and chikungunya (CHIKV) infections in the eastern part of India. In spite of efforts for confirmatory diagnosis, some samples remain undiagnosed every year. West Nile virus (WNV) infection may mimic either dengue (flavivirus) or chikungunya (alphavirus) like illness. WNV is endemic in the tropical region where its principal/potential vectors are Aedes and Culex.

Methods

We explored the existence of WNV within undiagnosed samples to identify the emergence of a new public health problem.

Results

Of 1278 sera samples, 574 were negative for DENV and CHIKV either by ELISA or by reverse transcriptase (RT)-PCR. Of these 574 negative samples, 83 (14.5%) and 141 (24.56%) were positive for WNV by ELISA and RT-PCR, respectively; no samples were positive for WNV by both methods. After assembling raw sequencing data, partial envelope genome sequence of West Bengal isolates, WNV was compared through BLAST with other WNV Indian strains and 98% homology detected. Phylogenetic analysis of one West Bengal isolates (Accession No. KY421790) and 28 Indian isolates available in GenBank, indicated close clustering.

Conclusions

The serological and molecular approaches have clearly established the emergence of WNV in West Bengal. Hence, for proper case management, detection of WNV in common febrile illness is strongly recommended.

Phylogenetic Analysis of Aedes aegypti Based on Mitochondrial ND4 Gene Sequences in Almadinah, Saudi Arabia

BACKGROUND

Aedes aegypti is the main vector of the yellow fever and dengue virus. This mosquito has become the major indirect cause of morbidity and mortality of the human worldwide. Dengue virus activity has been reported recently in the western areas of Saudi Arabia. There is no vaccine for dengue virus until now, and the control of the disease depends on the control of the vector.

OBJECTIVES

The present study has aimed to perform phylogenetic analysis of Aedes aegypti based on mitochondrial NADH dehydrogenase subunit 4 (ND4) gene at Almadinah, Saudi Arabia in order to get further insight into the epidemiology and transmission of this vector.

MATERIALS AND METHODS

Mitochondrial ND4 gene was sequenced in the eight isolated Aedes aegypti mosquitoes from Almadinah, Saudi Arabia, sequences were aligned, and phylogenetic analysis were performed and compared with 54 sequences of Aedes reported in the previous studies from Mexico, Thailand, Brazil, and Africa.

RESULTS

Our results suggest that increased gene flow among Aedes aegypti populations occurs between Africa and Saudi Arabia.

CONCLUSIONS

Phylogenetic relationship analysis showed two genetically distinct Aedes aegypti in Saudi Arabia derived from dual African ancestor.

Molecular characterization of chikungunya virus circulating in urban and rural areas of West Bengal, India after its re-emergence in 2006

BACKGROUND

In the state of West Bengal, chikungunya virus (CHIKV) has re-emerged in 2006 after its last occurrence in 1963-1965 in this state. The virus rapidly affected almost every district of this state, with high morbidity. Based on complete sequences of structural region of CHIKV genome, we determined the molecular characterization of the virus circulating in this state from 2006-2012.

METHODS

CHIKV was isolated from 20 acute CHIKV RT-PCR positive serum samples in C6/36 mosquito cell line. These samples were collected from 20 patients with a clinical history of ≤2 days of fever and chikungunya-like illness. Those patients were residing in some outbreak areas in the state of West Bengal during 2006-2012. Isolation was confirmed through RT-PCR and sequencing.

RESULTS AND CONCLUSIONS

Two sub-lineages of East-central-southern African (ECSA) genotype of CHIKV strains were circulating simultaneously in this state during the study period; one type was circulating in rural areas of the state from 2006 whereas another type was isolated from the metropolitan city of Kolkata in 2011 and 2012. The mutational pattern of those CHIKV strains suggests that the transmission of the viruses might be facilitated by different species of Aedes mosquitoes. Our results represent an important first step towards understanding the circulating strains of CHIKV in the state of West Bengal with the geographical variation.

Multiplex real-time RT-PCR for detecting chikungunya virus and dengue virus

Objective

To develop diagnostic test for detection chikungunya virus (CHIKV and Dengue virus (DENV) infection.

Methods

We have performed a rapid, accurate laboratory confirmative method to simultaneously detect, quantify and differentiate CHIKV and DENV infection by single-step multiplex real-time RT-PCR.

Results

The assay's sensitivity was 97.65%, specificity was 92.59% and accuracy was 95.82% when compared to conventional RT-PCR. Additionally, there was no cross-reaction between CHIKV, DENV, Japanese encephalitis virus, hepatitis C, hepatitis A or hepatitis E virus.

Conclusions

This rapid and reliable assay provides a means for simultaneous early diagnosis of CHIKV and DENV in a single-step reaction.

A comparative study of clinical features between monotypic and dual infection cases with Chikungunya virus and dengue virus in West Bengal, India

Chikungunya virus (CHIKV) and dengue virus (DENV) are circulating individually in the state of West Bengal, India. However, after 1965 the dual-infection caused by both viruses had not been recorded until 2010. In 2010, an investigation of the febrile cases was carried out to confirm the involvement of both viruses simultaneously. A total of 550 blood samples were tested for the detection of immunoglobulin M (IgM) antibody against both CHIKV and DENV. Serology by the enzyme-linked immunosorbent assay method confirmed that 131 (23.8%) and 104 (18.9%) patients had IgM antibody against CHIKV and DENV, respectively, whereas 68 (12.4%) had IgM antibodies against both CHIKV and DENV. Fever, joint pain, rashes, headache, myalgia, and nausea/vomiting are the common features in the case of both monotypic and dual-infection. Severe arthralgia and swelling of joints were common only in CHIKV-positive cases and abdominal pain was mainly associated with DENV infection. Diarrhea was reported only by the dual-infected patients (16.2%).