Metagenomic Analysis of Viromes of Aedes Mosquitoes across India.

Metagenomic analysis of Aedes aegypti and Ae. albopictus mosquitoes from diverse geographical regions of India revealed the presence of several insect viruses of human interest. Most abundant reads found in Ae. aegypti mosquitoes were of Phasi Charoen-like virus (PCLV), Choristoneura fumiferana granulovirus (CfGV), Cell fusing agent virus (CFAV), and Wenzhou sobemo-like virus 4 (WSLV4), whereas WSLV4 and CfGV constituted the highest percentage of reads in Ae. albopictus viromes. Other reads that were of low percentage included Hubei mosquito virus 2 (HMV2), Porcine astrovirus 4 (PAstV4), and Wild Boar astrovirus (WBAstV). PCLV and CFAV, which were found to be abundant in Ae. aegypti viromes were absent in Ae. albopictus viromes. Among the viromes analyzed, Ae. aegypti sampled from Pune showed the highest percentage (79.82%) of viral reads, while Ae. aegypti mosquitoes sampled from Dibrugarh showed the lowest percentage (3.47%). Shamonda orthobunyavirus (SHAV), African swine fever virus (ASFV), Aroa virus (AROAV), and Ilheus virus (ILHV), having the potential to infect vertebrates, including humans, were also detected in both mosquito species, albeit with low read numbers. Reads of gemykibivirus, avian retrovirus, bacteriophages, herpesviruses, and viruses infecting protozoans, algae, etc., were also detected in the mosquitoes. A high percentage of reads in the Ae. albopictus mosquito samples belonged to unclassified viruses and warrant further investigation. The data generated in the present work may not only lead to studies to explain the influence of these viruses on the replication and transmission of viruses of clinical importance but also to find applications as biocontrol agents against pathogenic viruses.

Genomic Characterization of Mosquito Isolates of Chikungunya Virus (Outbreak Strains 2022) Using Next-Generation Sequencing.

Background: A massive outbreak of dengue-like illness was reported from Pune district of Maharashtra, India during May-June 2022. Isolation and characterization of the etiological agent at genomic level for possible mutations that led to higher transmissibility is the topic of the study. Methods: Entomological investigations were carried out by ICMR-National Institute of Virology (Pune, India); Aedes aegypti mosquitoes were collected and processed for virus detection by molecular techniques. Positive mosquito pools were processed for virus isolation in cell culture. Sanger sequencing and whole-genome sequencing (WGS) using Oxford Nanopore Technology platform were used for genomic characterization. Results: Reverse transcriptase RT-PCR and qRT-PCR analysis detected chikungunya virus (CHIKV) in mosquito samples. Six CHIKV isolates were obtained. WGS revealed four nonsynonymous mutations in the structural polyprotein region, and five in the nonstructural polyprotein encoding region when compared with Yawat-2000 and Shivane-2016 strains. Sixty-four nucleotide changes in the nonstructural polyprotein region and 35 in the structural polyprotein region were detected. One isolate had an exclusive amino acid change, T1123I, in the nsP2 (protease) region. Conclusion: Abundant Ae. aegypti breeding and detection of CHIKV RNA in mosquitoes confirmed it as a chikungunya outbreak. Novel mutations detected in the epidemic strain warrants investigations to address their role in disease severity, transmission, and fitness.

Abundance of Phasi-Charoen-like virus in Aedes aegypti mosquito populations in different states of India.

Mosquitoes are known to harbor a large number of insect specific viruses (ISV) in addition to viruses of public health importance. These ISVs are highly species specific and are non-pathogenic to humans or domestic animals. However, there is a potential threat of these ISVs evolving into human pathogens by genome alterations. Some ISVs are known to modulate replication of pathogenic viruses by altering the susceptibility of vector mosquitoes to pathogenic viruses, thereby either inhibiting or enhancing transmission of the latter. In the present study, we report predominance of Phasi Charoen-like virus (PCLV, Family: Phenuviridae) contributing to >60% of the total reads in Aedes aegypti mosquitoes collected from Pune district of Maharashtra state using next generation sequencing based metagenomic analysis of viromes. Similar results were also obtained with mosquitoes from Assam, Tamil Nadu and Karnataka states of India. Comparison of Pune mosquito sequences with PCLV Rio (Brazil) isolate showed 98.90%, 99.027% and 98.88% homologies in the S, M and L segments respectively indicating less genetic heterogeneity of PCLV. The study also demonstrated occurrence of transovarial transmission as seen by detection of PCLV in eggs, larvae, pupae and male mosquitoes. Ae. aegypti mosquitoes collected from Pune also showed a large number of reads for viruses belonging to Baculoviridae, Rhabdoviridae, Genomoviridae and Bunyaviridae families. The role of PCLV in the replication of dengue and chikungunya virus is yet not clear. It warrants further studies to know the significance of PCLV and other ISVs on the replication and transmission of Ae. aegypti borne pathogenic viruses, especially in the absence of prophylactics or therapeutics.

Use of immunization as strategy for outbreak control of varicella zoster in an institutional setting.

BACKGROUND: Outbreaks of varicella gets reported often in India. However, outbreak in health care providers living in closed institutional setting and role of vaccination as post exposure prophylaxis for control of outbreak has not been studied extensively. This paper presents epidemiological investigation and control strategy undertaken in such scenario. METHODS: This is an epidemiological investigation of chickenpox in nursing students which highlights role of early identification and appropriate control strategy to prevent explosive outbreak in high risk vulnerable population. Vaccination of all susceptible in addition to isolation of cases, quarantine of suspects and proper screening for new cases was the major control strategy adopted. RESULTS: The index case was imported and all eight cases occurred within the incubation period of the case. Two cases occurred in students previously vaccinated for chickenpox. No second or third wave of infection occurred showing vaccination as effective tool in outbreak control strategy. CONCLUSION: Early identification of cases and vaccination of all susceptible contributed to effective control of the outbreak.