ORCID Profile
0000-0002-5557-4402
Current Organisation
Center for Health and Disease Studies
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Publisher: MDPI AG
Date: 06-01-2019
DOI: 10.3390/V11010032
Abstract: Japanese encephalitis virus (JEV) is a flavivirus that is maintained via transmission between Culex spp. mosquitoes and water birds across a large swath of southern Asia and northern Australia. Currently JEV is the leading cause of vaccine-preventable encephalitis in humans in Asia. Five genotypes of JEV (G-I–G-V) have been responsible for historical and current outbreaks in endemic regions, and G-I and G-III co-circulate throughout Southern Asia. While G-III has historically been the dominant genotype worldwide, G-I has gradually but steadily displaced G-III. The objective of this study was to better understand the phenomenon of genotype displacement for JEV by evaluating both avian host and mosquito vector susceptibilities to infection with representatives from both G-I and G-III. Since ducks and Culex quinquefasciatus mosquitoes are prevalent avian hosts and vectors perpetuating JEV transmission in JE endemic areas, experimental evaluation of virus replication in these species was considered to approximate the natural conditions necessary for studying the role of host, vectors and viral fitness in the JEV genotype displacement context. We evaluated viremia in ducklings infected with G-I and G-III, and did not detect differences in magnitude or duration of viremia. Testing the same viruses in mosquitoes revealed that the rates of infection, dissemination and transmission were higher in virus strains belonging to G-I than G-III, and that the extrinsic incubation period was shorter for the G-I strains. These data suggest that the characteristics of JEV infection of mosquitoes but not of ducklings, may have play a role in genotype displacement.
Publisher: Wiley
Date: 26-04-2019
DOI: 10.1002/ECE3.5198
Publisher: Elsevier BV
Date: 30-10-2021
DOI: 10.1186/S40657-021-00290-5
Abstract: Nepal, a small landlocked country in South Asia, holds about 800 km of Himalayan Mountain range including the Earth’s highest mountain. Within such a mountain range in the north and plain lowlands in the south, Nepal provides a habitat for about 9% of global avian fauna. However, this ersity is underrated because of the lack of enough studies, especially using molecular tools to quantify and understand the distribution patterns of ersity. In this study, we reviewed the studies in the last two decades (2000‒2019) that used molecular methods to study the bio ersity in Nepal to examine the ongoing research trend and focus. Although Nepalese Himalaya has many opportunities for cutting-edge molecular research, our results indicated that the rate of genetic/genomic studies is much slower compared to the regional trends. We found that genetic research in Nepal heavily relies on resources from international institutes and that too is mostly limited to research on species monitoring, distribution, and taxonomic validations. Local infrastructures to carry out cutting-edge genomic research in Nepal are still in their infancy and there is a strong need for support from national/international scientists, universities, and governmental agencies to expand such genomic infrastructures in Nepal. We particularly highlight avian fauna as a potential future study system in this region that can be an excellent resource to explore key biological questions such as understanding eco-physiology and molecular basis of organismal persistence to changing environment, evolutionary processes underlying ergence and speciation, or mechanisms of endemism and restrictive distribution of species.
Publisher: Cold Spring Harbor Laboratory
Date: 17-08-2022
DOI: 10.1101/2022.08.16.22278814
Abstract: Nepal has achieved and sustained elimination of leprosy as a public health problem since 2009, but 17 districts and 3 provinces have yet to eliminate the disease. Pediatric cases and grade-2 disabilities (G2D) indicate recent transmission and late diagnosis respectively, which necessitate active and early case detection. This operational research was performed to identify approaches best suited for early case detection, determine community-based leprosy epidemiology, and identify hidden leprosy cases early and respond with prompt treatment. Active case detection was performed by: house-to-house visits among vulnerable populations ( n= 26,469), contact examination and tracing ( n= 7,608) and screening prison populations ( n= 4,428) in Siraha, Bardiya, Rautahat, Banke, Lalitpur and Kathmandu districts of Nepal. New case detection rates were highest for contact tracing (250), followed by house-to-house visits (102) and prison screening (45) per 100,000 population screened. However, cost per case identified was cheapest for house-to-house visits (Nepalese rupee (NPR) 76,500/case), then contact tracing (NPR90,286/case) and prison screening (NPR298,300/case). House-to-house and contact tracing case paucibacillary/multibacillary (PB:MB) ratios were 59:41 and 68:32 female/male ratios 63:37 and 57:43 pediatric cases 11% in both approaches and G2D 11% and 5% respectively. Developing leprosy was similar among household and neighbor contacts (Odds ratios ( OR )=1.4, 95% confidence interval (CI), 0.24-5.85) and for contacts of MB versus PB cases ( OR= 0.7, 0.26-2.0). Attack rates were similar among household contacts of MB cases (0.32%, 0.07-0.94%) and PB cases (0.13%, 0.03-0.73) and neighbor contacts of MB cases (0.23%, 0.1-0.46) and PB cases (0.48%, 0.19-0.98). BCG vaccination with scar presence had a significant protective effect against leprosy ( OR= 0.42, 0.22-0.81). The most effective case identification approach here is contact tracing, followed by house-to-house visits in vulnerable populations and screening in prisons, though house-to-house visits were cheaper. The findings suggest hidden cases, recent transmission, and late diagnosis in the community exist and highlight the importance of early case detection.
Publisher: Springer Science and Business Media LLC
Date: 12-09-2014
DOI: 10.1007/S10393-014-0974-3
Abstract: Ranaviruses are significant pathogens of hibians, reptiles, and fishes, contributing to mass mortality events worldwide. Despite an increasing focus on ranavirus ecology, our understanding of ranavirus transmission, especially among reptilian hosts, remains limited. For ex le, experimental evidence for oral transmission of the virus in chelonians is mixed. Consequently, vector-borne transmission has been hypothesized in terrestrial turtle species. To test this hypothesis, mosquitoes captured during a 2012/2013 ranavirus outbreak in box turtles from southwestern Indiana were pooled by genus and tested for ranavirus DNA using qPCR. Two of 30 pools tested positive for ranavirus. Additionally, an in idual Aedes sp. mosquito observed engorging on a box turtle also tested positive for ranavirus. Although our approach does not rule out the possibility that the sequenced ranavirus was simply from virus in bloodmeal, it does suggests that mosquitoes may be involved in virus transmission as a mechanical or biological vector among ectothermic vertebrates. While additional studies are needed to elucidate the exact role of mosquitoes in ranavirus ecology, our study suggests that a greater focus on vector-borne transmission may be necessary to fully understand ranaviral disease dynamics in herpetofauna.
Publisher: MDPI AG
Date: 16-08-2018
DOI: 10.3390/V10080434
Abstract: The introduction of Zika virus (ZIKV) to the Americas raised concern that the virus would spill back from human transmission, perpetuated by Aedes aegypti, into a sylvatic cycle maintained in wildlife and forest-living mosquitoes. In the Americas, Sabethes species are vectors of sylvatic yellow fever virus (YFV) and are therefore candidate vectors of a sylvatic ZIKV cycle. To test the potential of Sabethes cyaneus to transmit ZIKV, Sa. cyaneus and Ae. aegypti were fed on A129 mice one or two days post-infection (dpi) with a ZIKV isolate from Mexico. Sa. cyaneus were s led at 3, 4, 5, 7, 14, and 21 days post-feeding (dpf) and Ae. aegypti were s led at 14 and 21 dpf. ZIKV was quantified in mosquito bodies, legs, and saliva to measure infection, dissemination, and potential transmission, respectively. Of 69 Sa. cyaneus that fed, ZIKV was detected in only one, in all body compartments, at 21 dpf. In contrast, at 14 dpf 100% of 20 Ae. aegypti that fed on mice at 2 dpi were infected and 70% had virus in saliva. These data demonstrate that Sa. cyaneus is a competent vector for ZIKV, albeit much less competent than Ae. aegypti.
Location: United States of America
No related grants have been discovered for Ajit Karna.