title: Development of a Real-Time qPCR Assay for Quantification of Covert Baculovirus Infections in a Major African Crop Pest.
abstract: Many pathogens and parasites are present in host individuals and populations without any obvious signs of disease. This is particularly true for baculoviruses infecting lepidopteran hosts, where studies have shown that covert persistent viral infections are almost ubiquitous in many species. To date, the infection intensity of covert viruses has rarely been quantified. In this study, we investigated the dynamics of a covert baculovirus infection within the lepidopteran crop pest Spodoptera exempta. A real-time quantitative polymerase chain reaction (qPCR) procedure using a 5' nuclease hydrolysis (TaqMan) probe was developed for specific detection and quantification of Spodoptera exempta nucleopolyhedrovirus (SpexNPV). The qPCR assay indicated that covert baculovirus dynamics varied considerably over the course of the host life-cycle, with infection load peaking in early larval instars and being lowest in adults and final-instar larvae. Adult dissections indicated that, contrary to expectation, viral load aggregation was highest in the head, wings and legs, and lowest in the thorax and abdomen. The data presented here have broad implications relating to our understanding of transmission patterns of baculoviruses and the role of covert infections in host-pathogen dynamics.
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK. rgraham@harper-adams.ac.uk.
authors.forename: Robert I
authors.initials: RI
authors.lastname: Graham
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK. yaminitummala@gmail.com.
authors.forename: Yamini
authors.initials: Y
authors.lastname: Tummala
authors.affiliation: Lake Ecosystems Group, Centre for Ecology and Hydrology, Bailrigg, Lancaster LA1 4AP, UK. glenn@ceh.ac.uk.
authors.forename: Glenn
authors.initials: G
authors.lastname: Rhodes
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada. jsc21@sfu.ca.
authors.forename: Jenny S
authors.initials: JS
authors.lastname: Cory
authors.affiliation: Biomedical and Life Sciences, Lancaster University, Lancaster LA1 4YQ, UK. a.shirras@lancaster.ac.uk.
authors.forename: Alan
authors.initials: A
authors.lastname: Shirras
authors.affiliation: Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent ME4 4TB, UK. d.grzywacz@greenwich.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Grzywacz
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK. ken.wilson@lancaster.ac.uk.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Wilson
keywords: Spodoptera exempta; TaqMan real-time qPCR; baculovirus; covert infections; nucleopolyhedrovirus