title: Natural populations of Spodoptera exigua are infected by multiple viruses that are transmitted to their offspring.
abstract: Sublethal infections by baculoviruses (Baculoviridae) are believed to be common in Lepidoptera, including Spodoptera exigua. In addition, novel RNA viruses of the family Iflaviridae have been recently identified in a laboratory population of S. exigua (S. exigua iflavirus-1: SeIV-1; S. exigua iflavirus-2: SeIV-2) that showed no overt signs of disease. We determined the prevalence of these viruses in wild populations and the prevalence of co-infection by the different viruses in shared hosts. Infection by S. exigua multiple nucleopolyhedrovirus (SeMNPV) and iflaviruses in S. exigua adults (N=130) from horticultural greenhouses in southern Spain was determined using qPCR and RT-PCR based techniques respectively. The offspring of these insects (N=200) was reared under laboratory conditions and analyzed to determine virus transmission. Overall, 54% of field-caught adults were infected by SeMNPV, 13.1% were infected by SeIV-1 and 7.7% were infected by SeIV-2. Multiple infections were also detected, with 8.4% of individuals harboring SeMNPV and one of the iflaviruses, whereas 2.3% of adults were infected by all three viruses. All the viruses were transmitted to offspring independently of whether the parental female harbored covert infections or not. Analysis of laboratory-reared insects in the adult stage revealed that SeIV-1 was significantly more prevalent than SeMNPV or SeIV-2, suggesting high transmissibility of SeIV-1. Mixed infection involving three viruses was identified in 6.5% of laboratory-reared offspring. We conclude that interspecific interactions between these viruses in co-infected individuals are to be likely frequent, both in the field, following applications of SeMNPV-based insecticides, or in laboratory colonies used for SeMNPV mass production.
authors.affiliation: Instituto de Agrobiotecnología, CSIC-Gobierno de Navarra, Mutilva 31192, Navarra, Spain; Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Navarra, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Virto
authors.affiliation: IFAPA, La Mojonera, 04745 Almería, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Navarro
authors.affiliation: IFAPA, La Mojonera, 04745 Almería, Spain.
authors.forename: M Mar
authors.initials: MM
authors.lastname: Tellez
authors.affiliation: Departamento de Genética, Universitat de València, 46100 Valencia, Spain.
authors.forename: Salvador
authors.initials: S
authors.lastname: Herrero
authors.affiliation: Instituto de Ecología AC, Xalapa, Veracruz 91070, Mexico.
authors.forename: Trevor
authors.initials: T
authors.lastname: Williams
authors.affiliation: Instituto de Agrobiotecnología, CSIC-Gobierno de Navarra, Mutilva 31192, Navarra, Spain; Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Navarra, Spain. Electronic address: rosa.murillo@unavarra.es.
authors.forename: Rosa
authors.initials: R
authors.lastname: Murillo
authors.affiliation: Instituto de Agrobiotecnología, CSIC-Gobierno de Navarra, Mutilva 31192, Navarra, Spain; Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Navarra, Spain.
authors.forename: Primitivo
authors.initials: P
authors.lastname: Caballero
mesh_terms: D000818:Animals; D005260:Female; D008297:Male; D017924:Nucleopolyhedroviruses; D010572:Pest Control, Biological / Q000379:methods; D015995:Prevalence; D012328:RNA Viruses; D013030:Spain; D018411:Spodoptera / Q000821:virology*
keywords: Adult infection; Alphabaculovirus; Co-infection; Iflavirus; SeMNPV