title: Challenges in the rabbit haemorrhagic disease 2 (RHDV2) molecular diagnosis of vaccinated rabbits.
abstract: Molecular methods are fundamental tools for the diagnosis of viral infections. While interpretation of results is straightforward for unvaccinated animals, where positivity represents ongoing or past infections, the presence of vaccine virus in the tissues of recently vaccinated animals may mislead diagnosis. In this study, we investigated the interference of RHDV2 vaccination in the results of a RT-qPCR for RHDV2 detection, and possible associations between mean Cq values of five animal groups differing in age, vaccination status and origin (domestic/wild). Viral sequences from vaccinated rabbits that died of RHDV2 infection (n=14) were compared with the sequences from the commercial vaccines used in those animals. Group Cq means were compared through Independent t-test and One-way ANOVA. We proved that RHDV2 vaccine-RNA is not detected by the RT-qPCR as early as 15days post-vaccination, an important fact in assisting results interpretation for diagnosis. Cq values of vaccinated and non-vaccinated infected domestic adults showed a statistically significant difference (p<0.05), demonstrating that vaccination-induced immunity reduces viral loads and delays disease progression. Contrarily, in vaccinated young rabbits higher viral loads were registered compared to non-vaccinated kittens. No significant variation (p=0.3824) was observed between viral loads of non-vaccinated domestic and wild RHDV2-victimised rabbits. Although the reduced number of vaccinated young animals analysed hampered a robust statistical analysis, this occurrence suggests that passively acquired maternal antibodies may inhibit the active immune response to vaccination, delaying protection and favouring disease progression. Our finding emphasises the importance of adapting kitten RHDV2 vaccination schedules to circumvent this interference phenomenon.
authors.affiliation: Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Núcleo da Mitra, 7000, Évora, Portugal.
authors.forename: C L
authors.initials: CL
authors.lastname: Carvalho
authors.affiliation: Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Instituto de Investigação e Formação Avançada (IIFA), Universidade de Évora, Núcleo da Mitra, 7000, Évora, Portugal; Departamento de Medicina Veterinária, Universidade de Évora, Núcleo da Mitra, 7000, Évora, Portugal.
authors.forename: E L
authors.initials: EL
authors.lastname: Duarte
authors.affiliation: Instituto Nacional de Investigação Agrária e Veterinária (INIAV), Av. da República, Quinta do Marquês, 2780-157 Oeiras, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Monteiro
authors.affiliation: Instituto Nacional de Investigação Agrária e Veterinária (INIAV), Av. da República, Quinta do Marquês, 2780-157 Oeiras, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Botelho
authors.affiliation: Instituto Nacional de Investigação Agrária e Veterinária (INIAV), Av. da República, Quinta do Marquês, 2780-157 Oeiras, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Albuquerque
authors.affiliation: Instituto Nacional de Investigação Agrária e Veterinária (INIAV), Av. da República, Quinta do Marquês, 2780-157 Oeiras, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Fevereiro
authors.affiliation: Instituto Nacional de Investigação Agrária e Veterinária (INIAV), Av. da República, Quinta do Marquês, 2780-157 Oeiras, Portugal.
authors.forename: A M
authors.initials: AM
authors.lastname: Henriques
authors.affiliation: Instituto Nacional de Investigação Agrária e Veterinária (INIAV), Av. da República, Quinta do Marquês, 2780-157 Oeiras, Portugal.
authors.forename: S S
authors.initials: SS
authors.lastname: Barros
authors.affiliation: Instituto Nacional de Investigação Agrária e Veterinária (INIAV), Av. da República, Quinta do Marquês, 2780-157 Oeiras, Portugal. Electronic address: margarida.duarte@iniav.pt.
authors.forename: Margarida Dias
authors.initials: MD
authors.lastname: Duarte
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017250:Caliciviridae Infections / Q000175:diagnosis / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D017929:Hemorrhagic Disease Virus, Rabbit / Q000235:genetics* / Q000276:immunology*; D008099:Liver / Q000276:immunology / Q000821:virology; D008168:Lung / Q000276:immunology / Q000821:virology; D057089:Pathology, Molecular / Q000592:standards*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012367:RNA, Viral / Q000032:analysis; D011817:Rabbits; D014611:Vaccination / Q000592:standards / Q000662:veterinary*; D014765:Viral Vaccines / Q000235:genetics / Q000276:immunology*
chemical_list: D012367:RNA, Viral; D014765:Viral Vaccines
keywords: Cq values; Molecular diagnosis; RHDV2; RHDV2 vaccines; RT-qPCR; Rabbit haemorrhagic disease virus; Vaccinated rabbits