Comparative study of HA and HNB staining RT-LAMP assays for peste des petits ruminants virus detection in West African Dwarf goats.

Peste des petits ruminants (PPR) cause severe economic losses to many countries of the world where the disease is endemic. It has been targeted for global eradication by 2030 following the successful eradication of rinderpest in 2011. The proposed eradication program would benefit from efficient and relatively reliable diagnostic tools for early PPR virus (PPRV) detection. A total of 33 eight to 12 months old West African Dwarf (WAD) goats were used. Nineteen goats infected by commingling with two PPR virus-positive animals formed the infected group (PPRV-infected goats) while 14 non-infected goats formed the control group (CTG). The suitability of hydroxyl naphthol blue (HNB) staining of reverse transcription loop-mediated isothermal amplification (RT-LAMP) and haemagglutination (HA) assays was compared for their sensitivity to detect the PPRV in PPRV-infected goats and non-infected CTG. PPR disease severity in WAD goats at different days post infection (dpi) was evaluated by clinical scoring and haemagglutination titre (HAT). HNB staining RT-LAMP reaction and HA showed sensitivities of 100% and 73.68%, respectively, for PPRV detection. Expression of PPR clinical signs began from 3 dpi, attained peak at 5 dpi, thereafter showed irregular patterns till 24 dpi. Evaluation of HAT in PPRV-infected goats at 12 dpi ranged from 2 to 64 haemagglutination units (HAU), while CTG goats had 0 HAU. In conclusion, HA could be a good tool for rapid diagnosis of PPRV in a developing country setting. However, HNB staining RT-LAMP assay demonstrated high sensitivity for accurate diagnoses of PPRV and as an important diagnostic tool when precise phenotyping is desired.

Deletion of the Viral Thymidine Kinase in a Meq-Deleted Recombinant Marek's Disease Virus Reduces Lymphoid Atrophy but Is Less Protective.

Marek's disease (MD) is a ubiquitous disease of domesticated chickens and its etiologic agent is the Gallid alphaherpesvirus 2 (GaHV-2), also known as Marek's disease virus (MDV). MD is currently controlled by vaccination using live attenuated strains of MDV (e.g., CVI988/Rispens), non-pathogenic serotypes of MDV (GaHV-3), or non-pathogenic strains of the related Melagrid alphaherpesvirus 1 (MeHV-1). One attractive strategy for the production of new vaccine strains is a recombinant MDV attenuated by the deletion of the major viral oncogene meq. However, meq-deleted variants of MDV cause atrophy of the bursa and thymus in maternal antibody-negative chickens, and the resulting immunosuppression makes them unsuitable. Herein we detail our attempt to mitigate the lymphoid atrophy caused by meq-deleted MDV by further attenuation of the virus through ablation of the viral thymidine kinase (tk) gene. We demonstrate that ablation of the viral tk from the meq-deleted virus rMd5B40/Δmeq resulted in a virus attenuated for replication in vitro and which spared chickens from atrophy of the lymphoid organs in vivo. When the rMd5B40/Δmeq/Δtk/GFP was used as a vaccine it was protective against challenge with the vv+MDV strain 686, but the protection was less than that provided by the CVI988/Rispens vaccine.