Experimental Study of the Mechanical Transmission of Rabbit Hemorrhagic Disease Virus (RHDV2/b) by Aedes albopictus (Diptera: Culicidae) and Phlebotomus papatasi (Diptera: Psychodidae).

Rabbit hemorrhagic disease (RHD) is caused by a lagovirus mainly affecting European rabbits (Oryctolagus cuniculus), although other European and North American lagomorph species are also susceptible to fatal infection by the new viral variant RHDV2/b. In the present work, direct mechanical transmission of the rabbit hemorrhagic disease virus (RHDV2/b variant) by the hematophagous Diptera Aedes albopictus (Skuse) (Diptera: Culicidae) and the sand fly Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) was tested. For each species, six and three laboratory rabbits were exposed to bites of dipterous females partially fed on RHDV2/b viral suspension 2 h and 24 h prior to exposure, respectively. The rabbits were then monitored for clinical changes and mortality for 35 d, and seroconversion was assessed by indirect ELISA. No rabbit died or showed clinical signs of disease, and seroconversion was recorded in two rabbits challenged with P. papatasi females fed the viral suspension 2 h prior to exposure. The number of RHDV2/b RNA copies/female was higher in Ae. albopictus than in P. papatasi but the decrease over time of RNA load in Ae. albopictus was greater than that in P. papatasi. The results of this study suggest the inability of Ae. albopictus to serve as a direct mechanical vector of RHDV2/b, but sand flies could play a role in the local transmission of RHD.

A new single nucleotide polymorphism in the calpastatin (CAST) gene associated with beef tenderness.

First we looked for putative causative mutations in the CAST and CAPN1 genes associated with meat tenderness and found a total of 31 and 7 polymorphisms, respectively, in the Parda de Montaña and Pirenaica breeds. Tenderness was not affected by mutations in CAPN1. However, three SNPs located at intron 5 (BTA7: g.98533962C>G on UMD 3.0), exon 7 (g.98535683A>G) and intron 12 (g.98545188T>A) of the CAST gene were significantly associated with meat tenderness at 7 days post-mortem in the Parda de Montaña breed. The haplotypes h2 and h5 showed significant associations with meat toughness being consistent with the SNP association results, which showed that the g.98535683A>G SNP in CAST might be the causative mutation of the effect found in this study. This mutation changes the amino acid sequence at position p.Thr182Ala (NM_174003). This amino acid substitution could affect the interacting regions between the calpastatin L-domain and calpain, and then could generate a more stable union between calpain and calpastatin.