RESUMEN
Infectious hematopoietic necrosis virus (IHNV) is among the most important pathogens affecting the salmonid industry. Here, we investigated the molecular evolution and circulation of isolates from 11 countries or regions all over the world, with a special focus on the epidemiological situation in France. The phylogeography, time to the most recent common ancestor (TMRCA) and nucleotide substitution rate were studied using 118 full-length glycoprotein gene sequences isolated from 9 countries (5 genogroups) over a period of 47 years. The TMRCA dates back to 1943, with the L genogroup identified as the likely root (67â%), which is consistent with the first report of this pathogen in the USA. A Bayesian inference approach was applied to the partial glycoprotein gene sequences of 88 representative strains isolated in France over the period 1987-2015. The genetic diversity of these 88 sequences showed mean nucleotide and amino-acid identities of 97.1 and 97.8â%, respectively, and a d N/d S ratio (non-synonymous to synonymous mutations) of 0.25, indicating purifying selection. The French viral populations are divided into eight sub-clades and four individual isolates, with a clear spatial differentiation, suggesting the predominant role of local reservoirs in contamination. The atypical 'signatures' of some isolates underlined the usefulness of molecular phylogeny for epidemiological investigations that track the spread of IHNV.
RESUMEN
In this study, the in vivo effects of chronic pollution by the active substance (AS) pendimethalin, a dinitroaniline herbicide, on the susceptibility of rainbow trout, Oncorhynchus mykiss L., to an experimental challenge with viral hemorrhagic septicemia virus (VHSV) were assessed. After four weeks of exposure to fresh water (C group) or 500 ng L(-1) of AS (P500 group), the fish were challenged by immersion in water containing 10(4) TCID(50) mL(-1) of VHSV. While exposure to pendimethalin was maintained throughout the experiment, mortalities were recorded during the 40 days post-infection (dpi) and organs were collected from dead fish for virological examination. At the end of the experiment, anti-VHSV antibodies and the classical pathway of complement activity were assessed in trout plasma. Exposure to pendimethalin significantly affected the distribution of cumulative mortality accelerating death in fish infected by VHSV. Pendimethalin appeared to decrease the Mean Time to Death (MTD) after virus treatment from 14.9 days (C-VHSV) to 10.2 days (P500-VHSV). Nevertheless, by the end of the experiment, differences in cumulative mortality were no longer observed between the two groups, which had reached the same stage (50 percent). Furthermore, a higher concentration of the virus was recovered from the pools of organs from the P500-VHSV group than the C-VHSV group. Moreover, at 40 dpi, although no significant difference was observed in the immune response between the two groups, more fish in the P500-VHSV group had set up an immune response by secreting antibodies than in the control viral group (C-VSHV).