The incubation period (IP) and the neuropathology of transmissible spongiform encephalopathies (TSEs) have been extensively used to distinguish prion isolates (or strains) inoculated into panels of inbred mouse strains. Such studies have shown that the bovine spongiform encephalopathy (BSE) agent is indistinguishable from the agent causing variant Creutzfeldt-Jakob disease (vCJD), but differs from isolates of sporadic CJD, reinforcing the idea that the vCJD epidemic in Britain results from consumption of contaminated beef products. We present a mouse model for genetic and environmental factors that modify the incubation period of BSE crossspecies transmission. We have used two mouse strains that carry the same prion protein (PrP) allele, but display a 100-day difference in their mean IP following intracerebral inoculation with primary BSE isolate. We report genetic effects on IP that map to four chromosomal regions, and in addition we find significant factors of host environment, namely the age of the host's mother, the age of the host at infection, and an X-cytoplasm interaction in the host.

Abstract.-The effects of hybridization on developmental stability and size of tooth characters were investigated in intersubspecific crosses between random-bred wild strains of the house mouse (Mus musculus domesticus and M. m. musculus). Fluctuating asymmetry (FA) and trait size were compared within and between parental, Fl> backcross, and F 2 hybrid groups. The relationship between FA and reproductive fitness within the F. hybrids was also studied. The results indicated that both FA and character size levels differed significantly between the two subspecies. The F 1 hybrids and the recombined groups (backcrosses and F 2 hybrids) showed heterosis for both parameters. No significant differences in the FA of fertile and sterile F 1 hybrid individuals were found. Comparison of the FA levels obtained in this study with those found in wild populations from the hybrid zone in Denmark showed that the levels of FA were lower in laboratory-bred samples than in the wild populations. This study provides further evidence that, in hybrids, the developmental processes underlying most of the morphological traits we studied benefit from a heterotic effect, despite the genomic incompatibilities between the two European house mice revealed by previous genetical and parasitological studies.Key words.-Developmental stability, experimental crosses, genomic coadaptation, heterosis, hybrid, Mus musculus, tooth characters, trait size.Received February 26, 1996. Accepted March 25, 1997 Coadaptation refers to the internal genomic balance between loci, at both the inter-and intrachromosomal levels, that was molded by selection during the evolutionary histories of populations (Dobzhansky 1937). The notion of coadaptation has played a prominent role in the study of the mechanisms of reproductive isolation and speciation because any breakdown of coadapted gene complexes would lead to a selective disadvantage. Two approaches have been used to estimate the degree of divergent coadaptation that occurs in differentiating populations. The first uses experimental crosses to assess the effects of hybridization on major fitness components such as viability and fertility. The second focuses on hybrid zones, i.e., sites where individuals from genetically distinct populations meet, mate and produce offspring (Barton 1979;Barton and Hewitt 1985;Hewitt 1988;Harrison 1990). In this case, the effects of different intergenomic combinations on hybrid fitness can be estimated indirectly from the introgression patterns of genetic markers.The hybrid zone between the two European subspecies of the house mouse, Mus musculus domesticus and M. m. musculus, which crosses Europe from Denmark to Bulgaria, has been the focus of extensive studies (for review see Boursot et al. 1993;Sage et al. 1993). Autosomal, mitochondrial, and sex chromosome markers have been analyzed across several transects of the hybrid zone in Denmark, Germany, and Bulgaria. The similarity between the patterns of differential introgression that occur in these geographically different transects l...

West Nile Virus (WNV) is the causative agent of a vector-borne, zoonotic disease with a worldwide distribution. Recent expansion and introduction of WNV into new areas, including southern Europe, has been associated with severe disease in humans and equids, and has increased concerns regarding the need to prevent and control future WNV outbreaks. Since 2010, 524 confirmed human cases of the disease have been reported in Greece with greater than 10% mortality. Infected mosquitoes, wild birds, equids, and chickens have been detected and associated with human disease. The aim of our study was to establish a monitoring system with wild birds and reported human cases data using Geographical Information System (GIS). Potential distribution of WNV was modelled by combining wild bird serological surveillance data with environmental factors (e.g. elevation, slope, land use, vegetation density, temperature, precipitation indices, and population density). Local factors including areas of low altitude and proximity to water were important predictors of appearance of both human and wild bird cases (Odds Ratio = 1,001 95%CI = 0,723–1,386). Using GIS analysis, the identified risk factors were applied across Greece identifying the northern part of Greece (Macedonia, Thrace) western Greece and a number of Greek islands as being at highest risk of future outbreaks. The results of the analysis were evaluated and confirmed using the 161 reported human cases of the 2012 outbreak predicting correctly (Odds = 130/31 = 4,194 95%CI = 2,841–6,189) and more areas were identified for potential dispersion in the following years. Our approach verified that WNV risk can be modelled in a fast cost-effective way indicating high risk areas where prevention measures should be implemented in order to reduce the disease incidence.