Statistical physics of vaccination

Historically, infectious diseases caused considerable damage to human societies, and they continue to do so today. To help reduce their impact, mathematical models of disease transmission have been studied to help understand disease dynamics and inform prevention strategies. Vaccination–one of the most important preventive measures of modern times–is of great interest both theoretically and empirically. And in contrast to traditional approaches, recent research increasingly explores the pivotal implications of individual behavior and heterogeneous contact patterns in populations. Our report reviews the developmental arc of theoretical epidemiology with emphasis on vaccination, as it led from classical models assuming homogeneously mixing (mean-field) populations and ignoring human behavior, to recent models that account for behavioral feedback and/or population spatial/social structure. Many of the methods used originated in statistical physics, such as lattice and network models, and their associated analytical frameworks. Similarly, the feedback loop between vaccinating behavior and disease propagation forms a coupled nonlinear system with analogs in physics. We also review the new paradigm of digital epidemiology, wherein sources of digital data such as online social media are mined for high-resolution information on epidemiologically relevant individual behavior. Armed with the tools and concepts of statistical physics, and further assisted by new sources of digital data, models that capture nonlinear interactions between behavior and disease dynamics offer a novel way of modeling real-world phenomena, and can help improve health outcomes. We conclude the review by discussing open problems in the field and promising directions for future research

Analysis of genetic variation in different sheep breeds using microsatellites

Genetic variation in three Egyptian indigenous sheep breeds namely: Barki, Ossimi and Rahmani were investigated using fourteen microsatellite loci. The total number of alleles ranged from 6 in CSSM47 locus to 14 in TGLA 377 locus. The fourteen tested loci were all polymorphic in the three breeds. Major differences between the breeds were found at ten of the tested loci, where the alleles at the highest frequency are different in the three breeds. While, at loci OARCP20, OARVH72, CSSM47 and OARAE129, two of the tested breeds have similar alleles at the highest allele frequency. The average direct count of heterozygosity overall loci in each tested breed was less than the expected heterozygosity. Tests of genotype frequencies for deviation from the Hardy-Weinberg equilibrium (HWE), at each locus overall breeds, revealed significant departure from HWE due to heterozygote deficiency. A slightly high rate of inbreeding within the three breeds was noticed (global FIS = 0.308). Low genetic differentiation was detected by estimation of FST index between all pairs of breeds. Cluster analysis revealed that Ossimi and Rahmani breeds clustered independently from Barki breed at 0.43 of genetic distance. The obtained results can be useful for the development of a rational breeding strategy for genetic improvement of sheep in Egypt