ABSTRACT Greg Albery - Georgetown University - US Age-related changes in social behaviour shape disease dynamics in a wild ungulate Gregory F Albery; Tim H Clutton-Brock; Alison Morris; Sean Morris; Josephine M Pemberton; Daniel H Nussey; Josh A Firth Georgetown University As they near the end of their lifespan, wild animals often experience profound declines in quality known as “senescence”. When older individuals exhibit weaker immunity (“immunosenescence”), they may be able to compensate by becoming less social, thereby reducing their exposure to pathogens. To date, despite an ever-expanding wealth of information on social networks in disease ecology, it is unclear whether wild animals experience age-related declines in social behaviours, how these changes alter exposure rates, and whether this process might compensate for immunosenescence. Here, I use a wild population of red deer (Cervus elaphus) on the Isle of Rum, Scotland, to investigate the links between ageing, social behaviour, helminth infection, and fitness. I employ a suite of novel spatial and social network analyses to show that a range of intrinsic and extrinsic processes contribute to age-related declines in social network centrality over the course of an adult deer’s lifespan. I further demonstrate that within-individual reductions in social behaviour are associated with reduced burdens of nematode parasites. Taken together, these results demonstrate that parasite infection is a potentially important driver of age-related behaviour changes that ultimately determine large-scale demographic structuring in this wild population. Moreover, they imply that age-related behavioural changes may be adaptive, functioning to balance the costs of a waning immune system, rather than emerging from physiological weakness and an inability to compete with younger conspecifics. ABSTRACT Brent Allman - Emory University - US Heterogeneity in viral infections increases the rate of deleterious mutation accumulation Brent Allman, Katia Koelle, Daniel Weissman Emory University RNA viruses have high mutation rates, with the majority of mutations being deleterious. We examine patterns of deleterious mutation accumulation over multiple rounds of viral replication, with a focus on how cellular coinfection and heterogeneity in viral output affect these patterns. When unique viral genotypes with differential fitness coinfect a cell, the production of viral progeny is likely to use proteins from multiple parental viral genotypes. This results in group-level phenotypes that have the potential to influence selection. Specifically, using agent-based intercellular simulations we find, in agreement with previous studies, that coinfection of cells by viruses relaxes the strength of purifying selection, and thereby increases the rate of deleterious mutation accumulation. We further find that cellular heterogeneity in viral output exacerbates the rate of deleterious mutation accumulation, regardless of whether this heterogeneity in viral output is stochastic or is due to variation in cellular multiplicity of infection. These results highlight the need to consider the unique life histories of viruses and their population structure to better understand observed patterns of viral evolution. ABSTRACT Maria Luiza Andreani - Univesity of Campinas – Brazil MCR bearing Salmonella enterica phylogeny and the evolution of antibiotic resistance Maria Luiza Andreani, Juliana José, Marcelo Brocchi University of Campinas The emergence of new antibiotic resistance mechanisms is a major public health concern. Colistin is a last resort antibiotic to which resistance genes have increasingly been reported, with at least 10 different variations registered to date. Although colistin is not a preference for clinical treatment, it is widely used in animal production, creating an environment where resistance can rise, spread, and be undetected. Salmonella enterica is a gram-negative bacterium that can infect both humans and livestock and has been shown to carry mobilized colistin resistance (mcr) genes, posing as a potential threat to public health. In order to control mcr spread and antibiotic resistance rise on Salmonella enterica a better understanding of evolutionary context is necessary. Here, we analyze the phylogenetic relationship among Salmonella enterica isolates coming from environmental and clinical context and harboring at least one plasmid with mcr genes (mcr-1 to mcr-9) as well as their pangenome. Moreover, we also analyze the phylogenetic relationship of the plasmids present on those isolates, unraveling the relationship among different mcr variants in Salmonella. This data provide a better understanding of colistin resistance spread and status on Salmonella and can be useful to prevent it by public health measures. ABSTRACT Callum Arnold - Pennsylvania State University - US Data4Action: SARS-CoV-2 Seroprevalence in a University Community *Arnold, Callum R.K. (MSc)1,2; *Srinivasan, Sreenidhi (PhD)2,3; Herzog, Catherine M. (PhD)2,3; Gontu, Abhinay (MVSc)4; Bharti, Nita (PhD)1,2; Small, Meg (PhD)5,6; Rogers, Connie J. (PhD)7; Schade, Margeaux M. (PhD)5; Kuchipudi, Suresh V2,4 (PhD); Kapur, Vivek (PhD)2,3,8; Read, Andrew (D.Phil)1,2,3; Ferrari, Matthew J. (PhD)1,2 1Department of Biology, Pennsylvania State University, University Park, PA, USA 16802; 2Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA, USA 16802; 3Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA 16802; 4Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, PA, USA 16802; 5College of Health and Human Development, Pennsylvania State University, University Park, PA, USA 16802; 6Social Science Research Institute, Pennsylvania State University, University Park, PA, USA 16802; 7Department of Nutritional Sciences, Pennsylvania State University, University Park, PA, USA 16802; 8Department of Animal Science, Pennsylvania State University, University Park, PA, USA 16802; * Contributed equally The COVID-19 pandemic has been characterized by great uncertainty, particularly during the earlier stages when less was known about transmission dynamics and the efficacy of preventative actions. Prior infectious disease research had highlighted the potential for large outbreaks in highly structured transient populations, such as returning University students interacting with local communities. Concern at Pennsylvania State University, home to approximately 35,000 returning students, prompted the development of a longitudinal cohort study to examine the communication and interaction between the two cohorts, and the effect on SARS-CoV-2 incidence within each, surrounding and during the 2020 Fall term. Despite high incidence observed within the returning student cohort (31.2% of 625 returned positive IgG titers), the seroprevalence within the surrounding community remained low and stable either side of the Fall 2020 term (5.5% prior; 8.2% post). Correcting for plausible values of antibody test specificity and sensitivity, no scenarios demonstrated a significant increase in community seroprevalence. 94.1% of students reported PCR tests prior to study enrollment, with only 15.8% listing a positive result, of which 93.3% occurred after the start of the Fall term. Only contact with a known COVID-positive individual, and attendance of gatherings up to 50 individuals, were significant predictors of antibodies among returning students. These results indicate that the majority of infections among returning students occurred on campus, and the potential for local-scale heterogeneity in mixing with rare transmission between cohorts. The underlying mechanism of the disparate transmission dynamics is currently not known, but is the subject of ongoing components of the Data4Action project: multiple waves of student and community resident serology samples and behavioral survey responses will allow for a deeper exploration of the individual risk factors within each cohort. ABSTRACT Tal Azagi - National Institute for Public Health and the Environment, RIVM. Academic Medical Center, AMC - The Netherlands Circulation of Babesia Species and Their Exposure to Humans through Ixodes Ricinus Tal Azagi *,Ryanne I. Jaarsma Arieke Docters van Leeuwen Manoj Fonville Miriam Maas ,Frits F. J. Franssen Marja Kik Jolianne M. Rijks Margriet G. Montizaan Margit Groenevelt Mark Hoyer Helen J. Esser Aleksandra I. Krawczyk ,David Modrý,Hein Sprong and Samiye Demir Centre for Zoonoses & Environmental Microbiology, Centre for Infectious Disease Control, National Institute for Public Health an Human babesiosis in Europe has been attributed to infection with Babesia divergens and, to a lesser extent, with Babesia venatorum and Babesia microti, which are all transmitted to humans by Ixodes ricinus ticks. These Babesia species circulate in the Netherlands, but autochthonous human babesiosis cases have not been reported so far. To gain more insight into the natural sources of these Babesia species, their presence in reservoir hosts and in I. ricinus was examined. In a cross-sectional study, qPCR-detection was used to determine the presence of Babesia in 4611 tissue samples from 27 mammalian species and 13 bird species. Reverse line blotting and qPCR detection of Babesia species were used to test 2849 questing I. ricinus. Babesia microti was found in two rodent species: Myodes glareolus and Apodemus sylvaticus, whereas B. divergens was detected in the geographically restricted