Exploring the brain-behaviour interface : the role of juvenile play experiences

In laboratory rats, juvenile play behavior has been shown to influence the development of the medial prefrontal cortex (mPFC) and the experience of interacting with multiple partners has been shown to influence the orbital frontal cortex (OFC). Several studies in this thesis further explored these relationships. Two main findings arose. 1).The play-induced changes to the mPFC and the partner-induced changes to the OFC differ in their longevity. The neural remodeling of the mPFC remains relatively unchanged into adulthood, whereas that of the OFC decreases over time, suggesting that these two areas of the prefrontal cortex serve different roles in social behavior. 2) Though wild rats play in a similar manner to domesticated rats, the play-induced changes to the mPFC are not present, suggesting that complex patterns of play fighting have evolved independently of their role in the development of the mPFC. These findings shed new light on play.Funding Agencies: Natural Science and Engineering Research Council of Canada, Alberta Innovates-Health Solution

Zoonotic Pathogens of Peri-domestic Rodents

Rodents are important vectors of disease as they have the potential, arguably more than any other wildlife species, to move pathogens across geographical distances. Although there is little known of the prevalence of zoonotic pathogens in UK rodents thus it is difficult to determine the public health risk. The aims of this project were to collect a large range of rodent sample from a variety of peri-domestic locations across the UK that could be used as a representation of the British rodent population and screen them for zoonotic pathogens that could be a potential risk to public health. Rodent species were sampled from 2014 to 2016 from peri-domestic locations across Northern England, North Wales and Southern Scotland. A total of 333 rodent specimens were collected from this project which included; brown rats (R. norvegicus, n=68), house mice (Mus musculus, n=105), wood mice (Apodemus sylvaticus, n=48), bank voles (Myodes glareolus, n=56), field voles (Microtus agrestis, n=23), red squirrels (Sciurus vulgaris, n=21) and grey squirrels (Sciurus carolinensis, n=12). Each rodent carcass was examined post mortem and tissue samples were taken. Viral zoonotic pathogens that were screened for in this project were Hantavirus (Seoul virus, SEOV, Puumala virus, PUUV and Tatenale virus, TATV), Lymphocytic choriomeningitis virus (LCMV) and Hepatitis E virus (HEV). RNA was extracted from kidney, lung and liver tissue. Each of the viruses were screened for using published pan RT-PCR assays specific to the viral genus. Positive PCR products were Sanger sequenced and phylogenetically analysed. Additional specific RT-qPCR assays were performed for SEOV and rat HEV. An LCMV ELISA was also performed on house mice serum samples. Histological examinations were performed on a subset of samples. SEOV RNA was detected in 13/68 (19%, 95% CI 0-40%) brown rats and 4/47 brown rats in an RT-qPCR assay. TATV RNA was detected in 7/23 (30.4%, 95% CI, 11.6-49.2%) field voles. No PUUV RNA was detected in this study. The PCR screening results for LCMV revealed an overall prevalence of 8% (26/331, 95% CI 15-36) with LCMV RNA present in 3.2% brown rats, 17.5% house mice, 2% wood mice and 4% bank voles liver tissue. There was no LCMV RNA detected in field voles, red squirrels or grey squirrels. Seroprevalence in house mice was 7% (3/43). No histological changes were observed in the kidney tissue of LCMV infected house mice. In this study, 8/61(13%, 95% CI, 4.6-21.4) of brown rat livers were positive for rat HEV RNA. Lesions and necrosis were observed histologically in 2/3 samples examined, which appears to be indicative of HEV infection based on observations in other HEV infected animals. RT-qPCR results confirmed rat HEV. No HEV RNA of any variant was detected in any other rodent species. This is the first reported detection of rat HEV in a wild rat from the United Kingdom. Bacterial zoonosis Campylobacter in rodents was also investigated in this study. Campylobacter from rodent faecal samples was cultured on Campylobacter specific media and DNA was extracted. An lpx gene PCR was performed to differentiate between C. jejuni and C. coli. In total, 28% (43/152) rodents were Campylobacter positive and of these, 86% (37/43) were shown to be either C. jejuni (20/43, 46%) or C. coli (17/43, 40%) and 14% (6/43) isolates that were lpx negative. House mice were shown to be most commonly infected with C. coli (8/10) and bank voles with C. jejuni (13/17). In brown rats, 50% (13/26) were positive in which 39% C. jejuni (5/13) and 61% C. coli (8/13) positive. Whole genome sequencing was also performed on a subset of isolates and sequence types ST-6561, ST-45 and ST-51were identified in brown rats and host-specific sequence type ST-3704 was present in bank voles. This project has proved that there are multiple zoonotic pathogens circulating in the wild rodent population that could be hazardous to human health. It has also highlighted gaps in our current knowledge, such as the unknown zoonotic potential of some pathogens, such as TATV. In order to comment on the significance of a pathogen to public health the zoonotic potential must be known. The prevalence of known pathogens with known zoonotic potential, such as SEOV, LCMV and rat HEV in people remains unknown. This project has also indicated that there may be possible occupational risks and geographical hot spots for rodent zoonosis. Although further investigation including human surveillance, improved diagnostics and mathematical modeling could be used to determine the risks. This could aid in the prevention of possible outbreaks through improvement of biosecurity, pest control as well as raising public awareness, reduce the risk of exposure and be beneficial for public health in the future

Vers une surveillance des zoonoses associées aux rats (Rattus norvegicus)

Rats (Rattus spp.) are a source of a number of zoonotic pathogens responsible for morbidity and mortality worldwide. These species are particularly problematic with regards to rat associated health risks because rats are living in close contact with people leading to potentially rat disease transmission. Based on the "One Health" approach, surveillance of zoonotic pathogens in rats and other susceptible hosts should help to improve animal and human health. Our aim was to develop the surveillance of rat-associated zoonoses in a source species (Rattus norvegicus) and, in some target populations (cattle, dogs and pigs) as sentinels of human exposure. The screening methods including DNA microarray developed for the purpose of the "WildTech" project and the spatial distribution of the risk were the major themes in this work. They have been documented based on 181 rats captured in the administrative unit “département du Rhône” between 2010 and 2013 and, diagnostic data of leptospirosis in cattle, dogs and pigs, recorded at "Laboratoire des Leptospires – Lyon" between 2008 and 2012. The application of various screening methods (direct and indirect) for the purpose of surveillance were relevant and detected four potentially zoonotic pathogens circulating in rats, (hantavirus Seoul, hepatitis E virus, Leptospira spp. and Toxoplasma gondii). Although the location of infected rats varied among a short geographic distance, Leptospira spp. and hantavirus Seoul were the predominant hazard with respectively 26%, IC95% = 20% -33% and 14%, IC95% = 8% -20% of infected rats. Their spatial distribution could be characterized with socio-economic indices and, regarding Leptospira-infected rats, a further study shown that the maintenance of strains was related to local and intrinsic factors. The study of leptospirosis in dogs and cattle revealed their increased exposure to the serogroup Australis, their heterogeneous spatial distribution and the significant increase of annual incidence in dogs. The same trends were observed in humans which underlines the relevance of surveillance of animal leptospirosis as sentinels of human exposure. All together, the information obtained contributes to a better understanding of the epidemiology of rat-associated zoonoses to support implementation of surveillance and public health decisions in the future.Le rat (Rattus spp.) est une source de nombreux pathogènes zoonotiques responsables de morbidité et de mortalité dans le monde. Ces espèces sont particulièrement problématiques en santé publique car leur mode de vie synanthrope favorise la proximité rat-Homme et la transmission potentielle de pathogènes. Selon l'approche « une seule santé », la surveillance sanitaire des rats et d'autres espèces animales sensibles devrait contribuer à améliorer la santé de ces dernières et de l'Homme. Notre objectif était de développer la surveillance des zoonoses associées aux rats chez une espèce source (R. norvegicus) et chez des espèces cibles (bovins, chiens et porcs) en tant que sentinelles de l'exposition de l'Homme. L'intérêt de méthodes de détection dont la micro-puce à ADN développée dans le cadre du projet européen « WildTech » et l'investigation de la distribution du risque étaient les thèmes majeurs de ces travaux. Ils ont été documentés à partir de 181 rats capturés dans le Rhône entre 2010 et 2013 et, de données diagnostiques de leptospiroses animales enregistrées au Laboratoire des Leptospires – Lyon entre 2008 et 2012. Les méthodes de détection directes et indirectes utilisées à des fins de surveillance ont montré leur intérêt par la mise en évidence de quatre pathogènes potentiellement zoonotiques chez les rats (Hantavirus Séoul, virus de l'hépatite E, Leptospira spp. et Toxoplasma gondii). Malgré la spatialisation hétérogène des statuts infectieux, Leptospira spp. et l'hantavirus Séoul étaient les dangers prédominants avec respectivement, 26%, CI95%=20%-33% et 14%, CI95%=8%-20% de rats infectés par ces agents. Leur distribution spatiale a été caractérisée par des indices socio-économiques et, dans le cas des infections par les leptospires, une étude approfondie des souches circulantes a montré que leur persistance relevait de facteurs locaux, intrinsèques à la colonie. L'étude des leptospiroses animales (chiens et bovins) suggère leur exposition accrue au sérogroupe Australis, leur distribution spatiale hétérogène et une croissance significative de l'incidence annuelle canine. Ces trois observations également rapportées chez l'Homme soulignent l'intérêt de la surveillance de ces espèces en tant que sentinelles. Les informations obtenues par l'ensemble des méthodes appliquées contribuent à une meilleure compréhension de l'épidémiologie des zoonoses associées aux rats et de la leptospirose en particulier, afin d'orienter la mise en œuvre de leur surveillance et les décisions de santé publique à venir

Comparative anatomy of the mammalian bony cochlea and its ontogenetic development in humans

The cochlea is the organ for sound reception. Mammals place varied functional demands on their sense of hearing to meet the requirements of a broad range of ecological niches and diverse behaviours. However, documenting potentially related adaptations of the cochlea to eco-behavioural traits is difficult due to its complex geometry. The present study aims to determine whether the bony cochlea carries eco-behavioural traits that can be used to contextualize our understanding of the fossil record and evolutionary transitions. This study also includes work on ontogenetic changes since these can yield important insights into evolutionary processes resulting in differences of the adult phenotypes. Advanced techniques in micro-CT imaging, 3D image visualization, geometric morphometrics and statistical methods were used to study morphological variations of the bony cochlea across 45 adult eutherian species. Also, the same set of techniques was used to study 12 human fetal (approximately four to nine months of gestation) cochleae in comparison with five adult cochleae. Results revealed that there was a considerable range of variation in form of the mammalian bony cochlea. Potential links between the bony cochlear morphology and hearing, ecology and behaviour were found. Dimensions of the bony cochlea may be indicative of the eco-behavioural niche that a mammal occupies; e.g., fewer than two spiral turns is associated with obligate marine species. Rodents also showed remarkable variation in the cochlear morphology, more so than any other group of mammals studied, reflecting their diverse eco-behavioural traits. Results from the human developmental study showed that whilst the general coiled shape was achieved at the midgestational age, there was size related morphological change during the postnatal period. The round window size reached mature state prior to birth, by approximately the second trimester, whereas the oval window continued to change in size after birth. The postnatal enlargement may be determined by functional requirements of air-borne hearing, particularly with respect to frequency range and sensitivity