Caterina Fiegna

Bio: Caterina Fiegna is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

Study of squirrelpox virus in red and grey squirrels and an investigation of possible routes of transmission

Abstract: ................................................................................................................................. 10 CHAPTER 1 .......................................................................................................................... 12 INTRODUCTION ................................................................................................................. 12 1.1 History of squirrels in the UK ................................................................................... 12 1.1.1 Grey squirrels in the UK pre-1930 ................................................................. 12 1.1.2 Red squirrels in the UK pre-1930 .................................................................. 14 1.1.3 Distribution of red and grey squirrels in the UK post-1930 ........................... 15 1.1.4 Evidence of the role of disease in the decline of the red squirrel in the UK .. 17 1.1.5 Pox disease in red squirrels ............................................................................ 18 1.2 Poxviruses ................................................................................................................. 21 1.2.1 Taxonomic structure of Poxviridae ................................................................ 22 1.2.2 Virion morphology and structure ................................................................... 23 1.2.3 Genome features of poxviruses ...................................................................... 25 1.2.4 Poxvirus replication ....................................................................................... 27 1.2.5 Immunopathogenesis of poxvirus infection ................................................... 29 1.2.6 The role of the host in poxvirus pathogenesis: host tropism .......................... 32 1.2.7 Transmission of poxviruses ........................................................................... 33 1.3 Poxvirus infection in lagomorphs and rodents .......................................................... 35 1.3.1 Myxoma virus ................................................................................................ 35 1.3.2 Shope fibroma virus ....................................................................................... 36 1.3.3 Cowpox virus ................................................................................................. 36 1.3.4 Monkeypoxvirus ............................................................................................ 38 1.3.5 Squirrel fibroma virus .................................................................................... 39 1.3.6 Squirrelpox virus ............................................................................................ 41 1.4 Aim of the thesis ....................................................................................................... 42 CHAPTER 2 .......................................................................................................................... 44 MATERIALS AND METHODS ........................................................................................... 44 2.1 Centrifuges and Common reagents ........................................................................... 44 2.2 Sample storage .......................................................................................................... 44 2.3 Virology .................................................................................................................... 44

Inter-specific viral infections: can the management of captive red squirrel collections help inform scientific research?

Abstract: Squirrel pox virus (SQPV) and adenovirus produce pathological disease in native red squirrels ( Sciurus vulgaris ). SQPV in particular is a significant factor in regional population declines and is generally prevalent in the UK's introduced grey squirrel ( Sciurus carolinensis ) population as an asymptomatic infection. Despite the role of the grey squirrel as a virus reservoir and potential inter-specific infection pathways being highlighted, there remains a paucity of field study data with known relative inter-specific infection rates and quantified frequency of interactions. Intriguingly, whilst captive zoological red squirrel collections are often present within woodland habitat containing wild grey squirrels, clinical pox cases are rarely observed unless red squirrels are released from the enclosures. In 2011 we monitored grey squirrel activity on an enclosure containing red squirrels. Grey squirrels were present for a cumulative total of 47.5 minutes within the twenty four hours of observation. A range of behaviours were recorded including feeding, and instances where discarded food fell into the red squirrel enclosures below. We interpret the value of these observations in the context of published theories of viral transmission. The local grey squirrels were subsequently culled and tested for evidence of both historical and current SQPV and adenovirus infections. Polymerase Chain Reaction (PCR) assays did not amplify adenovirus DNA from grey squirrel blood samples, but positive results were recorded in faeces (3/18, 17%) and (10/18, 56%) in parallel spleen samples from the same animals. This variation in tissue specific detection rates suggests that previous long-term surveillance of adenovirus in wild grey squirrels focussing on blood samples may have significantly underestimated true infection rates. Enzyme-Linked Immunosorbent Assay (ELISA) tests revealed exposure to SQPV by antibody presence in 33% of the animals. Additionally, 22% of the animals contained detectable levels of both viruses. In parallel with laboratory and field studies in 2011, we collated historical unpublished reports and archived data from a range of UK squirrel collections and highlight some key cases of infection. We recommend that further behavioural and viral screening studies are focussed within scenarios where captive red squirrels are sympatric with wild grey squirrels. Download the complete issue.

Analysis of some dynamical systems inspired by ecological interactions

Abstract: A community is a collection of populations of different species living in the same geographical area. Species interact with each other in the community and this interaction affects species distribution, abundance, and even evolution [5]. Species interact in various ways, for instance through competition, predation, parasitism, mutualism, and commensalism. Mutualism is an interaction between individuals of different species in which both individuals benefit. Examples include plants and nitrogen fixing bacteria, pollination of flowering plants by an insect, lichen between a species of algae and fungus [53]. Commensalism is a type of relationship among organisms in which one organism is benefited while the other organism is neither benefited nor harmed. For example, some birds live among cattle to eat the insects stirred up by the cows. Predation is an interaction in which one organism consumes either all or part of another living organism (the prey), causing direct negative effect on the prey [6]. The individuals of one species is benefited while individuals of the other species is harmed. Parasitism is considered as a special case of (or analogous to) predation [47]. Individuals compete with each other for limited resources. This is a negativenegative interaction, that is, each individual adversely affects another. Historically, competition has been viewed as an important species interaction. Now, competition is recognized as one of many interacting factors that affect community structure. We have two focuses in this thesis. One focus is analyzing the dynamical behaviors of the discretization systems of the Lotka-Volterra predator-prey model. It is well known that the dynamics of the logistic map is more complex compared with logistic differential equation. Period doubling and the onset of chaos in the sense of Li-York occur for some values. Inspired by this, we analyze the dynamical behaviors of the discretization systems of the Lotka-Volterra predator-prey model (articles I and II). In article I, we show that the system undergoes fold bifurcation, flip bifurcation and Neimark-Sacker bifurcation, and has a stable invariant cycle in the interior of R + for some parameter values. In article II, we show that the unique positive equilibrium undergoes flip bifurcation and Neimark-Sacker bifurcation. Moreover, system displays much interesting dynamical behaviors, including period-5, 6, 9, 10, 14, 18, 20, 25 orbits, invariant cycles, cascade of period-doubling, quasi-period orbits and the chaotic sets. We emphasize that the discretization of continuous models (articles I and II) are not acceptable as a derivation of discrete predator-prey models [26]. A discrete predatorprey model is also formulated in Section 2. We analyze the dynamics (articles I and II) from the mathematical point of view instead of biological point of view. The other focus is disease-competition in an ecological system. We propose a model combining disease and competition and study how a disease affects the two competing species (article III). In our model, we assume that only one of the species is susceptible to an SI type disease with mass action incidence, and that infected individuals do not reproduce but suffer from additional disease induced death. We further assume that infection does not reduce the competitive ability of the infected. We show that infection of the superior competitor enables the inferior competitor to coexist, either as a stable steady state or limit cycle. In the case where two competing species coexist without the disease, the introduction of disease is partially determined by the basic