Ixodes ricinus, the sheep tick: ecology and disease

Relevant literature was reviewed and the ecology of the sheep tick, Ixodes ricinus and associated disease problems studied in south west Scotland. The development and maintenance of a colony of I.ricinus in the laboratory to provide tick-borne fever (T.B.F.) infected and T.B.F. free ticks for electron microscopic and tick pyaemia transmission studies was described. Additionally development times for each instar were measured during routine colony maintenance. The activity and development of I.ricinus was measured over three years at two sites on Ayrshire sheep farms by blanket drags of pasture areas and tick counts on sheep. Engorged stages were placed in nylon mesh tubes under the vegetation mat, in order to monitor development to subsequent stages. In all instances development to the next instar occurred during the late summer or autumn. Activity patterns varied from year to year with a prolonged period of summer activity in 1984, a bimodal distribution in 1985 and a single spring peak in 1986. Meteorological data was recorded in an attempt, only partially successful, to apply the model devised by Gardiner and Gettinby (1983) to data from these studies. A postal questionnaire was circulated to 300 farmers in Ayrshire and Argyll concerned with seasonal and local distribution of ticks, disease problems and control measures. The replies indicated a high tick incidence in Argyll and marked disease problems in certain regions of Ayrshire where ticks were present. Several of the farms were investigated in more detail by farm visits and examination of blood samples. Experimental tick-borne fever (T.B.F.) infections induced in young lambs were monitored by measurement of rectal temperatures, haematology, assessment of parasitaemias and neutrophil function tests. The classical febrile response accompanied by acute parasitaemia, lymphocytopaenia and followed by neutropaenia was recorded. Additionally an impairment of neutrophil function was demonstrated prior to the neutropaenia using an in vitro assay of neutrophil function. A counter immunoelectrophoresis (CIE) test was developed to detect antibodies produced after T.B.F. infection. Sera from experimental infections in lambs and goats were used to determine the interval after primary infection before antibody could be detected, this was shown to be 9-11 days post intravenous inoculation of the organism and the period of persistence 6-10 weeks in lambs. Four hundred and thirteen ovine field sera obtained from sheep of all ages from predominantly tick infested regions of Scotland and the north of England were tested with a positive rate of 18.2%. When CIE serology was coupled with conventional examination of blood smears the detection rate for ovine T.B.F. was doubled. Additionally, antibodies were detected in a number of sera from cattle, goats and deer using CIE. An electron microscopic technique was developed to demonstrate C.phagocytophila in I.ricinus. This technique was subsequently applied to ticks collected from one sheep farm in an attempt to estimate the level of infection. C.phagocytophila infection was absent from larvae, while 44% of nymphae were infected and 32 % of adults. This result supports the previous finding that transovarial transmission does not occur. Recent publications have indicated that an important aspect of T.B.F. infection in lambs is the associated immunosuppression which allows invasion of secondary pathogens, notably Staphylococcus aureus the causal agent of tick pyaemia. Several experiments were therefore conducted in lambs and mice to examine this aspect. In mice B-lymphocytes were depressed using cyclophosphamide (CY) [ to mimic one aspect of T.B.F. infection] and the mice subsequently challenged with Staphylococcus aureus administered by various routes. Death rates , lesion formation and bacteriological isolations were greater in mice pre-treated with CY. The experiment was repeated in young lambs using T.B.F. rather than CY as a potential suppressive agent. Five days after T.B.F. infection, S.aureus contaminated ticks were allowed to attach and engorge upon the lambs. At necropsy, abscesses from which S.aureus was recovered, were present in the lungs and livers of lambs given T.B.F. and exposed to contaminated ticks, but not in controls which were only exposed to contaminated ticks. This is believed to be the first experimental production of tick pyaemia in lambs using the sheep tick I.ricinus as a mechanical vector of S.aureus.Control of I.ricinus is traditionally by whole body immersion in acaricidal preparations; however more recently synthetic pyrethroid pour-on formulations have been available. Field trials to assess the efficacy of two synthetic pyrethroid pour-on products are described. Tick counts were performed on treated and control lambs and hoggs, disease levels assessed and other effects of the treatment monitored. Results indicate a degree of tick control was achieved , but disease problems still occurred

Hotspots of Biased Nucleotide Substitutions in Human Genes

Genes that have experienced accelerated evolutionary rates on the human lineage during recent evolution are candidates for involvement in human-specific adaptations. To determine the forces that cause increased evolutionary rates in certain genes, we analyzed alignments of 10,238 human genes to their orthologues in chimpanzee and macaque. Using a likelihood ratio test, we identified protein-coding sequences with an accelerated rate of base substitutions along the human lineage. Exons evolving at a fast rate in humans have a significant tendency to contain clusters of AT-to-GC (weak-to-strong) biased substitutions. This pattern is also observed in noncoding sequence flanking rapidly evolving exons. Accelerated exons occur in regions with elevated male recombination rates and exhibit an excess of nonsynonymous substitutions relative to the genomic average. We next analyzed genes with significantly elevated ratios of nonsynonymous to synonymous rates of base substitution (dN/dS) along the human lineage, and those with an excess of amino acid replacement substitutions relative to human polymorphism. These genes also show evidence of clusters of weak-to-strong biased substitutions. These findings indicate that a recombination-associated process, such as biased gene conversion (BGC), is driving fixation of GC alleles in the human genome. This process can lead to accelerated evolution in coding sequences and excess amino acid replacement substitutions, thereby generating significant results for tests of positive selection

Learning Through Drawing

Learning Through Drawing 2015 Drawing is a fundamental communication tool and also the way in which an idea is developed and explored. Being able to make a mark on a piece of paper or the back of an envelope is often the starting point and an aid to discussion. An architectural student is taught how to draw but are they taught to “think through the pencil” and explore ideas and solve design issues through drawing and re draw to refine an outcome? As studio tutors we raised several questions: 1. At what point do architecture students realise the number and types of drawings made, from concept design through to completion? 2. When did we, as architects, first become aware of the complete design journey, resulting in the finished building? 3. Would exposure to the whole body of drawings made for a single case study give the student a greater insight into the methodology of working and thinking more thoroughly, reflectively and critically? 4. Would it allow a student to apply this method to the way they explore their design projects and give them confidence in the process before reaching the real world scenario

Teleporters, tunnels & time : Understanding warp devices in videogames

Catchment land uses, particularly agriculture and urban uses, have long been recognized as major drivers of nutrient concentrations in surface waters. However, few simple models have been developed that relate the amount of catchment land use to downstream freshwater nutrients. Nor are existing models applicable to large numbers of freshwaters across broad spatial extents such as regions or continents. This research aims to increase model performance by exploring three factors that affect the relationship between land use and downstream nutrients in freshwater: the spatial extent for measuring land use, hydrologic connectivity, and the regional differences in both the amount of nutrients and effects of land use on them. We quantified the effects of these three factors that relate land use to lake total phosphorus (TP) and total nitrogen (TN) in 346 north temperate lakes in 7 regions in Michigan, USA. We used a linear mixed modeling framework to examine the importance of spatial extent, lake hydrologic class, and region on models with individual lake nutrients as the response variable, and individual land use types as the predictor variables. Our modeling approach was chosen to avoid problems of multi-collinearity among predictor variables and a lack of independence of lakes within regions, both of which are common problems in broad-scale analyses of freshwaters. We found that all three factors influence land use-lake nutrient relationships. The strongest evidence was for the effect of lake hydrologic connectivity, followed by region, and finally, the spatial extent of land use measurements. Incorporating these three factors into relatively simple models of land use effects on lake nutrients should help to improve predictions and understanding of land use-lake nutrient interactions at broad scales

Coming out of COVID-19

Following the disruption of the pandemic, Missing in Architecture call for a radical rethink on how we teach architecture