Les canidés et félidés peuvent être hôtes définitifs d’Echinococcus multilocularis, Toxoplasma gondii ou Toxocara spp., parasites responsables de zoonoses transmissibles par l’alimentation. La consommation crue de fruits et légumes porteurs de leurs œufs ou oocystes peut être source de contamination humaine. Cette étude visait à évaluer et caractériser le risque d’exposition humaine lié au dépôt de fèces de chats, chiens et renards dans les terrains potagers localisés en régions d’endémie. Ce dépôt s’est avéré important dans certains potagers des Ardennes. De plus, l’ADN d’E. multilocularis et Toxocara spp. a été détecté dans 1/3 des fèces collectées et 23 % des rongeurs piégés autours des potagers ont été trouvés infectés par au moins un des parasites d’intérêt, confirmant le risque d’exposition des hôtes intermédiaires. Parallèlement, l’identification précise des facteurs responsables du dépôt de fèces de carnivores a été conduite sur 192 potagers familiaux ou professionnels des Ardennes et de la Moselle. Au total, 1016 fèces de carnivores (59% de chats, 31% de renards et 10% de chiens) ont été collectées au cours de huit sessions de prospection. Par modélisation, nous avons montré que la présence d’une clôture limite très efficacement le dépôt de fèces de renard, tandis que la présence de rongeurs ou d’arbres fruitiers à proximité le favorise. Enfin, la mise au point d’une méthode sensible a permis la détection de l’ADN d’E. multilocularis et Toxocara spp dans 42 % et 12 % des terrains potagers. Au final, l’exposition humaine aux parasites étudiés semble élevée dans certains potagers. Des mesures de prévention basées sur les résultats de l’étude sont proposées. / Canids and Felids can be definitive hosts of Echinococcus multilocularis, Toxoplasma gondii and Toxocara spp., which are food-borne parasites responsible of zoonoses. The consumption of raw fruit or vegetables carrying their eggs or oocysts can be source of human contamination. This study aimed to assess and characterize the risk of human exposure linked to the faecal deposition by cats, red foxes and dogs in kitchen gardens located in endemic areas. This deposit was found to be important in some kitchen gardens located in the Ardennes region. Furthermore, DNA of E. multilocularis and Toxocara spp were detected in 1/3 of the collected faeces and 23% of the rodents trapped in kitchen gardens proximity were found infected with at least one of the canids or felids parasites, confirming the risk of intermediate host exposure. Concurrently, the accurate identification of factors responsible for carnivore faeces deposit was conducted from eight prospection sessions of 192 kitchen gardens, family or professional ones, located in the Ardennes and Moselle regions. A total of 1016 carnivore faeces (59% from cats, 31% from foxes and 10% from dogs) were collected. By using models to test the effect of various variables on faeces deposit, we showed that fencing efficiently limits fox faeces deposit whereas presence of rodents or fruit trees in the vicinity increases it. Finally, thanks to the development of a sensitive method, E. multilocularis and Toxocara spp. DNA was detected in 42% and 12% of the kitchen gardens. In conclusion, the human exposure to canids and felids foodborne parasites seems high in certain kitchen gardens. Prevention methods are proposed based on our results.

The rosy apple aphid Dysaphis plantaginea (Passerini) (Homoptera: Aphididae) is the most serious pest apple aphid in view of the scale of damages inflicted to the fruits by a small number of individuals. Although numerous natural enemies have been associated with D. plantaginea, they are unable to halt infestations soon enough in most commercial apple orchards obliging fruit growers to control it chemically to prevent severe economic losses. In order to reinforce the contribution of indigenous aphidophaga in regulating rosy apple aphids, the use of insectary plants selected to support two groups of specialist aphid antagonists, notably aphid parasitoids and aphidophagous monovoltine syrphids, was investigated. 1. A first step consisted in selecting appropriate plant species. The rowan tree Sorbus aucuparia L. and the common elder Sambucus nigra L. were selected for their ability to support substitute aphids for the rosy apple aphid parasitoid E. persicae Froggatt (Hymenoptera: Braconidae, Aphidiinae) and monovotine syrphids (Diptera: Syrphidae) respectively. 2. Next, trials were conducted to induce substitute aphid infestations on their host plants by introducing eggs of Dysaphis sorbi Kaltenbach on rowan and small colonies of Aphis sambuci L. on elder. The resulting aphid populations which developed on their respective host plants in spring proved to be exploited by the natural enemies expected, i.e. E. persicae and monovoltine syrphids of the genus Epistrophe. Besides, diapause mummies of E. persicae and diapausing last-instar Epistrophe larvac were recorded on rowan and in the elder litter respectively, indicating the successful settlement of the antagonists in the orchard environment. A complementary investigation devoted to syrphid adults indicated that females of all species recorded ovipositing on the eider shrubs, including Epistrophe spp. had consumed a large majority of apple pollen grains as a protein source required for egg maturation. 3. To comfort our choice in the two groups of aphidophaga considered, a study dedicated to their respective phenology versus the one of D. plantaginea showed that they could both potentially halt rosy apple aphid infestations by attacking the aphids while the latter still occupied the primary, fundatrix-induced rosette leaf colonies, i.e. a critical moment in rosy apple aphid control. 4. Finally, marking methods were tested to label E. persicae internally and the egg load of gravid syrphids. These trials were intended to pave the way towards future mark-release-recapture experiments aimed to evaluate the antagonists’ activity range and thus strategically position the insectary plants for optimal aphid biological control in the whole orchard. The first step of new approach in the biological control of D. plantaginea has been set with this study. Its originality lies in the induction of economically indifferent aphid infestations on selected plants introduced in the orchard to encourage well-targeted groups of specialist aphid antagonists. Further trials are still needed to validate the field efficacy of the insectary plant systems developed and evaluate their possible integration within the whole array of pest management tools in both organic and integrated apple production. / Doctorat en sciences, Spécialisation biologie animale / info:eu-repo/semantics/nonPublished

Les invasions biologiques produisent des assemblages d'espèces souvent inédits et sources de nouvelles interactions spécifiques. L'impact écologique d'une invasion peut être : (i) indirect si l'espèce envahissante entre en compétition avec une ou des espèces résidentes, et (ii) direct si l'espèce envahissante consomme ou parasite une ou des espèces résidentes. Ces deux types d'impacts sont susceptibles de s'appliquer aux insectes envahissants du genre Megastigmus (Hymenoptera: Torymidae), qui exploitent généralement une niche étroite partagée avec d'autres espèces résidentes, et contribuent à d'importantes mortalités dans les populations d'hôtes du fait de leur spécialisation sur les graines. L'objectif de cette thèse est de tester ces prédictions à travers l'étude de l'impact de l'invasion en France de Megastigmus schimitscheki sur : (i) M. pinsapinis, un compétiteur résident, et (ii) les populations en expansion de son hôte obligatoire, le cèdre de l'Atlas (Cedrus atlantica).Un suivi spatio-temporel des populations françaises de Megastigmus spp. révèle que l'expansion rapide de M. schimitscheki est associée à un déclin important de M. pinsapinis. Un modèle mécaniste et statistique a été développé afin de déterminer la contribution relative de la variabilité temporelle de la disponibilité en graines et des divergences de traits d'histoire de vie dans la dynamique de coexistence-exclusion de M. schimitscheki et M. pinsapinis. Nos résultats montrent que la phénologie plus précoce de M. schimitscheki est le principal facteur déterminant le succès de l'invasion de M. schimitscheki et l'exclusion compétitive de M. pinsapinis dans les zones de sympatrie des deux espèces.Nous avons développé une approche théorique de l'impact indirect de M. schimitscheki sur C. atlantica basée sur les modèles de réaction-diffusion. Nos résultats montrent qu'un effet Allee résultant de la prédation des graines sur un front d'expansion peut accroître la contribution des hôtes situés à l'arrière de ce front au pool génétique de la population. Ce phénomène a pour conséquence de freiner l'érosion de la diversité génétique au cours du processus de colonisation.Les approches expérimentales et théoriques développées au cours de cette thèse montrent que l'invasion de M. schimitscheki a un impact indirect négatif sur la démographie d'une espèce résidente occupant la même niche écologique, alors qu'elle pourrait favoriser directement le maintien de la diversité génétique des populations d'hôtes en pleine dynamique de régénération naturelle. / Biological invasions produce novel species assemblages in communities that likely result in novel interspecific interactions. Ecological impacts of invasions may be: (i) indirect, if the invader enters competition with resident species, and (ii) indirect if the invader is a predator or a parasite of resident species. Both indirect and direct ecological invasion impacts are likely to apply to invasive wasps of the Megastigmus genus (Hymenoptera: Torymidae), which exploit narrow ecological niches that overlap with those of resident insect species, and contribute to high mortality levels in host plant populations due to their high specialization on seeds. This thesis aimed at testing such predictions by studying the impacts of the invasion of M. schimitscheki on: (i) its resident competitor for the seed resource M. pinsapinis, and (ii) the expanding populations of its obligatory host the Atlas cedar (Cedrus atlantica) in southeastern France.An extensive spatio-temporal survey of Megastigmus spp. populations indicated that the rapid expansion of M. schimitscheki was associated with a strong decline of M. pinsapinis. A mechanistic-statistical modelling approach allowed us to show that an earlier phenology of M. schimitscheki had a stronger explanatory power of both invasion success and the competitive exclusion of the resident than temporal variation in resource supply.A theoretical approach of the indirect impact of M. schimitscheki on C. atlantica expansion dynamics was based on reaction-diffusion models. We showed that an Allee effect resulting from seed predation at the expansion front of a host population may increase the genetic contribution of host individuals situated in the bulk of the expansion front. Interestingly, this phenomenon results in a limited erosion of genetic diversity during the expansion phase of the host population.The empirical and theoretical approaches developed showed that the invasion of M. schimitscheki in French cedar forests had a strong and negative indirect impact on the demography of a resident species, but, parallely, such invasion may directly favour the maintenance of genetic diversity in expanding host plant populations.

No description available.

The study of social evolution and virulence in parasites is concerned with fitness consequences of trade-offs between parasite life history traits and interactions between parasite species and/or genotypes with their hosts. I develop our understanding of social evolution and virulence in parasites in several ways. (1) I review empirical evidence for the fundamental predictions of virulence-transmission trade-off theory and demonstrate that the fit between theory and data is primarily qualitative rather than quantitative; that parasites differ in their degree of host generalism, and this is likely to impact virulence in four ways. (2) I take a comparative approach to examine the underlying causes of an observed statistical variation in the size of parasite infectious doses across taxa, revealing that mechanisms used by parasites to infect hosts are able to explain variation in both infectious dose and virulence. (3) I formally compare data on human pathogens to explain variation in virulence across taxa, revealing that immune subversion and not growth rate, explains variation in virulence. This allows me to predict that immune subverters and not fast growing parasites are likely to cause the most virulent clinical infections. (4) Using bacteria and their naturally infecting viruses (bacteriophage), I take an experimental approach to investigate the consequences of coinfection for parasite life history traits, and find that viruses cultured under a mix of single infections and coinfections evolved plasticity; they killed hosts more rapidly when coinfecting, and this resulted in high fitness under both single infection and coinfection conditions. (5) I experimentally investigate how selection within and between hosts and patches of hosts affects the fitness and virulence of populations of these viruses. I find that limited host availability favours virulent, faster killing parasites with reduced transmission; suggesting high, rather than low, virulence may be common in spatially structured host-parasite communities.

Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2007. / Honeybee queens typically inhibit the reproductive development of workers in the colony. However, African, Apis mellifera scutellata, honeybee queens seem to have little effect on neighbouring A. m. capensis honeybee workers as is evident in the huge losses of African honeybee colonies due to the invasion by ‘social parasitic’ Cape honeybees (pseudoclones). Certain factors; such as queen and brood presence, the level of colony defence and food availability may render host colonies more vulnerable to invasion by the Cape worker honeybees. In this study host African colonies were split to determine whether a “window of opportunity” existed for Cape honeybee infiltration and thus critical to the capensis problem. Nine African colonies were infected with native and pseudoclone Cape workers over different time periods; before, during and after splitting (treatments). I measured survival rates, as well as reproductive and pheromone development of introduced workers. The effect of brood pheromones on Cape worker reproduction was also examined. Approximately 70% of all workers were removed within 72 hours, a critical period to avoid detection by Cape workers. Queen absence significantly affected the success rate of intrusion and establishment by Cape honeybee workers (GLZ; Wald χ² = 4.49, df = 1, P = 0.033). 21% of 21-day old pseudoclones survived African queenless colonies and only 6% queenright colonies. Native Cape workers showed no difference in survival rates between African queenless (12%) and queenright (11%) colonies. Looking at introduction time, considerably more pseudoclone honeybee workers survived in treatment 1 than did native Cape honeybee workers while for treatment 3 the converse was true. These data show no obvious ‘window of opportunity’ surrounding the swarming process promoting Cape honeybee infiltration and establishment of African honeybee colonies, however the period immediately prior to colony fission represents the best opportunity for invasion by pseudoclones. As for ovary and mandibular gland secretion development, all surviving pseudoclones, irrespective of A. m. scutellata queen presence, fully developed their ovaries and concomitantly produced a mandibular gland secretion dominated by 9- oxo-2-decenoic acid (9ODA). Native Cape workers showed low levels of ovary development in queenright host colonies (8-17%) but this was not true for queenless colonies, with all but one worker developing their ovaries when introduced during and after splitting. Only 40% of native Cape workers introduced before splitting developed their ovaries suggesting that queen pheromones in the three days before splitting retarded ovary development in native Cape workers. These data strengthens the suggestion that the pseudoclone honeybee workers have advanced along the queen-worker developmental continuum. Preliminary studies on brood pheromones, an important factor regulating worker reproduction, indicated that Cape workers reproduce quicker and more eggs when exposed to African brood pheromones, compared to both A. m. capensis brood pheromones and no brood pheromones. Pheromones produced by African larvae therefore do not simply inhibit Cape worker reproductive development but accelerate the commencement of egg laying by these workers. On the whole, host African colonies, especially in the absence of their queen, appear vulnerable surrounding colony fission to invasion by both Cape honeybee worker populations even though there are low survival rates. I conclude that these two Cape honeybee worker populations do differ significantly regarding their reproductive capacity and ability in becoming social parasites.

Thesis (PhD (Botany and Zoology))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Insect societies utilize advanced chemical communication systems to organize many aspects of their social life, which among others, include reproduction, thus maintaining colony homeostasis. The queen pheromone complex (QMP), dominated by (E)-9-keto-2-decenoic acid (9ODA) is of integral importance in regulating worker reproductive development. Unique characteristics, associated with reproductive dominance, enabled the successful establishment of Apis mellifera capensis workers as social parasites (or pseudoqueens) in colonies of the neighbouring A. m. scutellata. This suggested that producing a queenlike pheromonal bouquet is one of the proximate factors in their success. In this study we attempted to address the pheromone communication dilemma by investigating whether the phenotypic expression of mandibular gland signals in honeybee workers are under genetic and/or environmental influence. It was hypothesized that the mandibular gland profiles of queens and workers may be closely correlated to specific genotypes in the colony. However, different ageing and rearing environments (social context) can ultimately influence gene expression with respect to mandibular gland signals, highlighting the fact that environmental influences are not necessarily non-significant. In our experiments, both environmental/social conditions and genotypes of our test individuals were manipulated. The capensis workers used in our experiment from their native range (Western Cape area are refered to as native workers, while capensis parasitic workers, from the clonal parasitic lineage, were obtained from the Gauteng area. A. m. scutellata workers were obtained from their native range, north of the hybrid zone. Both native and parasitic workers showed the potential to become reproductively active, but the rapid pheromonal development of parasitic workers placed them at a reproductive advantage. Parasitic workers started producing low levels of 9HDA, the precursor to the queen substance 9ODA, between 12-24 hrs, while native workers only did so after 24 hrs. Despite this, rapid signal development did not culminate in the parasitic clones always pheromonally out-competing native workers. Withinin groups of native workers and a single clonal parasitic worker, the mandibular gland profiles of most workers were dominated by 9ODA and 9HDA (> 80% of extracts) with only 43% of the single parasitic workers producing higher amounts of 9ODA than native workers. Mandibular gland pheromone profiles converged in groups of workers sharing a greater proportion of genes, providing support for a link to genotypic affects. Workers that were 75 – 99% related diverged significantly from groups with lower levels of relatedness was largely due to the presences of 9ODA (Spearman’s rank correlation r = 0.66, p < 0.0001). Despite the tendency for signal to convergence in groups of closer relatedness a considerable amount of signal variability was also observed under varying social conditions. Workers originating from a single capensis queen but aged under queenright and queenless conditions had very distinct mandibular gland profiles (Wilks’ lambda λ = 0.118, χ2 = 331.002, p < 0.0001). This variability was thus a result of the social environment that the workers were exposed to. The physiological traits, namely mandibular gland pheromone production, linked to reproductive potential in honeybee workers seem to be determined by a combination of environmental and genetic factors. Queen mandibular gland pheromone biosynthesis is genetically predisposed in certain workers however the final oxidation step to 9ODA is strongly influenced by the social environment. The signal plasticity observed in this study is adaptive and assists workers to realize their reproductive potential. / AFRIKAANSE OPSOMMING: Insek gemeenskappe gebruik gevorderde chemiese kommunikasie sisteme om verskeie aspekte van sosiale lewe, onder andere reproduksie, te organiseer en sodoende word korf homeostasis handhaaf. Die feromoon kompleks van die koninginby, wat hoofsaaklik uit (E)-9-keto-2-decenoic acid (9ODA) bestaan speel ʼn belangrike rol in die regulering van reproduksie in heuningby werkers. Die suksesvolle vestiging van Apis mellifera capensis werkers as sosiale parasiete (pseudo koninginne) in die korwe van die naburige A. m. scutellata, is bewerkstellig deur hul unieke kenmerke, wat met reproduktiewe oorheersing verband hou. Dit suggereer dat die produksie van ʼn tipiese koningin feromoon sein een van verskeie beduidende faktore is in capensis werkers se sukses. In hierdie studie het ons die dilemma van feromoon kommunikasie probeer aanspreek deur te ondersoek of die fenotipiese uitdrukking van seine van die mandibulêre kliere deur genetiese en/of omgewings faktore beïnvloed word. Die hipotese was dat die mandibulêre klier profiele van koninginne en werkers korreleer met spesifieke genotipes in die korf. Die verskillende omgewings waarin werkers groot gemaak word en verouder (sosiale konteks), kan uiteindelik die uitdrukking van gene, raakende mandibulêre kliere, beïnvloed. Dit beklemtoon die feit dat omgewings faktore nie noodwendig onbeduidend is nie. Beide omgewings/sosiale toestande and genotipes van toets individue is in ons eksperimente gemanipuleer. Die capensis werkers afkomstig uit hul natuurlike habitat (Weskaap area) wat in ons eksperimente gebruik is word na verwys as inboorling werkers, terwyl parasitiese capensis werkers, van klonies parasitiese afkoms, vanuit die Gauteng area verkry is. A. m. scutellata werkers was vanuit hul natuurlike habitat, noord van die, hybried sone, verkry. Beide inboorling en parasitise werkers het die potensiaal getoon om reproduktief aktief te word, maar versnelde feromoon ontwikkeling van parasite werkers het hulle ʼn reproduktiewe voordeel gegee. Parasiet werkers het reeds lae hoeveelhede 9HDA, die voorganger van 9ODA, begin produseer tussen 12 – 24 uur, terwyl inboorling werkers produksie eers na 24 uur begin het. Ten spyte van die versnelde ontwikkeling in parasiet werkers het dit nie gelei daartoe dat kloniese parasiete altyd feromonies die oorhand oor inboorling werkers gekry het nie. In groepe bestaande uit inboorling werkers en ʼn enkele parasite werker, was die mandibulêre klier profiele altyd deur 9ODA en 9HDA (> 80% van ekstrakte) gedomineer. Slegs 43% van parasite werkers het groter hoeveelhede 9ODA as inboorling werkers geproduseer. In groepe werkers, wat ʼn groter proporsie gene in gemeen gehad het, het mandibulêre klier profiele konvergeer. Dit ondersteun die bestaan van ʼn verband met genotipiese invloed. Werkers van 75 – 99% verwantskap het beduidend verskil van groepe met laer verwantskapsvlakke, hoofsaaklik as gevolg van die teenwoordigheid van 9ODA (Spearman’s rank korrelasie r = 0.66, p < 0.0001). Ten spyte van die konvergerende neiging van profiele, van meer verwante groepe, was aansienlike veranderlikheid onder verskillende sosiale toestande waargeneem. Werkers, afkomstig vanaf ʼn enkele capensis koninginby, maar òf in die teenwoordigheid òf afwesigheid van ʼn koningin verouder is, het baie kenmerkende mandibulêre klier profiele getoon (Wilks’ lambda λ = 0.118, χ2 = 331.002, p < 0.0001). Die veranderlikheid was dus ʼn gevolg van die sosiale omgewing waaraan die werkers blootgestel was. Dit blyk asof die fisiologiese kenmerke wat met reproduksie potensiaal in heuningbye verband hou, naamlik mandibulêre klier feromoon produksie, deur ʼn kombinasie van genetiese – en omgewings faktore beïnvloed word. Sekere werkers is meer geneig tot die biosintese van koningin mandibulêre klier feromoon as gevolg van hul genetika, terwyl die finale oksidasie na 9ODA onder sterk omgewings invloed is. Die plastisiteit in mandibulêre seine waargeneem in hierdie studie, is aanpasbaar en help werkers om hul reproduksie potensiaal te bereik.

<p>Användandet av obehandlat avloppsvatten inom jordbruket är en växande företeelse i många delar av världen. Speciellt i vattenfattiga områden där avloppsvattnet ses som en värdefull och pålitlig resurs. Det höga näringsinnehållet minskar behovet av konstgödsel och detta ökar böndernas inkomster. Men med användandet av avloppsvattnet följer vissa hälsorisker. Bland annat har man sett en högre förekomst av inälvsmaskar hos bönder som använder orenat avloppsvatten jämfört med de som använder rent vatten. Den här vattenkvalitetstudien har utförts längs floden Musi i Andhra Pradesh, Indien. Musi rinner igenom staden Hyderabad och mycket av stadens avloppsvatten dumpas i floden. Nedströms Hyderabad används detta vatten för bevattning. Längs med floden är dammar byggda, för att avleda vattnet i bevattningskanaler. Reservoirer bildas då flödeshastigheten minskar. Studieområdet sträcker sig från Hyderabad och 28.7 km nedströms. Hypotesen var att reservoirerna fungerar som biodammar och syftet var att kvantifiera dammarnas inverkan på vattenkvaliteten och utvärdera dess lämplighet utifrån ett hälso- och jordbruksperspektiv. Inom studieområdet är reningen med avseende på BOD, Nematoder och E coli 86,9%, 99,9% respektive 99,9%. Trots att reningen är så hög överstiger Nematod- och E coli-koncentrationerna Världshälsoorganisationens riktlinjer och utgör en hälsorisk för bönder och konsumenter. Syre- och salthalt ökar nedströms och den höga salthalten kan ha negativ inverkan på jordbrukets avkastning. Genom att titta på reningsmönster och förändring av olika vattenkvalitetsparametrar är en av slutsatserna av detta arbete att reningen i dammarna motsvarar den rening som sker i de anaeroba bassängerna i ett biodammsystem.</p> / <p>The use of untreated domestic sewage in agriculture is a growing practice in many parts of the world. It is being looked upon as a valuable and reliable resource in water scarce communities. Wastewater is usually rich in nutrients and the use results in high yields without the need for artificial fertilisers. But with the use of untreated wastewater follows a number of associated health risks, e.g. a higher prevalence of helminth infections has been seen among wastewater users compared to non-users. This water quality study was performed along the River Musi in Andhra Pradesh, India. The Musi River flows through the city of Hyderabad carrying the most of the town’s wastewater. Downstream of Hyderabad the wastewater is used by farmers for irrigation. Along the river weirs are constructed which diverts the irrigation water into canals and reservoirs are formed where the flow velocity slows down. The study area stretches from Hyderabad and 28.7 km downstream. The hypothesis was that the existing irrigation infrastructure acts like Wastewater Stabilisation Ponds and the aim was to quantify the impact of the weirs on water quality and to evaluate the irrigation water quality in reference to associated health risks and agricultural suitability. Within the study area the BOD, E coli and Nematode removals were 86.9%, 99.9% and 99.9% respectively. Despite the high removal the E coli and Nematodes, the concentrations exceed WHO guidelines for unrestricted and restricted irrigation, and there exists an excess risk of intestinal nematode- and enteric infections for farmers. Dissolved oxygen and salinity increases downstream and due to the high salinity farmers could experience reduced crop yields. By looking at removal patterns, and the change in water quality parameters, the conclusion can be made that the reservoirs act like anaerobic ponds in a Wastewater Stabilisation Pond system.</p>

This thesis presents an investigation into Gyrodactylus species recognition, making use of machine learning classification and feature selection techniques, and explores image feature extraction to demonstrate proof of concept for an envisaged rapid, consistent and secure initial identification of pathogens by field workers and non-expert users. The design of the proposed cognitively inspired framework is able to provide confident discrimination recognition from its non-pathogenic congeners, which is sought in order to assist diagnostics during periods of a suspected outbreak. Accurate identification of pathogens is a key to their control in an aquaculture context and the monogenean worm genus Gyrodactylus provides an ideal test-bed for the selected techniques. In the proposed algorithm, the concept of classification using a single model is extended to include more than one model. In classifying multiple species of Gyrodactylus, experiments using 557 specimens of nine different species, two classifiers and three feature sets were performed. To combine these models, an ensemble based majority voting approach has been adopted. Experimental results with a database of Gyrodactylus species show the superior performance of the ensemble system. Comparison with single classification approaches indicates that the proposed framework produces a marked improvement in classification performance. The second contribution of this thesis is the exploration of image processing techniques. Active Shape Model (ASM) and Complex Network methods are applied to images of the attachment hooks of several species of Gyrodactylus to classify each species according to their true species type. ASM is used to provide landmark points to segment the contour of the image, while the Complex Network model is used to extract the information from the contour of an image. The current system aims to confidently classify species, which is notifiable pathogen of Atlantic salmon, to their true class with high degree of accuracy. Finally, some concluding remarks are made along with proposal for future work.

In total, 76 birds, mainly breeding females, were captured in years 2007-2009. Birds were inspected for the presence of avian influenza (AI) viruses and the AI antibodies. They were inspected as well for the presence of bacteria Borrelia burgdorferi s. l. and Anaplasma phagocytophilum and protozoan Leucocytozoon simondi in blood. The feces were examined for the oocysts and eggs of intestinal parasites. AI viruses were found in 4 cases, while over 80% of inspected birds had AI antibodies. Bacteria B. burgdorferi s. l. and A. phagocytophilum were found in 2 and 1 case respectively. Protozoan L. simondi was not found in any blood smear. The oocysts from protozoan genera Eimeria and Tyzzeria and eggs from roundworm genera Capillaria, Amidostomum and Echinuria were observed in feces. Statistical analyses were due to the small size of our data set inconclusive.