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Loma salmonae is a microsporidian parasite that infects economically important Chinook salmon (Oncorhynchus tshawytscha) farmed in British Columbia, Canada. Here a variety of research efforts aimed at improving early detection and diagnostic tools, developing preventative strategies, and increasing understanding of the parasite/host interactions are presented. First, the development of chicken-derived polyclonal antibodies (IgY) specific for L. salmonae is described. These antibodies have proven useful for immunohistochemical detection of parasites very early in the infection process. Next, the immune-modulating effects of intra-peritoneal β-glucan inoculation of Chinook salmon are presented. Intensity of L. salmonae infection was significantly reduced in fish inoculated with β-glucan 3 weeks prior to parasite exposure, although prevalence was not reduced in these fish. Gene expression analysis of head kidney from glucan-inoculated fish measured at 1, 2 and 3 weeks post-inoculation (PI) revealed that the majority of differential expression occurred at 1 week. Pathways related to antioxidant defence, innate immune responses, antigen presentation, as well as oxidative metabolism were up-regulated in glucan-inoculated fish at 1 week PI. Finally, temporal gene-expression analysis on gill and kidney tissue from Chinook salmon infected with L. salmonae is described. Analysis at 4 weeks post-exposure (PE) in the gill revealed an early up-regulation of gas transport, whereas numerous pathways including oxidative metabolism, antioxidant defences, monooxygenases and immune receptors were down-regulated in the gill at the same time point. Similarly, oxidative metabolism, antioxidant defences, and monooxygenases were down-regulated in the kidney at 4 weeks PE. However, there is evidence for a developing immune response over time. Antigen processing and presentation pathways were up-regulated in the kidney at 4 weeks and in both tissues at 8 weeks PE. In addition a number of immune receptors and genes involved with innate immune functions were also up-regulated at 4 and 8 weeks PE in the kidney. / Graduate / 0306

This thesis investigates the ecological determinants of chewing louse (Insecta: Phthiraptera) host-specificity on four species of Malaysian swiftlets (Aves: Apodidae). Influences of host coloniality on louse ecology were also demonstrated, illustrating the dependence which these permanent ectoparasites have on their hosts. Louse collections were made to look for incidences of host-specific lice occurring on the "wrong" host ("straggling"). Straggling was observed, implying that lice disperse among host species. Thus, opportunity for louse dispersal (or lack thereof) does not govern the host-specificity of chewing lice on swiftlets. Experimental transfers of lice between hosts were conducted. Louse survival was reduced on foreign host species. This implies adaptation to specific host characters, suggesting that specialisation governs chewing louse host-specificity on swiftlets. There was no evidence for reciprocal adaptation of swiftlets to their normal louse species. Lice had no impact on the fitness of either swiftlets or the related common swift. Furthermore, neither swiftlet nor swift lice were transmitting pathogenic endoparasites. This implies that chewing lice and Malaysian swiftlets have not "coevolved". Survival of transferred lice was determined by the relatedness of donor and recipient hosts. Closer related swiftlet species are more similar in body size and feather dimensions. When the feather dimensions of the microhabitat distributions of the same louse species on different hosts were compared the results suggested that lice keep the dimensions of barb and barbule diameter, at which they occur, "constant" through microhabitat shifts. This suggests that feather dimensions are the host characters which determine the survival (and host-specificity) of chewing lice on birds. The ability of chewing lice to survive on hosts with similar feather morphology implies that "host-switching", between distantly related hosts with similar morphological characters (due to parallel or convergent host evolution), may have been an important factor in the evolution of bird-louse associations.

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In this study, data collected in a survey of Scottish sheep farmers was used to corroborate and augment secondary data available in the literature on sheep ectoparasites and their control in 1999/2000.  The data was used to design and construct a decision tree model, which was used to determine probability weighted profit-maximising control strategies for six flock types/size groups that were representative of Scottish sheep farms.  Organophosphate (OP) based dips, applied in both the autumn and spring/summer, were found to be the profit-maximising control strategy for five flock types/size groups.  The exception was for small (100-ewe) lowground flocks, where two applications of cypermethrin in pour-on formulation maximised the avoidable disease losses. Each of these strategies can give rise to animal welfare, human health and /or environmental externalities.  OP dips can damage human health and the environment but minimise animal welfare losses, and cypermethrin pour-on, while non-damaging to human health and the environment, can result in some avoidable welfare losses, as ectoparasite control is less effective than for OP dips. Using multi-criteria analysis (MCA), the economics of sheep ectoparasite control from a social standpoint has also been examined.  Some profit-maximising control strategies do not necessary maximise social benefits.  A conflict can arise between the farmer and society.  The minimum cost that society would need to be willing to accept in order to finance possible incentives for sheep farmers to switch from the profit-maximising control strategy to strategies that provide different bundles of social benefits is estimated.

This research involved survey, laboratory and field studies. First, an evaluation of the present status of intestinal parasitic infections was made in the Jordanian population. Second, laboratory investigations were conducted on the development of a new technique to detect the viability of Ascaris eggs. Third, field studies were carried out to investigate the survival and occurrence of indigenous parasite eggs and indicator pathogens in domestic waste sludges in Jordan. Field investigations were also conducted on the effect of open natural drying beds on the inactivation of parasite eggs and bacterial pathogens. The results of this study and a survey of available literature indicated a need for a universally accepted definition of a "viable" Ascaris egg. A staining technique for detecting Ascaris egg viability was developed in conjunction with research studies of Ascaris eggs in sludge. The vital stain Crystal violet showed high correlation with the incubation method, and was more precise than the other stains tested. Crystal violet showed the best spontaneous detection of changes in egg viability and, within certain limits, it was found to be a strong indicator of the state of egg viability; furthermore it did not show any evidence of toxicity. In the staining method, Crystal violet stain is added directly to an egg preparation and observations are then made immediately using a light microscope. The results are available in only 10 minutes, compared to the 30 days required for the Incubation method. Since only stained or unstained eggs were observed, the method is less subjective than the Incubation method. In order to evaluate the versatility of the staining method, the effect of UV light and temperature was also investigated. The ultimate disposal of domestic wastewater treatment plant sludges has been recognised recently as a problem in Jordan, and has never previously been investigated from the point of view of pathogen survival and transmission. This study showed that a huge volume of sludge (36,600 m3 dry weight basis) accumulated from 1985-1993 in six anaerobic ponds, now requires desludging, treatment and disposal. Anaerobic pond sludges displayed some physico-chemical similarities to digested primary sludge. This research concludes that sludge drying beds can be an effective method for inactivating parasite eggs, particularly in warmer geographic locations, and thus the treated sludge can be considered safe in terms of parasite transmission for application to agricultural land. Ascaris eggs had degenerated when the percentage of total solids was recorded as more than 88%; this took a shorter time in sand than in gravel drying beds. The inactivation of Ascaris eggs in drying beds is probably due to more factors than desiccation alone. Temperature, oxygen content, solar radiation, exposure time, mould activity, type of sludge, type of media etc., may also affect survival of the eggs. Anaerobic pond sludge bacterial counts showed higher resistance to desiccation and treatment conditions in drying beds compared with oxidation ditch sludge.

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No description available.

No description available.

Cyathocotyle bushiensis and Sphaeridiotrema globulus were previously implicated in the annual mortality of wild ducks in southern Quebec. Of 21 snail species collected from nine aquatic communities in southern Quebec and southeastern Ontario, May to October 1989 and 1990, only Bithynia tentaculata was heavily and consistently infected with C. bushiensis metacercariae. Although infection levels varied spatially, a consistent concave seasonal pattern of prevalence and abundance was found which may be due to overwintering metacercariae and the almost simultaneous onset of cercarial transmission and recruitment of new snails in mid-summer. Even though S. globulus metacercariae were found in 18 of 21 snail species, B. tentaculata is believed to contribute most to transmission to ducks. The variety of seasonal patterns and large scale spatial heterogeneity in the prevalence and abundance of S. globulus suggested that cercariae may be from more than one source. Some of the spatial variation in metacercarial levels may be due to small scale processes; extensive spatial heterogeneity at a scale of 10 m was detected in S. globulus cercarial transmission to sentinel snails. This small scale heterogeneity may be due to B. tentaculata having small home ranges as suggested by mark-recapture studies on movement. In aquaria, even though smaller B. tentaculata were more active than larger ones and intraspecific microhabitat preferences were found, preliminary results from ducks (Anas discors) feeding on snail communities in pools suggested that snails are ingested in proportion to their presence. Therefore, the importance of a snail species or size class in the transmission of the two parasites to ducks may depend only on its density and metacercarial abundance. Finally, another mode of transmission is proposed for S. globulus: ducks may become infected by consuming empty snail shells containing viable cysts.