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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Factors affecting infection of soil-transmitted helminths among primary school children in Vientiane, Lao P.D.R. /

Chosa, Michiko, Som-arch Wongkhomthong, January 2000 (has links) (PDF)
Thesis (M.P.H.M. (Primary Health Care Management))--Mahidol University, 2000.
42

The prevalence of helminths in warthogs, bushpigs and some antelope species in Limpopo Province, South Africa

Conradie, Ilana. January 2008 (has links)
Thesis (MSc (Veterinary Tropical Diseases.))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.
43

Influence of hydrocortisone on the susceptibility of chickens to the nematode, Ascaridia galli (Schrank, 1788)

Johnson, John Ronald. January 1962 (has links)
Call number: LD2668 .T4 1962 J65
44

Comparison between migratory behavior of Toxocara canis and Baylisascaris procyonis larvae in orally and parenterally infected mice

Al-Lebban, Huda Mohammad Hussain. January 1979 (has links)
Call number: LD2668 .T4 1979 A431 / Master of Science
45

Effect of X-irradiation (post larvation) on development, mortality and antigenicity of Ascaridia galli (Schrank, 1788)

Ruff, Michael David. January 1966 (has links)
Call number: LD2668 .T4 1966 R923 / Master of Science
46

Appreciating the Importance of Parasites: Analyzing and Understanding the Ecology of Parasite-Host Interactions

O'Brien, Chris January 2008 (has links)
There is a growing interest in the nature of parasite-host interactions, the role these relationships play in ecological communities, and how human activities alter these associations. Furthermore, because inference about these interactions is usually gained by methods of statistical hypothesis testing, additional importance should be placed on the analysis and interpretation of parasite-host interactions. In this dissertation I address these ideas in three separate but interrelated studies with the three following questions: 1) How do two parasites with complex life-cycles alter the behavior of a novel amphipod host, and how do host and non-host predators respond to infected amphipod prey? In contrast to other studies, I found that two parasites of an endemic amphipod at Montezuma Well had little affect on their amphipod host, and that these associations had little affect on predation rates by both host and non-host predators. Results from this study underscore the importance of further investigating novel parasite-host interactions and placing them in their phylogenetic and evolutionary context. 2) Does human recreation affect spatial patterns of infection in an otherwise natural ecosystem? This study demonstrates that human visitors to Montezuma Castle National Monument alter patterns of waterfowl space use that in turn affect spatial patterns of disease in invertebrate hosts. This is the first study to document such an effect, and I discuss the important implications of this finding. 3) How is hypothesis testing applied in studies of wildlife disease, what conclusions can we make about the relative usefulness of these methodologies, and how can the analysis and interpretation of wildlife disease studies be improved? In this final study I conducted a literature review, computed statistical power for methodologies used in the literature, and re-analyzed published data to provide an example of the advantages of my suggested approach. I conclude that many studies report findings using methods that could be more informative and some studies may lack statistical power, demonstrating the importance of using prospective power analysis in the design of future studies. Furthermore, using statistical techniques that estimate the observed effect size can aid in increasing information transfer in studies of wildlife disease.
47

The helminthfauna of the beaver in western Maryland

Joyner, Robert Louis January 1970 (has links)
The objectives were (1) to survey the helminthfauna of the beaver, <i>Castor canadensis</i>, collected in western Maryland, particularly Garrett County, (2) to relate the helminth infections to sex, age, weight, and general condition of the beaver, and (3) to record any evidence of gross pathology involving helminths. A sample of 63 beaver, 31 males and 32 females, was obtained from Garrett, Alleghany, and Washington Counties in Maryland through fur sealing stations and the University of Maryland Natural Resources Institute at LaVale. Five helminths were found. <i>Travassosius americanus</i> infected 98,4%; <i>Castorstrongylus castoris</i>, 96.8%; <i>Stichorchis subtriquetrus</i>, 50.8%; <i>Trichostrongylus</i> sp., 36.5%; and <i>Gongylonema</i> sp., 11.1%. The unknown <i>Trichostrongylus</i> species is probably a new host record, while the <i>Gongylonema</i> sp. confirms a tentative description by another researcher in 1916 who speculated on the description of another researcher from an 1896 report. The 63 beaver surveyed were infected with at least one helminth, with a mean number of worms per infection of 220.49 (±67.52). Infections ranged between 8 and 837 helminths. The combined number of helminths per infection decreased with age; the sex had little effect, except for <i>S. subtriquetrus</i> where the rate was slightly greater in females (59%) than in males (42%). The 1½ to 3 year old beaver appear to have higher mean numbers of worms per infection with <i>T. americanus</i> and <i>C. castoris</i> than do younger or older hosts. <i>Gongylonema</i> sp. Was more prevalent in older beaver where they had a greater mean number of worms. The males and females of the helminth occurred in the esophagus of the beaver embedded parallel to each other in zipper-like burrows which caused severe irritation of the mucosal lining. <i>Gonglyonema</i> sp. Appeared to be the only helminth which had obvious pathology connected with its presence in beaver. / M.S.
48

Significance of cross-reactive antibody responses and isotype bias in malaria-helminth co-infection

Fairlie-Clarke, Karen Jane January 2011 (has links)
The socio-economic and geographical distribution of malaria overlaps with that of many parasitic helminths and in these areas co-infections are common. Co-infection with helminths can influence disease outcome causing either exacerbation or amelioration of malaria. Understanding the complex host-parasite interactions that lead to these different disease outcomes is important for the success of control programmes aimed at these parasites. The immune system has evolved diverse types of response (e.g. T-helper 1 (Th1) and T-helper 2 (Th2)) to efficiently combat infection with ‘microparasites’ and helminths respectively. When faced with co-infection however, the need for the host to multitask means it must manage these counter-regulatory responses. In this study a murine model of malaria-hookworm (Plasmodium chabaudi- Nippostrongylus brasiliensis) co-infection was utilised to investigate how changes in T-helper bias affect malaria disease outcome. Antibody isotypes were used as indicators of Th1/Th2 bias and revealed that helminth co-infection reduced the malaria-specific Th1 response. Counter-intuitively this resulted in ‘protection’ from malaria with co-infected mice having reduced peak P. chabaudi parasitaemia and suffering less severe anaemia. In addition to providing a measure of Th1/Th2 bias, analysis of antibody responses revealed the occurrence of cross-reactive antibodies. The potential for these crossreactive antibodies to influence disease outcome was investigated but in this murine model resource-mediated mechanisms of parasite regulation appear to be responsible for the ‘protection’ that co-infection affords. The question of why cross-reactive antibodies are produced has important immunological and ecological implications. Cross-reactive responses may arise through some physiological constraint on the immune mechanisms that usually result in antibody-specificity. However experiments designed to investigate if the specificity of antibodies is constrained by availability of antigen suggest that this is not the case in the model system used here. There is also the possibility that production of cross-reactive antibodies represents an evolutionary optimal strategy for a host faced with unpredictable exposure to a variety of parasites. However a major finding of this study indicates these two taxonomically distinct parasite species share antigens, which in itself is crucial to understanding host-parasite interactions in a co-infection setting. The main findings of this thesis are relevant to co-infection studies in general and the implications for both evolutionary and applied biology are discussed.
49

Effect of measurement error in the estimation of prevalence of infection and epidemiological associations for helminths

Tarafder, Mushfiqur R. January 2009 (has links) (PDF)
Thesis (Ph. D.)--University of Oklahoma. / Includes bibliographical references.
50

The influence of helminths on immune responses to HIV.

Mkhize-Kwitshana, Zilungile L. January 2009 (has links)
In South Africa, co-infection with HIV and intestinal parasites is a major challenge in disadvantaged communities who live in densely populated under-serviced urban informal settlements. This pilot cross sectional study evaluates the immunological effects of co-infection with Ascaris lumbricoides and Trichuris trichura on the immune response to HIV. The work was a substudy of a prospective double blind, placebo-controlled investigation to test whether regular deworming changes the immune profile of HIV positive individuals with concurrent helminth infection. The substudy has a cross sectional design and presents pilot data that defines immune profiles of HIV-1 positive individuals with and without gastrointestinal helminth (Ascaris lumbricoides and Trichuris trichura) infection. The hypothesis was that concurrent helminth infection adversely affects immune responses against HIV. It was conducted in an area of high helminth endemnicity and limited infrastructural resources. Individuals with known HIV infection were recruited from an HIV Support Group and HIV negative individuals residing in the same area (for demographic matching) were used for comparison. The substudy was to provide pilot data for future larger scale and possible interventional studies. The current work is limited by the cross sectional design, moderate sample size and practical challenges. The profile of lymphocyte phenotypes, viral loads, eosinophils, activation markers, expression of the nuclear proliferation antigen-Ki67 and activation regulator antigen CTLA-4 were analysed using flow cytometry in HIV positive and negative subgroups with or without helminth infection. The type-1, type-2 and inflammatory cytokines were analysed using multiplex cytokine array technology. These were correlated with immune responses to HIV. Non parametric statistics were used to describe differences in the variables between the subgroups. A major finding of the study was the result of the supplementary use of the serological marker, Ascaris lumbricoides-specific IgE in addition to the presence (or absence) of helminth eggs in stools to classify intestinal helminth infection status. Two significant outcomes of this measure were the enhancement of diagnosis of current or recent helminth infection and, more importantly, the distinction of different phenotypes of individuals who displayed different immunological responses to co-infection with HIV and helminths. The different helminth infection phenotypes are defined by stool egg positivity (egg⁺) or negativity (egg⁻) with either high or low Ascaris-specific IgE (IgEhi or IgElo) respectively. The four subgroups, egg⁺IgEhi, egg⁺IgElo, egg⁻IgEhi and egg⁻IgElo showed different interactions with regards to immune response to HIV. It should be noted that no Trichuris specific IgE tests are commercially available but that there is significant antigenic cross-reactivity with Ascaris antigen. The presence of helminth stool eggs and high Ascaris IgE (egg⁺IgEhi) was associated with the following characteristics: reduction in numbers of all lymphocyte populations, frequent eosinophilia, highly activated immune profiles, antigen specific proliferative hyporesponsiveness, impaired type 1 cytokine responses in unstimulated and antigen stimulated cells and increased TNFα levels. In HIV infected individuals, the egg⁺IgEhi helminth infection status was associated with lower but not significant CD4⁺ counts and higher viral loads. A strong negative correlation was observed between viral loads, CD4⁺ and CD8⁺ cells in this subgroup. Subgroups with high IgE (egg⁺IgEhi and egg⁻IgEhi) had elevated Th2 markers with lower CD4⁺ counts and higher viral loads in the HIV⁺ group. The inverse correlation between viral load and CD4⁺ counts found in all the HIV⁺ participants was strongest in these two subgroups. Individuals with parasite eggs in stool and low Ascaris IgE (egg⁺/IgElo) presented a modified Th2 profile. This subgroup had high absolute numbers of all lymphocyte subsets in both HIV⁻ and HIV⁺ groups with higher CD4⁺ counts in the HIV⁻ and lower viral load in the HIV⁺ groups as well as higher interferon gamma, lower IL-4 and higher IL-10. In conclusion, the results suggest that helminth infections may be associated with deleterious effects on the immune responses to HIV in certain groups of susceptible individuals. The underlying reasons for the different stool egg/Ascaris IgE combinations in settings with high exposure to helminthes is currently not clear but genetic predisposition and environmental factors could play a role. Future studies of helminth- HIV co-infection have to ensure adequate definition of helminth infection status by the use of both stool examination and measurement of helminth-specific IgE as the infection phenotype is associated with differential effects on HIV associated immune responses. This may also apply to co-infection with other pathogens, including tuberculosis. The long-term effect of helminth co-infection in HIV positive people was not assessed in this study but requires further studies. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2009.

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