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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.
1

Factors associated with HIV infection in older South African women in Soweto, Johannesburg

Nyaundi, Christian Aguta 19 January 2012 (has links)
Introduction: The spread and prevalence of the HIV epidemic has resulted in extensive social, cultural and economic consequences in sub-Saharan Africa. It is estimated that about 60% of adults living with HIV in sub-Saharan Africa are women. South Africa, with 5.2 million HIV infected people, is estimated to have the largest number of people living with HIV/AIDS in the world. HIV among older women is not well documented, despite high prevalence rates amongst women 45 years and older. Moreover, few HIV-related interventions are directed to the elderly in South Africa. HIV risk factors among older women have also not been well documented. It is important to determine the factors associated with older women, and how they affect their HIV infection rates. Understanding these factors may lead to better HIV prevention strategies. This study aimed to determine the HIV prevalence in older South African women and to determine the factors associated with HIV infection in older South African women living in Soweto, Johannesburg. Materials and Methods: We did an analytical cross-sectional study on a convenience sample of 500 women (45 years and older) recruited from various venues in Soweto, a large urban African setting in Johannesburg, South Africa, and who accepted to be tested for HIV. Private face-to-face interviews were conducted and included an assessment of socio-demographic characteristics and behavioural factors thought to be associated with HIV. Results: 449 women were included in the study and 52 (11.6%) women were found to be HIV positive. Increased odds of HIV infection was associated with condom use (OR=3.75, 95%CI: 1.71–8.19), transactional sex (OR=2.44, 95%CI: 1.04–5.69) and marital status. Compared to a married woman, a woman was more likely to be HIV positive if she was single, widowed or “cohabiting”. Decreased odds of HIV infection was associated with age (OR=0.90, 95%CI: 0.85–0.96) and education. With respect to a woman with less than 5 years of education, a woman was less likely to be HIV infected if she had more than 5 years of education. Conclusion: Further research needs to be done to determine the exact HIV prevalence amongst older women, as well as risk factors associated with HIV infection. It is also important that older women be encouraged to use condoms, as they are known to be an effective barrier to HIV infection. There is need for HIV-related interventions targeted to older women.
2

Prevalence of antibodies to Bovine Leukemia virus, Neospora caninum and risk factors, and biosecurity practices in beef cow-calf herds in Canada.

Olaloku, Olaniyi Agboola 14 April 2011 (has links)
A total of 4,778 cows from 179 herds were tested for antibodies to N. caninum using a commercially availableELISA. Neospora caninum herd-level seroprevalence ranged from 25.0% to 75.9% (a herd was considered positive with ¡Ý 2 cows testing positive). The true cow prevalence was estimated as 5.2% (95% CI= 4.6 ¨C 5.8). ¡°Pre-calving use of dry lots¡±, ¡°separation of cow-calf pair from other cows after calving¡±, ¡°use of standing water in summer¡±, ¡°use of running water in winter¡±, ¡°feeding heifers with manure handling equipment¡±, ¡°abortion and stillbirths left for canids¡± and ¡°number of sightings of wild canids per year¡± (categorized into three categories: less than 10 times per year, 11¨C 25 times per year, and greater than 26 times per year) were positivelyassociated with herd serological status. However, ¡°washing boots between visits to livestock farms¡± was negatively associated with serological status. These 8 variables were included in a multivariable logistic regression model. Province and herd size were considered potential confounders and kept in the model regardless of significance. Only 4 variables remained significant in the final model.Risk factors associated with prevalence included the use of dry lots/corrals as pre-calving area (OR=2.8; 95% CI =1.3 ¨C 6.2), the use of natural standing water in summer (OR=3.2; 95%CI=1.31 ¨C 8.0), and leaving abortions/stillbirths for dogs or wild canids (OR=2.5; 95%CI=1.0 ¨C 5.9). As the frequency of sighting coyotes and foxes increased so did herd seroprevalence to N. caninum. Risk factors suggested the likely role of horizontal transmission in the transmission of N. caninum in these beef cow-calf herds. Beef herd managers might consider biosecurity practices such as preventing the access of wild canids to fetuses and stillbirths thereby preventing pasture contamination and controlling contamination of water source with oocyst of N. caninum thereby reducing chances of infection. Aherd was considered positive for Bovine leukemia virus (BLV) if ¡Ý 1 animal tested positive.Estimates of cow-level seroprevalence was 1.01% (95% CI= 0.73% ¨C 1.29%) while herd seroprevalence was 12.4% (95% CI= 7.57 ¨C 17.23). Potential risk factors examined for BLV transmission included the use of blade or surgical castration without disinfection between animals, using gouger and saw dehorning methods, multi-use of common rectal sleeve between cows without disinfection and the use of communal pasture where mating occurred. No associations existed between potential risk factors and seropositivity to BLV because the number of herds testing positive to BLV were too few to find any association. However, management practices observed in this study may have the potential to transmit infections. Lapses in biosecurity practices identified were addition of new animals to the herds(73.7%, 132/179), the use of communal grazing (24.0% (43/179) of herds using with 28% (12/43) using more than one communal pasture where mating occurred(93%, 40/43) with bulls from other herds. During communal grazing, contact herds ranged between 1 and 25 (mean = 7.4). Large herds (¡Ý111) animals were more likely to use communal pasture compared to medium sized or small herds (¡Ü46) (P<0.01). Domestic and wild canids had access to stored grain in 19% (34/179) of herds. The odds of wildlife gaining access to stored gain is twice as high (OR=2.37, P<0.02) in western Canada compared to eastern Canada. Purebred herds were less likely to be fed on the ground compared to cross-bred herds (P<0.03). Herds from western Canada administered more feedstuffs on the ground compared to herds from eastern Canada (P<0.01). Large herds were more likely to store feedstuffs outdoors compared to small herds (P<0.01). Herds from western Canada were more likely to store their feedstuffs outside compared to herds from eastern Canada (P<0.01). The odds of not removing surface manure from maternity pens was almost three times (OR=2.98, P<0.01) in herds from western Canada compared to eastern Canada. 78.7% (140/179) of herds disposed ofmanure by spreading on surface ground. 52% (93/179) of herds borrowed manure contaminated equipment from other producers for use on their farms. Thirty three percent (53/179) of herds performed breeding soundness examinations in breeding bulls and 9.5% (17/179) of herds performed trichomonas testing on breeding bulls. Large herds were more likely to co-mingle cows and heifers during the breeding season (P<0.01) compared to small herds. Cow-calf pair separation from other cows after calving occurred more in large herds compared to medium sized or small herds (P<0.01). The odds of using maternity pen as hospital pen was twice in western compared to the eastern Canada (OR=2, P=0.04). Sixty percent (107/179) of herds used the same area for calving and winter-feeding. Herds from western Canada were more likely to use the same area for calving and winter feeding compared to herds from eastern Canada (P<0.01). Forty-one percent (73/179) of herds used hospital pens as maternity pens during calving season. 35.8% (64/179) of herds transported animals to veterinary clinic for treatment. In nine percent (16/179) of herds visitors or outside employees changed their boots, and in18% (32/179) visitors washed their boots. Eighty two percent (146/179) of herds dehorned cattle, of which 74% (109/148) used non-bloodless methods. Of herds using non-bloodless dehorning methods, 28.4% (31/109) disinfected dehorning equipment between animals. 73.7% (132/179) of herds reported castrating animals, of which 32.6% (43/132) used surgical castration method. Of herds using surgical castration method, 81.4% (35/43) disinfected surgical equipment between animals. 12.2% (22/179) of herds disinfected or used new needles between animals when injecting drugs or vaccines. Thirty five percent (63/179) of herds changed sleeves between animals when performing rectal examinations.Over twenty nine percent (29.6%, 53/179) of herds left abortions for dogs and coyotes while 27.4% (49/179) of herds left stillbirths for dogs and coyotes.The risk of adding calves persistently infected (PI) with Bovine Viral Diarrhea (BVD) virus exists with 13% (23/179) of herds adding unweaned beef calves and 18.4% (33/179) adding weaned beef calves without pre-purchase testing.PI calves are known for shedding large amounts of BVD virus and spreading BVD virus infection in beef herds. BVD virus vaccination may compensate for exposure to the virus in a cowherd by mitigating the risk of fetalinfection; however, the timing of vaccination is essential to offer protective immunity. BVD virus vaccine administered during pregnancy check may not protect the fetus against BVDV infection.There is likelihood of infection in-utero resulting in immunotolerant fetus persistently infected (PI) with BVDV and carried to term. This may occur if calf was infected in-utero before 125 days of gestation. Herds in this study administered BVD virus vaccination to breeding cows prior to breeding (60%, 118/179), during pregnancy check (28%, 50/179), and at other times (6%, 11/179). In replacement heifers, BVD vaccination was administered prior to breeding (79%, 142/179), during pregnancy check (13.4%, 24/179), and at other times (7.3%, 13/179).Herds vaccinating breeding cows for BVD virus were 63.1% (113/179), of which 29.1% (52/179) used modified live vaccine and 34.1% (61/179) used killed vaccine. Herds vaccinating replacement heifers for BVD were sixty percent (107/179), of which 25.1% (45/179) used modified live virus vaccine and 34.6% (62/179) used killed vaccine. The role ofthe veterinarianis essential in educating producers on what constitute risky practices and how to mitigate such risks. Approach to mitigating risks may not necessarily be the same for all cow-calf herds; it must be tailored to each production unit. Initial risk assessment will identify what constitutes risky management practices, after which sound mitigation measure are designed to address such risks. On-farm biosecurity practices needs approach within the framework of risk assessment and periodic review for effectiveness.
3

Prevalence of antibodies to Bovine Leukemia virus, Neospora caninum and risk factors, and biosecurity practices in beef cow-calf herds in Canada.

Olaloku, Olaniyi Agboola 14 April 2011
A total of 4,778 cows from 179 herds were tested for antibodies to N. caninum using a commercially availableELISA. Neospora caninum herd-level seroprevalence ranged from 25.0% to 75.9% (a herd was considered positive with ¡Ý 2 cows testing positive). The true cow prevalence was estimated as 5.2% (95% CI= 4.6 ¨C 5.8). ¡°Pre-calving use of dry lots¡±, ¡°separation of cow-calf pair from other cows after calving¡±, ¡°use of standing water in summer¡±, ¡°use of running water in winter¡±, ¡°feeding heifers with manure handling equipment¡±, ¡°abortion and stillbirths left for canids¡± and ¡°number of sightings of wild canids per year¡± (categorized into three categories: less than 10 times per year, 11¨C 25 times per year, and greater than 26 times per year) were positivelyassociated with herd serological status. However, ¡°washing boots between visits to livestock farms¡± was negatively associated with serological status. These 8 variables were included in a multivariable logistic regression model. Province and herd size were considered potential confounders and kept in the model regardless of significance. Only 4 variables remained significant in the final model.Risk factors associated with prevalence included the use of dry lots/corrals as pre-calving area (OR=2.8; 95% CI =1.3 ¨C 6.2), the use of natural standing water in summer (OR=3.2; 95%CI=1.31 ¨C 8.0), and leaving abortions/stillbirths for dogs or wild canids (OR=2.5; 95%CI=1.0 ¨C 5.9). As the frequency of sighting coyotes and foxes increased so did herd seroprevalence to N. caninum. Risk factors suggested the likely role of horizontal transmission in the transmission of N. caninum in these beef cow-calf herds. Beef herd managers might consider biosecurity practices such as preventing the access of wild canids to fetuses and stillbirths thereby preventing pasture contamination and controlling contamination of water source with oocyst of N. caninum thereby reducing chances of infection. Aherd was considered positive for Bovine leukemia virus (BLV) if ¡Ý 1 animal tested positive.Estimates of cow-level seroprevalence was 1.01% (95% CI= 0.73% ¨C 1.29%) while herd seroprevalence was 12.4% (95% CI= 7.57 ¨C 17.23). Potential risk factors examined for BLV transmission included the use of blade or surgical castration without disinfection between animals, using gouger and saw dehorning methods, multi-use of common rectal sleeve between cows without disinfection and the use of communal pasture where mating occurred. No associations existed between potential risk factors and seropositivity to BLV because the number of herds testing positive to BLV were too few to find any association. However, management practices observed in this study may have the potential to transmit infections. Lapses in biosecurity practices identified were addition of new animals to the herds(73.7%, 132/179), the use of communal grazing (24.0% (43/179) of herds using with 28% (12/43) using more than one communal pasture where mating occurred(93%, 40/43) with bulls from other herds. During communal grazing, contact herds ranged between 1 and 25 (mean = 7.4). Large herds (¡Ý111) animals were more likely to use communal pasture compared to medium sized or small herds (¡Ü46) (P<0.01). Domestic and wild canids had access to stored grain in 19% (34/179) of herds. The odds of wildlife gaining access to stored gain is twice as high (OR=2.37, P<0.02) in western Canada compared to eastern Canada. Purebred herds were less likely to be fed on the ground compared to cross-bred herds (P<0.03). Herds from western Canada administered more feedstuffs on the ground compared to herds from eastern Canada (P<0.01). Large herds were more likely to store feedstuffs outdoors compared to small herds (P<0.01). Herds from western Canada were more likely to store their feedstuffs outside compared to herds from eastern Canada (P<0.01). The odds of not removing surface manure from maternity pens was almost three times (OR=2.98, P<0.01) in herds from western Canada compared to eastern Canada. 78.7% (140/179) of herds disposed ofmanure by spreading on surface ground. 52% (93/179) of herds borrowed manure contaminated equipment from other producers for use on their farms. Thirty three percent (53/179) of herds performed breeding soundness examinations in breeding bulls and 9.5% (17/179) of herds performed trichomonas testing on breeding bulls. Large herds were more likely to co-mingle cows and heifers during the breeding season (P<0.01) compared to small herds. Cow-calf pair separation from other cows after calving occurred more in large herds compared to medium sized or small herds (P<0.01). The odds of using maternity pen as hospital pen was twice in western compared to the eastern Canada (OR=2, P=0.04). Sixty percent (107/179) of herds used the same area for calving and winter-feeding. Herds from western Canada were more likely to use the same area for calving and winter feeding compared to herds from eastern Canada (P<0.01). Forty-one percent (73/179) of herds used hospital pens as maternity pens during calving season. 35.8% (64/179) of herds transported animals to veterinary clinic for treatment. In nine percent (16/179) of herds visitors or outside employees changed their boots, and in18% (32/179) visitors washed their boots. Eighty two percent (146/179) of herds dehorned cattle, of which 74% (109/148) used non-bloodless methods. Of herds using non-bloodless dehorning methods, 28.4% (31/109) disinfected dehorning equipment between animals. 73.7% (132/179) of herds reported castrating animals, of which 32.6% (43/132) used surgical castration method. Of herds using surgical castration method, 81.4% (35/43) disinfected surgical equipment between animals. 12.2% (22/179) of herds disinfected or used new needles between animals when injecting drugs or vaccines. Thirty five percent (63/179) of herds changed sleeves between animals when performing rectal examinations.Over twenty nine percent (29.6%, 53/179) of herds left abortions for dogs and coyotes while 27.4% (49/179) of herds left stillbirths for dogs and coyotes.The risk of adding calves persistently infected (PI) with Bovine Viral Diarrhea (BVD) virus exists with 13% (23/179) of herds adding unweaned beef calves and 18.4% (33/179) adding weaned beef calves without pre-purchase testing.PI calves are known for shedding large amounts of BVD virus and spreading BVD virus infection in beef herds. BVD virus vaccination may compensate for exposure to the virus in a cowherd by mitigating the risk of fetalinfection; however, the timing of vaccination is essential to offer protective immunity. BVD virus vaccine administered during pregnancy check may not protect the fetus against BVDV infection.There is likelihood of infection in-utero resulting in immunotolerant fetus persistently infected (PI) with BVDV and carried to term. This may occur if calf was infected in-utero before 125 days of gestation. Herds in this study administered BVD virus vaccination to breeding cows prior to breeding (60%, 118/179), during pregnancy check (28%, 50/179), and at other times (6%, 11/179). In replacement heifers, BVD vaccination was administered prior to breeding (79%, 142/179), during pregnancy check (13.4%, 24/179), and at other times (7.3%, 13/179).Herds vaccinating breeding cows for BVD virus were 63.1% (113/179), of which 29.1% (52/179) used modified live vaccine and 34.1% (61/179) used killed vaccine. Herds vaccinating replacement heifers for BVD were sixty percent (107/179), of which 25.1% (45/179) used modified live virus vaccine and 34.6% (62/179) used killed vaccine. The role ofthe veterinarianis essential in educating producers on what constitute risky practices and how to mitigate such risks. Approach to mitigating risks may not necessarily be the same for all cow-calf herds; it must be tailored to each production unit. Initial risk assessment will identify what constitutes risky management practices, after which sound mitigation measure are designed to address such risks. On-farm biosecurity practices needs approach within the framework of risk assessment and periodic review for effectiveness.
4

Hepatitis E virus seroprevalence in Canada

Weger, Steven 02 February 2017 (has links)
Hepatitis E virus (HEV) is the main cause of acute viral hepatitis worldwide, predominantly in developing areas where it is endemic. Recently, HEV has gained more attention in the developed world, prompting several industrialized countries to assess seroprevalence rates using blood donor samples. The seroprevalence among Canadian blood donor samples collected from July 2013 - December 2015 was 5.84% (240/4,107). None of the 14,053 samples tested were positive for HEV RNA. There was no significant increase in the high-risk groups we tested. HIV was determined to be a significant risk-factor for HEV infection in a retrospective study of Kenya-based sex-worker cohorts, but not so in a Canadian cohort of HIV-positive intravenous drug users. Overall, HEV seroprevalence in Canada is lower than that published in other countries. This together with failing to detect HEV RNA in Canadian blood donations indicates that HEV currently poses low risk to the Canadian blood supply. / February 2017
5

Cytomegalovirus infection in pregnancy : outcome and risk factors

Tookey, Patricia Ann January 2000 (has links)
No description available.
6

Comparison of male and female HIV seroprevalence rates from a coal mining community and mobile clinic in Mpumalanga, South Africa

Hurkchand, Hitesh Pravinchundra 14 May 2009 (has links)
Comparison of HIV seroprevalence between males and females at clinic and community level in Mpumalanga South Africa. Background: Two cross-sectional surveys were conducted in Embalenhle community (February 2002) and Dunusa community mobile clinics (November 2001), to establish prevalence of HIV and STIs (Chlamydia trachomatis and Neisseria gonorrhea). Methods: Multiple logistic regression models were fitted to the combined data from the two sites, to identify factors associated with HIV prevalence and also to check whether the effects were consistent over the two sites. Results: HIV Prevalence was 33.5% (30.2%vs.35.9% in males and females respectively, p=0.124) at community site and 34.8% at clinic site (22.8%vs.47.4% in males and females respectively, p=0.001). The models show a significant site by sex interaction i.e. the effect of sex differs in the 2 sites (p=0.036). After adjusting for agegroup and Neisseria gonorrhea, predicted probabilities from the logistic regression model shows that the sex difference is much greater in community mobile clinics (23%vs.44.1% in males and females respectively) than at the community site (29.9%vs.34.9% in males and females respectively). After adjusting for site and Neisseria gonorrhea, the model showed an agegroup by sex interaction (p<0.001). Predicted probabilities show a difference, where HIV in males is higher than in females; in males in the 25-34 year age group from 18-24 years (36.3 vs 18.2 % respectively), while in females the prevalence is very similar in the 18-24 year and 25-34 year age groups. There were no interactions between Neisseria gonorrhea and other variables. Conclusions: The different HIV–age distribution for males and females are consistent with the results of previous studies. We found that the sex difference in prevalence was much smaller at the community level than at the clinic level. The traditional interpretation of national antenatal surveillance data assumes a fairly large difference in male and female seroprevalence (a ratio of 7:10 is used in extrapolating results of the South African National antenatal seroprevalence survey to males). These results suggest that more work is needed in checking that assumption.
7

Role of antiretroviral therapy exposure host genetics on cytomegalovirus infection status and association with gut microbiome profiles among pregnant black African women

Mhandire, Doreen Zvipo 11 February 2021 (has links)
Cytomegalovirus (CMV) is an important antenatal infection that is prevalent in the developing world. The disabling and potentially fatal effects of CMV acquisition or reactivation during pregnancy on the developing foetus and or neonate are known but, factors predisposing pregnant women to CMV are not well studied. CMV has a wide host cell tropism that includes gut epithelial cells. CMV infection in the gut epithelial cells results in a leaky gut and potential gut microbial dysbiosis. In this study, we set out to determine the prevalence of CMV infection as well as factors associated with CMV reactivation in a cohort of pregnant Zimbabwean women. We also aimed to determine the role of CMV infection and CMV susceptibility host genetics on gut bacterial profiles. Seroprevalence of CMV was determined using the enzyme-linked immunosorbent assay. A high prevalence of previous exposure to CMV, as denoted by the presence of anti-CMV IgG antibodies in participants' sera, was observed. Anti-CMV IgM antibodies that denote active CMV infection were detected in the sera of 4.6% (n=35/524) study participants. Prevalence of CMV was also determined using real time PCR, CMV reactivation was higher (6.7%) when using PCR than when using immunological assays (4.6%). The presence of CMV DNA was significantly associated with HIV positivity (p=0.04). PCR is the gold standard for CMV diagnosis, thus, CMV DNA positivity was used to denote CMV infection status in this thesis. The second objective was to determine if the differential effect of CMV acquisition or reactivation among HIV infected participants was due to variability in plasma efavirenz containing antiretroviral therapy (ART) exposure. Efavirenz (EFV) plasma concentrations were determined using high performance liquid chromatography (HPLC). Single nucleotide polymorphisms (SNPs) in the CYP2B6 gene, which encodes the main EFV metabolizing enzyme were genotyped. Carriers of CYP2B6 poor metaboliser (PM) genotypes (c.516T/T and c.983T/C) had significantly higher mean plasma EFV concentration compared to carriers of CYP2B6 fast metabolizer genotypes (i.e., c.516G/G and c.983T/T). CYP2B6 PM genotype carriers were significantly less likely to be positive for CMV DNA when compared with fast metabolizer genotype carriers (pC (p=0.002), TLR7 rs179008A>C (pC (p=0.003). In contrast, presence of the IL6 rs10499563T>C polymorphism was inversely correlated with CMV infection (p=0.002). The reported genetic variants are reported to modulate proteins involved in immune responses against viral infections, thus, their association with susceptibility to CMV infection. Such findings may assist in the designing of a muchneeded candidate CMV vaccine. Lastly, we set out to determine the possible role of CMV infection in shaping gut microbiota profiles. We report on a significant difference (p=0.001) in the beta diversity of gut bacterial profiles between HIV- and age-matched CMV-infected (cases) and CMVuninfected (controls) participants. Using linear discriminant analysis (LDA) effect size (LefSe), significant differences in the relative abundance of specific bacterial taxa were observed between cases and controls (p2). Significantly lower abundance of Lactobacillus reuteri and Roseburia, genera associated with lower microbial translocation was observed in cases than controls. Lower relative abundance of Lactobacillus and Roseburia, is consistent with microbial translocation and heightened inflammation, respectively, hence higher likelihood of microbial translocation and inflammation occurring in cases than controls. Furthermore, Prevotella copri, a species that has been association with cytokine release and chronic inflammation was significantly more abundant in cases than controls. CMV is a known chronic inflammatory condition, and this study provides further confirmation through the higher relative abundance of P.copri in cases than controls. Biomarker identification has proven to be a successful means of translating molecular data into clinical practice, such as vaccine development in the case of CMV infection. Overall, this study reports the possible interaction of various host factors in facilitating CMV acquisition or reactivation during pregnancy. In the setting of HIV-CMV coinfection, our findings emphasise on the need for genotype guided drug dosage to achieve therapeutic EFV so as to maintain the balance between host and coinfecting microbes in HIV management. Comprehensive genotype guided drug dosage, if taken as a once-off test should be affordable especially in resource-limited settings. This is particularly important in pregnant women who are at a risk of vertically transmitting infection to the immunologically immature foetus and or neonate. Data from this study may assist in curbing the host associated challenges in designing an effective CMV vaccine. Moreover, the biomarkers reported may assist in diagnosis and management of potential CMV acquisition or reactivation during pregnancy. However, bigger prospective, functional studies would be needed to confirm the exact roles of the biomarkers identified in this study in the diagnosis, prognosis and therapeutics of CMV infection.
8

Epidemiologic and Economic Analysis of Avian Influenza in Nepal

Karki, Surendra 16 December 2013 (has links)
Many countries, including Nepal, have been affected with highly pathogenic avian influenza (HPAI) outbreaks. There have been human mortalities in some countries and large numbers of poultry either died or were culled due to HPAI. The overall objective of this thesis was to improve our understanding of the epidemiology and economics of avian influenza (AI), and particularly HPAI, in Nepal. We determined the seroprevalence of and risk factors for AI virus antibodies presence in ducks in Kathmandu, Nepal. The estimated true prevalence of AI viruses (AIV) antibodies was 27.2% [95% Confidence Interval (CI): 24.6- 29.5]. Age of the ducks was identified as the only risk factor for AIV seropositivity. Ducks older than one year were more likely to be seropositive compared to ducks less than six months of age [Odds Ratio= 2.17 (95% CI: 1.07- 4.39)]. This study provided baseline information about seroprevalence of AIVs in Kathmandu that will benefit further research to differentiate the subtypes of AIVs circulating in Kathmandu. We also evaluated alternatives to the current control program (CCP) for HPAI in Nepal. The considered alternatives were: (i) absence of control measures (ACM) and (ii) vaccinating 60% of the domestic poultry flock twice per year. Cost-benefit analysis approach was used to evaluate the economic feasibility of the programs. In terms of the benefit-cost ratio, our findings indicated that there is a return of 1.96 dollars for every dollar spent in the CCP compared to ACM. The net present value of the CCP versus ACM was US$ 989,918. The vaccination program yielded a return of 2.41 dollars for every dollar spent when compared to the CCP. The net present value of vaccination versus implementing the CCP was US$ 13,745,454. These results support a continued investment into the CCP rather than ceasing to implement government regulated control measures and suggest that vaccination may be an even better control alternative. In summary, our studies have highlighted the value of epidemiologic and economic analysis in research of AI. Our results are expected to lead to an improved understanding and awareness of AI in Nepal and to formulation of better control strategies.
9

Contagious bovine pleuropneumonia (CBPP) in the Maasai ecosystem of south-western Kenya : evaluation of seroprevalence, risk factors and vaccine safety and efficacy

Mtui-Malamsha, Niwael Jesse January 2009 (has links)
Contagious bovine pleuropneumonia (CBPP) is a bovine bacterial disease of major economic importance in sub-Saharan Africa. Vaccination has been recommended to control the disease in endemic areas such as the Maasai ecosystems of Kenya and Tanzania; however, the currently used live attenuated vaccine has been reported to have poor vaccine safety and efficacy. To compare standard (current) and an improved (buffered) version of the live CBPP-vaccine, several epidemiological studies were carried out in Maasai cattle in Kenya between 2006 and 2008. Specifically, the aims were to estimate CBPP seroprevalence at herd and animal level; to identify risk factors for seroprevalence at both levels; to investigate the spatial distribution of seroprevalence; to compare post vaccination adverse events in cattle vaccinated with a standard and a buffered vaccine, and finally to compare efficacy of the two vaccines to induce seroconversion and to prevent development of clinical signs suggestive of CBPP. A cross-sectional study was carried out in 6872 cattle in 175 randomly selected herds from Loita and Mara divisions. A competitive ELISA revealed that 85% of the herds in the area had at least one seropositive animal and that seropositive herds were harbouring 11% seropositive cattle. A complement fixation test revealed that 46% of the herds had at least one seropositive animal and that seropositive herds were harbouring 4% seropositive cattle. A multivariable logistic regression analysis of the seroprevalence indicated that previous vaccination against CBPP, a history of CBPP outbreaks in the herd, animal age and the location of the herd in the division of Mara were positively correlated to seroprevalence. To investigate the observed difference in herd seroprevalence between the two divisions further, a spatial analysis was conducted. A SatScan test revealed clusters in Mara in areas identified by veterinary personnel as CBPP ‘hot spots’. A logistic regression using spatial information identified that location in the midland agro-ecological zone or close to a river and vaccination were positively associated with seroprevalence. To compare safety and efficacy of a standard and a buffered vaccine, two cohorts of approximately 40,000 cattle were used. The study showed that within 100 days post vaccination, 6.2 cattle per 1000 vaccinates developed adverse events, 4.1 of which were specifically attributable to vaccination and ranging from swelling of the tail to the tail sloughing off. This study revealed a slightly higher incidence of adverse events in cattle vaccinated with the buffered vaccine compared to the standard vaccine. A comparison of the efficacy of the two vaccines revealed that cattle vaccinated with the buffered vaccine had higher odds of seroconversion and lower odds of developing symptoms of CBPP, three and twelve months post vaccination respectively. The epidemiological studies conducted clearly show wide spread seroprevalence in the Maasai cattle. Given the (spatial) heterogeneity observed, control measures should probably be targeted in areas of increased risk (clusters). However, positive association of vaccination and seropositivity call for better diagnostics tests that can differentiate vaccinated from infected animals. Vaccination with buffered vaccine resulted in increased seroconversion, decreased clinical signs indicative of CBPP post vaccination and low seroprevalence post ‘outbreak’. Nevertheless, the increase in adverse events related to the buffered vaccine calls for further research into safer CBPP vaccines.
10

Validação de estratégias a campo para o controle de Salmonella sp. na cadeia de produção de suínos

Costa, Eduardo de Freitas January 2014 (has links)
O Brasil ocupa uma posição de destaque mundial em relação à produção agropecuária, sendo necessário fornecer segurança microbiológica aos consumidores. Salmonella é um agente causador de infecções alimentares em seres humanos, de forma que os produtos de origem suína são responsáveis por cerca de 5-10% dos surtos em humanos. O controle depende do conhecimento da distribuição da bactéria desde o rebanho até o frigorífico. Em regiões com altas prevalências no campo, esforços direcionados primeiramente em reduzir a prevalência nos rebanhos visam minimizar os riscos de contaminação dos produtos. Neste sentido, medidas de biossegurança, seguindo boas práticas de produção agropecuária, são fundamentais. Além disso, a aplicação de intervenções complementares são, possivelmente, formas de reduzir a prevalência em um período de tempo mais curto. Desta forma o objetivo deste trabalho foi validar três estratégias: 1) utilização de um prebiótico Actigen®™ na ração dos animais, (PRE); 2) uma vacina viva Enterisol SC 54®, (VAC) e 3) o sistema de wean-to-finish, (WTF). Estes grupos foram comparados entre si e com o sistema tradicional em três sítios, o grupo controle (GC), frente à soroprevalência e contaminação em carcaças. Cada estratégia foi realizada em três repetições, sendo colhidas amostras de sangue de 55 animais de cada lote no dia do alojamento na terminação e quatro dias antes do abate. Suabe de 40 carcaças de cada lote foram colhidas antes do resfriamento. As soroprevalências e frequências de isolamento foram comparadas entre os grupos por meio de teste de qui-quadrado. A soroprevalência pré-abate foi estatisticamente menor no grupo PRE 50,3% em relação ao WTF, VAC e GC, com 99%, 96,9% e 98,8% respectivamente. As frequências de isolamentos em superfície de carcaça variaram de 0% a 29,1% nos grupos PRE e VAC respectivamente, sendo que ambas diferem significativamente entre si e dos grupos CG 18,33% e WTF 15% (p<0,05). Pode-se comprovar a eficácia do prebiótico em prevenir a infecção a campo frente às demais estratégias. Em relação às contaminações de carcaças, os resultados corroboram com os conhecimentos acerca do papel da pressão de infecção do campo nas contaminações na planta frigorífica. / Brazil has been increasing its worldwide position in relation to agricultural production, and is necessary providing food safety to consumers. Salmonella is a foodborne pathogen for humans and pork products play an important role in the amount of outbreaks. The control depends on the knowledge of the distribution of the bacteria occurrence from the herd to the slaughterhouse. In regions with high on farm prevalence, efforts are primarily directed to reduce the prevalence in the swine population in order to minimize the risks of products contamination. In this sense, biosecurity measures and good production practices are useful. Moreover, increase the knowledge about additional interventions, to reduce on farms prevalence in a shorter period of time, also is important. Therefore, the objective of this work was to validate three strategies: 1) use of Actigen ® ™ prebiotic in animal feed, (PRE); 2) a live vaccine Enterisol SC54® (VAC); and 3) the system of wean- to-finish, (WTF). Seroprevalence and contamination on carcasses surface in these groups were compared with the traditional system in three sites (the control group-CG). Each strategy was performed in three replicates, and blood samples were collected from 55 animals of each batch at the first day of finishing phase and four days before slaughter. Swabs of 40 carcasses were taken from each batch before chilling. The seroprevalence and isolation frequencies were compared between groups using logistic regression. The seroprevalence before slaughter was lower in PRE (50.3%) compared with the WTF, VAC and GC groups, with 99%, 96.9% and 98.79%, respectively. The frequency of Salmonella isolation was lower in PRE group 0%, when compared with the other groups (p<0.05). The results prove that prebiotic is able to prevent infection in the field compared to the other strategies. Regarding the carcass contamination, these finds are consistent with the knowledge on the role of infection pressure in the field contamination in the plant.

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