Thesis and Dissertations

Comparative Evaluation of Humoral antibody Responses to various Newcastle disease Vaccines in Chickens at Andassa Livestock Research Center, Northwest Ethiopia

2025-07-29T08:09:05Z

Comparative Evaluation of Humoral antibody Responses to various Newcastle disease Vaccines in Chickens at Andassa Livestock Research Center, Northwest Ethiopia Belayneh Lulie on their comparative efficacy across different vaccine types and chicken breeds. Therefore, this experimental study was conducted from October 2024 to January 2025 at the Andassa Livestock Research Center poultry farm to evaluate the humoral antibody response of NCD vaccines in Tillili and Koekoek chicken breeds.The study comapared three vaccines (I2 thermostable, LaSota, and HB1) along with a positive control. The specific objectives of the study were to evaluate the antibody responses to the three vaccines and the positive control in both breeds, to identify risk factors associated with variations in antibody responses,to determine the magnitude of mortality and survival of chickens and to assess differences in maternally-derived antibody levels between the Tillili and Koekoek breeds. A Completely Randomized Design with a 2x4 factorial arrangement was employed. A total of 480 day-old chicks (DOCs), comprising 240 indigenous Tillili and 240 exotic Koekoek, were randomly assigned to 24 pens (20 birds/pen). A total of 1,092 blood samples were collected one day before and 14 days after each vaccination, with 964 samples successfully processed. Antibody titers against NCD were quantified using an indirect ELISA. Independent and paired t-tests were used to compare mean antibody titers between the treatment and control groups before and after vaccination, respectively. Additionally, multiple linear regression, and Cox regression were used to evaluate and quantify the effect of covariates on mean antibody titer and chicken mortality rates, respectively. The overall chick mortality percentage across all treatment groups was 4.6%. During the study period, 76% of chickens developed protective antibody levels against NCD across the four treatments. Koekoek chickens exhibited significantly higher maternal antibody levels (mean titer 4,460.3) compared to Tillili chickens (mean titer 202.3) during the first week of life. A relatively higher antibody response (5475.4 ± 2821.1) was also detected in Koekoek compared to Tillili (4200.9 ± 2092.8. Overall, antibody responses were higher at 42days postvaccination with thermosatble vaccines (6031.2±420.2), Comparison of vaccine types revealed significant differences in antibody levels before and after vaccination among bleeding dates (P = 0.0274) and between treatment groups (P = 0.0002). However, an independent t-test comparing the positive control and treatment groups revealed no significant difference (P=0.1954) in antibody responses. The Multiple linear regression revealed that sex (P = 0.0172), bleeding time (P = 0.001), and age (P = 0.000) were statistically significant with mean antibody titer. In conclusion, all three vaccines elicited protective immunity, with the positive control achieving relatively the highest efficacy, followed by the thermostable vaccine. This suggests that the thermostable vaccine demonstrates comparable practical advantages for field use, especially in areas where cold chains are limited.

Epidemiological investigation of Goat Mastitis,associated risk Factors and antimicrobial resistance Patterns of its Causative Bacteria In Waghimra Zone, Northeastern Ethiopia

2025-07-29T07:57:37Z

Epidemiological investigation of Goat Mastitis,associated risk Factors and antimicrobial resistance Patterns of its Causative Bacteria In Waghimra Zone, Northeastern Ethiopia Abebe Tibebu Mastitis is a multifactorial disease of mammals that has substantial implications on production, welfare, and public health, but it is far less studied in goats than in cows. A cross-sectional study with simple random sampling at the lowest unit was conducted in selected districts of Northeastern Amhara, Ethiopia, from September 2024 to May 2025. The objectives of the study were to assess knowledge, attitudes, and practices (KAP) levels of herders on mastitis in goats, estimate its prevalence, assess associated risk factors, identify bacteria, and evaluate their antimicrobial susceptibility. A semi-structured questionnaire survey was utilized to evaluate KAP levels, while a physical examination and the California mastitis test were employed to examine mastitis in goats. Laboratory tests for bacterial identification and antimicrobial resistance were conducted following standard protocols. Stata17 and WHONET software were used for statistical analyses. Out of the 275 survey participants, 30.68% reported mastitis incidents in goats during the study period. The average scores for knowledge, attitude, and practice related to mastitis were 47.78%, 69.39%, and 46.18%, respectively. The majority of respondents did not attend school, and their knowledge of causes of goat‟s mastitis, zoonotic diseases, and subclinical mastitis was significantly associated with district and age demographics. Out of the 397 lactating goats examined, mastitis prevalence was 24.74% at goat level (CM: 2.52%, SCM: 22.22%) and 16.60% in udder halves (CM: 1.39%, SCM: 15.21%). Multivariable logistic regression analysis revealed that lactation stage (OR=1.92; 95% CI: 1.89-6.30), districts (OR=3.47; 95% CI: 1.01-3.65), parity (OR=2.73; 95% CI: 1.11-6.67), and mastitis history (OR = 13.6; 95% CI: 4.64-40.15) (p<0.05) were statistically associated with the occurrence of goat mastitis. Upon bacterial isolation and identification, the most common bacterial isolate was Staphylococcus (39.83%), followed by E. coli (10.17%), Enterococcus, Micrococcus, and Klebsiella (all < 5%). Staphylococcus was resistant to ampicillin and tetracycline, with a multidrug-resistant (MDR) prevalence of 21.16%, whereas E. coli was resistant to ampicillin, with an MDR prevalence of 8.3%. The overall MDR prevalence was found to be 17.31%. In conclusion, herders lacked good knowledge and practices about mastitis and zoonotic risks, which most likely contributed to the high prevalence of mastitis and antimicrobials -resistant bacteria. As a result, tailored training on the causes of mastitis and zoonotic risks, control and prevention for goat farmers, and further research on bacterial species and resistance factor identification are recommended. Furthermore, kanamycin and gentamycin were found to be effective against staphylococci and thus recommended for use, while tetracycline and streptomycin were found to be effective against E. coli and thus recommended.

Spatiotemporal analysis and associated risk factors of Dogmediated Human Rabies in the Amhara Region, Northwest Ethiopia

2025-07-29T07:32:36Z

Spatiotemporal analysis and associated risk factors of Dogmediated Human Rabies in the Amhara Region, Northwest Ethiopia Yeshambel Muluye Although dog-mediated rabies poses a significant public health and economic burden in Ethiopia, the spatiotemporal epidemiology of the disease remains poorly defined and understood. The objective of this study was to explore the spatiotemporal dynamics and identify possible risk factors for dog-mediated human rabies in the Amhara region of Northwest Ethiopia. A retrospective time-series ecological study was employed on dogmediated human rabies in Northwest Ethiopia. The study utilized time-series rabies surveillance data collected in the Amhara region between January 2016 and December 2023. Descriptive epidemiological analysis, spatial statistics (including choropleth mapping, GetisOrd Gi* hot spot detection, Moran’s I spatial autocorrelation, and Kulldorff’s space-time scan statistics), and negative binomial regression models were employed to examine incidence trends, identify cluster formations, and assess associated environmental and demographic risk factors. Among 14159 reported dog-mediated human rabies cases, the annual incidence rate ranged from 2.75 to 14.12 per 100,000 population, with a mean of 7.34 and a median of 6.78 over the study period. The overall trend indicated an increasing trend in rabies cases from 2016 up to around mid-2022, peaking between late 2022 and early 2023. The temporal trend showed relative stability in incidence rates between 2016 and 2017 (IR=4.99 to 5.17), with a significant decline in 2018 and a sharp rise from 2020 to 2022 (IR=9.27 to 14.12), and a drop in 2023 (IR=8.39). Seasonal decomposition indicated peaks of cases in summer and autumn. The spatial analysis revealed that the Bahir Dar Special Zone was the most significant hotspot from 2020–2023 with an incidence risk (IR) of 168.65 and a space-time cluster relative risk (RR) of 65.12. Persistent hot spots were detected in the North Gondar zone in 2016, 2020, and 2022 (p < 0.05) and East Gojam zone in 2021, 2022 (p < 0.05) and in 2023 (p < 0.01). Significant spatial autocorrelation of the incidence of cases was also identified in the region in the year 2020 (Moran’s I=0.36, P < 0.05) and 2023 (Moran’s I=0.52, P < 0.01). Negative binomial regression revealed a positive association of rabies incidence in the zones with higher population density, incidence rate ratio (IRR=1.004), temperature (IRR=1.217), and precipitation (IRR=1.001), while dog vaccination coverage was negatively associated (IRR=0.905, p<0.001). Significant risk variation was observed across zones, with the Bahir Dar Special Zone (IRR=2.13) showing the highest risk. In conclusion, this study revealed that dog-mediated human rabies remains a public health threat in Northwest Ethiopia, characterized by pronounced spatiotemporal, seasonal, and geographic heterogeneity. Therefore, multidisciplinary and targeted interventions using a One Health approach are essential to reduce and ultimately eliminate dog-mediated rabies in the study area.

Sero-Epidemiology of Brucellosis in Small Ruminants and Humans in Selected Districts of West Gojjam Zone, North Western Ethiopia

2025-02-28T08:42:58Z

Sero-Epidemiology of Brucellosis in Small Ruminants and Humans in Selected Districts of West Gojjam Zone, North Western Ethiopia Robel Tsega A quantitative cross-sectional and retrospective study design was carried out between November 2022 to April 2023 on small ruminant and human brucellosis, respectively. This study was conducted in Bahir Dar Zuria and North Mecha Districts, and at Bahir Dar University’s Tibebe Ghion Specialized Hospital, West Gojjam Zone, North West Ethiopia. The objectives of the study were to; i) estimate the prevalence of small ruminant Brucellosis, ii) estimate the prevalence of brucellosis in humans, iii) identify the associated putative risk factors affecting the sero-prevalence of brucellosis both in small ruminants and humans. A multistage stratified sampling technique was used to sample study Districts and the respective small ruminant producers and animals. Whereas purposive sampling was used to obtain human serum samples at Tibebe Ghion Specialized Hospital. A pre-tested structured interview questionnaire was used to collect data from small ruminant producers and hospitalized human respondents. A total of 384 small ruminant and 384 human samples were taken and analyzed for this study. All serum samples were first screened using Rose Bengal Plate test (RBPT) and finally confirmed by Complement Fixation test (CFT). Among the 384 small ruminant serum samples tested by RBPT and CFT, only 12 (3.13%) and 0 (0%) samples were found positive, respectively. Similarly, out of 384 human serum samples tested by RBPT and CFT; only 16 (4.16%) and 2 (0.52%) were found positive, respectively. The putative risk factors which were assumed to have associations with small ruminant and human brucellosis was not examined due to insufficient Brucella positive samples. However, the prevalence of human brucellosis was apparently higher in North Mecha District, in male, married and uneducated human respondents. In conclusion, unlike human brucellosis, the occurrence of small ruminant brucellosis was not detected in the study areas. The detection of human brucellosis in human population can pose a significant public health concern in the study area. Therefore, educating the community about the zoonotic importance of the brucellosis and its transmission mechanisms could help to control brucellosis in humans. This can be successfully implemented through a ONE health approach, in which a synergetic effort among veterinarians and human health experts is required. Besides, this study didn’t explore the association between livestock farming and brucellosis in humans, further comprehensive epidemiological investigation of brucellosis among animals and humans is warranted in the study areas.