Comparative evaluation of the immune responses of seven chicken ecotypes to vaccination against Newcastle disease

Newcastle disease (ND) is a highly contagious viral disease of poultry with high mortality. The local velogenic viral pool of the ND strains  influences its severity and occurrence. ND vaccination is the most feasible approach to control the disease. However, some ND-vaccinated groups within chicken populations are susceptible to velogenic ND infection developing outbreaks with marked pathological lesions and shedding of the virus. Vaccine strain-related factors as well as inadequate vaccine application and delivery methods during vaccination might explain the suboptimum ND vaccine efficacy. In this study, however, we propose that host factors may contribute to the suboptimal vaccine efficacy in vaccinated chickens. We, therefore, compared the immune response of five Ethiopian chicken ecotypes to ND  immunization in the presence of two reference breeds (Fayoumi and Bovans). All chickens received initial immunization at age of 21 days with HB1 ND vaccine followed by two-times LaSota booster immunization at age 50 and 120 days. Subsequently, serum was collected fortnightly post-vaccination at age 35, 65, and 135 days for immune response analysis using the hemagglutination inhibition (HI) test. HIantibody was significantly higher at days 135 > 65 > 35 in each ecotype following the third, second, and first vaccination, respectively. The different chicken ecotypes had significant differences in HI antibody response to the ND vaccination. Accordingly, the HI titer was  significantly higher in Jarso > Cheffe > Fayoumi > Arsi > Bovans > Tepi > Horro suggesting antibody titer and ND vaccine efficacy of the ND vaccine depends on host factors. Moreover, some chicken groups within each ecotype had low HI titer. Chicken ecotypes with weak immune responses may not completely clear the virus from their body; thus, they can serve as a reservoir host by maintaining the ND  virus. We conclude that herd immunity level and blanket vaccination program based on the results of a single host genetic group can be misleading during developing and recommending a new vaccine. Hence, understanding the host determinant factors in the immune response during vaccination can lead to improved efficacy and protection against ND in chicken populations

Study on prevalence of bovine mastitis and its major causative agents in West Harerghe zone, Doba district, Ethiopia

Other bacterial species were isolated at lower rates. Antimicrobial susceptibility test showed that most of the isolates in the study area were found to be highly sensitive to cloxacillin, gentamycin and amoxicillin, and moderately sensitive to ampicillin and oxytetracycline. Nevertheless, Streptococcus and Staphylococcus species isolated were resistant to streptomycin and penicillin. Age, parity, stage of lactation and hygienic conditions were found to be important risk factors associated with the occurrence of mastitis

Survey of Anaplasma phagocytophilum and Anaplasma sp. ‘Omatjenne’ infection in cattle in Africa with special reference to Ethiopia

Abstract Background As evidence of the infection of domestic animals by Anaplasma phagocytophilum and Anaplasma sp. ‘Omatjenne’ is presently becoming available, understanding the epidemiological and ecological significance of infection is important to quantify the clinical and socio-economic impact of the diseases they cause. Methods The first aim of this study was to analyse the occurrence of A. phagocytophilum and Anaplasma sp. ‘Omatjenne’ in cattle samples collected from selected African countries using a polymerase chain reaction and restriction enzyme fragment length polymorphism. Secondly, this study was aimed at the molecular identification of Ehrlichia spp. and Anaplasma spp. infection in ruminants raised under different production systems in selected sites in central Ethiopia. Results In total, 695 samples from cattle in six African countries were analysed. Overall, 45 positive results were obtained for Anaplasma sp. ‘Omatjenne’ (6.47%) and 19 for A. phagocytophilum (2.73%). Anaplasma sp. ‘Omatjenne’ was detected in all countries except Tanzania while A. phagocytophilum was detected only in samples from Ethiopia. The proportion of samples tested positive for Anaplasma sp. ‘Omatjenne’ ranged from 1.2% in Morocco to 16% in Rwanda. The occurrence of both agents is now confirmed in African cattle. For the survey in Ethiopia a semi-nested 16S rDNA polymerase chain reaction followed by restriction fragment length polymorphism was used for the identification of Ehrlichia spp. and Anaplasma spp. in blood samples. Randomly selected samples were also analysed by pCS20 polymerase chain reaction for the detection of E. ruminantium. Positive results were obtained for E. ruminantium and five species of Anaplasma including a zoonotic species. To our knowledge, this is the first report of infection of domestic ruminants with A. phagocytophilum, A. ovis and Anaplasma sp. ‘Omatjenne’ in Ethiopia. Conclusion The present study showed widespread occurrence of Anaplasma sp. 'Omatijenne' in African cattle and five Anaplasma species in Ethiopia

Epidemiological investigations of Salmonella and Escherichia coli associated morbidity and mortality in layer chickens in Hawassa city, Southern Ethiopia

Background: This study was conducted with the objectives of estimating the morbidity and mortality rates in layer chickens, identifying the risk factors associated with morbidity and mortality, and identifying the major bacterial pathogens affecting small-scale commercial layers in Hawassa. A longitudinal observational study design was employed from November 2019 to March 2020. The chickens on selected farms were checked for morbidity and mortality twice a week. During each visit, clinical examination of sick birds and pathological investigation of dead birds were conducted. Cloaca samples were collected for isolation and identification of Salmonella spp. and E. coli. A Cox proportional hazard model was used to quantify the effects of various risk factors on the morbidity and mortality rates observed. Results: Of the 8976 chickens followed, 106 developed clinical disease, giving a morbidity of 1.18% (95% CI: 0.97, 1.43). The overall morbidity rate was 2.37 (95% CI: 1.94, 2.87) per 1000 chicken months. A total of 101 of the chickens under study were found dead, yielding a mortality of 1.13% (95% CI: 0.92, 1.37) and a mortality rate of 2.26 (95% CI: 1.84, 2.75). Multivariable Cox regression analysis showed that farm hygiene, the experience of farm manager, housing condition, housing systems, the availability of veterinary services and age of chicken were important risk factors for morbidity and mortality. Out of 58 cloacal samples collected from sick chickens, 7 (12.07%; 95% CI: 4.99, 23.29) yielded positive results for Salmonella spp., while 25 (43.10%; 95% CI: 30.16, 56.77) yielded positive results for E. coli. Out of swabs collected from 8 randomly selected sick chickens after necropsy, 3 (37.5%) were found to be positive for Salmonella spp. Four (50%) of them were positive for E. coli. Swabs were collected and cultured from 15 dead chickens, and of these, 2 (13.33%) and 7 (46.67%) were found to be positive for Salmonella spp. and E. coli, respectively. Farm hygiene, age of chickens, housing conditions and frequency antibiotics use were important risk factors for colibacillosis and salmonellosis. Conclusions: Although the incidence of chicken morbidity and mortality was relatively low in the present study, important risk factors have been identified in the poultry farms of Hawassa City, southern Ethiopia. Therefore, comprehensive poultry farm management practices are needed to mitigate risk factors for morbidity and mortality as well as colibacillosis and salmonellosis. Identification of the serotypes of Salmonella spp. and E. coli should be carried out

Anaplasma, Ehrlichia and rickettsial pathogens in ixodid ticks infesting cattle and sheep in western Oromia, Ethiopia

Although ticks are widely distributed in all agro-ecological zones of Ethiopia, information on tick-borne pathogens is scarce. This study was conducted to determine the presence of Anaplasma spp., Ehrlichia spp., and Rickettsia spp. in Rhipicephalus evertsi and Rhipicephalus (Boophilus) decoloratus collected from cattle and sheep at Bako, western Oromia, Ethiopia, using polymerase chain reaction and sequencing. Anaplasma ovis and Anaplasma spp., Ehrlichia ruminantium and Ehrlichia spp. were detected in Rh. decoloratus, while only A. ovis was detected in Rh. evertsi. Both tick species were found to harbor DNA belonging to Rickettsia spp. and Rickettsia africae. Our findings highlight the risk of infection of animals and humans with these zoonotic tick-borne bacteria in Ethiopia

Molecular Survey and Identification of Campylobacter spp. in Layer Farms in Central Ethiopia

Few data are available on Campylobacter spp. presence in chickens in Ethiopia. Due to its importance for both the poultry sector and public health, a sampling activity was planned to evaluate Campylobacter spp. presence in layer farms in Bishoftu and Mojo, Central Ethiopia. Twenty cloacal pooled samples were collected and tested with molecular assays for detection and Sanger-sequenced for species identification. As a secondary aim, samples were also tested for Salmonella spp. by PCR, and all samples were negative. On the other hand, 70% of cloacal swab pools were positive for Campylobacter spp.: 71.4% of the positive samples belonged to C. jejuni species, 21.4% to C. avium and 7.1% to C. helveticus. Campylobacter spp. was identified in almost all farms regardless of farm and flock size, age and hybrid types of the birds and antimicrobial treatment. Campylobacter jejuni is a common finding in chickens, whereas species such as C. avium and C. helveticus were newly reported in Ethiopia, revealing a variability that needs to be monitored in light of the public health significance of this pathogen