Humoral Immune Response in Calves Vaccinated with Monovalent Vaccines or a Trivalent Combination Thereof and Matching of These Vaccines to the Selected Circulating Foot-and-Mouth Disease Viruses in Ethiopia.

Foot-and-mouth disease (FMD) is an endemic, highly contagious, and devastating disease of livestock production in Ethiopia. Control of this disease relies mainly on prophylactic vaccination by willing farmers without a countrywide vaccination program. The objectives of this study were to quantify the humoral immune response and evaluation of the serological relationship of the vaccine strain used with representative field strain isolates. This was performed by primo vaccination of 6-9-month-old Holstein Friesian calves (35 treatment and 4 control calves) on day one and booster vaccination on day 28. Calves were vaccinated using the locally available National Veterinary Institute (NVI), Bishoftu, Ethiopia, inactivated aluminum hydroxide adjuvant monovalent (either O, A, SAT-2 alone) or trivalent (combination of A, O, SAT-2) vaccine (A/ETH/6/2000 (G-VII, O/ETH/38/2005(EA-3) and SAT-2/ETH/64/2009(XIII)). A 2 mL or 4 mL dose was used to vaccinate all calves except the animals that served as a control. In the case of the trivalent vaccine, a 4 mL dose was used to vaccinate calves. The serum was collected at 7, 14, 21, 28, and 56 days post-vaccination (d.p.v.). The humoral immune response was quantified by the solid-phase competitive enzyme-linked immunosorbent assay (SPC ELISA) and the virus-neutralization test (VNT). The serological relationship of heterologous and homologous viruses was also evaluated by adjuvant vaccine matching tests. The r1-value was determined using serum collected 21 d.p.v. An increase in immune response was observed from 7 d.p.v. to 28 d.p.v. in calves who received a 4 mL dose containing a 107.24 antigen load of 100 tissue culture infective dose (100TCID50) virus titer in the formulation. Upon receiving a booster dose on day 28, the humoral immune response was checked on the 56th day post-initial vaccination. Amounts of 54%, 72%, 79%, and 72% of inhibition for A, O, SAT-2, and trivalent vaccine in the three serotypes SPCE, respectively, was measured. Here, it was found that the immune response of calves increased from day 7 to 56, as evidenced by SPCE analysis. Likewise, an increase in antibody titer measured by a one-dimensional virus neutralization assay was also in line with SPCE analysis. This indicates that the vaccine is capable of inducing a neutralizing antibody that confers a protective immune response in 70%, 62%, and 100% heterologous field strains of A, O, and SAT-2 isolates, respectively, and has an average antigenic relationship of >0.3 with a standard deviation of +0.05 (N = 3) to the vaccine strains A/ETH/6/2000, O/ETH/38/2005 and SAT-2/ETH/64/2009, respectively, when using the one-dimensional virus neutralization test. The contribution and importance of this study is a confirmation of the vaccine and the field strain serological relationship for serotype SAT-2 strain and further research/change of vaccination strategy/ improvement in the currently used vaccine to cover a wide range of prevailing genotypes/lineages and induction of sound immune response after vaccination for serotype A and O strain. This study suggests that the trivalent vaccine produced by the National Veterinary Institute containing viral isolates from serotype O, A, and SAT-2 has a good serological relationship with the majority of circulating field strains in Ethiopia.

Isolation and Molecular Detection of Marek's Disease Virus from Outbreak Cases in Chicken in South Western Ethiopia.

Background: Marek's disease virus is a devastating infection, causing high morbidity and mortality in chickens in Ethiopia. Methods: The current study was conducted from March to November, 2021 with the general objective of performing antemortem and postmortem, isolation, and molecular detection of Marek's disease virus from outbreak cases in southwestern Ethiopia. Accordingly, based on outbreak information reported from the study sites namely, Bedelle, Yayo, and Bonga towns in southwestern Ethiopia, 50 sick chickens were sampled. The backyard and intensive farming systems of chickens were included in the sampling and priorities were given for chickens that showed clinical signs that are characteristics of Marek's disease. Results: By clinical examinations, paralysis of legs and wings, gray eye, loss of weight, difficulty in breathing, and depression were recorded on all chickens sampled for this study and death of diseased chickens was observed. In addition, enlargement of the spleen and gross lesions of the liver and heart were recorded during postmortem examination. The death of infected chickens was observed in both vaccinated and non-vaccinated flocks. Out of 50 pooled feather follicle samples, Marek's disease virus was isolated from 14/50 (28%) by cell culture method and out of six tissue samples, the virus was isolated from 5/6(83.30%). By Real time polymerization chain reaction technique, which was targeted to detect the Meq gene, Marek's disease virus was detected from 18/50 feather follicles which accounts for 36% of sampled chickens. Conclusion: In general, current study showed that the circulating Marek's disease virus in southwestern Ethiopia was caused by the oncogenic Gallid herpesvirus-2 (Serotype-1). Further research on molecular characterization of revolving virus in current and other regions is recommended for effective control of the disease through vaccination.

Community Wastewater-Based Surveillance Can Be a Cost-Effective Approach to Track COVID-19 Outbreak in Low-Resource Settings: Feasibility Assessment for Ethiopia Context.

Wastewater surveillance systems have become an important component of COVID-19 outbreak monitoring in high-income settings. However, its use in most low-income settings has not been well-studied. This study assessed the feasibility and utility of wastewater surveillance system to monitor SARS-CoV-2 RNA in Addis Ababa, Ethiopia. The study was conducted at nine Membrane Bio-reactor (MBR) wastewater processing plants. The samples were collected in two separate time series. Wastewater samples and known leftover RT-PCR tested nasopharyngeal swabs were processed using two extraction protocols with different sample conditions. SARS-CoV-2 wastewater RT-PCR testing was conducted using RIDA GENE SARS-CoV-2 RUO protocol for wastewater SARS-CoV-2 RNA testing. Wastewater SARS-CoV-2 RNA RT-PCR protocol adaptation, optimization, and detection were conducted in an Addis Ababa, Ethiopia context. Samples collected during the first time series, when the national COVID-19 case load was low, were all negative. Conversely, samples collected during the second time series were all positive, coinciding with the highest daily reported new cases of COVID-19 in Ethiopia. The wastewater-based SARS-CoV-2 surveillance approach is feasible for Addis Ababa. The COVID-19 wastewater based epidemiological approach can potentially fill the evidence gap in distribution and dynamics of COVID-19 in Ethiopia and other low-income settings.

Isolation and Molecular Detection of Newcastle Disease Virus from Field Outbreaks in Chickens in Central Ethiopia.

Background: Newcastle disease is a major viral disease of poultry. The virus is a major problem for chickens in Ethiopia and there is a scarcity of updated information on the virological and molecular status of confirmation of Newcastle disease outbreak cases in the country. Methods: Newcastle disease outbreaks were investigated from February 2021 to October 2021 in central Ethiopia to isolate and detect the virus by cell culture and reverse transcriptase PCR. A total of 44 pooled tissue specimens were sampled from sick and recently dead chickens showing typical clinical signs of Newcastle disease. Virus isolation were performed using DF-1 cells and detection of the virus was done by real-time PCR. Results: Out of 44 collected tissue samples, 38.63% (17/44) were positive on DF-1 cells. The result shows 17 of the clinically sick and dead chickens were positive for the virus by reverse transcriptase polymerase chain reaction. Based on the sample type, 54.54% (6/11) of the brain samples, 36.36% (4/11) of the intestines, 54.54% (6/11) of lung and trachea, 9% (1/11) of pooled liver, kidney, heart, and spleen samples were positive. Viruses were isolated in the proportions 37.5% (6/16), 25% (2/8), 50% (2/4), 25% (1/4), 50% (2/4) and 50% (4/8) from Sebeta, Bishoftu, Sululta, Nifas Silk, Kolfe and Yeka, respectively. Conclusion: This study showed that Newcastle disease is a major viral disease causing death of chickens in the study area. Therefore, any control approach should focus on the appropriate characterization of the virus strain causing the outbreak in the study area.