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Marek’s disease (MD) is a highly contagious and oncogenic viral disease of poultry, causing significant economic losses due to mortality and reduced performance. The rapid evolution of Marek’s disease virus (MDV) has been reported in poultry farms, often overcoming vaccination and leading to disease outbreaks. This study aimed to detect and molecularly characterize circulating MDV strains in Tanzania, with a focus on their genetic relationship with the vaccine strains currently in use (HVT and CVI988). Samples were collected from six livestock representative zones in Tanzania (Central, Eastern, Southern, Southern Highlands, Lake, and Northern Zone) and analyzed using polymerase chain reaction (PCR) and sequencing of key oncogenic genes (meq, pp38, and vIL-8). Phylogenetic analysis was conducted using MEGA 12 software to determine the genetic relationships between Tanzanian isolates and MDV strains from Africa and other continents. The results confirm the widespread circulation of MDV in Tanzania, with an overall prevalence of 18.08% across all surveyed zones. Molecular characterization of the meq, pp38, and vIL-8 genes revealed high sequence similarity with previously reported MDV strains from Egypt, Nigeria, Israel, and China, with clustering observed in the phylogenetic analysis. Notably, Tanzanian MDV strains exhibited amino acid substitutions associated with increased virulence, particularly in the meq gene, which plays a crucial role in MDV-induced tumorigenesis. These findings suggest that MDV strains in Tanzania have undergone genetic changes that could potentially affect vaccine efficacy. Therefore, this study provides valuable information for vaccine manufacturers, poultry farmers, and policymakers in Tanzania, enabling informed decisions when selecting vaccines for MD control.

Rift Valley fever (RVF) is a mosquito-borne zoonosis that causes periodic and explosive epizootics/epidemics in Africa and the Arabian Peninsula. In Rwanda, RVF virus (RVFV) circulation has resulted into two major outbreaks in 2018 and 2022, both of which involving humans. Information on the magnitude of human exposure to RVFV in the country is scarce. This cross-sectional study aimed to investigate the seroprevalence of RVFV and associated risk factors in humans in the Eastern province of Rwanda, 3 years after the end of the 2018 outbreak. A total of 552 outpatients at health facilities in five districts of the Eastern province were randomly sampled and interviewed between December 2021 and February 2022. Exposure to RVFV was examined by detection of anti-RVFV IgG/IgM antibodies in serum samples using a competitive enzyme linked immunosorbent assay (c-ELISA). Bivariate and multivariate logistic regressions were used to assess the association between risk factors and RVFV seropositivity. The findings revealed an overall seroprevalence of 9.6%. The highest seropositivity, but without significant difference, was observed in Bugesera district (12.9%), followed by Kayonza, (10.8%), Kirehe (8.6%), Rwamagana (7.0%) and Ngoma (6.8%). Odds of seropositivity were significantly higher in people with a history of slaughtering animals (OR 2.26, 95% CI 1.04 - 4.91, p = 0.03), and milking (OR 2.60, 95% CI 1.23 - 5.49, p = 0.012). Sex and age-related differences were not significant. This study is a first serological survey of RVFV spillover to humans in the country and shows that rural communities in Rwanda have been exposed to RVFV. These findings suggest the Eastern province of Rwanda as a potential hotspot for RVFV circulation, and emphasize the need for a countrywide One Health-based surveillance, prevention, and control strategy to minimize the effects of RVFV in the country.

The emergence of new virulent genotypes and the continued genetic drift of Newcastle disease virus (NDV) implies that distinct genotypes of NDV are simultaneously evolving in different geographic locations across the globe, including throughout Africa, where NDV is an important veterinary pathogen. Expanding the genomic diversity of NDV increases the possibility of diagnostic and vaccine failures. In this review, we systematically analyzed the genetic diversity of NDV genotypes in Africa using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Information published between 1999 and 2022 were used to obtain the genetic background of different genotypes of NDV and their geographic distributions in Africa. The following genotypes were reported in Africa: I, II, III, IV, V, VI, VII, VIII, XI, XIII, XIV, XVII, XVIII, XX, and XXI. A new putative genotype has been detected in the Democratic Republic of the Congo. However, of 54 African countries, only 26 countries regularly report information on NDV outbreaks, suggesting that this number may be vastly underestimated. With eight different genotypes, Nigeria is the country with the greatest genotypic diversity of NDV among African countries. Genotype VII is the most prevalent group of NDV in Africa, which was reported in 15 countries. A phylogeographic analysis of NDV sequences revealed transboundary transmission of the virus in Eastern Africa, Western and Central Africa, and in Southern Africa. A regional and continental collaboration is recommended for improved NDV risk management in Africa.

Rift Valley fever (RVF), a mosquito-borne transboundary zoonosis, was first confirmed in Rwanda’s livestock in 2012 and since then sporadic cases have been reported almost every year. In 2018, the country experienced its first large outbreak, which was followed by a second one in 2022. To determine the circulating virus lineages and their ancestral origin, two genome sequences from the 2018 outbreak, and thirty-six, forty-one, and thirty-eight sequences of small (S), medium (M), and large (L) genome segments, respectively, from the 2022 outbreak were generated. All of the samples from the 2022 outbreak were collected from slaughterhouses. Both maximum likelihood and Bayesian-based phylogenetic analyses were performed. The findings showed that RVF viruses belonging to a single lineage, C, were circulating during the two outbreaks, and shared a recent common ancestor with RVF viruses isolated in Uganda between 2016 and 2019, and were also linked to the 2006/2007 largest East Africa RVF outbreak reported in Kenya, Tanzania, and Somalia. Alongside the wild-type viruses, genetic evidence of the RVFV Clone 13 vaccine strain was found in slaughterhouse animals, demonstrating a possible occupational risk of exposure with unknown outcome for people working in meat-related industry. These results provide additional evidence of the ongoing wide spread of RVFV lineage C in Africa and emphasize the need for an effective national and international One Health-based collaborative approach in responding to RVF emergencies.

Newcastle disease virus (NDV) is an extremely contagious and deadly virus that affects numerous bird species, posing serious threats to poultry production on a global scale. In addition to implementing biosecurity practices in farming systems, vaccination remains the most effective means of controlling Newcastle disease (ND). However, while existing commercial vaccines provide some level of protection, the effectiveness of these vaccines can be questionable, particularly in field settings where the complexity of vaccination program implementation poses significant challenges, especially against virulent genotypes of NDV. A genotype-matched NDV DNA vaccine could potentially offer a more effective vaccination approach than currently available live attenuated vaccines. By being specifically tailored to match circulating strains, such a vaccine might improve efficacy and reduce the risk of vaccine failure due to genotype mismatch. To develop an alternative vaccine approach, two ND DNA vaccines were constructed in this study. Each vaccine developed in this study contains the fusion (F) and haemagglutinin-neuraminidase (HN) genes of a virulent NDV genotype VII isolate from Tanzania. Interferon lambda-3 (IFNλ3; IL-28b), which has demonstrated capacity to significantly enhance specific adaptive immune responses and decreased levels of inflammatory cytokines, as well as improved protective responses at a high viral challenge dose, was included in one of the developed vaccines. These plasmids were designated pTwist-F-HN-VII-IL28b and pTwist-F-HN-VII. The two plasmids differed in that pTwist-F-HN-VII-IL28b contained the cytokine adjuvant IL-28b. Transfection of cells and subsequent immunofluorescence assays indicated that both plasmids expressed high levels of NDV F-HN proteins. In vivo immunization demonstrated that chicks intramuscularly immunized with pTwist-F-HN-VII-IL28b exhibited significant immune responses compared to chicks immunized with pTwist-F-HN-VII or the commonly used LaSota vaccine (LaSota), which was used as a control. The protective efficacy of pTwist-F-HN-VII-IL28b was 80% after challenge with the highly virulent NDV strain ON148423, compared to 60% for chicks vaccinated using LaSota, and pTwist-F-HN-VII. The findings of this study indicate that IL-28b can be employed as a molecular adjuvant for NDV vaccines. This study represents a key milestone in Newcastle disease vaccine research, particularly in the development of a genotype-matched DNA vaccine candidate. Additionally, this study demonstrated that the combination of F, HN, and IL-28b elicits an efficacious immune response against virulent NDV strains.

Rift Valley fever virus (RVFV) is an emerging mosquito-borne arbovirus of One Health importance that caused two large outbreaks in Rwanda in 2018 and 2022. Information on vector species with a role in RVFV eco-epidemiology in Rwanda is scarce. Here we sought to identify potential mosquito vectors of RVFV in Rwanda, their distribution and abundance, as well as their infection status. Since an outbreak of RVF occurred during the study period, data were obtained both during an interepidemic period and during the 2022 Rwanda RVF outbreak. Five districts of the eastern province of Rwanda were prospected using a combination of unbaited light traps and Biogents (BG Sentinel and Pro) traps baited with an artificial human scent during three periods, namely mid-August to mid-September 2021, December 2021, and April to May 2022. Trapped mosquitoes were morphologically identified and tested for viral evidence using both RT-PCR and virus isolation methods on a Vero cell line. A total of 14,815 adult mosquitoes belonging to five genera and at least 17 species were collected and tested as 765 monospecific pools. Culex quinquefasciatus was the most predominant species representing 72.7% of total counts. Of 527 mosquito pools collected before the 2022 outbreak, a single pool of Cx. quinquefasciatus showed evidence of RVFV RNA. Of 238 pools collected during the outbreak, RVFV was detected molecularly from five pools (two pools of Cx. quinquefasciatus, two pools of Anopheles ziemanni, and one pool of Anopheles gambiae sensu lato), and RVFV was isolated from the two pools of Cx. quinquefasciatus, from Kayonza and Rwamagana districts, respectively. Minimum infection rates (per 1000 mosquitoes) of 0.4 before the outbreak and 0.6–7 during the outbreak were noted. Maximum-likelihood phylogenetic analysis indicates that RVFV detected in these mosquitoes is closely related to viral strains that circulated in livestock in Rwanda and in Burundi during the same RVF outbreak in 2022. The findings reveal initial evidence for the incrimination of several mosquito species in the transmission of RVFV in Rwanda and highlight the need for more studies to understand the role of each species in supporting the spread and persistence of RVFV in the country.

Poultry production is one of the fastest-growing agricultural sub-sectors in Nigeria. However, it faces numerous challenges, mainly from frequent Newcastle disease (ND) outbreaks even in vaccinated flocks, causing huge economic losses. The recurring outbreaks raise concerns about the efficacy of ND vaccine and the need to understand the immunomodulatory mechanism of the ND virus (NDV). This study investigated a recent outbreak of NDV that resulted in 95% mortality in a vaccinated broiler parent stock in Nigeria by utilizing immunoinformatic tools to elucidate the possible immune evasion features of the disease-causing NDV. Genetic analysis of the complete fusion gene showed that the NDV isolate belong to sub-genotype XIV.2, a virulent strain prevalent in Nigeria. Predicted immunogenic peptides from the sub-genotype XIV.2 proteins revealed notable amino acid variations (R114Q, V118I, A220V) in both Major Histocompatibility Complex class I and II epitopes compared to common NDV vaccine and other prominent field strains. Modelling and structural validation of the BF2*2101 chicken allele showed 99% residues within the allowed regions in Ramachandran plot and − 6.61 Z-score, confirming its reliability. Immune simulation indicated that LaSota-Komorov prime-boost vaccine-simulation could not confer protection against sub-genotype XIV.2 virus simulated-challenge, despite eliciting humoral immune response. These results provide a valuable insight for developing ND vaccines that could effectively counter the immune cell interference of sub-genotype XIV.2, although further experimental validation is needed to characterize key biological interactions. A multifaceted approach encompassing improved biosecurity and the development of an effective sub-genotype XIV.2-matched vaccine is crucial to mitigate the persistent threat of ND in Nigeria.

African swine fever (ASF) is a hemorrhagic disease of domestic pigs and wild boars. The ASF virus (ASFV), a sole member of the family Asfarviridae and genus Asfivirus , causes this devastating disease. In sub‐Saharan Africa, ASFV is maintained through three interlinked cycles: the domestic cycle, the pig‐tick cycle, and the sylvatic cycle, which collectively sustain its endemic presence in the region. Interaction between wild and domestic pigs at livestock–wildlife interfaces, particularly in protected areas, poses a significant threat to smallholder farmers. This study aimed to investigate the socioeconomic impact and identify potential risk factors associated with ASF in Serengeti National Park’s (SNP’s) wildlife management area (WMA) in Tanzania. A cross‐sectional study involving 110 domestic pig‐keeping households in the five villages of SNP’s WMA was carried out. A semistructured questionnaire was used to collect data on risk factors and socioeconomic impact associated with ASF from consenting smallholder farmers. Additionally, the observational approach was used to assess pig production’s facilities, behaviors and practices involved in domestic pig production and management. Tissue samples including spleen, lymph nodes, and kidney were also collected from dead domestic pigs belonging to two villages, Nattambiso and Robanda, to confirm the existence of the virus in the study area by using polymerase chain reaction (PCR). Descriptive statistics, univariable, and multivariable logistic analyses were performed to determine risk factors associated with ASF occurrence between October 2021 and April 2022 in the study area. A total of 12 ASF outbreaks affecting 1198 cases that led to 969 domestic pig deaths were reported. The ASFV was confirmed to be positive in all domestic pigs from which tissue samples were collected in the included villages. The case fatality rates (CFRs) from the reported previous ASF incidence varied from 77.5% to 85.2% with an overall CFR of 80.8%. A sum of 163,300,000 Tanzanian Shillings (approximately equivalent to 70,085 USD) loss was recorded in the studied WMA. The major risk factors that correlated with ASF occurrence were encountered ASF previously (odds ratio [OR] = 13.58, 95% confidence interval [CI] = 2.79–87.28), selling pig products with ASF before (OR = 9.43, CI = 1.76–70.02), whilst taking no risk action to prevent loss (OR = 0.14, CI = 0.03–0.63) and swill treatment (OR = 0.10, CI = 0.01–0.54) negatively correlated with ASF. Improving awareness on farm‐level biosecurity, husbandry, and management practices is vital to preventing ASF outbreaks and wildlife spillover, safeguarding livestock health, and promoting economic stability in wildlife–livestock–human interfaces.

Introduction: Peste des petits ruminants (PPR) is an infectious disease that imposes substantial economic burdens on small ruminants (SR) production. For Tanzania to develop efficient management and eradication plans, it is essential to comprehend the seroprevalence of PPR designated for global elimination by 2030. Methodology: This study investigated the prevalence of PPR in animals kept under pastoral and agropastoral communities in Tanzania. A total of 1,128 blood samples from SR were collected and analyzed for PPR-specific antibodies using the HPPR-b ELISA technique. Multivariate logistic regression was used to analyze the risk factors Results: The overall seroprevalence was 10%. Higher seropositivity was observed in the Kiteto, Longido, and Simanjiro districts of the northern zone and the Mbarali district of the southern highlands, with the seroprevalence decreasing trend from the northern to southern zones. Multivariate logistic regression analysis for risk factors identified significant differences in seroprevalence across disease surveillance zones, with odds ratios (OR) ranging from 2 to 3. Conclusions: Agropastoral production systems exhibited lower PPR seroprevalence compared to pastoral systems. The increasing seropositivity in the Mbarali district suggests a southward spread of PPR, increasing a threat to Tanzania`s southern regions and neighboring countries. The disease`s dissemination is closely linked to livestock trading infrastructure, highlighting the need for periodic seromonitoring. Control efforts should prioritize highly affected northern zones and implement strict regulations on animal movement to protect less-affected southern areas.

Background Lumpy Skin Disease (LSD) is endemic in sub-Saharan countries and is currently a global threat to the cattle industry. Information on the circulating Capripoxvirus lumpyskinpox, formerly known as Lumpy Skin Disease Virus (LSDV), and other poxviruses infecting cattle is very scant in Tanzania. The current study aimed to confirm and characterize LSDV and other poxviruses infecting cattle, from LSD suspected outbreaks in Tanzania. Methods A total of 24 samples were collected from four LSD suspected outbreaks reported in Tanzania between February and May 2023. Samples were screened for LSDV genome by real-time PCR and then subjected to a high-resolution multiplex melting (HRM) assay where 10 samples were positive for Capripoxvirus (CaPV) and one sample was Parapoxvirus (PPV) positive. Four LSDV genes; RPO30, GPCR, EEV glycoprotein and B22R and the partial B2L gene of PPVs were analyzed. Results All targeted LSDV genes from the Tanzanian isolates showed 100% similarity and isolates clustered with commonly circulating LSDV field isolates. Furthermore, the single nucleotide polymorphism (SNP) at position 240 (A-> G) of the EEV gene differentiates the Tanzanian LSDVs from the group of ancient Kenyan LSDV isolates while the B22R sequences of the Tanzanian LSDV isolates differed from the LSDV Neethling and LSDV KSGP-0240 derived vaccines. Sequence analysis of the partial B2L gene of the Tanzanian parapoxvirus bovinestomatitis, formerly known as Bovine papular stomatitis virus (BPSV) showed a different BPSV strain circulating compared to publicly available sequences. Conclusion These findings confirm the presence of LSDV in Tanzania, which suggesting the need for establishing an effective control program and continuous monitoring. The presence of a typical profile for Tanzania BPSV is an indication that, although never reported before, BPSV is established in the country therefore this virus should be included in the differential diagnosis of LSDV.