Molecular basis of susceptibility to Newcastle disease virus challenge in exotic and local Tanzanian chicken

A Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of Doctor of Philosophy in Life Sciences of the Nelson Mandela African Institution of Science and Technology, Arusha, TanzaniaThis research aimed to investigate genetic mechanisms of susceptibility to Newcastle disease virus (NDV) in exotic and local Tanzanian chicken. In the first experiment kuroiler, broiler and local Tanzanian chickens were vaccinated with live La Sota Newcastle disease (ND) vaccine, and body weight gain and antibody responses were used as phenotypes to evaluate chicken susceptibility to NDV. Results showed higher (P < 0.05) antibody titres in kuroilers (3.81 ± 0.06) as compared to local chickens (3.73 ± 0.07) and broilers (3.53±0.06) at day 10 post-vaccination. However, antibody titres were not different (P > 0.05) between kuroilers and local Tanzania chickens at day 21 post-vaccination. Although results showed differences between vaccinated and control groups, the results could not give clear cut differences on variations in susceptibility, probably because a less virulent strain of NDV was used and the housing environment might have created some confounding variables. Therefore, in the second experiment virulent NDV and chicken embryo model were used to investigate chickens variation in susceptibility to NDV where time of death post-challenge was used as a phenotype. A total of 355 (87 Sasso, 129 kuroiler and 139 local) 16-day-old chicken embryos were challenged with virulent NDV, and death time was recorded post-challenge. Candidate gene and selective genotyping approaches were deployed, and therefore, chicken embryos from high (15%) and less (15%) susceptible cohorts were genotyped for selected genes (myxovirus resistance gene (Mx) and LEI0258). As expected, chicken embryos survival time was highly variable within a breed. Furthermore, it was demonstrated that chicken Mx gene G2032A genotypes (AA, AG, and GG) were associated (P < 0.05) with susceptibility. Interestingly, for the first time, findings demonstrated an association between chicken Mx gene promoter polymorphisms and chicken embryos susceptibility to virulent NDV. Specifically, SNP4 G>A mutation located within IFN-stimulating response element was associated (LR: 6.97, P = 0.03) with susceptibility. Also, haplotype ACGC was associated (OR: 9.8, 95% CI: 1.06 – 79.43, P = 0.042) with the same trait, and had a protective effect. The present findings are very useful in breeding programs designed to develop chicken genotypes, which are less susceptible to NDV

Seroprevalence of bovine paratuberculosis in Arusha, Northern Tanzania

Research Article published by American Journal of Research Communication Vol 2(10)Bovine paratuberculosis or Johne’s disease is chronic, contagious granulomatous enteritis of cattle which is caused by Mycobacterium avium subspecies Paratuberculosis (MAP). The disease was first reported in Tanzania in two farms located in Kilimanjaro region in 1960. Despite of quarantine measures that were instituted in the area between 1960-1963, additional cases were reported in Arusha (1976), Mpwapwa (1984), Morogoro (1994). The disease was last reported in the country more than 14 years ago at Kitulo dairy farm in Mbeya region. The paucity of cases has created an impression that the disease is absent from the country. However, the well-known persistence of (MAP) once introduced in the area suggests that the disease may still be present and spreading unnoticed in the country. To obtain information on current state of bovine paratuberculosis, a seroprevalence of the disease in cattle was conducted on bovine serum samples kept in the repository at the Arusha Tanzania Veterinary Laboratory Agency. A total of 207 bovine sera that were collected from urban and peri-urban Arusha as part of contagious bovine pleuropneumonia surveillance in 2011 were tested for MAP-pecific antibodies using the commercial ELISA. The overall seroprevalence was 5.3% (95% CI: 2.3 to 8.4%). These results confirm presence of bovine paratuberculosis in Arusha and indicate the disease may be prevalent in other parts of the country. This is the first seroprevalence report for paratuberculosis in Tanzania

Immune response following Newcastle disease immunization and growth performance of kuroiler, broiler and local Tanzanian chickens

This research article was published by Academic Journals in 2020Chicken is a major livestock species raised by smallholder households in rural areas in developing countries of Sub-Saharan Africa as a chief source of meat protein and income generation. However, Newcastle disease largely compromises the production of this precious bird under backyard production settings. The purpose of the study was to assess antibody responses and growth performance following Newcastle disease vaccination in kuroiler, broiler, and local Tanzanian chickens raised under the same tropical environmental condition. In the experiment, a total of 358 chickens comprised of 127 kuroilers, 121 broilers, and 110 local Tanzanian chickens were raised for seven weeks, and body weights were recorded weekly. Birds were vaccinated at four weeks, and blood samples were collected at days 10, and 21 post-vaccination for antibody titres quantification by ELISA test. Results demonstrated higher (P < 0.05) antibody titres in kuroilers (3.81 ± 0.06) as compared to local chicken (3.73 ± 0.07) and broilers (3.53±0.06) at day 10 post-vaccination. The growth performance of local Tanzanian chickens was comparable to that of kuroilers. The present findings contribute to on-going work in understanding chicken immune responses against NDV and inform breeding programs designed for developing chickens with increased resistance to NDV

Association of Chicken Mx1 Polymorphisms with Susceptibility in Chicken Embryos Challenged with Virulent Newcastle Disease Virus

This research article published by Science Alert, 2020Background and Objective: Genetic selection of chicken genotypes that are less susceptible to Newcastle disease virus (NDV) is a promising option. The present study aimed to investigate polymorphism of chicken Mx1 gene G2032A SNP in different chicken breeds in Tanzania and association with chicken embryos susceptibility to virulent NDV. Materials and Methods: A total of 355 (87 Sasso, 129 Kuroiler and 139 local) 16 days old chicken embryos were infected with 0.1 mL minimum lethal dose (103/0.1 mL) of virulent NDV suspension. The time of death was recorded and selective genotyping was deployed where chicken embryos from high (15%) and less (15%) susceptible cohorts were genotyped by PCR-length polymorphism. Two forward and a reverse primers were used to generate 2 different sizes of PCR product of A and G alleles of chicken Mx1 gene G2032A SNP. Results: As expected chicken embryos survival was highly variable within a breed. The frequency of allele A was higher than allele G in chicken breeds. Furthermore, using Pearson’s X2 test of independence, it was demonstrated that chicken Mx1 gene G2032A genotypes (AA, AG and GG) were associated (p<0.05) with chicken embryos susceptibility to virulent NDV infection. The frequency of genotype AA was higher in less susceptible chicken embryos, whereas, frequency of genotype GG and AG was higher in high susceptible chicken embryos. Conclusion: Results from the present study provide valuable information on the potential role of Mx1 gene polymorphism for selection of chickens that are resistant to virulent NDV infection

Transcriptional Innate Immune Response of the Developing Chicken Embryo to Newcastle Disease Virus Infection

Traditional approaches to assess the immune response of chickens to infection are through animal trials, which are expensive, require enhanced biosecurity, compromise welfare, and are frequently influenced by confounding variables. Since the chicken embryo becomes immunocompetent prior to hatch, we here characterized the transcriptional response of selected innate immune genes to Newcastle disease virus (NDV) infection in chicken embryos at days 10, 14, and 18 of embryonic development. The results suggest that the innate immune response 72 h after challenge of 18-day chicken embryo is both consistent and robust. The expression of CCL5, Mx1, and TLR3 in lung tissues of NDV challenged chicken embryos from the outbred Kuroiler and Tanzanian local ecotype lines showed that their expression was several orders of magnitude higher in the Kuroiler than in the local ecotypes. Next, the expression patterns of three additional innate-immunity related genes, IL-8, IRF-1, and STAT1, were examined in the highly congenic Fayoumi (M5.1 and M15.2) and Leghorn (Ghs6 and Ghs13) sublines that differ only at the microchromosome bearing the major histocompatibility locus. The results show that the Ghs13 Leghorn subline had a consistently higher expression of all genes except IL-8 and expression seemed to be subline-dependent rather than breed-dependent, suggesting that the innate immune response of chicken embryos to NDV infection may be genetically controlled by the MHC-locus. Taken together, the results suggest that the chicken embryo may represent a promising model to studying the patterns and sources of variation of the avian innate immune response to infection with NDV and related pathogens

Seroprevalence of Paratuberculosis in Goats and Sheep in Arusha, Northern Tanzania

Research Article published by International Journal of Science and Research (IJSR) Volume 3 Issue 9, September 2014A retrospective cross‐sectional study was conducted to investigate the seroprevalence of paratuberculosis in small ruminants in the Arusha Municipality. A total of 383 samples comprising of 192 goat‐ and 191 sheep‐sera from Arusha Municipality collected in the late 2010 and early 2011 by Tanzania Veterinary Investigation Agency – Arusha for surveillance on peste des petits ruminants were tested for antibodies specific to Mycobacterium avium subspecies paratuberculosis using the commercially available PARACHEK®2 indirect ELISA kit. Twenty one (21) of 192 (10.9%: 95% CI; 7.3 – 16.1%) goat sera were positive; however none of 191 sheep sera screened were sero-positive for paratuberculosis. This is the first report on seroprevalence of paratuberculosis in goats in Arusha and in Tanzania as a whole. The fact that seropositive cattle were previously detected in samples collected in the same flock at the same time indicates the disease is well established in the Arusha. Furthermore, the co-infection of cattle and goats may have implication on the epidemiology of the disease in the area. The sero-negativity of all sheep samples tested is yet to be established but may be due one or a combination of factors. Since the Parachek ELISA kit is capable of detecting responses in sheep, one of the possible reasons may be that the prevalent M.paratuberculosis strain(s) in Arusha is type II or C strain that preferentially infects cattle and goats as opposed to type I or S strain which preferentially infects sheep. Alternatively, the prevalence and or the antibody titres in sheep may have been too low to be detected within the sensitivity of the Parachek ELISA kit

Current Trend and Future Perspectives of Paratuberculosis in Tanzania

Paratuberculosis prevalence, economic and public health significance in animal populations is well documented in most of the developed countries. In African countries however, information on paratuberculosis is sparse mainly due to lack of surveillance and research on the disease. In Tanzania, the disease was first reported in Kilimanjaro in year 1960 and up until year 2014, different cases have been reported in almost all agro ecological zones of the country, but there is no epidemiological information to link the cases. This creates an impression that the disease is absent in Tanzania. However, it is recently realized that in any African country that has done some surveillance, the disease has been confirmed to be present. The aim of the present review is to revisit the trend of paratuberculosis in Tanzania from 1960 when the disease was first reported to the current situation in year 2022. Attempt is made to highlight the possible link between the cases and suggest future strategies to enable the country grips with the disease. It is anticipated that this review is going to raise awareness on paratuberculosis in Tanzania and catalyze the institution of paratuberculosis surveillance and control programs in Tanzania

Epidemiology of Newcastle disease in poultry in Africa: systematic review and meta-analysis

This research article was Springer Nature, 2022The present study intended to determine the prevalence of Newcastle disease in unvaccinated backyard poultry in Africa. Using the PRISMA approach, a systematic review and meta-analysis of 107 epidemiological studies was conducted. The meta-analysis identified significant variation of both seroprevalence (I2 = 99.38, P = 0.00) and Newcastle disease virus prevalence (I2 = 99.52, P = 0.00) reported in various studies included in this review. Publication bias was not detected in either case. Seroprevalence of Newcastle disease was 40.2 (95%CI 32.9–47.8). Seroprevalence was significantly influenced by sampling frame and the African region where the studies were conducted. The prevalence of Newcastle disease virus (NDV) was 12% (95%CI 7.3–17.8), and the variation was influenced by sampling frame, diagnostic test, and regions where the studies were conducted. Also, Newcastle disease (ND) accounted for 33.1% (95%CI 11.9–58.1) of sick chickens. Results also indicated that genotypes VI and VII are widely distributed in all countries included in the study. However, genotype V is restricted in East Africa, and genotypes XIV, XVII, and XVIII are restricted in West and Central Africa. On the other hand, genotype XI occurs in Madagascar only. In addition, virulent genotypes were isolated from apparently healthy and sick birds. It is concluded that several genotypes of NDV are circulating and maintained within the poultry population. African countries should therefore strengthen surveillance systems, be able to study the viruses circulating in their territories, and establish control programs

The genetic diversity of local african chickens: A potential for selection of chickens resistant to viral infections

Research Article published by Poultry Science Association Inc.Viral infections impose a great threat to backyard chicken production among poor rural households in developing countries. These infections limit the contribution of chicken production in improving the livelihoods of poor communities, particularly in Africa. Chicken viral infections lack treatment options; control and prevention depend primarily on adoption of vaccines and good farm management practice such as the institution of biosecurity measures. In backyard production systems, these control options are less practical and less feasible to implement. Research has demonstrated the role of genetic diversity of farmed animals and birds in explaining variation in resistance to infectious diseases and suggests that heterogeneous populations are less susceptible to disease than homogeneous populations. Local African chicken ecotypes have high genetic diversity and have demonstrated the ability to survive persistent exposure to pathogens and harsh environmental conditions. This suggests that local African chickens have the genetic potential to enhance breeding strategies for resistance to viral infections. Despite the ongoing threat of infectious disease and dynamic of diseases epidemiology attributed by climate change, little has been done to harness the genetic potential of local African chicken ecotypes to breed for resistant traits. To lay the foundation for future research, this review paper presents a summary of challenges facing current chicken viral infections control and prevention options in local African chickens, and gives an overview of documented information on the genetic diversity and population structure of local African chicken ecotypes

Association of LEI0258 marker alleles and susceptibility to virulent Newcastle Disease Virus infection in Kuroiler, Sasso, and Local Tanzanian Chicken Embryos

This research article published by Hindawi, 2020Newcastle disease (ND) control by vaccination and an institution of biosecurity measures is less feasible in backyard chicken in developing countries. Therefore, an alternative disease control strategy like the genetic selection of less susceptible chicken genotypes is a promising option. In the present study, genetic polymorphism of LEIO258 marker and association with susceptibility to virulent Newcastle disease virus (NDV) infection in Kuroilers, Sasso, and local Tanzanian chicken embryos were investigated. Samples from high (15%) and less (15%) susceptible cohorts were genotyped by sequencing of LEI0258 marker. A total of 75 DNA sequences comprised of 29 Kuroiler, 29 local Tanzanian chickens, and 17 Sasso were analyzed. Neighbor-joining phylogenetic trees were constructed to depict the clustering of LEI0258 marker alleles and relationship with susceptibility. Alleles with frequency ≥3 were considered for association with susceptibility by the use of the inference technique. The present findings suggest that some LEI0258 marker genetic polymorphisms apart from LEI0258 marker allelic based on sizes may be linked with chicken MHC-B haplotypes that confer chickens variability in resistance or susceptibility to infections. Furthermore, these results demonstrate the presence of relationship between LEI0258 marker polymorphisms and variations in chicken susceptibility to NDV infection, which could be utilized in breeding programs designed to improve chicken disease resistance