Newcastle Disease (ND) is a continuing global threat to domestic poultry, especially in developing countries, where severe outbreaks of velogenic ND virus (NDV) often cause major economic losses to households. Local chickens are of great importance to rural family livelihoods through provision of high-quality protein. To investigate the genetic basis of host response to NDV, three popular Tanzanian chicken ecotypes (regional populations) were challenged with a lentogenic (vaccine) strain of NDV at 28 days of age. Various host response phenotypes, including anti-NDV antibody levels (pre-infection and 10 days post-infection, dpi), and viral load (2 and 6 dpi) were measured, in addition to growth rate. We estimated genetic parameters and conducted genome-wide association study analyses by genotyping 1399 chickens using the Affymetrix 600K chicken SNP chip. Estimates of heritability of the evaluated traits were moderate (0.18–0.35). Five quantitative trait loci (QTL) associated with growth and/or response to NDV were identified by single-SNP analyses, with some regions explaining ≥1% of genetic variance based on the Bayes-B method. Immune related genes, such as ETS1, TIRAP, and KIRREL3, were located in regions associated with viral load at 6 dpi. The moderate estimates of heritability and identified QTL indicate that NDV response traits may be improved through selective breeding of chickens to enhance increased NDV resistance and vaccine efficacy in Tanzanian local ecotypes.

Background Free-range local chickens (FRLC) farming is an important activity in Tanzania, however, they have not been well-characterized. This study aimed to phenotypically characterize three Tanzanian FRLCs and to determine their population structure. A total of 389 mature breeder chickens (324 females and 65 males) from three popular Tanzanian FRLC ecotypes (Kuchi, Morogoro-medium and Ching’wekwe) were used for the phenotypic characterization. Progenies of these chickens were utilized to assess population structure. The ecotypes were collected from four geographical zones across Tanzania: Lake, Central, Northern and Coastal zones. Body weights and linear measurements were obtained from the mature breeders, including body, neck, shanks, wingspan, chest girth, and shank girth. Descriptive statistics were utilized to characterize the chickens. Correlations between the linear measurements and differences among the means of measured linear traits between ecotypes and between sexes were assessed. A total of 1399 progeny chicks were genotyped using a chicken 600 K high density single nucleotide polymorphism (SNP) panel for determination of population structure. Results The means for most traits were significantly higher in Kuchi relative to Ching’wekwe and Morogoro-medium. However, shank length and shank girth were similar between Kuchi and Morogoro-medium females. All traits were correlated with the exception of shank girth in Morogoro-medium. Admixture analyses revealed that Morogoro-medium and Ching’wekwe clustered together as one population, separate from Kuchi. Conclusions Phenotypic traits could be used to characterize FRLCs, however, there were variations in traits among individuals within ecotypes; therefore, complementary genomic methods should be considered to improve the characterization for selective breeding.

Cassava, an important food crop in the tropical regions of the world, is known to carry varying levels of cyanogenic glucosides that are potential poison to humans. In Tanzania, cases of cyanide poisoning have been reported in many cassava producing areas. This study was launched to quantify cyanide in fresh tubers of so called “sweet” cassava varieties and to gauge peoples’ perception on cyanide poisoning in Kagera and Morogoro regions. The study employed a questionnaire survey and a cross-sectional research design to identify different cassava varieties and their cyanide content using alkaline titration method. Findings showed that cyanide content in all of the analyzed tubers were above the internationally accepted levels in human consumables. Some sweet varieties were found to be wrongly classified as sweet because their cyanide content was above acceptable limits. For the same variety tubers sampled from a lowland area had significantly higher (P < 0.01) cyanide content than those from a highland point. It was also found that the upper (slippery) parenchymal tissue had more cyanide content (P < 0.05) than the inner tissue. Nearly 80% of the studied population was unaware of cyanide poisoning, its health effects and how to reduce cyanide content prior to consumption. It is concluded that consumption of raw cassava tubers can lead to undesirable health effects despite of some of them being categorized as sweet. The public should be sensitized on the issues of cyanide in cassava and should avoid consuming raw cassava tubers as preventive measures against cyanide poisoning.

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This study is aimed at evaluating antibody responses, viral loads, viral clearance and growth rate of Tanzanian free-range local chicken (FRLC) challenged with LaSota strain of Newcastle disease virus (NDV) as indicator traits for selection of chickens for breeding with enhanced resistance to the disease and economic value. Three popular free-range local chicken ecotypes: Kuchi, Ching'wekwe and Morogoro-medium from three ecological zones of Tanzania were used for the experiments. Progenies from the breeder chickens were challenged with 10 7 titer of 50% egg infectious dose (EID 50 ) of the virus at 28 days of age. The viral loads and viral clearance rates evaluated by qRT-PCR from tear samples collected at 2-and 6-days post infection (dpi) showed that Kuchi could clear NDV better than Morogoromedium and Ching'wekwe. Anti-NDV antibody levels determined from blood samples collected at 10 dpi using ELISA showed that Kuchi ecotype expressed higher mean anti-NDV antibodies compared to Morogoro-medium and Ching'wekwe. Growth rates determined from body weights collected for 38 days from day of hatch (D0) to 10 dpi showed higher growth rate for Kuchi than Morogoro-medium and Ching'wekwe chickens. Kuchi chickens were potentially more resistant to ND compared to Morogoromedium and Ching'wekwe.