Host response to successive challenges with lentogenic and velogenic Newcastle disease virus in local chickens of Ghana.

Newcastle disease (ND) is a highly contagious viral disease that constantly threatens poultry production. The velogenic (highly virulent) form of ND inflicts the most damage and can lead to 100% mortality in unvaccinated village chicken flocks. This study sought to characterize responses of local chickens in Ghana after challenging them with lentogenic and velogenic Newcastle disease virus (NDV) strains. At 4 wk of age, chicks were challenged with lentogenic NDV. Traits measured were pre- and post-lentogenic infection growth rates (GR), viral load at 2 and 6 d post-lentogenic infection (DPI), viral clearance rate and antibody levels at 10 DPI. Subsequently, the chickens were naturally exposed to velogenic NDV (vNDV) after anti-NDV antibody titers had waned to levels ≤1:1,700. Body weights and blood samples were again collected for analysis. Finally, chickens were euthanized and lesion scores (LS) across tissues were recorded. Post-velogenic exposure GR; antibody levels at 21 and 34 days post-velogenic exposure (DPE); LS for trachea, proventriculus, intestines, and cecal tonsils; and average LS across tissues were measured. Variance components and heritabilities were estimated for all traits using univariate animal models. Mean pre- and post-lentogenic NDV infection GRs were 6.26 g/day and 7.93 g/day, respectively, but mean post-velogenic NDV exposure GR was -1.96 g/day. Mean lesion scores ranged from 0.52 (trachea) to 1.33 (intestine), with males having significantly higher (P < 0.05) lesion scores compared to females. Heritability estimates for the lentogenic NDV trial traits ranged from moderate (0.23) to high (0.55) whereas those for the vNDV natural exposure trial were very low (≤ 0.08). Therefore, in contrast to the vNDV exposure trial, differences in the traits measured in the lentogenic challenge were more affected by genetics and thus selection for these traits may be more feasible compared to those following vNDV exposure. Our results can form the basis for identifying local chickens with improved resilience in the face of NDV infection for selective breeding to improve productivity.

Mapping of plumage colour and blood protein loci on the microsatellite linkage map of the Japanese quail.

The objective of this work was to map classical markers (plumage colours and blood proteins) on the microsatellite linkage map of the Japanese quail (Coturnix japonica). The segregation data on two plumage colours and three blood proteins were obtained from 25 three-generation families (193 F2 birds). Linkage analysis was carried out for these five classical markers and 80 microsatellite markers. A total of 15 linkage groups that included the five classical loci and 69 of the 80 microsatellite markers were constructed. Using the BLAST homology search against the chicken genome sequence, three quail linkage groups, QL8, QL10 and QL13, were suggested to be homologous to chicken chromosomes GGA9, GGA20 and GGA24, respectively. Two plumage colour loci, black at hatch (Bh) and yellow (Y), and the three blood protein loci, transferrin (Tf), haemoglobin (Hb-1) and prealbumin-1 (Pa-1), were assigned to CJA01, QL10, QL8, CJA14 and QL13, respectively.

A first-generation microsatellite linkage map of the Japanese quail.

A linkage map of the Japanese quail (Coturnix japonica) genome was constructed based upon segregation analysis of 72 microsatellite loci in 433 F(2) progeny of 10 half-sib families obtained from a cross between two quail lines of different genetic origins. One line was selected for long duration of tonic immobility, a behavioural trait related to fearfulness, while the other was selected based on early egg production. Fifty-eight of the markers were resolved into 12 autosomal linkage groups and a Z chromosome-specific linkage group, while the remaining 14 markers were unlinked. The linkage groups range from 8 cM (two markers) to 206 cM (16 markers) and cover a total map distance of 576 cM with an average spacing of 10 cM between loci. Through comparative mapping with chicken (Gallus gallus) using orthologous markers, we were able to assign linkage groups CJA01, CJA02, CJA05, CJA06, CJA14 and CJA27 to chromosomes. This map, which is the first in quail based solely on microsatellites, is a major step towards the development of a quality molecular genetic map for this valuable species. It will provide an important framework for further genetic mapping and the identification of quantitative trait loci controlling egg production and fear-related behavioural traits in quail.

Chicken microsatellite primers are not efficient markers for Japanese quail.

Domestic fowl or chicken (Gallus gallus) and Japanese quail (Coturnix japonica) belong to the family Phasianidae. The exchange of marker information between chicken and quail is an important step towards the construction of a high-resolution comparative genetic map in Phasianidae, which includes several poultry species of agricultural importance. We tested chicken microsatellite markers to see if they would be suitable as genetic linkage markers in Japanese quail. Twenty-six per cent (31/120) of chicken primers amplified individual loci in Japanese quail and 65% (20/31) of the amplified loci were found to be polymorphic. Eleven of the polymorphic loci were excluded as uninformative because of the lack of amplification in some individuals or high frequency of nonspecific amplification. The sequence information of the remaining nine loci revealed six of them to contain microsatellites that were nearly identical with those of the orthologous regions in chicken. For these six loci, allele frequencies were estimated in 50 unrelated quails. Although the very few chicken markers that do work well in quail could be used as anchor points for a comparative mapping, most chicken markers are not useful for studies in quail. Therefore, more effort should be committed to developing quail-specific markers rather than attempting to adapt chicken markers for work in quail.

Fifty microsatellite markers for Japanese quail.

A Japanese quail genomic library enriched for (CA/GT)n simple sequence repeats was screened and positive clones were sequenced. Fifty original microsatellite sequences were isolated that consisted mainly of perfect repeats of the dinucleotide (CA/GT)n motif and a corresponding number of polymerase chain reaction (PCR) primer pairs complementary to unique DNA sequences flanking the microsatellite repeats were designed to detect the repeats. Forty-six percent (23 of 50) of the markers revealed polymorphism in two unrelated quail individuals (one male and one female) randomly sampled from a population of wild quail origin. All 50 primer pairs were tested in the PCR for their ability to amplify chicken genomic DNA. Amplification products were obtained for 14 (28.0%) of the markers at the annealing temperature optimized for quail. These results provide an opportunity to begin characterizing the quail genome for the development of a genetic map for this economically valuable species and the eventual construction of a comparative genetic map in Phasianidae, which comprises a number of agriculturally important species of poultry.

Detection of Trypanosoma brucei, T. congolense and T. vivax infections in cattle, sheep and goats using latex agglutination.

A monoclonal antibody-based latex agglutination test for detection of circulating trypanosome antigens in animal serum was evaluated for the ability to detect natural T. brucei, T. congolense and T. vivax infections in cattle, sheep and goats in Ghana. The test detected antigens in 180/422 (42.7%) of cattle, 27/131 (20.6%) of sheep and 14/79 (17.7%) of the goats. By comparison, the microplate-based antigen-ELISA gave similar results (P > 0.01), detecting trypanosome antigens in 41.7% of the cattle, 19.8% of the sheep and 17.7% of the goats. Trypanosomes were demonstrated in the blood of 30 (7.2%) cattle, 7 (5.3%) sheep and 3 (3.8%) goats using the buffy coat technique (BCT). Of these, 26 cattle (86.7%), 6 sheep (85.7%) and all 3 goats (100%) were antigenaemic. The most prevalent single infection in all 3 animal species involved T. vivax, and the most common mixed infection involved all 3 trypanosome species in cattle and sheep. There was no mixed infection in goats. Compared with the antigen-ELISA, the sensitivity of the latex agglutination test was 98.3% in cattle and 100% in both sheep and goats, whilst the specificity was 97.2% in cattle, 99% in sheep and 100% in goats. False positivity with the latex agglutination test was 3.9% in cattle and 3.7% in sheep. There were no false-positive reactions with the test in goats. The latex agglutination assay promises to be ideal for testing small numbers of animals under field conditions.