Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

Browse

Subject: search.filters.subject.Johne's disease

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A comparative study between milk- and serum-based antibody detection assays for Johne's disease in New Zealand dairy cattle
    (Elsevier B.V., 2025-08-27) Venkatesh KM; Lopez-Villalobos N; Gupta SK; Udy GB; Laven R; Chiu S-J; Bugde P; Furuya Y; Dukkipati VSR
    Dairy cattle are affected by Johne's disease. It is caused by Mycobacterium avium subspecies paratuberculosis (MAP). Suboptimal diagnostic tests add more to the productivity loss resulting from this disease. Agreement between and within different commercial kits is crucial in the decision-making process of disease surveillance programmes. This study compared two ELISAs, that is, Johne's disease commercial antibody detection kits (A and B), using milk and serum samples from New Zealand dairy cattle. These results were also compared with a subset of faecal PCR results. Five scenarios were considered for the comparison of ELISA tests. The point estimates of kappa coefficients (k) between the serum (0.84–0.94) assays were higher than the milk assays (0.59–0.82). The point estimates of kappa coefficients between serum and milk ELISA outcomes were higher for kit B (k = 0.79–0.86) than for kit A (k = 0.55–0.79). The point estimates of kappa coefficients between the ELISA and faecal PCR outcomes varied between 0.43 and 0.74. ELISA tests had point estimates of sensitivity ranging from 0.67 to 0.88 and specificity from 0.62 to 0.93, relative to the faecal PCR test. Results suggest that serum provides a better choice of sample type when both commercial kits A and B are used for Johne's disease surveillance of dairy cattle in New Zealand. Milk assays can be cost-effective to diagnose MAP-positive animals; kit B can be best suited for New Zealand conditions, provided the repeatability of the results is validated.
  • Thumbnail Image
    Item
    Comparative Genomics of Mycobacterium avium Subspecies Paratuberculosis Sheep Strains
    (Frontiers Media S.A., 2021-02-15) Mizzi R; Timms VJ; Price-Carter ML; Gautam M; Whittington R; Heuer C; Biggs PJ; Plain KM; Salgado M
    Mycobacterium avium subspecies paratuberculosis (MAP) is the aetiological agent of Johne's disease (JD), a chronic enteritis that causes major losses to the global livestock industry. Further, it has been associated with human Crohn's disease. Several strains of MAP have been identified, the two major groups being sheep strain MAP, which includes the Type I and Type III sub-lineages, and the cattle strain or Type II MAP lineage, of which bison strains are a sub-grouping. Major genotypic, phenotypic and pathogenic variations have been identified in prior comparisons, but the research has predominately focused on cattle strains of MAP. In countries where the sheep industries are more prevalent, however, such as Australia and New Zealand, ovine JD is a substantial burden. An information gap exists regarding the genomic differences between sheep strain sub-lineages and the relevance of Type I and Type III MAP in terms of epidemiology and/or pathogenicity. We therefore investigated sheep MAP isolates from Australia and New Zealand using whole genome sequencing. For additional context, sheep MAP genome datasets were downloaded from the Sequence Read Archive and GenBank. The final dataset contained 18 Type III and 16 Type I isolates and the K10 cattle strain MAP reference genome. Using a pan-genome approach, an updated global phylogeny for sheep MAP from de novo assemblies was produced. When rooted with the K10 cattle reference strain, two distinct clades representing the lineages were apparent. The Australian and New Zealand isolates formed a distinct sub-clade within the type I lineage, while the European type I isolates formed another less closely related group. Within the type III lineage, isolates appeared more genetically diverse and were from a greater number of continents. Querying of the pan-genome and verification using BLAST analysis revealed lineage-specific variations (n = 13) including genes responsible for metabolism and stress responses. The genetic differences identified may represent important epidemiological and virulence traits specific to sheep MAP. This knowledge will potentially contribute to improved vaccine development and control measures for these strains.