Biomathematics & Statistics Scotland
Parasitic nematodes have devastating effects on animal health and production, affecting food security worldwide. In temperate regions such as Scotland, the principal cause of parasitic gastroenteritis in small ruminants is the nematode Teladorsagia circumcincta. This is commonly controlled by repeated applications of anthelmintics, but unfortunately resistance of T. circumcincta to anthelmintics is emerging rapidly. Since sheep can acquire immunity against this nematode after continual exposure, vaccination may be an alternative control strategy.
With scientists from MRI, BioSS analysed several trials of the effectiveness of a candidate vaccine based on recombinant proteins, using a range of statistical tools. Linear mixed modelling was applied to compare antigen-specific antibody responses over time; multivariate methods were used to explore antibody responses to recombinant proteins; negative binomial generalised linear models were fitted to model nematode burdens in the stomach. A novel generalised additive mixed modelling approach was formulated to explicitly model all the key aspects of faecal worm egg counts, including nonlinearity over time. Overall, our analyses of MRI’s experimental data suggest that vaccination with recombinant proteins can protect sheep against infestation by T. circumcincta.
Biplot showing the mucosal IgG antibody responses
to the recombinant proteins. Open circles represent
immunized sheep; closed circles represent control,
non-immunized sheep. The axes represent the
different antigens, with arrows indicating directions
of higher antigen-specific antibody responses.
Immunized sheep show higher mean responses than
control sheep.
Further details from: Javier Palarea
Article date 2013
