This project focuses on the development and application of vaccines to control diseases that negatively impact production and welfare of Scottish livestock, caused by parasitic gastrointestinal nematodes (GIN). Researchers at MRI tested the efficacy of simplified and complex vaccines against Teladorsagia circumcincta in lambing ewes in a two-year study on common species of parasitic nematodes of sheep. The analysis gave rise to no statistically significant evidence of any effects from either vaccine for the ewes or their lambs.

Previously, a prototype recombinant vaccine was developed against one of the most common and important gastrointestinal nematodes (GIN) of sheep, Teladorsagia circumcincta, based on studies with penned lambs and ewes. While this vaccine targets just one species of GIN, adequate worm control requires multiple species to be addressed, so the efficacy of the vaccine was tested in lambing ewes challenged with multiple species in an on-field study.

Researchers at MRI designed a simplified version of the vaccine, comprising two of the eight antigens that were in the original, complex, formulation. In the first year this simplified version of the vaccine was trialled, with the original, complex version trialled in the second year. Sheep were allocated to 12 paddocks, with 12 ewes per paddock; the paddocks had been prepared so as to provide an effective worm challenge, having in previous years been rotationally grazed by ewes and their spring born lambs, where the former had been challenged with common species of parasitic nematodes of sheep. Each study year, ewes in six of the paddocks received four vaccinations, three in the autumn and a fourth booster in the spring, while the lambs received no vaccinations. The goal was to reduce pasture contamination during the period where the ewe’s immunity to parasites would typically be relaxed, which occurs around lambing, in turn reducing the exposure of the young lambs when these start to graze.

Faecal egg counts (FEC) from multiple nematode species were monitored throughout the experiment for both the ewes and the lambs. The FEC of the ewes and lambs were analysed separately in each year using generalised linear mixed models with negative binomial response variables to investigate the effects of each vaccine on FEC trends while allowing for the random effects of individual paddocks, ewes and lambs. The analysis clearly showed trends over time for the ewes, with higher mean FEC burdens seen around the lambing period and lower burdens throughout the rest of the year, for both control and vaccinated ewes, but evidenced no statistically significant effects for either vaccines for either the ewes or their lambs.

Read the paper on this work: Frontiers | Field testing of recombinant subunit vaccines against Teladorsagia circumcincta in lambing ewes demonstrates a lack of efficacy in the face of a multi-species parasite challenge (frontiersin.org)

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This work was done in collaboration with Alasdair J. Nisbet, Daniel R.G. Price, Yvonne Bartley and Margaret Oliver at the Vaccines and Diagnostics Department, Moredun Research Institute, and Tom N. McNeilly, Dave McBean, Leigh Andrews, Gillian Mitchell, and Fiona Kenyon at the Disease Control Department, Moredun Research Institute. The work was funded under the Underpinning National Capacity element of the Scottish Government's Strategic Research Programme for environment, agriculture and food.