The role of lambs, time and space in persistence of Dichelobacter nodosus, the causal agent of footrot
Lead Research Organisation:
University of Warwick
Department Name: School of Life Sciences
Abstract
Footrot is an endemic disease of sheep in Great Britain, which is detrimental to the health and welfare of individual sheep, and the economics of the farm due to losses in production and costs of disease control. While control of footrot appears to be improving, it remains an endemic problem, with a global mean period prevalence of 5% found in 2013 (Winter et al., 2015). However, farmers report an epidemic aspect to the disease- with an epidemic occurring in lambs in the spring time. This project aims to address the reasons behind why this occurs.
There are four possible hypotheses for the epidemic of footrot in lambs in spring. The first is that lambs are born with passive immunity to footrot, which then wears off by spring time, resulting in the epidemic. The second is that the contact structure within the flock is altered as a result of the birth of the lambs. Norton et al., (2012) found an overall increase in connectivity within flocks as a result of the presence of lambs and increased contact rates can result in increased transmission of disease. The third is that the the increase in density of the flock due to the birth of lambs may sufficient in itself to create an epidemic. Finally, the spring climate may be more conducive to the spread of footrot than at other times of the year.
This project will investigate these hypotheses, firstly by using an existing dataset, and then designing a longitudinal observational study. Patterns of disease severity and risks for occurrence in lambs will be described, and then the impact of lambs on the incidence rate of footfot in ewes and lambs will be investigated. The results of this analysis will influence the design of the longitudinal study, where occurrence of lameness, climate data and spatial location and contact patterns between ewes and lambs will be recorded. This will improve understanding of the spread of disease, allowing an evidence based approach to be formulated for management of footrot in in spring time.
There are four possible hypotheses for the epidemic of footrot in lambs in spring. The first is that lambs are born with passive immunity to footrot, which then wears off by spring time, resulting in the epidemic. The second is that the contact structure within the flock is altered as a result of the birth of the lambs. Norton et al., (2012) found an overall increase in connectivity within flocks as a result of the presence of lambs and increased contact rates can result in increased transmission of disease. The third is that the the increase in density of the flock due to the birth of lambs may sufficient in itself to create an epidemic. Finally, the spring climate may be more conducive to the spread of footrot than at other times of the year.
This project will investigate these hypotheses, firstly by using an existing dataset, and then designing a longitudinal observational study. Patterns of disease severity and risks for occurrence in lambs will be described, and then the impact of lambs on the incidence rate of footfot in ewes and lambs will be investigated. The results of this analysis will influence the design of the longitudinal study, where occurrence of lameness, climate data and spatial location and contact patterns between ewes and lambs will be recorded. This will improve understanding of the spread of disease, allowing an evidence based approach to be formulated for management of footrot in in spring time.
Publications
Lewis KE
(2022)
Social behaviour and transmission of lameness in a flock of ewes and lambs.
in Frontiers in veterinary science
Lewis KE
(2021)
Multiple model triangulation to identify factors associated with lameness in British sheep flocks.
in Preventive veterinary medicine
Lewis KE
(2020)
Management Practices Associated With Prevalence of Lameness in Lambs in 2012-2013 in 1,271 English Sheep Flocks.
in Frontiers in veterinary science
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| BB/M01116X/1 | 01/10/2015 | 31/03/2024 | |||
| 1937618 | Studentship | BB/M01116X/1 | 02/10/2017 | 22/09/2021 | Katharine Lewis |
| Description | The project has highlighted some novel behaviour of farmers when treating lambs. Models created from a survey of 1271 flocks in 2013 highlighted non-linear effects of treatment, where farmers were more likely to use parenteral antibiotics to treat lambs when >2-5% of lambs were lame compared with =2%. Flocks where large numbers of lambs (>10%) were lame were likely to delay treatment by considering only sheep with high (>2) locomotion scores as lame, and in addition practised inappropriate footbathing, culling of lame sheep and biosecurity. This could lead to improved advice available to farmers on treatment of lambs, which could impact the prevalence of lameness seen in ewes in the flock, namely that prompt, appropriate treatment with antibiotics is likely to lead to lower prevalence of lame lambs, and overall reduced antibiotic use. These results can be found in Lewis and Green (2020), Management Practices Associated With Prevalence of Lameness in Lambs in 2012-2013 in 1,271 English Sheep Flocks Further models created from a survey of 450 sheep flocks in Great Britain highlighted further risk factors identified with prevalence of lameness in lambs. Some of these were direct, such as higher prevalence of lameness in flocks where lambs were treated in >3 days compared to 0-3 days after recognition of lameness, while others were to do with management of the ewe flock (such as causing bleeding in 5-100% of sheep feet during a routine foot trim compared to not foot trimming at all. Data from this questionnaire was used to provide an example of how multiple model triangulation, and bootstrap methods, can be used to help to prevent over-fitting of models to the sample data, helping to ensure results are applicable to as many farmers as possible. This has now been published in Lewis et al., 2021, Multiple model triangulation to identify factors associated with lameness in British sheep flocks. Proximity sensors were used to collect high-resolution data in a flock of ewes and young (<6 week old lambs), combined with daily observations of the sheep's locomotion scores. The contact data was combined with the locomotion scores to provide insight into how lameness impacts sheep behaviour, and into potential transmission routes of footrot through the flock. As this stage of the production cycle, it is most likely that lambs became infected from their dam, and twins became lame at a slower rate than singles. That twins are less likely to become lame than singles has been found by other work (Kaler al., 2010), and this study provided a potential explanation for this - twins spend less time with their mothers than singles, and consquently are less exposed to the D. nodosus that is shed by their mother into the environment. Additionally, lame sheep spend less time in close contact with other sheep. Since sheep are highly social animals, this reduction in social contact potentially highlights a reduction in emotional welfare for lame sheep, as a result of the pain that results from lameness. |
| Exploitation Route | The questionnaire-based work could lead to further investigation of the use of antibiotics in lambs, and definition of a "best practice" treatment for lambs with footrot. Further work with contact data and the relationship to lameness could explore how social contact at different points of the production cycle is related to transmission of lameness. For example, when lambs are very young (as in the current work), they spend most of their time with their dam or sibling if they are a twin, and work from the project suggested that non-family based routes of transmission of footrot were not significant at this stage of the lambs life. However, but it is possible that as lambs age, and form "play-gangs" (a known behaviour for lambs), the increased contact between lambs as a result of these "play-gangs" provides a lamb-lamb transmission route, which is related to the outbreaks of lameness in lambs that farmers report seeing in the spring. |
| Sectors | Agriculture, Food and Drink |
| Description | Results from the questionnaire study have been written into a magazine article for the Sheep Farmer, the magazine distributed to members of the National Sheep Association by the association, and into two articles for the Agriculture and Horticulture Development Board, which have been published on their website, which is accessible to sheep farmers. |
| First Year Of Impact | 2018 |
| Sector | Agriculture, Food and Drink |
| Description | BSAS conference |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Postgraduate students |
| Results and Impact | Talk at the BSAS 2021 conference about the use of multiple model triangulation to increase the robustness of modelling results, using the example of lameness in British sheep flcks. |
| Year(s) Of Engagement Activity | 2021 |
| Description | Ruminant Health Meeting (Nottingham University) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Postgraduate students |
| Results and Impact | A talk was presented to an audience consisting of researchers (from PhD Students to Principal Investigators) involved in ruminant health. There was opportunity for questions, and the work presented was one of the first to identify unusual behaviour of farmers and use of antibiotics in lambs. |
| Year(s) Of Engagement Activity | 2019 |
| Description | Social Network Analysis workshop |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | The workshop was an opportunity to learn some of the latest tools in analysis of social networks, and a mini-conference was incorporated into the workshop. A talk was given called "Investigating the role of contact between ewes and their lambs in transmission of footrot in a flock of sheep in England", and a poster on the same work was presented. |
| Year(s) Of Engagement Activity | 2020 |