The role of lambs, time and space in persistence of Dichelobacter nodosus, the causative agent of footrot (PhD)

Summary

Reduced project results are available below. The final report and full project results will be available in the near future.

Recommendations for treatment of sheep with footrot:

DO treat even mildly lame lambs and ewes within 3 days of becoming lame (rapid treatment) to reduce the spread of footrot and CODD and so reduce the level of lameness in the flock
The best treatment for footrot and CODD is antibiotic injection, and topical spray to all 4 feet without trimming hoof horn. Lambs with scald can be treated with topical treatment only
DO separate treated ewes and lambs wherever possible - this prevents spread of disease
Rapid treatment minimises use of antibiotics to treat lameness - as there will be less animals to treat
DO NOT wait until sheep are severely lame before treatment - as this allows spread of footrot and CODD through the flock
DO NOT trim foot horn

Recommendations around flock management:

High levels of lameness in ewes are associated with high levels of lameness in lambs.
DO NOT practice routine foot trimming and footbathing
DO quarantine new and returning sheep for more than 3 weeks and treat cases of lameness
DO select replacements from ewes that have never been lame (if you purchase replacements ask your supplier to do this too)
Vaccination with Footvax™ may reduce levels of lameness after 5 years

The role of the environment:

Flocks on peat soil have lower levels of lameness in both ewes and lambs than those on other soil types
Consider ways to reduce the spread of footrot and CODD. These include - low stocking density, regular movement of sheep between fields, separation of lame sheep at treatment until they are sound

The full published papers are both Open Access and can be found at:

Lewis, KE, Green, MJ, Witt, J and Green, Multiple model triangulation to identify factors associated with lameness in British sheep flocks, Preventive Veterinary Medicine, 105395

https://www.sciencedirect.com/science/article/pii/S0167587721001392

Lewis KE and Green LE, 2020, Management Practices Associated With Prevalence of Lameness in Lambs in 2012–2013 in 1,271 English Sheep Flocks, Frontiers in Veterinary Science, 7:519601, doi: 10.3389/fvets.2020.519601

https://www.frontiersin.org/articles/10.3389/fvets.2020.519601/

Sector:

Beef & Lamb

Project code:

61110066

Date:

01 October 2017 - 30 September 2021

Funders:

BBSRC MIBTP

AHDB sector cost:

£44,800

Total project value:

£80,000

Project leader:

University of Warwick

About this project

The Project

Each spring, the size of the national flock increases from around 14 million ewes to include approximately 18 million lambs. Consequently, an average lowland flock of sheep increases in number by approximately 260% as each adult ewe produces an average of 1.6 lambs. One observation is that in many years there is an epidemic of lameness in ewes and lambs in spring. For example, from a 2012-3 study of 1200 farmers, we see that May and June are the months that many farmers report their highest levels of lameness attributable to interdigital dermatitis (ID) (scald) in their ewes and lambs. The likely number of lambs that become lame is one to two million per year, with growth rate reductions of three to six weeks longer to finishing. An episode of lameness results in extremely high costs to the industry.

There is robust evidence that interdigital dermatitis (scald) and footrot are part of the same disease process and are caused by the bacterium Dichelobacter nodosus (Witcomb et al., 2014). Research at Warwick has focused on identifying managements to reduce lameness from footrot and ID in ewes. There is now a clear evidence base for prompt appropriate treatment of ewes with footrot and ID (Kaler et al., 2010) to minimise the impact of lameness on the affected animal and to reduce onward spread of disease (Wassink et al., 2010). In addition, minimising routine foot trimming and footbathing and targeting quarantine and segregation of lame sheep reduce the prevalence of footrot and ID (Wassink et al., 2003, 2004; Kaler and Green 2009; Winter et al., 2015). There is little evidence for the space and time intervals that reduce transmission between sheep, however quarantining for more than three weeks and stocking density of four sheep per hectare have been associated with reduced spread of footrot, but these practices are not very relevant to managing ewes with lambs at foot. To date, little research has been targeted at preventing lameness from ID in lambs. Anecdotally, some farmers who have controlled footrot in ewes report that they rarely see an epidemic of lameness in lambs. Whilst this is believed by some, others consider ID to be a separate disease primarily driven by weather conditions.

The Challenge

The aims of the project is to investigate four possible hypotheses for epidemic of footrot in lambs in spring:

Lambs are born with some passive immunity that protects them against footrot (including ID) and this protection wanes after several weeks and that they then become susceptible to disease. This results in an epidemic of disease in spring when lambs become susceptible en masse
Lambs have many contacts with other lambs and ewes in the flock and that this may increase transmission of infectious diseases
The increase in stocking density of the flock due to lambs on the ground might be sufficient to create the epidemics observed
Climate is more conducive to spread footrot in spring.

The objective is to describe patterns of footrot disease severity and risks for occurrence in lambs, and to investigate the impact of lambs on the incidence rate of footrot to ewes and lambs.

Two existing datasets will be used to investigate the hypotheses and then to design and conduct a study to test at least one of them. It is likely that a longitudinal observational study where ewes and lambs of known age are tagged with data loggers that record spatial location and close contact with other ewes and lambs will be used. Climate and occurrence of lameness will also be recorded. These data will enable the roles of contact and pasture contamination to be quantified, and the hypotheses to be tested.

Student

Kate Lewis