Late last year, two veterinary practices – Synergy and Bishopton – founded the Cattle Lameness Academy in a quest to bridge the gap between research and foot services on the ground. Ann Hardy reports from the academy’s inaugural seminar.
The prospect of a vaccine for the prevention of bovine digital dermatitis (BDD) is moving rapidly closer, and UK research is leading the way. A vaccine would represent a significant step forward in the control of digital dermatitis, and could have implications for other lesions in cattle as broad ranging as pressure sores and ischaemic teat necrosis.
Details of the latest developments were described by Stuart Carter, professor of Infection Biology at the University of Liverpool’s Institute of Infection and Global Health, when he addressed vets, farmers and foot trimming professionals at the Lameness Academy seminar in Somerset.
He explained how techniques developed at the Institute had enabled 120 isolates of treponeme bacteria – the primary cause of BDD – to be purified, identified and grown, compared with just 22 identified throughout the rest of the world. This gave the university a clear lead in the development of a vaccine which, he said, was on the verge of being tested through a pilot scheme.
Explaining why a vaccine could be so important, he said: “There are no effective treatments for BDD at the moment. There are some which make it go away but it will come back.”
This problem stemmed from the fact BDD was primarily caused by treponemes, which could penetrate the skin and initiate a lesion and which were followed by secondary infections which inflamed the local area.
“Most antibiotics only work on the secondary infection, so the disease occurs again and again,” he said.
“And penicillin and macrolides are the most effective against treponemes, but they are not readily usable in milking cows.”
Footbaths were also said to be increasingly limited as modern antibiotics such as cephalosporins were not permitted for foot-bathing, while other chemicals such as formalin and copper sulphate were ‘slowly being banned across Europe’ due to their potential environmental threats.
These developments, together with an apparent ‘recent increase in the range of tissues affected’ and widespread pressure to reduce antibiotic use, has added urgency to the requirement for a vaccine, which Prof Carter said was being developed using genome sequencing and the latest ‘reverse vaccinology’ technology.
Tests at the university had revealed treponemes were present in all the lesions studied, including those associated with the non-healing forms of white line disease, sole ulcers and toe necrosis. However, isolation of these bacteria in pressure sores, hock lesions and – within the past few months – in lesions associated with ischaemic teat necrosis was said to represent a new era in the disease.
“These organisms make the lesions very difficult to treat,” said Prof Carter. “So, although digital dermatitis is the primary target for the vaccine, we are confident it will make a contribution to treating severe, non-healing forms of white line disease, sole ulcer, toe necrosis and other treponeme-associated lesions.”
However, although vaccination was expected to represent a breakthrough in BDD prevention, Prof Carter said high levels of biosecurity were essential.
This has been highlighted by recent findings revealing that foot-trimming tools may carry infection and could be spreading treponemes to other farms and animals. “Foot trimming professionals have responded very positively,” said Prof Carter. “Some have even chosen to leave their trimming equipment on farms, which is a good development.”
The next step, he said, was vets and foot trimmers trying different antiseptics to clean their equipment, and plans were being developed to send swabs to the university where each chemical’s efficacy would be tested.
“I have had hundreds of emails from them since the findings on ischaemic teat necrosis were published just before Christmas, and they’ve come up with positive ideas as a profession and are driving this forward.”
With an estimated annual cost of BDD to UK dairying of £26 million, and treponemes now present in every dairying nation worldwide and transmitting across many species, the development of a vaccine could be well worth the effort, he said.
Prof Huxley’s advice follows extensive evidence that shows once a cow has become lame, her lameness is likely to recur, in a similar pattern to a cow with mastitis.
“Farmers intuitively understand once a cow gets mastitis, she is more likely to get mastitis in the future, and if they delay treatment, the case will be more difficult to treat and the cow will be more likely to have a future case,” he said.
“If you apply that intuitive knowledge to lameness and throw in NSAIDs, the general approach will be about right.” Although the study on which he based his advice was still under way, he said: “All the work is screaming NSAID use associated with lameness can only be positive.
“Particularly, do not reserve NSAIDs for the bad cases,” he said. “Clearly, those animals need them but once they get bad, the cow is probably consigned to a lifetime of lameness risk so you should probably have used them earlier.”
Citing their analgesic and anti-inflammatory properties, he recommended farmers spoke to their vets about holding NSAIDs on farm to allow for their use as soon as required. Although there was discussion among vets at the seminar about the positive effects of inflammation as part of the immune response, the benefits of reducing inflammation were said to far outweigh any potential advantage of not doing so.
Mike Kerby, a vet with the Delaware Group in Castle Cary, said NSAIDs also had a role to play in mitigating the effects of lameness on fertility.
Describing the effects of pain and inflammatory chemicals on the brain and on hormone production, he said: “NSAIDs look like having an ever more important role in affected individuals from a welfare, recovery and dry matter intake perspective, and probably because of their effects on the brain, ovaries and testes.” He also emphasised the importance of early diagnosis and prompt treatment of lameness to help keep fertility on track.