Despite becoming a common cause of lameness in sheep in recent years, scientists and vets have only a limited understanding of Contagious Ovine Digital Dermatitis (CODD).
The condition was first discovered in 1997 and recent surveys indicate that over 35% of UK sheep farmers have seen it in their flocks.
Researchers at the University of Liverpool have been studying CODD for over a decade and are recognised as leading authorities on the disease.
“When we first started in 2009, we were genuinely shocked about how severe the disease could be in terms of the lesions present and the number of animals infected,” said Dr Jennifer Duncan.
CODD causes the hoof to come apart from the foot and it typically starts at the coronary band, where the top of the hoof meets the bottom of the leg. In severe cases, red ulcers, known as granulomas, form on the foot and the hoof that grows back after a CODD infection is usually permanently damaged.
Speaking in a webinar organised by the National Sheep Association (NSA), Duncan said that studies involving X-ray scanning have found that CODD can cause the bone in the foot to become deformed.
Footrot, another common cause of lameness in sheep, typically starts at the bottom of the hoof. The different starting point is the main method to distinguish between CODD and footrot.
However, Duncan points out that mixed infections of both CODD and footrot appear to be common and her team is currently trying to understand the relationship between the two conditions.
Treatment
CODD is typically much harder to treat than other forms of lameness, such as footrot and scald.
“The main bugs that we think cause CODD are a group of bacteria known as treponeme,” Duncan said.
In studies conducted in laboratories and on farms, treatment with long-acting penicillin, such as amoxicillin-based products, had a cure rate of around 78%.
However, Duncan highlighted that treponeme infections in humans usually require a course of antibiotics lasting from 14 to 28 days, so multiple injections of amoxicillin are often needed to treat CODD.
“You might have to do repeat doses, which can be problematic in different sheep farm circumstances. You also need to treat early before the disease gets too in-depth in the foot,” she said.
Another treatment option for CODD are antibiotics that are classified as macrolides, such as Micotil and Zactran.
These drugs are listed as “highest priority critically important antibiotics” so they should not be used as a first resort or as a whole flock treatment to eradicate CODD.
There is also doubt as to whether a whole flock treatment would be effective, with Duncan pointing out that tightly controlled trials on blanket use of macrolides have found that CODD eventually appeared in the flocks again.
However, she was clear that treating individual cases of CODD with macrolides can be justified in some individual cases, although it should be done in consultation with a vet.
Prevention
Researchers at the University of Liverpool have also found that vaccinating for footrot can help reduce cases of CODD in sheep. In a trial of 748 lambs, Footvax was administered to half the flock and lameness incidents in the two groups were recorded afterwards.
“We found that the vaccine prevented 32% of CODD cases and 62% of footrot cases. It shows that the vaccine will not prevent all cases, but it is a helpful part of a lameness control plan,” Duncan said.
For farmers who do not have CODD circulating in their flocks, the focus should be on keeping it out by having good biosecurity, such as a quarantine period for bought-in sheep of at least four weeks.
It is also recommended to lift all bought-in sheep to check feet for infections, even if they are not lame. This is because infected sheep can be spreading CODD without being lame.
Other advice for preventing CODD includes isolating infected sheep, culling repeatedly lame animals and not trimming hoofs unless absolutely necessary. If trimmers are used, they should be disinfected between each sheep.
Knowledge gap
When research into CODD began over a decade ago, there was effectively no understanding of how to treat and prevent the disease, but even now, substantial knowledge gaps remain.
Unanswered questions include do sheep eventually become immune to CODD, is it possible to create a vaccine, how long does the bacteria exist in the environment without a host and can digital dermatitis in cattle cause CODD in sheep?
“There is a lot of research still to be done,” Duncan acknowledged.
Foot bathing can be counterproductive
The panel of speakers on the NSA lameness webinar were sceptical about the effectiveness of foot bathing on many UK sheep farms.
The main concern surrounds sheep picking up infections by walking over high-traffic areas in farmyards.
“In general, with foot bathing, you need excellent facilities to make sure sheep are not running the same way they came in and they are going somewhere clean,” said vet and researcher Liz Nabb.
Devon sheep farmer Bryan Griffiths said that he has been doing less foot bathing in recent years and is “probably better off”.
“The benefit is that we don’t gather them as much. We used to have a lot of sheep through small, muddy gateways,” he said.
Griffiths has had issues with CODD in his 740-ewe flock and has found that amoxicillin-based antibiotics work around 75% of the time, but macrolides are needed in cases that do not clear up.
Hoof trimming as a lameness treatment was also strongly discouraged by all speakers on the online discussion.
“There is likely to be much more harm caused by hoof trimming. Certainly, with footrot we know that it is harmful to the healing process and with CODD we know that it is a route for disease transmission,” said Dr Jennifer Duncan.
CODD is a bacterial disease that causes painful lameness in sheep. Infected animals require prompt treatment with antibiotics.Good biosecurity and quarantine protocols are needed to keep CODD out of flocks.Foot bathing and hoof trimming can be counter-productive.
Despite becoming a common cause of lameness in sheep in recent years, scientists and vets have only a limited understanding of Contagious Ovine Digital Dermatitis (CODD).
The condition was first discovered in 1997 and recent surveys indicate that over 35% of UK sheep farmers have seen it in their flocks.
Researchers at the University of Liverpool have been studying CODD for over a decade and are recognised as leading authorities on the disease.
“When we first started in 2009, we were genuinely shocked about how severe the disease could be in terms of the lesions present and the number of animals infected,” said Dr Jennifer Duncan.
CODD causes the hoof to come apart from the foot and it typically starts at the coronary band, where the top of the hoof meets the bottom of the leg. In severe cases, red ulcers, known as granulomas, form on the foot and the hoof that grows back after a CODD infection is usually permanently damaged.
Speaking in a webinar organised by the National Sheep Association (NSA), Duncan said that studies involving X-ray scanning have found that CODD can cause the bone in the foot to become deformed.
Footrot, another common cause of lameness in sheep, typically starts at the bottom of the hoof. The different starting point is the main method to distinguish between CODD and footrot.
However, Duncan points out that mixed infections of both CODD and footrot appear to be common and her team is currently trying to understand the relationship between the two conditions.
Treatment
CODD is typically much harder to treat than other forms of lameness, such as footrot and scald.
“The main bugs that we think cause CODD are a group of bacteria known as treponeme,” Duncan said.
In studies conducted in laboratories and on farms, treatment with long-acting penicillin, such as amoxicillin-based products, had a cure rate of around 78%.
However, Duncan highlighted that treponeme infections in humans usually require a course of antibiotics lasting from 14 to 28 days, so multiple injections of amoxicillin are often needed to treat CODD.
“You might have to do repeat doses, which can be problematic in different sheep farm circumstances. You also need to treat early before the disease gets too in-depth in the foot,” she said.
Another treatment option for CODD are antibiotics that are classified as macrolides, such as Micotil and Zactran.
These drugs are listed as “highest priority critically important antibiotics” so they should not be used as a first resort or as a whole flock treatment to eradicate CODD.
There is also doubt as to whether a whole flock treatment would be effective, with Duncan pointing out that tightly controlled trials on blanket use of macrolides have found that CODD eventually appeared in the flocks again.
However, she was clear that treating individual cases of CODD with macrolides can be justified in some individual cases, although it should be done in consultation with a vet.
Prevention
Researchers at the University of Liverpool have also found that vaccinating for footrot can help reduce cases of CODD in sheep. In a trial of 748 lambs, Footvax was administered to half the flock and lameness incidents in the two groups were recorded afterwards.
“We found that the vaccine prevented 32% of CODD cases and 62% of footrot cases. It shows that the vaccine will not prevent all cases, but it is a helpful part of a lameness control plan,” Duncan said.
For farmers who do not have CODD circulating in their flocks, the focus should be on keeping it out by having good biosecurity, such as a quarantine period for bought-in sheep of at least four weeks.
It is also recommended to lift all bought-in sheep to check feet for infections, even if they are not lame. This is because infected sheep can be spreading CODD without being lame.
Other advice for preventing CODD includes isolating infected sheep, culling repeatedly lame animals and not trimming hoofs unless absolutely necessary. If trimmers are used, they should be disinfected between each sheep.
Knowledge gap
When research into CODD began over a decade ago, there was effectively no understanding of how to treat and prevent the disease, but even now, substantial knowledge gaps remain.
Unanswered questions include do sheep eventually become immune to CODD, is it possible to create a vaccine, how long does the bacteria exist in the environment without a host and can digital dermatitis in cattle cause CODD in sheep?
“There is a lot of research still to be done,” Duncan acknowledged.
Foot bathing can be counterproductive
The panel of speakers on the NSA lameness webinar were sceptical about the effectiveness of foot bathing on many UK sheep farms.
The main concern surrounds sheep picking up infections by walking over high-traffic areas in farmyards.
“In general, with foot bathing, you need excellent facilities to make sure sheep are not running the same way they came in and they are going somewhere clean,” said vet and researcher Liz Nabb.
Devon sheep farmer Bryan Griffiths said that he has been doing less foot bathing in recent years and is “probably better off”.
“The benefit is that we don’t gather them as much. We used to have a lot of sheep through small, muddy gateways,” he said.
Griffiths has had issues with CODD in his 740-ewe flock and has found that amoxicillin-based antibiotics work around 75% of the time, but macrolides are needed in cases that do not clear up.
Hoof trimming as a lameness treatment was also strongly discouraged by all speakers on the online discussion.
“There is likely to be much more harm caused by hoof trimming. Certainly, with footrot we know that it is harmful to the healing process and with CODD we know that it is a route for disease transmission,” said Dr Jennifer Duncan.
CODD is a bacterial disease that causes painful lameness in sheep. Infected animals require prompt treatment with antibiotics.Good biosecurity and quarantine protocols are needed to keep CODD out of flocks.Foot bathing and hoof trimming can be counter-productive. 
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