Digital Dermatitis; Footbath as a control not cure

Nick Barradale BVSc MRCVS, Molecare Veterinary Services

We often find that it is not what the farms are doing that is the issue but more what they are not doing. Understanding the disease goes a long way to righting this when integrated to a complete control plan. This relatively young disease was discovered in 1974 by an Italian named Mortellaro, hence the staging abbreviations below;

Digi lesion staging:

M1- Subclinical stage (‘pea’ lesion, non-lame)

M2- Acute clinical stage (classic strawberry)

M3- Healing stage (recovering strawberry)

M4- Chronic stage (Carrier scarred state)

M4.1- Re-eruption from a chronic carrier

You often only see and struggle with M2’s, the classic strawberry lesion which produces a lame animal. The problem is that when we are alerted to an M2 lesion with a lame event the damage is done and that animal becomes infected for life. She will then progress to an M4 and constantly cycle through the infectious lesions at various times for the rest of her productive life. The active M2 cows are the reservoir of infection to establish new M1 lesions in susceptible animals like heifers and bought-in animals.

Digi control plan has to be founded in multiple factors:

Footbath

Infectious status of individuals

Animal grouping/management

Environment/tool hygiene

Foot trimming

Early topical/systemic treatment

Record keeping

Once you understand the lesion staging of digi it is easier to grasp how to win with disease management. This then impacts on management of disease at group level. Environment and hoof knife hygiene is well documented. Hoof angle, heel height and tidying up of poor horn with routine foot care is essential to limiting digi risk. The only way to manage digi well and quickly when it has progressed to an M2 lesion is with topical therapy or even injectable antibiotics. Lastly, if you get to a place where you could potentially eradicate digi from your herd then ID of carrier status cows with record keeping is essential.

This leaves us with footbathing..the mainstay of digi control. The most common failure I find is lack of frequency. The footbath is only effective at controlling M1 and M4.1 lesions and preventing establishment of chronic carrier animals and infection transfer. With lacking frequency of bathing, whether it is as cows go dry or with turn out over summer, M1 lesions are missed allowing progression. I often get the complaint that digi “explodes as cows are housed in autumn” or “it’s always the freshly calved cows that struggle”. This is M1s that have developed to M2s but only really shown as lame animals as they hit slurry and higher pressure environments. These situations tell me that bathing frequency is not doing its job on these farms.

Digi control plans have to be farm specific, shaped by infectious load, environment and group/management dynamics. The end result however has to be the same; prevention of M2 lesions. To that end I try to design a footbath with the farm that will work and not cost the earth. Increased frequency and cost can be negated by correct volume and reduced concentrations as situation improves. Ultimately though, there is little more costly than footbathing and still struggling with lame animals.

Golden footbath rules:

1L per cow per walk through

3m long

12cm deep

Width dictated by volume required

Positioned near water and product source for ease

Located to limit cow flow issues but cows quickly become accustomed to regular bathing

Bathe all groups frequently as required; with issues likely daily over winter and every other day through summer

Higher the frequency, reduced concentrations

Leaving contaminated baths for long periods reduces efficacy

Frequency can allow cheaper product selection

Manage M2 lesions topically rather than with bath

Featured is a simple bath we installed on one of our farms that has changed their foot health in a matter of months at minimal cost. The farm continue to bath daily all year without prompting because it is easy and cheap. Talk to your advisors today about creating an effective digi control plan.