Digital Dermatitis in Cow / Calf and Feedlot Cattle

Veterinary Diagnostic and Production Animal
Medicine Publications

Veterinary Diagnostic and Production Animal
Medicine

8-2015

Digital Dermatitis in Cow/Calf and Feedlot Cattle
J. K. Shearer
Iowa State University, [email protected]

P. J. Plummer
Iowa State University, [email protected]

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Digital Dermatitis in Cow/Calf and Feedlot Cattle
Abstract

Our lameness research team at Iowa State University, comprised of faculty members Drs. Paul Plummer, Pat
Gorden and Jan Shearer, and graduate students Drs. Adam Krull and John Coatney, has been actively studying
digital dermatitis for the past six years. Our work has been focused on identifying causative agents for the
purpose of developing better strategies for its treatment and control. In the following article, we review
current understanding of this disease and highlight some of our research findings.
Disciplines

Large or Food Animal and Equine Medicine | Veterinary Microbiology and Immunobiology | Veterinary
Preventive Medicine, Epidemiology, and Public Health
Comments

This article is published as JK Shearer and PJ Plummer. Digital Dermatitis in Cow/Calf and Feedlot Cattle.
Progressive Cattleman. August 2015, v. 5, no. 8, pp.28-29. Posted with permission.

This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/vdpam_pubs/95

PC WEST MAIN

Digital dermatitis in cow-calf and feedlot cattle
J.K. Shearer and P.J. Plummer for Progressive Cattleman
Our lameness research team at
Iowa State University, comprised of
faculty members Drs. Paul Plummer,
Pat Gorden and Jan Shearer, and
graduate students Drs. Adam Krull
and John Coatney, has been actively
studying digital dermatitis for the
past six years. Our work has been
focused on identifying causative
agents for the purpose of developing
better strategies for its treatment and
control. In the following article, we
review current understanding of this
disease and highlight some of our
research findings.

Digital dermatitis
in dairy and beef cattle

Digital dermatitis (DD) is
considered to be the most common
infectious disease affecting housed
dairy cattle worldwide. It is estimated
to affect nearly 100 percent of dairy
herds and up to 20 percent of all
dairy cattle. A study published in
2000 of cull dairy and beef cattle in
the southeastern U.S. also found a
higher prevalence of digital dermatitis
in dairy compared with beef cattle.
Researchers examined the left hind
foot for lesions of digital dermatitis in
a total of 815 cattle during four visits
to a slaughterhouse. Twenty-two of 76
(29 percent) dairy cattle and 29 of 739
(4 percent) beef cattle were observed
to have lesions of digital dermatitis.
Male beef cattle were more likely
to have lesions compared with beef
females. Results of this study confirm
that although prevalence is lower, DD
does occur in cow-calf operations as
well.
In 1974, a veterinary practitioner
from Vicksburg, Mississippi,
reported observing papillomas
(warts) occurring on the feet of a
mature Angus bull. Lesions were
described as beginning on the pastern
and coronet of the rear feet and
gradually spreading upward to the
dewclaws and fetlock. Attempts to
isolate viruses from the lesions were
unsuccessful, and despite multiple
attempts at therapy, the disease was
refractory to treatment. Of interest,
none of the treatment approaches
involved topical antibiotics. It’s
unknown whether the condition
described here was actually DD;
however, considering its similarities to
digital dermatitis, one might wonder
if topical antimicrobial therapy might
have proved beneficial based on DD
treatment observations.
In feedlot cattle, DD occurs
sporadically in some locations and in
near-epidemic proportions in others.
Although there are no published data
on incidence, clinical observation
suggests incidence rates as high as 50
percent or more in pens of affected
cattle. One of the troubling features
of DD is that lameness is often
inconsistent. Less than half of affected
cattle may demonstrate obvious
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August 2015

signs of lameness. Observations
from a large study at Iowa State
University over a three-year period
strongly suggest nearly all early
lesions and a significant percentage
of advanced lesions fail to result in
visually detectable lameness (i.e., a
locomotion score greater than 3 on
a 5-point scale). In our study, only
a portion of the cows with clinical
lesions had lameness. Similar results
were observed where only 39 percent
of the cows with severe DD lesions
had lameness. These observations
suggest lameness is not a good means
of identifying the prevalence of cows
with DD lesions. It simply misses too
many.
Detection is often based on direct
observation of lesions or a finding of
variable degrees of lameness among
cattle within a pen. Cattle with
lesions on rear feet often exhibit a
characteristic posture wherein they
will shift weight to the less severely
affected foot and place weight on the
painful foot onto the toe, thereby
placing less stress on the skin on the
plantar surface (Figure 1).

Characteristic appearance
of DD lesions

Lesions of DD are typically
observed in one of three locations of
the foot: on the skin of the plantar
aspect of the rear foot adjacent to the
interdigital cleft, on the interdigital
skin and at the skin-horn junction of
the heel bulbs. Less frequently, lesions
may be observed near or above the
dewclaws.
Our team finds it helps to
categorize lesions into two major
groups: pre-clinical and clinical.
Pre-clinical lesions are the early stages
of lesion development that are easier
to treat and generally do not cause
clinical lameness. Clinical lesions
are those that have a deeper-seated
infection, making them more difficult
to treat, and are capable of causing
clinical lameness. For research
purposes, we can subdivide these
stages into additional classification to
better understand lesion development
and treatment; however, that level of
complexity is not generally necessary
for making clinical decisions.
Early (“pre-clinical”) stages of
developing lesions generally have
either a red circular or oval lesion
with a raw ulcerated surface located
adjacent to the interdigital cleft
(Figure 3 top left), or in some cases
a more widespread proliferative
crust formation on the heels and
interdigital cleft (Figure 3 top right).
As the lesions mature and become
“clinical,” they develop a granularappearing surface similar to that of a
wart. Some have characterized these
mature lesions as having a terrycloth
towel-like surface. The borders of
mature lesions are clearly demarcated
by the presence of hypertrophied

Progressive Cattleman

Figure 1
Typical posture of a steer with
digital dermatitis affecting the
plantar interdigital cleft.

hairs (Figure 3 lower left). More
chronic lesions are characterized by
a thick bed of granulation tissue, and
in some cases, epithelial outgrowths
that appear as long hairs extending
from the surface of the granulation
tissue bed; (Figure 3 lower right),
thus, the common name: hairy heel
wart. Digital dermatitis lesions are
extremely sensitive and very painful
when touched or disturbed.
Lesions also have a characteristic
odor believed to be caused by the
breakdown of keratin and the
presence of secondary bacterial
infection. Finally, mature and
particularly chronic lesions are
accompanied by significant erosion of
the heel horn. The heel erosion may
be diffuse, in the form of fissures or
in the shape of a “V.” In some cases,
the erosion may result in significant
undermining of heel horn.
As mentioned, pain is a key
feature of DD lesions, so animals
will naturally learn to adjust posture
and walk in a manner that avoids
discomfort. Hoof trimmers know
to carefully examine a foot with an
abnormally long heel or toe because
the shape of a hoof is an important
indicator of foot problems. In the case
of chronic DD lesions, animals will
adjust their posture and gait to avoid
contact with flooring surfaces. For
example, when lesions occur on the
plantar surface of the foot, animals
will shift their weight to the toe,
as shown in Figure 1. This causes
greater wear at the toe and less at the
heel, permitting the heel to become
abnormally long. Lesions occurring
on the front of the foot will cause the
animal to shift its weight to the heel,
resulting in a longer toe and shorter
heel. Therefore, claw conformation
can be a very useful diagnostic
indicator of DD lesions in cattle.

Causes of DD

Despite its known existence for

Figure 2
A lesion of digital dermatitis
affecting the interdigital cleft
of the rear foot.

nearly 40 years, the precise organisms
responsible for this disease are not
entirely known. Early reports of
digital dermatitis suggested a viral
etiology because of the wart-like
appearance of lesions. However,
no one has been able to detect
viruses associated with DD. Lesions,
lameness and pain all regress rapidly
following treatment with antibiotics.
If the cause were a virus, this would
not likely occur.
For the past 25 years, researchers
have consistently isolated bacterial
spirochetes from DD lesions. The
majority of these spirochetes have
been identified as belonging to the
genus Treponema sp., causing many
to conclude that treponemes are the
most likely causative agent of DD.
However, the bacterial flora of the
foot includes a multitude of other
bacteria, some capable of causing
disease and some not. Nonetheless,
questions remain as to whether
DD is solely caused by treponemal
spirochetes, by other associated
bacteria, or is it a combination of
both?
Our work at Iowa State University
suggests that more than treponemes
are likely involved. Evidence for this
comes from several observations:
Attempts to reproduce the disease by
skin inoculation with pure cultures of
these micro-organisms have largely
failed to cause disease, vaccines
prepared against spirochetes have
not proven to be effective for control
of DD, a large number of different
bacterial organisms can be identified
in the lesions including multiple types
of treponemes, and the lesions of DD
respond favorably to antibiotics.
At present, the data suggest that
the disease process is polybacterial,
meaning that multiple species of
bacteria need to be present at the
same time in order to induce disease.
A very similar disease process
associated with similar treponeme

PC WEST MAIN

species is human gingivitis, where
there is a large body of evidence that
multiple bacterial species are required
to induce disease. Not surprisingly,
polybacterial diseases are much more
complex to study and understand,
which likely explains the difficulty
researchers have experienced in
determining the cause of this disease.

Effects on performance

Few studies have attempted
to assess the effects of DD on
performance, and those that have
were done in dairy cattle. Effects on
milk production are generally mild or
insignificant. More significant are the
effects on reproductive performance,
where at least one study found an
increase of 20 days in the time
from previous calving to the next
conception in affected cows. To date,
there are no reports in the literature
on the impact of DD on rate of gain
or other performance parameters of
interest to the cattle feeding industry.

Treatment/control
in feedlot settings

The experience of many feedlot
owners and managers is that cattle
enter the lot free of clinical evidence
of DD. However, after about 120 to
150 days on feed, cattle break with
the disease. This can be frustrating
to managers since this disease break
often occurs about the time they are
ready to move cattle on to slaughter.
Work at Iowa State University
suggests the average time required
for lesions to develop from an early
to mature stage requires on average
120 to 150 days. This explains why
we see lesions occurring about the
time we are ready to move these
animals to slaughter. In addition, this
suggests that lesions are present well
before they cause clinical disease (i.e.,
lameness).
Many have also observed that
lesions observed in feedlot dairy
steers/heifers are oftentimes more
advanced or chronic compared with
those observed in beef steers/heifers.
One explanation for this may be that
dairy animals are infected earlier
(prior to feedlot entry due to exposure
at the dairy farm of origin) and enter
the feedlot with lesions that much
further along in their development. As
a result, their lesions are more severe
earlier in the feeding period and also
more refractory to treatment.
Treatment of individual animals
with an antibiotic compound such
as oxytetracycline or tetracyclinesoluble powder with or without a
bandage is the most common form
of individual treatment. It is laborintensive and effectiveness depends
upon the nature of the lesion with
respect to chronicity (i.e., early,
mature or chronic).
Our research group has been
evaluating the clinical response to
treatment with topical antibiotics.
Several key factors have been
confirmed. First, we have confirmed
the results of other researchers that
demonstrate that the majority of

lesions treated a single time with
topical tetracycline fail to completely
heal. Treatment does often improve
lameness and the lesions tend to
improve and return to a pre-clinical
lesion; however, over time the
majority of these lesions persist or
recrudesce (reoccur). Second, our
data suggest there is not a significant
difference in lesion recrudescence
between the mature and more chronic
lesions. So treatment of all observed
clinical DD lesions is warranted.
Finally, we have demonstrated that
when lesions heal completely (i.e.,
return to normal skin) they are much
less likely to recrudesce. This finding
would suggest that more aggressive
follow-up to topical treatment with
re-treatment until the skin completely
heals may be warranted.
Topical antibiotic sprays have
been shown to be very effective
for treatment of DD. Although
labor-intensive, it offers a couple of
advantages over footbath treatment
approaches. For one, this treatment
method is not affected by freezing
temperatures, and secondly, DD
lesions can be sprayed with fullstrength solutions that haven’t been
subject to contamination and possible
neutralization by organic matter.
While this approach to treatment and
control may seem too cumbersome,
some argue spraying is easier than
trying to construct and manage a
footbath.

Walk-through footbaths

The use of a walk-through
footbath is the most popular approach
to treatment of DD in dairy cattle,
but there is little information in the
scientific literature to support its
efficacy. Products or compounds
suggested for use usually include
copper sulfate, zinc sulfate, formalin
and various antibiotics. In feedlot
conditions, one of the first challenges
is finding the best location for a
footbath so it can be properly used
and maintained. The next issue is
design of the footbath; if the footbath
is too short, animals will jump over
it, and if it is too narrow, animals will
step around it. Based on the dairy
industry’s experience, longer (12 feet)
footbaths are likely to increase the
number of foot immersions per trip
through the bath.
Possibly more important is the
footbathing strategy applied. For
example, since many cattle entering
the feedlot may have very early
lesions, footbathing on arrival or
shortly thereafter would seem to be
ideal for controlling and preventing
further development of lesions.
Follow-up footbathing at weekly,
biweekly or monthly intervals
until cattle are moved to slaughter
should reduce the impact of DD on
performance and prevent clinical
disease that may preclude marketing
animals on time. The objective is not
to eliminate the disease but rather
to keep it in check throughout the
feeding period until movement to
slaughter.

Figure 3
Typical appearance of different stages of digital dermatitis lesion
development. The top pictures demonstrate the two pre-clinical
lesion types. The bottom pictures show clinical lesions with the
mature lesion on the left and a more chronic lesion on the right.
(Note lesions are shown on dairy cattle with white feet to make
the lesions easier to visualize).

Pre-clinical Lesions

Clinical Lesions

Mature

Chronic

Other treatment approaches

Systemic therapy would be a
far more convenient option for the
treatment of digital dermatitis in
feedlot cattle. However, there are
no controlled studies that support
the efficacy of parenteral treatment.
This is an area in need of further
study to confirm the possible
benefits of treatment with some of
the newer long-acting antibiotics.
Some have wondered if feed-through
antibiotics might be effective. In
short, it is illegal to use antibiotics
in an extra-label manner in feed.
Since no oral antibiotics have a
digital dermatitis claim, any use of
feed-grade antibiotics to control or
prevent digital dermatitis would
be prohibited. Others have tried
surgical removal, burning or cautery,
and even cryosurgery (freezing) of
DD lesions – to no avail. In short,
based upon available literature and
experience, the best treatments at the
present time are individual treatment
with topical antimicrobials, topical
spray or a well-designed and managed
footbath.

Vaccination

History suggests developing a
vaccine may be difficult. Results from
early studies of a treponema bacterin
for control of DD in cattle concluded
that immunization could reduce
clinical disease. However, commercial
use proved otherwise, and the vaccine
was eventually removed from the
market. The U.S. experience with
vaccination for DD was corroborated
by German researchers, who found
no benefit from a vaccine containing
herd-specific pathogens, including

Treponema sp. While interest in
finding a vaccine continues to be
the focus of many who research this
disease, there are many questions
to be answered in the process of
finding permanent solutions through
vaccination.
P.J. Plummer is with the Veterinary
Microbiology and Preventive
Medicine, College of Veterinary
Medicine, Iowa State University.
References available on request.

J.K. Shearer
Professor and Extension
Veterinarian
College of Veterinary
Medicine
Iowa State University
[email protected]

www.progressivecattle.com

August 2015

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