Papillomatous digital dermatitis footwarts in California dairy by benbenzhou


Papillomatous digital dermatitis footwarts in California dairy

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									J Vet Diagn Invest 10:67–76 (1998)

 Papillomatous digital dermatitis (footwarts) in California dairy
          cattle: clinical and gross pathologic findings
                                          Deryck H. Read, Richard L. Walker

         Abstract. Clinical, gross pathologic, and therapeutic studies were performed on a contagious, painful, wart-
      like digital disease of unknown etiology in California dairy cattle. The disease was called papillomatous digital
      dermatitis (PDD). Survey indicated that the disease spread geographically throughout southern California over
      the past few years. In 1991, 31% of herds had papillomatous digital dermatitis, whereas in 1994, 89% were
      affected. Increased incidence occurred during late spring and summer, 1–3 months after the rainy season. Within-
      herd morbidity ranged from 0.5% to 12% per month. Study of 93 cows in 10 drylot dairies revealed that 91%
      had characteristic circumscribed, erosive to papillomatous, intensely painful lesions often surrounded by a ridge
      of hyperkeratotic skin bearing hypertrophied hairs. Lesions were 2–6 cm across (88%), circular to oval (78%),
      and raised (59%) and had surfaces that were uniformly erosive and granular (31%), uniformly papillary (28%),
      or composites of both appearances (41%). Lesions were most frequently seen in lactating heifers (31%) and 3-
      year-old cows (43%). Clinical signs were characterized by lameness, with walking on toes and clubbing of
      hooves. Lesions exclusively involved the hind limbs in 82% of cows and the plantar/palmar regions in 84% of
      cows. Lesions had high (89%) prediliction for plantar/palmar skin bordering the interdigital space. Lesions
      exclusively involved either the medial or lateral digit in 10% and 28% of cows, respectively. In 50% of cows,
      both medial and lateral digits of individual limbs were involved; in most cows (31%), lesions apposed each
      other across the plantar interdigital space, whereas in others (19%), lesions confluently involved the entire
      plantar/palmar commissural skin folds. In another 12% of cows, lesions were axial. High proportions of lesions
      showed complete therapeutic responses to antibiotics: parenteral penicillin (9/9) and ceftiofur (41/44), and
      topical oxytetracycline (4/4). Recurrence or new lesion development occurred in 48% of cows reexamined 7–
      12 weeks after complete therapeutic response was observed. Overall, the findings indicated that PDD is a
      distinct disease entity of economic importance in which bacteria may play an important pathogenic role.

   Papillomatous digital lesions were reported in dairy                  nificant problem in many dairy herds in Italy, The
cows and beef bulls in various parts of the USA ap-                      Netherlands, France, England, the Czech Republic,
proximately 20 years ago.1,17 Similar lesions of a high-                 Slovakia, Denmark, Slovenia, Germany, and Ire-
ly contagious nature emerged in several dairy herds in                   land.3,7,10,14,35 More recently, the disease has been re-
New York state in the late 1970s.26 In 1 herd, morbid-                   ported to occur in Japan,16 Iran,20 and Israel.2
ity reached 73% over a 3-month period. Associated                           In southern California, a papillomatous erosive dig-
lameness caused economic loss due to decreased milk                      ital disease occurred in dairy cattle in 1992; the disease
yield, poor reproductive performance, and loss of body                   was similar in histologic character to interdigital pap-
weight. The authors named the condition interdigital                     illomatosis.25 Since 1992, the disease has spread geo-
papillomatosis because the lesions commonly involved                     graphically throughout southern and central Califor-
skin bordering the interdigital space and, histological-                 nia.28 It has also been confirmed histologically in 8
ly, the lesions resembled viral papillomatosis. At-                      other states in the USA and in 1 state in Mexico (D.
tempts to demonstrate viral involvement by culture                       H. Read, unpublished). Recent reports indicate its
and electron microscopy were negative. In Europe, a                      widespread occurrence throughout the USA and Can-
similar but less papillomatous entity (Mortellaro dis-                   ada.8,9 High morbidity rates similar to those reported
ease) was reported in dairy cows in the Po valley of                     for interdigital papillomatosis have been reported
Italy in 1974.11 The authors named the entity digital                    throughout North America34 (L. C. Allenstein, J. S.
dermatitis (DD). Since 1974, DD has spread geograph-                     Britt, J. M. Gay, and C. L. Guard, personal commu-
ically to several European countries and is now a sig-                   nication).
                                                                            A recent European review of DD suggested that in-
  From the School of Veterinary Medicine, California Veterinary          terdigital papillomatosis and DD are the same dis-
Diagnostic Laboratory System, University of California–Davis, San        ease.14 The authors contended that the gross pathologic
Bernardino Branch Laboratory, PO Box 5579, San Bernardino, CA
92412 (Read), and Central Reference Laboratory, PO Box 1770,
                                                                         differences in the degree of papillomatous change
Davis, CA 95617 (Walker).                                                merely reflected different emphases related to the stage
  Received for publication October 23, 1995.                             or form of the lesion most frequently seen. Recent re-
68                                                          Read, Walker

ports from England, Italy, and Slovenia support this                 The remaining 11 cows in 1 herd were only visually ex-
view on clinical and histopathologic grounds.6,29,35                 amined from the rear at a distance of 1 m as the cows
Consistent with these reports, we and others36 prefer                stood in the milking parlor. A total of 350 feet were exam-
to use the name papillomatous digital dermatitis                     ined. Feet were washed with water, and lesions were pho-
                                                                     tographed and recorded. Visual assessments were also made
(PDD) because the lesion is primarily inflammatory in
                                                                     of corral foot environment (n 7 dairies), trauma of plantar/
nature yet it often appears papillomatous.                           palmar skin of the feet (n        68 cows), and the size and
  The purpose of this report is to characterize PDD in               shape of the interdigital space (IS) of all feet (n 29 cows).
California in terms of occurrence and clinical signs,                Selected lesions (n 85 in 54 cows) were anaesthetized by
anatomic distribution and gross appearance of lesions,               locally infiltrating 2% lidocaine into the subcutis and then
and response of lesions to treatment.                                biopsied for laboratory evaluation by either complete exci-
                                                                     sion or by use of a 6-mm-diameter punch biopsy instrument.a
                  Materials and methods                              Results of histopathologic and bacteriologic evaluations on
   Investigative rationale. During 1990–1994, lameness was           biopsy materials have been published.23,25,31
investigated in 10 dairy herds in southern California by farm           Classification of lesions. Erosive digital skin lesions (n
visits, physical examination of the lower limbs of cows, and         183 in 93 cows) were classified by anatomic location and
laboratory evaluation of biopsies of digital skin lesions.           gross appearance, and representative lesions (n       85) were
Farm visits occurred at various times of the year and with           examined histopathologically. Pathologic criteria classified
variable frequency, interval, and total duration. Two dairies        these lesions into 3 categories: PDD, interdigital dermatitis
requested an investigation because of an outbreak of lame-           (IDD), and pastern flexural skin fold ulcer (PFSFU).23 Le-
ness in November 1991 and November 1992, respectively.               sions were histopathologically classified as PDD if they con-
This investigation involved 4 visits, 3 of which were made           sisted of 1) a circumscribed plaque of eroded acanthotic epi-
to 1 dairy 7 days apart to assess therapeutic response. An-          dermis attended by parakeratotic papillomatous proliferation
other 6 dairies provided affected cows for clinical observa-         profusely colonized by spirochete-dominant bacterial flora,
tion and biopsy from March to July 1991–1994. Two other              2) loss of stratum granulosum, 3) invasion of stratum spi-
dairies provided affected cows for treatment response trials,        nosum by spirochetes, and 4) infiltration of neutrophils, plas-
which entailed 11 visits from February to May 1992 and 2             ma cells, lymphocytes, and eosinophils in dermis. Lesions
visits in November 1993, respectively.                               were classified as IDD if they were located within the IS
   Herd management. All cows were Holsteins and were                 and had a histologic character similar to that of PDD, except
housed outdoors all year in drylot soil corrals in the Chino         for demarcated margins and papillomatous change. Lesions
and San Jacinto dairy preserves. Average annual rainfall was         were not classified as IDD if they were grossly confluent
38 cm (range, 25–89 cm), almost all occurring from January           with lesions of PDD. Lesions were classified as PFSFU if
to March. Accumulated fecal waste was scraped from the               they were deep ulcers attended by pyoderma, folliculitis, fu-
corrals during summer months and from concrete feedbunk              runculosis, serum crusting, and absence of spirochetes. A
platforms and alleyways periodically throughout the year.            possible association between PDD and IDD was examined
Routine footbathing with copper sulfate was employed on 1            in 38 feet involved by PDD bordering the IS.
dairy. The herds ranged from 500 to 2,200 cows. Approxi-                Additional classification was confined to PDD because it
mate age composition of the milking herds was 2–3 yr                 was the most prevalent and painful lesion. These additional
(50%), 4–5 yr (40%), and 6 yr (10%). Diet consisted of a             studies consisted of anatomic distribution of lesions (n
basic ration of alfalfa hay supplemented with various food           129 in 68 cows) and size, shape, contour, color, and surface
commodities and by-products, such as cotton seed meal, cot-          appearance of lesions (n 134 in 82 cows).
ton seed, soybean meal, rolled grains (corn, barley, wheat),            Effect of treatments. The effect of various treatments was
almond hulls, and vitamin–mineral mixtures.                          assessed on 72 lesions of PDD in 35 cows in 3 herds (herds
   Interviews. Interviews were held with 5 commercial hoof           5–7). Treatments consisted of procaine penicillin G,b 18,000
trimmers, 8 veterinarians, and 4 dairyowners in southern             units/kg intramuscularly twice daily for 3 days (7 cows);
California. These individuals gave historical and general in-        ceftiofur sodium,c 2 mg/kg daily for 3 days (14 cows); oxy-
formation about approximately 130 dairy herds managed                tetracycline,d single topical application of approximately 5 g
similarly to those investigated. One veterinarian and 1 hoof         of soluble powder bandaged directly onto a clean lesion for
trimmer had local information relative to the past 17 and 25         7 days (3 cows); formaldehyde,e 39% v/v, single topical ap-
years, respectively. Information about PDD was obtained on           plication (5 cows); hydrochloric acid,e 36% v/v, single top-
geographic prevalence, morbidity, age distribution, anatomic         ical application (4 cows); surgical excision (4 cows); and
location and gross appearance of lesions, and response of            chlorodifluoromethane dimethylether,f 2 min of topical cryo-
lesions to treatment.                                                genic spray until lesion and margin were frozen solid and
   Physical examination of lower limbs. Ninety-three cows            white (1 cow). Two cows that received no treatment served
in 10 herds were selected for examination because of lame-           as untreated controls. Therapeutic response was assessed at
ness or grossly visible erosive or papillomatous digital skin        posttreatment days 7 (4 cows), 7 and 14 (23 cows), and 7,
lesions. Age was determined by herd record or ear tag in-            14, and 21 (7 cows). Therapeutic response was considered
formation or tooth eruption pattern in a total of 49 cows.           complete if there was entire transformation of moist, red,
The majority of cows (n          82 in 9 herds) were restrained      raw, painful surfaces that were prone to bleeding to dry, dark
in a tilt chute to facilitate close inspection of all lower limbs.   brown, firm, rubbery, keratinous, nonpainful surfaces adher-
                                                  Papillomatous digital dermatitis in cattle                                                69

  Table 1. Classification and anatomic location of 183 erosive
digital skin lesions in 93 Holstein cows in 10 California dairy herds.

                                                      No.      No.
                  Lesion/location                    cows    lesions§

A. Papillomatous digital dermatitis
    1. Proximal border of interdigital space         76*      123†
    2. Proximal border of heel bulb                   7        11
    3. Interdigital space                             3         3
    4. Plantar pastern                                5        10
B. Interdigital dermatitis                           18        27
C. Pastern flexural skin fold ulcer                    9         9
  * 25 of these 76 cows also had lesions listed in other categories:
A2, 2 cows; A2 and A4, 2 cows; A3, 2 cows; B, 16 cows; C, 3
  † A great majority of these lesions extended a few millimeters
distally to involve the skin of the interdigital space.

ent to underlying pink healthy appearing skin. The preva-
lence of recurrent and new lesions was evaluated in 23 cows
in herds 6 and 7 that had previously responded to treatment
7–12 wk prior to follow-up examination. Another 6 lesions
of PDD in 4 cows in herd 4 were reexamined 5 wk after
total surgical excision.

   Occurrence. The interviews revealed that sporadic
cases of undefined wart-like digital lesions were clin-
ically observed on the feet of dairy cows in southern
                                                                            Figure 1. Cow at feedbunk. Papillomatous digital dermatitis in-
California approximately 15 years ago. PDD was first                      volves right hind limb. Cow is thin and shows pain in plantar region
confirmed histologically as a herd problem in San Ja-                     of right hind foot. Affected limb is bearing little or no weight and
cinto in 1988, although a clinical report suggested that                 is resting on its toes. Lesion is adjacent to bulbs of heel and inter-
it first occurred in the area as early as 1985. Similar                   digital space (arrow). Environment of forefeet during feeding is drier
                                                                         than that of hind feet.
disease was also observed clinically in a few herds in
the Chino district in 1988. By 1991, PDD had spread
throughout both areas to involve approximately 31%                       Chino suddenly increased to serious proportions, i.e.,
of 350 herds. By June 1993, an estimated 89% of herds                    about 15% morbidity in many herds.
were affected. Within-herd morbidity estimates dif-                         Classification of erosive digital skin lesions. Prev-
fered widely among herds, from 0.5% to 12% per                           alence of PDD, IDD, and PFSFU is shown in Table 1.
month. PDD appeared contagious because several clin-                     The majority of cows (91%) had PDD, smaller num-
ically affected cows were observed in 2 dairies that                     bers had IDD, and occasional cows had PFSFU. Some
had no previous history of PDD within a few months                       overlap occurred: 19% and 4% of cows with PDD also
after introduction of single affected animals. In all                    had separate lesions of IDD and PFSFU, respectively.
herds, lesions were most frequently observed in lac-                     Also, a majority of feet (82%) involved by PDD le-
tating heifers (31%) and 3-year-old cows (43%), but it                   sions bordering the IS had confluent IDD lesions ex-
was not possible to estimate true age prevalence be-                     tending several millimeters into the IS.
cause of selection bias. Bulls and prelactation heifers                     Clinical signs of PDD. Cows lame with PDD usu-
were occasionally affected. No obvious difference in                     ally exhibited signs of plantar or palmar pain (Fig. 1).
prevalence was noted between dry cows and lactating                      Severely affected cows were reluctant to move; the
cows. Increased lameness due to PDD occurred in late                     affected limb was often held shaking in partial flexion
spring to early summer, approximately 1–3 months af-                     as if in intense pain. Less severely affected limbs rest-
ter the end of the rainy season (Jan–Mar). During the                    ed or bore weight on the toes, and if unresolved,
rainy season, the lower limbs of most cows were in                       hooves became clubbed with atrophy of the bulbs of
almost continual contact with stale manure-rich mud                      the heels. Secondary effects of the lameness included
and slurry. In June 1993, the prevalence of PDD in                       loss of body weight. Little or no diffuse digital swell-
70                                                               Read, Walker

   Table 2. Anatomic location of 129 lesions of papillomatous dig-         Table 3. Gross appearance of 134 lesions of papillomatous dig-
ital dermatitis in 68 Holstein cows in 8 California dairy herds.*       ital dermatitis in 82 Holstein cows in 9 California dairy herds.*

                                                  Cows      Lesions                                                      Lesions†

                Anatomic location                 n   %     n     %                                              Small   Medium       Large
                                                                                                                (1 cm)   (2 cm)     (3–6 cm)
                                                                                   Lesion characteristic        n    %    n   %      n   %
  Right hind                                     24   35    41    31
  Left hind                                      22   32    38    29    Shape
  Right and left hind                            10   15    27    21     Circular/oval                         16 12     52 39      53 39
  Hind and fore                                   3    5    11     9     U-shaped                               0 ···     0 ···     12 9
  Fore                                            9   13    13    10     Linear                                 0 ···     0 ···      1 1
Plantar/palmar/dorsal                                                   Contour
  Plantar/palmar                                 57 84     115 88        Concave                                 4   3    0 ···     0 ···
  Dorsal                                          9 13      13 10        Flat                                    5   4   22 16      17 13
  Plantar/palmar and dorsal                       2 3        2 2         Raised                                  7   5   30 22      49 37
Medial/lateral digits/axial†                                            Color and surface
 Medial                                           7   10     9     6     Red, granular                           8   6   16 12      17 13
 Lateral                                         19   28    31    24     Red, granular with yellow/gray
 Biaxial                                         21   31    50    39        papillary areas                      5   4   21 16      29 22
 Axial                                            8   12    15    12     Gray/brown/black, extensively
 Extensive (axial and medial and/or lateral)     13   19    25    19        papillary                            3   2   15 11      20 14
  * Herds 2, 4–10. In herds 1 and 3, all 4 feet were not systemati-       * Herds 1, 2, 4–10. In herd 3, lesions were not systematically
cally examined.                                                         examined.
  † Pertaining to an individual limb.                                     † Greatest dimension across lesion, rounded up/down to nearest

ing was observed. Fissuring and necrosis of the skin
of the IS were not seen. Heel horn erosion was com-                     aspects were involved in 3% of cows. No obvious pre-
monly seen in feet with or without PDD.                                 dilection of lesions for medial or lateral digits was ob-
   Anatomic location of PDD lesions. The anatomic                       served. Both medial and lateral digits of an affected
distribution of PDD lesions with respect to affected                    individual limb were involved in 51% of cows: some
limb and anteroposterior, mediolateral, and digital lo-                 (31%) of these lesions opposed each other across the
cations are shown in Tables 1–3. Lesions were con-                      IS (Fig. 2C), whereas others (19%) confluently in-
fined to the digits and were not observed above the                      volved the entire commissural skin fold bordering the
level of the dewclaws. Lesions exclusively involved                     IS (Fig. 2E). Either medial or lateral digits of an in-
the hind limbs in 56 of 68 cows (82%) (Table 2). Of                     dividual limb were involved in 10% and 28% of cows,
these, 24 had right limb involvement, 22 had left limb                  respectively. With respect to digital site, 76 of 85 cows
involvement, and 10 had both hind limbs involved.                       (89%) with PDD had lesions involving skin bordering
The forelimbs were exclusively involved in 13% of                       the IS (Table 1); lesions rarely involved the abaxial
cows, and all 4 limbs were involved in 5% of cows.                      aspects of the digits. Lesions uncommonly involved
Plantar (or palmar) aspects alone were involved in                      skin bordering the base of the bulb of the heel (7/85
84% of cows. The dorsal aspect alone was involved in                    cows), within the IS (3/85 cows), or in plantar pastern
13% of cows, and combined plantar/palmar and dorsal                     flexural skin folds (5/85 cows). The lesions affecting

  Figure 2. Hind feet of cows with papillomatous digital dermatitis involving plantar interdigital commissural skin fold and illustrating
variable gross morphology (white arrow        interdigital cleft). A. Four-week-old, circumscribed, uniformly erosive–granular lesion with
keratin tags (black arrow). This lesion appeared to develop from an eroded area in adjacent interdigital skin observed 4 weeks previously.
Bar     1 cm. B. Slightly raised extensive lesion of unknown age consisting of several erosive–granular areas interspersed with areas of
yellow-white ragged keratosis (K) and circumscribed by a ridge of keratotic skin and hypertrophied hairs. Note expansive growth and
replacement of soft perioplic horn (P) of heel bulb of 1 digit and heel horn erosion (white arrowheads). C. Raised lesions of unknown age
apposing each other across the interdigital space (IS) and bearing large numbers of small filiform papillae (black arrows) on their eroded
surfaces. D. Raised lesions of unknown age apposing each other across the IS and bearing numerous long filiform papillae (black arrows).
This lesion was incompletely responsive to parenteral penicillin and ceftiofur and recurred after surgical excision. E. Raised
U-shaped lesion of unknown age uniformly involving the plantar interdigital commissural skin fold with extensive granular erosion. Note
solitary curled filiform papilla (black arrowhead). F. Lesion E, 14 days after parenteral penicillin therapy. Note diminution in overall size
of lesion and transformation of moist red raw surfaces to dry brown/white keratinous scabrous layers (K) adherent to healthy appearing
Papillomatous digital dermatitis in cattle   71
72                                                          Read, Walker

   Figure 3. Gross appearance of a highly papillomatous digital dermatitis lesion of a cow. A. External surface is densly covered by
filiform papillary growths which, at the periphery, are intermingled with erect hypertrophied hairs. B. Perpendicular sectioned surfaces
reveal that the lesion is a broadly pedunculated hemispherical mass consisting of dermal fibrous connective tissue supporting a convex
plaque of uniformly thickened epidermis (e) which in turn gives rise to many filiform papillary growths. Bar 1 cm.

the IS were situated on the crest of a corn (2 cows) or              were U-shaped because they involved the entire com-
involved the entire space from plantar to dorsal aspects             missural fold of skin that borders the plantar/palmar
(1 cow). Six cows had lesions involving more than 1                  IS (Fig. 2E).
site; collectively all 4 sites (Table 1) were involved,                 Regardless of size, shape, and contour, lesions were
and no pattern was observed. Occasionally, as many                   characteristically circumscribed or delineated by a dis-
as 7 lesions involved an individual limb.                            crete line of raised hyperkeratotic skin (Fig. 2A–C)
   The visual assessments of corral foot environment,                often bearing erect hairs 2–3 times longer than normal
trauma of plantar/palmar skin, and size and shape of                 (Figs. 2B, 2C, 2E, 3). They were also partially to com-
the IS gave the following results: 1) hind feet were                 pletely alopecic, and their surfaces were moist, prone
submerged deeper in slurry than were forefeet during                 to bleeding, and intensely painful to touch. Lesions
feeding (due to feedbunk flatform slope) but not at                   proximal and adjacent to the heel bulb characteristi-
other times; 2) no evidence of consistent trauma was                 cally expanded to involve and replace perioplic horn
seen in hind feet or forefeet; and 3) the dorsal two-                (Fig. 2B). Some lesions undermined the horn of the
thirds of the IS of hind feet and forefeet was markedly              heel bulb for a distance of several millimeters, but sup-
more expansive than the plantar/palmar one-third,                    purative underrunning of horn was not observed. De-
which was slit-like and difficult to open manually. No                fects in the wall were observed in 2 cows, and in both,
obvious differences were noted in the size and shape                 the defects were related to proximal PDD lesions in-
of the plantar region of the IS compared with its pal-               volving the coronary band.
mar counterpart.                                                        Effect of treatments. PDD lesions were highly re-
   Gross appearance of PDD. The size, shape, con-                    sponsive to parenteral or topical antibiotics or topical
tour, color, and surface characteristics of 134 lesions              caustic chemicals (Table 4). Sixty-five of 72 lesions
are presented in Table 3. The majority of lesions were               involving 30 of 35 cows treated with antibiotics or
medium to large (2–6 cm across at their greatest di-                 caustics showed a complete therapeutic response by
mension) (88%), circular to oval (90%), raised (64%),                posttreatment (PT) day 21. Response was character-
and variable in color and in degree of papillary pro-                ized by complete transformation of moist, red, raw,
liferation. Washed surfaces were typically either ex-                painful surfaces that were prone to bleeding to dry,
tensively red and granular (31%) (Fig. 2A) or a com-                 dark brown, nonpainful, tough rubbery keratinous sur-
posite of white-yellow, gray, brown, and/or black pap-               faces (Fig. 2E, 2F). The keratinous layer was tightly
illary areas interspersed with red granular areas (42%)              adherent to underlying white-pink healthy appearing
(Fig. 2B). Lesions extensively covered by large num-                 skin. These changes were observed in 66% of cows
bers of papillae comprised 27% of the total (Figs. 2C,               by PT day 7. By PT day 21, diminution in size and
2D, 3). Papillae were usually filiform, about 0.5–1 mm                partial restoration of hair growth were also observed.
in diameter and 1 mm to 3 cm in length. Small lesions                   Mean therapeutic response times as determined by
(1 cm diameter) were uncommonly observed (12%),                      desiccation and keratinization of surfaces and absence
and their features were similar to those of medium and               of pain were slightly longer for cows treated parenter-
large lesions except that most had extensively red                   ally with ceftiofur (11.1           ¯
                                                                                                    4.5 [x    SD] days, n
granular surfaces. A small proportion of large lesions               13) than for those treated parenterally with penicillin
                                                    Papillomatous digital dermatitis in cattle                                                   73

  Table 4. Effect of various treatments on 72 lesions of papillo-         silateral limb were completely responsive to the first
matous digital dermatitis in 35 Holstein cows in 3 California dairy       treatment by PT day 7. In the 2 hydrochloric acid-
                                                                          treated cows, the incomplete responses were charac-
                                                         No. lesions      terized by persistence of small, painful, deep ulcers.
                                No. cows assessed        assessed†        The lesion treated with cryogenic spray did not re-
           Treatment            Treated Responded Treated Responded       spond.
Antibiotics                                                                  The prevalence of recurrent and new lesions in 27
 Penicillin G procaine IM‡         7        7           9            9    treated cows in 3 herds is shown in Table 5. Lesions
 Ceftiofur IM                     15       13          44           41    recurred in 9 cows and new lesions developed in 4
 Oxytetracycline, topical          3        3           4            4    other cows that had previously responded completely
Topical caustics                                                          to treatment 7–12 weeks prior to follow-up examina-
 Formaldehyde (39%)                5          5          8          8     tion. Two cows that had recurrent lesions also had new
 Hydrochloric acid (35%)           4          2          6          3     lesions. The combined rate of recurrence and new le-
Physical agent                                                            sion development in treated cows was 48%. Recur-
 Cryogenic spray                   1          0          1          0     rence and new lesion development were observed in
                                                                          cows treated with either ceftiofur or penicillin. New
  * Herds 5–7.
  † Therapeutic response was assessed at posttreatment days 7 (5          lesions occurred in cows treated with hydrochloric
cows), 7 and 14 (23 cows), and 7, 14, and 21 (7 cows). Fifty-five          acid, and recurrent lesions occurred in cows treated by
lesions bordered the interdigital space; 9 bordered the base of the       surgical excision.
heel bulb, and 8 involved flexural plantar pastern skin fold.
  ‡ IM intramuscular.                                                                                      Discussion
                                                                             In our preliminary report,25 we used the name in-
(8.2 2.5 days, n 7) or topical applications of oxy-                       terdigital papillomatosis to denote the disease de-
tetracycline (7 days, n     3), formaldehyde (7 days, n                   scribed here. We adopted this name in deference to an
   5) or hydrochloric acid (7 days, n 2). No consis-                      earlier report by other workers who described a his-
tent differences in response time were observed in le-                    tologically identical entity in the USA.26 We have since
sions of different sizes or at different sites.                           renamed the California disease papillomatous digital
   Incomplete responses occurred in 2 cows treated                        dermatitis22–24 to acknowledge that the primary disease
with ceftiofur and in 2 other cows treated with hydro-                    process is inflammation, not neoplasia. The new name
chloric acid. In 1 of the 2 ceftiofur-treated cows, 2                     will also serve to alert clinicians and pathologists that
large, raised papillary lesions on 1 limb (Fig. 2D) were                  PDD lesions are often grossly and histologically in-
refractory over a PT period of 73 days despite a sec-                     distinguishable from squamous papillomas. The name
ond course of antibiotics (parenteral penicillin), where-                 PDD could reliably be used throughout North America
as 6 similar medium-sized papillary lesions on the ip-                    without confusion because, histopathologically, the

  Table 5. Prevalence of recurrent and new lesions of papillomatous digital dermatitis in 27 Holstein cows in 3 herds* that previously
completely responded to treatment 7–12 weeks prior to follow-up examination.

                                              Responsive†                           Recurrent‡                              New§

        Treatment                      No. cows       No. lesions        No. cows            No. lesions         No. cows          No. lesions

 Penicillin G procaine IM                 3                  3           1¶                       1               2                 4
 Ceftiofur IM                            11                 30           4¶                       6               2                 2
Topical caustics
 Formaldehyde (39%)                       6                  8           0                        0               0                 0
 Hydrochloric acid (36%)                  3                  4           0                        0               2                 3
Surgical excision                         4                  6           4                        6               0                 0
Totals (%)                               27                 51           9 (33)                  13 (26)          6 (22)            9 (18)
  * Herds 4, 6, and 7.
  † Criteria for complete therapeutic response were absence of evincible pain and transformation of exudative surfaces to dry brown/black
rubbery hyperkeratotic layers adherent to white-pink healthy appearing skin.
  ‡ Recurrence of a lesion at a previously responsive affected site.
  § Occurrence of a lesion at a previously nonaffected site.
   IM intramuscular.
  ¶ 1 cow also had a new lesion.
74                                                  Read, Walker

disease is identical in all areas of the USA, Canada,       lesional invasive spirochetes23,25 provide convincing
and Mexico studied thus far (D. H. Read, unpub-             evidence that bacteria may play an important role in
lished).                                                    the pathogenesis of the disease. Also, the histologic
   The clinical and gross pathologic features of PDD        similarity of PDD to yaws, a papillomatous condition
described here are essentially identical to those re-       of the feet and lower legs of people living in the trop-
ported for DD in Canada, Europe, England, and Ire-          ics caused by Treponema pallidum subsp. pertenue,13
land,3,6–8,10,11,14,35 interdigital papillomatosis in New   adds further support. Although we have isolated
York,26 and verrucose dermatitis and digital papillo-       Treponema-like organisms from PDD lesions,31 their
matosis in Japan.16 These features also serve to differ-    pathogenic significance along with several other an-
entiate PDD from other specific inflammatory diseases         aerobes isolated (R. L. Walker, unpublished) remains
of the digital skin of cattle. The most striking distin-    to be proven. Intralesional invasive spirochetes have
guishing feature noted in the present study was the         also been demonstrated in DD6,29,35 and in verrucose
anatomic predilection of lesions for hind limbs and         dermatitis in Japan.16 Various attempts to demonstrate
skin–horn junctions, especially those bordering the         viruses,3,25,26 structural group antigens of papillomavi-
plantar aspect of the IS. Lesions only rarely involved      rus,25,29,35 and bovine papillomavirus types 1–622 in
the IS per se. Such selective vulnerability appears to      PDD,22,25 DD,3,29,35 and interdigital papillomatosis26
be highly distinctive because it is not reported as a       have been negative. Histologic examination for Der-
hallmark of other bovine digital skin diseases.4,15,32      matophilus, fungi, and parasites also have been nega-
Other characteristic features of PDD lesions are that       tive.22
they often develop filiform papillae and are intensely          In this study, the incidence of PDD in southern Cal-
painful to touch, prone to bleed, and demarkated by a       ifornia increased in late spring to early summer, as
raised line of hyperkeratotic skin, often bearing hy-       later confirmed by an epidemiologic survey.28 A sub-
pertrophied hairs. Overall, these features indicate that    sequent epidemiologic case-control study of 57 dairies
PDD, like DD,7,15 represents a single specific disease       in southern California revealed that muddiness of cor-
entity.                                                     rals was strongly linked to a high prevalence of PDD.27
   Interdigital necrobacillosis (footrot) differs from      Consistent with this association was a marked regional
PDD because it primarily involves interdigital skin and     increase in incidence in June 1993, 2 months after an
is characterized by fissuring, caseous necrosis of sub-      extraordinary wet winter and spring. In the UK and
cutis, and diffuse digital swelling.12,15 IDD also pri-     Europe, poor foot hygiene has also been linked with
marily involves interdigital skin and causes only mild      the occurrence of DD in winter-housed cattle.5,7,21 Sug-
lameness.15,32 Although IDD has been widely consid-         gested predisposing factors include prolonged contact
ered a separate entity,34 its identity has been recently    of the lower limbs with manure-rich stale slurry,5 a
questioned because, histopathologically, it shares some     foot environment similar to that observed during the
features in common with DD5 and PDD,23 and it has           rainy season in California. However, our observation
been associated with DD in the field.5,30 In the present     was confounded by another observation in this study,
study, 82% of feet that had PDD bordering the IS also       i.e., that some outbreaks occurred in late fall, approx-
had contiguous IDD. These observations and the re-          imately 5 months after the corrals had largely dried
cent isolation of an identical spirochete in PDD and        out. Other investigators agree that predisposing factors
IDD lesions31 indicate that further study is required to    for outbreaks of DD are not always clearly evident,35
clarify the interrelationships of these 2 entities.         and still others report outbreaks associated with ex-
   A few cows in this study had involvement of flex-         cellent hygiene in housed3 and pastured14 cattle. In ad-
ural skin folds of the pastern by either deep ulcers or     dition to muddiness of corrals, another risk factor re-
PDD. The 2 conditions appeared histologically differ-       vealed by the California case-control study was the
ent,23 but their prediliction for the same site suggests    introduction of heifer replacements.27 Other investi-
some commonality in their pathogenesis. Similar ul-         gators in the USA and Europe also attribute the spread
cers or fissures and diffuse exudative dermatitis are        of PDD/DD to sharing of cows among herds14 or in-
reported to occur on the lower limbs of cattle housed       troduction of sound heifers from affected herds.10,21,34
under prolonged wet unhygienic conditions.18                   The reason why PDD or DD lesions have a high
   Our epidemiologic observations indicate that PDD         prediliction for plantar/palmar skin bordering the IS is
behaves as an infectious disease, as does DD.10,14,21 The   not known. Our visual assessment of corral underfoot
geographic spread, evidence of contagion, high prev-        environment showed that hind limbs were exposed to
alence in young cows, and high within-herd morbidity        deeper slurry during feeding than were forelimbs, but
observed here are consistent with this view. In addi-       we were unable to assess the significance of this dif-
tion, the marked sensitivity of PDD lesions to paren-       ference because the preferential site for PDD is almost
teral or topical9 antibiotics and the presence of intra-    at ground level. With respect to the possibility of trau-
                                               Papillomatous digital dermatitis in cattle                                                 75

ma, we found no evidence of continual abrasion of                           outbreaks of ‘‘Morterello disease.’’ Proc Int Symp Dis Ruminant
either plantar or palmar digital skin. Visual evaluation                    Digit 8:183.
                                                                       3.   Basset HF, Monaghan ML, Lenham P, et al.: 1990, Bovine dig-
of the size and shape of the IS clearly showed that                         ital dermatitis. Vet Rec 126:164–165.
plantar and palmar regions were slit-like because the                  4.   Blowey RW: 1992, Diseases of the bovine digit. In Pract 14:
bulbs were in close apposition. The plantar/palmar                          85–90.
regions of the IS were, therefore, much more prone to                  5.   Blowey RW: 1994, Interdigital causes of lameness. Proc Int
being continually moist, compared with their more                           Symp Dis Ruminant Digit 8:142–154.
                                                                       6.   Blowey RW, Done SH, Cooley W: 1994, Observations on the
open dorsal counterparts. Because IDD and PDD/DD                            pathogenesis of digital dermatitis in cattle. Vet Rec 135:115–
are favored by a continually moist foot environ-                            117.
ment,5,15,28,32 this observation may help to explain why               7.   Blowey RW, Sharp MW: 1988, Digital dermatitis in dairy cattle.
lesions of these entities occur more frequently at these                    Vet Rec 122:505–508.
locations than elsewhere. In a study on the natural evo-               8.   Borgmann IE, Bailey J, Clark EG: 1996, Spirochete-associated
                                                                            bovine digital dermatitis. Can Vet J 37:35–37.
lution of DD, 90% of early erosive lesions began at                    9.   Britt JS, Gaska J, Garret EF, et al.: 1996, Comparison of topical
the plantar border of the IS and then, by proximal local                    application of three products for treatment of papillomatous dig-
extension, developed into typical strawberry-like le-                       ital dermatitis in dairy cattle. J Am Vet Med Assoc 209:1134–
sions.19 The plantar/palmar region of the IS may there-                     1136.
fore possess special conducive factors for the devel-                10.    Brizzi A: 1993, Bovine digital dermatitis. Proc Annu Conf Am
                                                                            Assoc Bov Pract 26:33–37.
opment of PDD, one of which may be a moisture re-                    11.    Cheli R, Morterello C: 1974, La dermatite digitale del bovine.
tention property.                                                           Proc Int Meet Dis Cattle 8:208–213.
   In the present study, PDD was observed most fre-                  12.    Edmondson AJ: 1990, Interdigital necrobacillosis (footrot) of
quently in lactating heifers, a finding also reported by                     cattle. In: Large animal internal medicine, ed. Smith BP, pp.
other investigators in the USA28 and Europe.7,10,14 The                     1173–1175. CV Mosby, Baltimore, MD.
                                                                     13.    Engelkens HJH, Judanarso J, Oranje AP, et al.: 1991, Endemic
reason for this apparent age prevalence is unknown,                         treponematosis, part 1. Yaws. Int J Dermatol 30:77–83.
but cows may become immune as they age. However,                     14.    Gourreau JM, Scott DW, Rousseau JF: 1992, La dermatite dig-
our observation of recurrence or new lesion develop-                        itee des bovins. Le Point Vet 24:49–57.
ment in 48% of cows reexamined 7–12 weeks after a                    15.    Greenough PR, MacCallum FJ, Weaver DA: 1981, Diseases of
complete therapeutic response does not support this                         the digital skin and subcutis. In: Lameness in cattle, ed. Weaver
                                                                            DA, 2nd ed., pp. 151–169. Wright Scientechnica, Bristol, UK.
hypothesis. Treatment may only afford a temporary                    16.    Kimura Y, Masahiro T, Matsumoto N, et al.: 1993, Verrucose
cure, and immunity may be poor at best. Answers to                          dermatitis and digital papillomatosis in dairy cows. J Vet Med
these questions will impact future strategies for treat-                    Jpn 46:899–906.
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                     Acknowledgements                                18.    McLennan MW, Daniel RCW: 1991, An outbreak of sebor-
                                                                            rhoeic dermatitis (greasy heal) in cattle. Aust Vet J 68:76–77.
   This study was supported in part by funds from the Cal-           19.    Morterello CM, Romussi S, Scavia G: 1994, Preliminary report
ifornia Milk Advisory Board. Clinical and epidemiologic in-                 on the onset and evolution of digital skin disease in a group of
formation was provided by veterinary clinicians (R. Bush-                   32 heifers. Proc Int Symp Dis Ruminant Digit 8:177–179.
nell, R. Gutierrez, F. Koning, J. Lovell, R. Petty, D. Senes-        20.    Nowrouzian I: 1994, Risk factors in the development of digital
                                                                            dermatitis in dairies in Tehran, Iran. Proc Int Symp Dis Rumi-
traro, D. Thomas, T. Worthington) and hoof trimmers (A. de
                                                                            nant Digit 8:155.
Jong, R. Van der Zwan, K. Taylor, R. West-Styne, R. Wig-             21.    Nutter WT, Moffitt JA: 1990, Digital dermatitis control. Vet Rec
boldy). Dairy owners (J. McCune, M. Oosten, R. Tuls, R.                     126:200–201.
Van Dam) provided herd information and cows for treatment            22.    Read DH: 1995, Papillomatous digital dermatitis. Proc 4-State
response trials. The manuscript was prepared by Manolita                    Dairy Appl Nat Manage Conf 1995:134–143.
Bisnar.                                                              23.    Read DH, Walker RL: 1994, Papillomatous digital dermatitis:
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c.   Naxcel , The Upjohn Co., Kalamazoo, MI.                         25.    Read DH, Walker RL, Castro AE, et al.: 1992, An invasive
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e.   Fisher Scientific, Pittsburg, PA.                                       cattle. Vet Rec 130:59–60.
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