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- 67 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 cows. † 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. Results 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) Limb 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 centimeter. 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 skin. 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- herds.* 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 Antibiotics 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. ment and control. 17. Lindley WH: 1974, Malignant verrucae of bulls. Vet Med Agric Pract 69:1547–1550. 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: pathologic ﬁndings. Proc Int Symp Dis Ruminant Digit 8:156– Sources and manufacturers 157. 24. Read DH, Walker RL: 1994, Papillomatous digital dermatitis: a. Miltex Instrument Co., Lake Success, NY. clinical characteristics. Proc Int Symp Dis Ruminant Digit 8: b. G. C. Hanford Manufacturing Co., Syracuse, NY. 159–163. c. Naxcel , The Upjohn Co., Kalamazoo, MI. 25. Read DH, Walker RL, Castro AE, et al.: 1992, An invasive d. Terramycin - 343 , Pﬁzer Animal Health, New York, NY. spirochete associated with interdigital papillomatosis of dairy e. Fisher Scientiﬁc, Pittsburg, PA. cattle. Vet Rec 130:59–60. f. Brand Spray, Stockman Products, Castledown, Isle of Man, UK. 26. Rebhun WC, Payne RM, King JM, et al.: 1980, Interdigital papillomatosis in dairy cattle. J Am Vet Med Assoc 177:437– References 440. 27. Rodriguez-Lainz A, Hird DW, Carpenter TE, Read DH: 1996, 1. Allenstein LC: 1992, Wart-like foot lesions caused lameness. Case-control study of papillomatous digital dermatitis in south- Hoard’s Dairyman 137:696–697. ern California dairies. Prev Vet Med 28:117–131. 2. Bargai U: 1994, Excessive dietary protein as the cause of herd 28. Rodriguez-Lainz A, Hird DW, Walker RL, Read DH: 1996, 76 Read, Walker Papillomatous digital dermatitis in 458 dairies. J Am Vet Med chetes isolated from dairy cattle with papillomatous digital der- Assoc 209:1464–1467. matitis and interdigital dermatitis. Vet Microbiol 47:343–355. 29. Scavia G, Sironi G, Morterello CM, Romusi S: 1994, Digital 32. Weaver AD: 1988, Cattle foot problems, part 1. Introduction dermatitis: further contribution on clinical and pathological as- and interdigital skin disease. Agri-Practice 9:34–38. pects in some herds in northern Italy. Proc Int Symp Dis Ru- 33. Weaver AD: 1994, International terminology of digital disease. minant Digit 8:174–176. Proc Int Symp Dis Ruminant Digit 8:25–27. 30. Toussaint Raven E, Cornelisse JL: 1971, The speciﬁc conta- 34. Whittier WD: 1988, Footwarts. Dairy June 10:12–13. gious inﬂammation of the interdigital skin in cattle. Vet Med 35. Zemljic B: 1994, Current investigations into the cause of der- Rev 2:223–247. matitis digitalis in cattle. Proc Int Symp Dis Ruminant Digit 8: 31. Walker RL, Read DH, Loretz KJ, Nordhausen RW: 1995, Spiro- 164–167.