Pathology in Practice

Heather R. Herd Department of Veterinary Pathobiology, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078.

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Paola Cazzini Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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Saskia E. Houghton Eastside Animal Medical Center, 1835 Grayson Hwy, Grayson, GA 30017.

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Wesley L. Lee Red River Equine Hospital, 325 Rubicon Rd, Benton, LA 71006.

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Claire E. Freeman Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.

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Kaori Sakamoto Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

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History

A 15-month-old 431-kg (950-lb) Aberdeen Angus heifer was evaluated at the University of Georgia Large Animal Teaching Hospital because of a 3- to 4-week history of a rapidly growing, interdigital mass on the right hind limb (Figure 1) and grade 1 of 5 lameness. The owner reported that several other bovids in the herd had similar lesions.

Figure 1—
Figure 1—

Photograph of a bilobed mass at the interdigital and coronary band region of the right hind limb of a 15-month-old Aberdeen Angus heifer. Over a 3- to 4-week period, the mass had grown rapidly and the cow was somewhat lame (grade 1/5 lameness). Other bovids in the herd had similar lesions.

Citation: Journal of the American Veterinary Medical Association 246, 7; 10.2460/javma.246.7.749

Clinical and Gross Findings

The cow was placed in a chute for a thorough examination of the interdigital mass. A large (approx 5 × 2 × 2-cm), bilobed mass was present within the interdigital cleft and dorsal coronary region (Figure 1). The mass had a soft consistency and a pink, multifocally ulcerated surface, covered with white-tan, hair-like projections. The cow resented handling of the hoof, suggesting the lesion was painful. The mass was confined to the dermis and was removed after the heifer received IV regional anesthesia (ie, Bier block) by injection of 35 mL of lidocaine into the common digital vein.1

Histopathologic Findings

The excised bilobed mass was submitted for histologic examination. On histologic examination, the epidermis was markedly hyperplastic, with diffuse parakeratotic hyperkeratosis and uneven areas of superficial erosions (Figure 2). Thickening of the rete pegs was present and was often characterized by bridging. The keratinocytes were swollen and faintly eosinophilic (intracellular edema), and the cells were separated by slight clear spaces with prominent desmosomal connections (spongiosis). The epidermal surface was often elevated in frond-like projections. Multifocally, variably sized aggregates of bacteria (rods and filamentous bacteria) were present in the keratin debris (Figure 3). The filamentous bacteria reacted with Warthin-Starry stain, which highlighted a spirochetal appearance, and the rod-shaped bacteria were gram positive. Large numbers of eosinophils were associated with the dermal-epidermal junction, particularly surrounding blood vessels. Multifocal, lymphoplasmacytic, perivascular infiltrates were also present below the dermal-epidermal junction.

Figure 2—
Figure 2—

Photomicrograph of a histologic section of nonhaired skin from the mass excised from the cow in Figure 1. Notice the markedly hyperplastic epidermis with diffuse parakeratotic hyperkeratosis. H&E stain; bar = 500 μm.

Citation: Journal of the American Veterinary Medical Association 246, 7; 10.2460/javma.246.7.749

Figure 3—
Figure 3—

Photomicrographs of histologic sections of nonhaired skin from the mass excised from the cow in Figure 1. A—Markedly hyperplastic epidermis with uneven areas of superficial erosions is evident. H&E stain; bar = 20 μm. B—Aggregates of filamentous bacteria are present within keratin debris. Warthin-Starry stain; bar = 20 μm.

Citation: Journal of the American Veterinary Medical Association 246, 7; 10.2460/javma.246.7.749

Morphologic Diagnosis and Case Summary

Morphologic diagnosis: moderate, chronic-active, locally extensive, proliferative, erosive, and eosinophilic dermatitis, with parakeratotic hyperkeratosis and superficial spirochetal and rod-shaped bacteria.

Case summary: papillomatous digital dermatitis (PDD) in a cow.

Discussion

The presence of multiple affected cows in the herd, the location of the mass, and the gross and histopathologic findings provided a definitive diagnosis of PDD for the cow of this report. Papillomatous digital dermatitis, also known as hairy heelwarts or footwarts, is a contagious, painful, wart-like lesion that commonly affects the skin of the interdigital space on the hind feet of cattle.2 As for the present case, PDD is usually present in multiple animals within a herd.

Among cattle, PDD is an economically important disease that results in weight loss, decreased milk production, and poor reproductive performance.3 The pathogenesis of PDD is not fully understood, and despite the fact that the term footwarts implies a viral cause, the etiopathogenesis is considered bacterial. This supposition is based on the finding of spirochetal bacteria (Treponema spp) as well as the lack of demonstrable viral pathogens within lesions. Other evidence of a bacterial cause includes response of lesions to antimicrobial treatment and signs of a specific humoral response against spirochetal bacteria in affected animals.3 Papillomatous digital dermatitis has been predominantly described as affecting cattle, particularly dairy replacement heifers, but a similar disease in horses and sheep has also been described.4,5 Cattle that stand for long periods in wet and soiled environments are more likely to be exposed to the microaerophilic bacteria thought to be responsible for this disease.2 Treponema spirochetes are commonly detected in histologic sections with silver stains and by immunohistochemical analysis or PCR assay of tissue samples.6 Although not routinely performed, isolation of the invading microorganisms by means of anaerobic culture or incubation in selective treponeme isolation broth is also possible.7

Because PDD is often a recurring disease, proper management and preventative measures are most important in its control. Key points for proper PDD control include environmental hygiene, vaccination, topical or systemic antimicrobial treatment, and use of footbaths.8 The most effective treatment for PDD is antimicrobials, such as tetracycline and oxytetracycline,8 which can be administered topically or systemically to affected animals. Topical administration of antimicrobials is labor-intensive and costly, especially when a large herd requires treatment. Footbaths provide an alternative for large-scale treatment. Although footbaths are comparatively easier and more cost-effective, the water must be changed frequently or the feet of affected animals must be prerinsed because the antimicrobials and disinfectant present are inactivated by organic material (eg, manure and dirt).8 A vaccine has been developed, but consistent prevention of PDD associated with its use has yet to be demonstrated.9

In the case described in the present report, treatment included surgical removal of the lesion and application of tetracycline powder packed into gauze. No recurrence of the lesion was observed.

References

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  • 3. Ginn PE, Mansell JEKL, Rakich PM. Papillomatous digital dermatitis. Chapter 5: skin and appendages. In: Maxie MG, ed. Jubb, Kennedy, and Palmer's pathology of domestic animals. 5th ed. Philadelphia: Elsevier Saunders, 2007;692693.

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  • 7. Walker RL, Read DH, Loretz KJ, et al. Spirochetes isolated from dairy cattle with papillomatous digital dermatitis and interdigital dermatitis. Vet Microbiol 1995; 47:343355.

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  • 8. New Mexico State University. Hairy foot warts. Available at: aces.nmsu.edu/pubs/_b/B-122.pdf. Accessed Jan 17, 2013.

  • 9. Kirk J. Field evaluation of a vaccine against papillomatous digital dermatitis (PPD; footwarts) in dairy cattle. In: 2003 annual report, California Animal Health and Food Safety Laboratory System.Davis, Calif: University of California-Davis School of Veterinary Medicine, 2004;2324.

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