Diagnosis of Bovine Digital Disease

Transcription

1 A System for the Recording of Clinical Data as an Aid in the Diagnosis of Bovine Digital Disease LAURIE L. MILLS, DOUG H. LEACH, MARION E. SMART AND PAUL R. GREENOUGH Department of Veterinary Internal Medicine (Mills, Smart), Department of Veterinary Anatomy (Leach) and Department of Veterinary Anesthesiology, Radiology and Surgery (Greenough), Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan 57N 0 WO ABSTRACT A form for the clinical evaluation of bovine digital disease was developed. In this article, each section of the resulting Digit Evaluation Form is discussed and justified. By following the Digit Evaluation Form guidelines in examination of 1 13 cattle (904 digits), objectives in two major areas were met: 1) Fundamental diagnostic techniques were consistently applied to clinical cases of bovine digital disease. 2) An accurate recording system was developed, largely due to the clinical application of a 12 zone system in graphic description of lesions. Key words: Bovine, digit, lameness, diagnosis, recording. R E SUM E Un systeme d'enregistrement des donnees cliniques, destine a aider au diagnostic des maladies des onglons des bovins Les auteurs ont developpe un formulaire pour l'evaluation des maladies des onglons des bovins. Dans cet article, ils en commentent et justifient chaque section. En l'utilisant pour proceder a l'examen des 904 onglons de 113 bovins, ils reussirent a atteindre leurs deux principaux objectifs, a savoir: 1 l'application constante de techniques fondamentales de diagnostic a des cas cliniques de maladies des onglons des bovins; 2 - le developpement d'un systeme d'enregistrement precis, grace surtout a l'application clinique d'un systeme de 12 zones, dans la description graphique des lesions. Mots cles: bovins, onglons, boiterie, diagnostic, enregistrement. I N T R O D U C T O N A routine diagnostic method is essential to the practice of veterinary medicine. A uniform method, repeated for every case of disease, can reduce errors of omission and emphasize important abnormalities. Diagnosis of bovine digital disease is no exception. The components of a clinical examination and the various aspects of diagnosis (1) are readily applicable to diseases of the bovine digital region. When combined with an accurate recording system, accurate diagnosis and thorough examination can insure effective reevaluation of cases and substantially expand the available data base on bovine digital disease. Relatively little has been done to develop a system which improves both the diagnosis and recording of digital disease in cattle. Previous surveys have indicated the incidence of various types of disease within a geographic locale (2,3,4,5,6). Others have addressed location of lesions. Important steps in the diagnosis and treatment of various digital disorders have been emphasized (7,8,10,11, 12,13,14). The Western College of Veterinary Medicine Bovine Digital Evaluation Form (DEF) is an attempt to record clinical aspects of bovine digital disease as it occurs in western Canada. This form is unique in that it combines information and techniques from numerous reference sources, specifically addresses solution of the immediate disease problem, and provides a data base for further studies into prevalent lesions. In addition, lesions in the external hoof wall may be described by reference to 12 zones. This may prove helpful in diagnosis and in the detection of lesions in underlying structures. Table I (The distribution of lesions according to zones) is a summary of the lesions noted in the examination of 904 digits. The percentage of the total number of each lesion found within zones 1 through 12 is listed to allow comparison with literature citing a relationship between diagnosis and location of lesion (4,8,9). BACKGROUND INFORMATION Sections A-D of the Digit Evaluation Form A. History An essential component of the diagnostic method is an accurate complete history, with the appropriate signalment. In this clinic, signalment (age, breed, sex), client's name, address and telephone number, and case number are recorded on a card which becomes a part of a permanent file. This type of identification expedites record storage and retrieval, computer analysis of case information, and follow-up studies. Reprint requests to Dr. L.L. Mills, Department of Veterinary Medicine and Surgery, Veterinary Teaching Hospital, University of Missouri, Columbia, Missouri This study was supported by The Dean's Agriculture Canada Fund and the Saskatchewan Horned Cattle Trust. Can Vet J 1986; 27:

2 A. HISTORY: Elective Gait BOVINE DIGIT EVALUATION FORM1 trimming or postural abnormalities Duration Previous treatment Pertinent history: dietary, environmental & production B. Regular hoof trimming: Y N If Y, how often? CLINICAL EVALUATION: Body Score Physical condition and description of gait and/or postural abnormality: C. DIAGNOSTIC PROCEDURES: Radiographs Manual Palpation Hoof Testers Microbiology Removal of Surface Hoof Horn Aspiration Nerve Blocking Washing of Digital Area Debridement Photographs Exploration of Tracts D. TREATMENT: Removal of excess horn Soaking of digits Parenteral antibiotics Technovit & lift Exposure & drainage Topical treatment Bandaging Surgical No treatment Debridement Details of treatment & client education: Attending Clinician FIGURE 1. Western College of Veterinary Medicine Bovine Digit Evaluation Form (front side). 294

3 The history recorded on the DEF (Figure 1) includes a means to specifically differentiate between animals presented because of a lameness (gait or postural abnormality), and those presented for elective digital horn trimming. This step facilitates recording of overgrowth as a specific diagnosis, and assessment of the client's perception of the digital lesion. This is important, because many clients do not recognize certain lesions as potentially harmful, and are unaware of the effect the lesions have on the animal's performance. The duration of the perceived gait abnormalities and response to previous treatment are helpful in determining differential diagnosis, possible pathogenetic mechanisms, and prognosis. Acute lameness may indicate a lesion produced by trauma, while a gait abnormality which progressively worsens may indicate a septic or other invasive process (9). In bovine digital disease, as in disease of any system, pertinent dietary, environmental, and production information is an important component of the history. Laminitis, sole ulceration, focal hemorrhage, and defects resulting from poor horn quality are all lesions which may be related to diet and/ or high milk production (15,16,17). Conversely, a drop in milk production, weight loss, or substandard weight gains may indicate digital disease of sufficient duration or severity to prevent adequate feed intake (3). Environment plays an important role in cases of bovine digital disease, as many lesions are created or exacerbated by improper environment. Examples include interdigital dermatitis, heel erosion (18,19,20), sole ulcers (21,22,23), separation of the zona alba (18), overworn sole (24), punctured sole and septic extension (25), and vertical fissure (18). The role of environment in other conditions such as overgrowth and deformities is less clearly defined but could be important. The last portion of section A records hoof trimming. If regular hoof trimming is not part of the herd management program, client education must stress the importance of hoof maintenance. Routine trimming of digital horn by a qualified individual has been shown to reduce the incidence of sole ulcers (15,21), vertical fissure (9) and separation of the white line (18). B. Clinical Evaluation When using the DEF, a record is made of the animal's general body condition. This is necessary to complete the clinical record, and to allow possible relationships between digital disease and body score to be examined (26). Poor body condition may indicate prior disease, which can be reflected in poor hoof horn quality, reduction in horn growth rate and growth arrest lines (9,27). Physical condition may also reflect severity and/ or duration of a digital disease, if foraging capabilities are reduced. Animals suffering from laminitis lose body condition through mechanisms which are not completely understood (28). C. Diagnostic Procedures Eleven types of diagnostic procedures are listed under section C of the DEF. Manual palpation, removal of surface hoof horn, and washing of the digital area have all been identified as. important procedures in the routine examination of every bovine digit (9,13). Radiographs, hoof testers and palmar or plantar digital nerve blocks may be used separately or in conjunction as tools in the diagnosis of osteomyelitis, septic arthritis, osteoarthritis, periostitis, fractures and luxations (29). Desensitization of the areas supplied by the palmar/ plantar digital nerves is relatively nonspecific, which limits the diagnostic usefulness of these if used alone (30). However, they may aid in examination of animals with particularly painful digital lesions. The use of hoof testers to discern areas of pressure-induced pain is helpful when radiographic services are not available. When radiography is available, more clearly defining the affected area increases the diagnostic efficiency of the procedure. Exploration of tracts, aspiration and debridement may be necessary to define the extent of many septic processes, most of which are sequelae to penetration of the external hoof capsule. D. Treatment A review of pertinent literature provided information necessary for selection of treatment categories. Previous surveys have simplified this information into two major categories: surgical and medical (8). However, more detailed information is necessary for production of a complete medical record and for purposes of reevaluation. LESION DESCRIPTION Reverse Side of the Digit Evaluation Form Careful description of the initial site of hoof capsule penetration is necessary for 1) correct diagnosis of the lesion, which may depend directly on location, 2) assessment of healing, and 3) prevention of recurrence or complication. The reverse side of the DEF (Figure 2) was divided into four sections, one for detailed description of the lesions of each digital region. Diagnostic categories A-P were chosen as a result of review of prior surveys and past case records at this clinic, and were based on international nomenclature (7,8). The 12 zones for division of the bovine external hoof accepted by the International Council on Bovine Digital Disease in 1978 were utilized for graphic lesion description because they are internationally recognized, create divisions in the external hoof wall which are recognized in the live specimen by related anatomical structures, and because published information indicates that each zone may be involved in characteristic lesions (7,8). Description of Zones Zones numbered 1 through 5 are used to describe the weight bearing surface, which is composed of the wall, sole and bulb (Figure 3). Zone I - This portion of the weightbearing surface contains several structures which are frequently involved in digital abnormalities: the zona alba (white zone), paries corneus (hoof wall), corpus soleae (body of the sole), apex soleae (apex of the sole), and apex tori (apex of the bulb). 295

4 LEFT RLIGHT N A-sole ulcer g / / B-sep.of DIAGNOSIS zonaalba DIAGNOSIS C-abscess at zona alba 0-punctured sole/sepsis E-foreign body F-over worn sole G-hemm. in sole H-normal overgrowth DIAGNOSIS 1-deformity of DIAGNOSIS hoof walldigos J-vertical fissure K-interdigital hyper pla sia L-interdigital necr oba c illosis M-interdigital dermatitis N-heel erosion 0-deep sepsis (a rthritis,osteomye.) P-other FIGUE 2 Weter Coleg ofvetrinry ediinebovne igi EvluaionFor (rvere sde) FIGURE 2. Western College of Veterinary Medicine Bovine Digit Evaluation Form (reverse side). 296

5 Weight Bearing Surfaoe FIGURE 3. Bovine external digit: Anatomical structures and numbered zones. Lesions diagnosed in this zone which involved these structures were: separation of the zona alba (white line disease), overworn sole, and hemorrhage within the sole (Table I). Separation of the zona alba is the most common cause of lameness in the United Kingdom dairy cow population (18). Several factors predispose this region to injury and penetration. It is a comparatively weak junction between the sole and the hoof wall, and conditions such as laminitis, wet environment, overgrowth, and claw deformities further weaken the area (18,24,32). Under these circumstances, the shearing force created at the zona alba by contact between the hoof wall and the ground will contribute to the clinical lesion. The largest part of the sole lies in zone 1. The sole is not a major weightbearing surface in the normal claw (33). Therefore an overworn, thin sole suggests abnormalities elsewhere in the digit, or excess trimming of the bulb and abaxial wall (34). The apex of the distal phalanx lies proximal to the apex tori. In this survey, two cases of distal phalangeal fracture and seven cases of osteomyelitis were initially suspected (and later radiographically confirmed) due to pressure-induced pain in the area of the apex tori. Zone 2 Pressure plate studies have shown that the highest pressures generated during contact of the digit with the ground occur at the abaxial wall of the digit during mid-stance (35). Therefore, due to the additive effects of pressure, conditions which weaken the sole and/or cause abnormal growth or wear may be exhibited first in zone 2. The angulus soleae abaxialis (abaxial angle of the sole) and the abaxial white line lie within zone 2. Because these are extensions of structures which also lie within zone 1, lesions which were frequently diagnosed in zone 2 were similar to those of zone 1. One exception was punctured sole/ sepsis. Sepsis of varying extent is the sequel to a solar puncture (25,3 1). The vascular supply for the production and maintenance of the epidermis (sole) is located in the corium or dermis, which lies under the sole (30). Penetration of the sole provides access for organisms from the environment, which initiates a coriitis. If left unchecked, the majority of the sole and/or bulb may be separated from the corium by a layer of purulent exudate. Of greater consequence is damage to the underlying structures, the flexor tendon attachment to the distal phalanx, the navicular bursa, and the distal interphalangeal joint, which may become involved through extension of the septic process (23,31). Zone 3 The angulus soleae axialis 297

6 TABLE I THE DISTRIBUTION OF LESIONS ACCORDING TO ZONES Total Number % of Lesions Zones Lesions of Lesions Involving the Zone separations at Zona alba excess wear focal hemorrhage abscess at Zona alba separations at Zona alba excess wear punctured sole/sepsis excess wear separation at Zona alba punctured sole/sepsis excess wear punctured sole/sepsis sole ulcer heel erosion excess wear punctured sole/sepsis overgrowth deformity of hoof wall overgrowth deformity of hoof wall vertical fissure vertical fissure overgrowth deformity of hoof wall vertical fissure overgrowth deformity of hoof wall vertical fissure overgrowth overgrowth (axial angle of the sole) and the axial white line lie within zone 3, close to the axial groove. Clinical findings in this zone were similar to those in zone 2. Zone 4 - Careful examination of zone 4 is important because it is the specific location of sole ulceration, also known as pododermatitis circumscripta (7), typical lesion of the sole (34), and specific traumatic sole ulceration (2). The condition occurs almost invariably in the lateral hind claws of housed cattle and results from localized damage to the corium. The damaged corium produces defective horn which rapidly wears away in a characteristic circular pattern. The exposed corium responds by formation of granulation tissue and clinically detectable lameness soon follows. Septic sequelae are frequent and may include septic laminitis, heel abscess, osteomyelitis of the palmar/ plantar part of the distal phalanx, necrosis and rupture of the deep digital flexor tendon, septic navicular bursitis, and osteoarthritis (25). The etiology of sole ulceration is not understood, although localized circulatory disturbances, preexisting laminitis, abnormal weight-bearing, and faulty trimming have all been advanced as important factors in development of the lesion (20,22,32). It may be prevented and treated by corrective trimming of the hoof horn. The objective of such trimming is to normalize and redistribute weightbearing in the digit, and lends credence to the observation that sole ulceration is exacerbated, if not created, by conditions which result in inappropriate contact between the digit and the ground. Incidence of this lesion varies between geographic locales, which may be related to differences in housing and management. For instance, in a Quebec survey, this was the most frequently observed condition (6). Zone 5- The basis tori, or base of the heel, is the structure affected by heel erosion. This lesion produces little lameness unless fissured areas extend into the corium. A painful cellulitis often follows the initial septic coriitis, and may extend to involve tendon sheaths, the navicular bursa, and other deep supporting structures (20). These sequelae may cause permanent gait impairment, even with appropriate therapy. Zones The abaxial external wall is divided into five zones. The most frequent diagnoses in all five zones were overgrowth, deformity of the hoof wall, and vertical fissure (sand crack). The distal abaxial border of the wall contacts the ground, and is an important part of the weight-bearing surface (33). Normal wear at this point is approximately equal to growth, which is 0.5 cm per month (27). Many situations alter either, or both sides of this physiological equation. Lack of wear occurs during wet seasons when ground is soft. A similar situation occurs in housed cattle which are kept in wet, deep bedding or manure. Overgrowth due to acceleraged horn production or production of poor quality occurs in cases of laminitis (28). Accelerated horn production occurs at the mid and palmar/ plantar wall (Zones 9 and 10) in cases of corkscrew claw (27). Corkscrew claw is a deviation fo the abaxial wall in an axial-dorsal direction, and was the most common deformity diagnosed in our survey. Reasons for this comparatively rapid growth have included localized periostitis at the abaxial attachment of the distal interphalangeal joint capsule, trauma, or other damage to the coronary band (9,18,36). Early diagnosis of corkscrew claw, and frequent trimming can help to delay the onset of secondary exostoses at ligament attachments and permanent gait alteration. This lesion may have economic impact because of impaired breeding capability in 298

7 affected bulls, and because it may be a heritable condition (36). Thirty-four cases of vertical fissure were diagnosed in the survey. Zones involved were 7, 8, 9 and 10. Vertical fissure is a separation which begins at the coronary border of the hoof wall (Zone 8). The lesion is predisposed by dry conditions and loss of the periople, a thin, translucent covering of the hoof wall which protects and reduces moisture loss, thus preserving the hoof wall's resilience (37). An abnormally dry hoof wall does not expand with impact on the bearing surface, and because it lacks resilience, may crack (8). Although the lesion is unsightly, it does not cause lameness unless the crack extends through the full thickness of the epidermis. A septic laminitis follows such penetration, and may rapidly extend to involve a large part of the dorsal laminae, or become sequestered in the form of an abscess (7,18,25). Because the hoof wall is relatively nondistensible, purulent material trapped underneath it by a septic process frequently migrates proximally and distends the coronary area. This is followed by necrosis of soft tissues and formation of fistulous tracts (7,15) An important structure underlying the central dorsal portion of zone 8 is the distal interphalangeal joint. Abnormal findings in this area require quick attention and careful diagnosis to prevent permanent articular damage. Zones 11 and 12 - The paries axialis or axial hoof wall contains the axial groove, which is an approximate anatomical separation between zones 11 and 12. This is a relatively weak junction between the axial wall and bulb. Interdigital trauma may affect this groove, and is of clinical concern because the distal interphalangeal joint is accessible to penetration at this site. Besides overgrowth, the most frequent diagnosis which involved zones 11 and 12, heel erosion may also extend to involve the axial face of the heel (Zone 12). DISCUSSION The Western College of Veterinary Medicine Bovine Digital Evaluation Form provides the clinician with a useful tool for recording aspects of cases of bovine digital disease and improves the diagnostic method by providing consistent guidelines. Adaptation of the zone system for division of the external hoof wall provides a means of relating clinical lesions to the anatomical structures involved. In addition, use of the system emphasizes the importance of accurate recording in diagnosis of digital disease and prevention of sequelae to externally visible lesions. Use of the DEF is encouraged to promote improvement in the approach to diagnosis of disease of the bovine digit and to provide a basis for further study of prevalent lesions. A C K N O W L E D G M E N T S Special thanks to Gary Cody, Medical Illustrator and Arnold Duke, Animal Health Technician for their assistance in completing this project. REFERENCES 1. BLOOD DC, RADOSTITS OM, HENDERSON JA. Veterinary medicine, 5th ed. London: Bailliere Tindall, 1979: ARKINS S. Preliminary results from a survey of lameness in Irish dairy cows. III International Symposium on Disorders of the Ruminant Digit. Vienna, Austria, NEW ZEALAND DAIRY BOARD. Lameness survey Fiftieth Farm Production Report, OTTO H. Occurrence, incidence, localization and causes of diseases of limbs seen at the Hannover cattle clinic Inaug Diss Tierarztl Hochschule, Hannover 1963: RUSSELL AM, ROWLANDS GJ, SHAW SR, WEAVER AD. Survey of lameness in British dairy cattle. Vet Rec 1982; 3: CHOQUETTE-LEVY L, BARIL J, LEVY M, ST- PIERRE H. A study of foot disease of dairy cattle in Quebec. Can Vet J 1985; 26: GREENOUGH PR. The nomenclature of anatomical features of the bovine digits. 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