Skin Diseases of Swine Alan R

D,AGNOST,C NOTES' Skin diseases of swine Alan R. Doster, DVM, PhD he skin is the largest bodyorgan and in the normal state, can be examined directly for the presence of mites or dermato- forms a complete anatomic and physiologic barrier be- phytes after placing them in 10% solution of potassium hydrox- Ttween the animal and its environment While providing ide. However,remember that Microsporum nanum does not in- protection against a variety of noxious physical, chemical, and vade hair shafts.Growthis limited to keratinized skin. Therefore, microbiological agents, it serves as a sensory organ which is in epidermal crusts are the specimens of choice and must be exam- constant communicationwith internal body systemsand reflects ined carefully in order to demonstrate mycelial filaments of M. pathological processes that may be either primary or secondary nanum. in origin (Figure 1), In addition, the skin is responsible for ther- Take skin swabs for bacteriologic culture in cases of exudative moregulation,vitaminD synthesis,and immunoregulation, dermatoses, Because of the likelihood of secondary contamina- Skin disease in a swineherd can adverselyimpact production by tion, results of surface cultures should be interpreted with cau- causing a significantdecrease in growthrate and feed efficiency,l tion. Comparing results from bacteriologic cultures collected Skinlesions can decrease carcass value by causingdamageto the from several different lesions or sites mayyield useful informa- hide and excess trimming at the packing plant In the case of tion regarding the bacterial flora that maybe involvedin the dis- breeding stock and feeder pigs, poor cosmetic appearance can ease process. havea detrimentaleffecton reputation and sales, Vesicular diseases may be diagnosed by collecting fluid from The number of important skin diseases in swine are fewer than vesicles and submitting samples for virus isolation and electron' encountered in companion animal medicine, but diagnosing and microscopyexamination.However,iflesions haveprogressed and treating them can be no less challenging, As with all diseases, a vesicles are no longer present, other methods for diagnosismust complete clinical history is an essential component of a thorough be used. diagnostic workup. Note the age, morbidity and mortality, distri- Skin biopsies are important in diagnosing dermatoses. Your pri- bution of lesions, appearance and progression of lesions, and any mary goal is to submit samples characteristic of primary lesions other clinical signs that exist concurrently. Then, physically exam- and to avoid sampling areas that may not yield useful information. ine a number of animals in various stages of disease. Often the lo- If possible, multiple samples that are representative of the disease cation and gross appearance of lesions can lead to a presumptive process should be included. Most "wedge biopsies" can be ob- diagnosis and initiation of proper therapy. tained using local anesthesia and minimal chemical or physical It may be necessary to collect appropriate samples to obtain a de- restraint The area selected for biopsy should not be scrubbed, finitive diagnosis, Many tests can be performed in the veterinary cleansed, or unduly prepared in any manner as surface materials clinic by trained personnel. Skin scrapings are useful for diagnos- are important components of the specimen and may yield signifi- ing dermatomycosis and mange. When you suspect dermatophyto- cant information regarding the condition in question. The biopsy sis, take scrapings from the edge of several lesions (Figure 2). should include normal epidermis, dermis, and subcutis. Prior to Transfer the material to a commercially available dermatophyte placing them in 10% buffered formalin, samples may be touched culture medium (Fungassay, Synbiotics Carp., San Diego, Califor- to the surface of a blood agar plate, which can be submitted for nia 92127; and InTray DMTM,Biomed Diagnostics, San Jose, bacterial culture and sensitivity testing. With widespread lesions, California 95112) 01:submit it to a veterinary diagnostic labora- it may be beneficial to include large areas of skin from a necropsy tory for fungal culture. Include hairs plucked from the edge of the for laboratory evaluation. lesion in the sample. Hair and material from suspected lesions Bacterial dermatoses Veterinary Diagnostic Center, East Campus Loop and Exudative epidermitis (greasy pig disease) Fair Street, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0907. Exudativeepidermitis is caused byStaphylococcus hyicus and is most commonlyseen in pigs 1-8 weeks of age.2Lesionsgenerally Published as journal series article 11225 of the University of start on the face and progress over the body.In the acute form, Nebraska Agricultural Research Division.The author wishes to affected pigs are covered by an odoriferous, moist, greasy exu- acknowledge the photographic contributions of Drs. Alex Hogg and Douglas G. Rogers. date comprised of sebum and bacteria (Figure 3), In the chronic Diagnostic notes are not peer-reviewed 256 Swine Health and Production- November and December, 1995 form, lesions consist of scabby patches of skin, which are most ing parvovirus in the lesions using fluorescent antibody micros- prominent over the head and shoulders (Figure 4). copy or virus isolation. Similar lesions have been described in swine acutely infected with Staphylococcus hyicus, suggesting Porcine cutaneous spirochetosis that the condition may occur as a result of concurrent viral and Porcine cutaneous spirochetes may be occasionally encountered bacterial infections.7 in a group of pigs but frequently go undiagnosed because lesions resemble those caused by a variety of other bacteria, including Swine pox Fusobacterium necrophorum and Actinomyces pyogenes. Le- Swine pox is a common skin disease that has little economic im- sions consist of a severe ulcerative dermatitis.3 Borrelia suis is pact and is often associated with poor sanitation. Clinical signs the etiologic agent. Lesions are seen most often in young pigs are typical of those seen with a pox virus infection. Pigs less than shortly after weaning. They often develop secondary to trauma in- 3-4 months of age are more commonly infected than adults. Ani- flicted by ear biting, fighting, or castration and are frequently as- mals become immune after clinical disease subsides and serve as sociated with poor sanitary conditions. The most common site of the reservoir of infection for the remainder of the herd. Congeni- occurrence is at the base of the pinna and extending along the tal infection is occasionally noted.s Lesions are most obvious on ventral margin to the tip of the ear. Lesions are characterized by the nonhaired portions of the body (Figure 7). Pox lesions are necrosis and ulceration, which may result in extensive granula- self-limiting and resolve over 3-4 weeks. Secondarybacterial in- tion tissue formation (Figure 5). In sows, affected areas are seen fection is common and may obscure the primary condition unless on the ventral abdomen and consist of a severe ulcerative derma- you carefully examine affected animals early in the course of dis- titis. Diagnosis is based on observing numerous motile spiro- ease.9 The swine louse, Haematopinus suis, has been implicated chetes by dark-field examination of smears of fresh tissue. Silver as a vector in the spread of swine pox. stains can be use to identify organisms in histological sections. Porcine necrotic ear syndrome Mycotic dermatoses This skin condition may occur as a progression of porcine cuta- Ringworm neous spirochetosis although spirochetes have not been demon- Microsporum nanum and Trichophyton verrucosum are the strated in typical lesions, which consist of massive necrosis of the most common dermatophytes of swine, although M. canis, M. pinna. Staphylococcus hyicus and beta hemolytic streptococci have been recovered from cultures of typical lesions but their gypseum, and T. mentagrophytes have been reported to occur. 10 Each is a zoonotic pathogen. Incidence of infection with M. presence may reflect secondary involvement.4 The pathogenesis of nanum and T. verrucosum is sporadic but may reach 100% in the lesion is complex and thought to be initiated by damage to the groups of closely confined sows. Lesions begin as small reddish epidermis followed by bacterial invasion. brown foci, 1 to 2 cm in diameter, that spread concentrically and may reach up to 12 cm in diameter (Figure 8). Foci may be cov- Vesicular and viral ered with a thin loose crust and may be either single or coales- dermatoses cent. They may occur anywhere on the body but are most commonly found behind the ears. Hair loss and pruritus are generally When confronted with acute vesicular disease in swine, you minimal. Diagnosis is based on typical gross lesions and demon- should be aware of the possibility of a reportable or foreign dis- strating the organisms in skin scrapings or histological sections. ease. While the probability of an exotic disease is remote, you Culture and identification are needed for a etiologic diagnosis. should immediately seek the diagnostic assistance of state and federal authorities. Vesicular diseases of swine include foot and mouth disease, vesicular stomatitis, vesicular exanthema, and Parasitic dermatoses swine vesicular disease. Vesicular stomatitis is not a foreign animal disease but clinical signs and gross lesions are indistinguish- Sarcoptic and demodectic mange able from other exotic vesicular diseases. Laboratory tests

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