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 are re- Parasiticskin diseasesof swineincludesarcopticmange, quired for identification. Consider each case of vesicular disease demodectic mange, lice, and flies.ll Other biting insects, such as in swine to be foot and mouth disease until laboratory tests con- fleas, are rarely important in swine production. Sarcoptes firm otherwise because of its highly contagious nature and huge scabiei var. suis is the most economicallyimportant ectoparasite economic consequences.s of swine and can significantlyreduce the rate of gain and effi- ciencyof feed conversion.1,12 Infection is often unrecognized due Parvovirus dermatitis to its ability to become endemic in a herd. Infection can be mani- Avesicular-like dermatitis has been described in young pigs rang- fested as a chronic dermatitis affecting a few pigs or a cutaneous ing from 1-4 weeks of age.6 Lesions initially consist of vesicles on allergic response to the mites that involves most members of the the snout, coronary band, interdigital band, and tongue, which herd and produces intense pruritus.13 Sarcoptic mites are perma- rupture to form erosions (Figure 6). Concurrently diarrhea, con- nent parasites of the epidermis and live in tunnels within the epi- junctivitis, and rhinitis may be observed. Gross and microscopic dermis. Lesions resembling a hypersensitivity reaction occur as lesions are not pathognomonic. Diagnosis relies on demonstrat- early as 3 weeks after contact with the mites. They begin as small

Swine Health and Production- Volume 3, Number 6 257 Typical cutaneous rhomboid lesions seen with ErysiPelo- Trichophyton verrucosum infection in a pig. Samples for thrix rhusiopathiae infection in swine. The centers of diagnostic evaluation should include deep skin scrapings several lesions are undergoing necrosis, desiccation, and detachment. and hairs plucked from the edges of lesions.

Ventral abdomen from pig acutely infected with Staphylo- Chronic Staphylococcus hyicus infection involving the coccus hyicus.The skin is covered with a greasy, brown, head and ears. moist exudate consisting of serum and sebum.

Cross section of the pinna of ear from pigwith chronic Ruptured vesicles and focal erosions are present on the Borreliasuisinfection.Marked dermal fibrosis is noted on snout of a feeder pig infected with parvovirus. medial and lateral sides of the auricular cartilage (A). Foci of suppuration are present in the dermis (arrows).

258 Swine Health and Production- November and December, 1995 Ventral abdomen of a piginfected with swine pox. Numerous coalescing scalyerythematous plaques due to Numerous papules covered with dry epithelialcrusts are Trichophytonspp. infection are seen over the body of a observed. feeder pig.

Cutaneous hypersensitivity reaction consisting of many Marked hyperkeratosis and acanthosis are seen in a pig small erythematous papules is noted on a pig infected with chronic sarcoptic mange infection. with sarcoptic mange.

Microscopic section of skin containing numerous mites Scalyerythematous plaques are present on the ventral in hair follicles of a pig infected with Demodex phylloides. abdomen of a feeder pigwith pityriasisrosea.

Swine Health and Production- Volume 3. Number 6 259 focal erythematouspapules over the back and abdomen (Figure Physical and chemical 9). Hair loss and skin abrasions may result as sequelae to rub- dermatoses bing. Fewanimals develop chronic dermatitis even though incidence of infectionin the herd maybe quite high (Figure 10). Au- Sunburn, photosensitization, frost-bite, and exposure to ricular infections are probably the most common. Diagnosisis dermotoxic chemical agents are occasionally encountered in made by use of deep scrapings from affected skin and examina- swine practice.17Physicallyexaminingaffected animals and col- tion of exudate from the external auditory canal for the presence lecting a thorough clinical historyusuallyleads to a definitivedi- of mites. Often samples obtained from the auditory canal are agnosis without laboratory assistance. Photodynamicsubstances more rewarding than skin scrapings for demonstrating the found in alfalfa, clover, rape, oats, buckwheat, St.-john's-wort, mites.13 lucerne, and various drugs including phenothiazine, tetracy- clines, and sulfonamidesmaycause an acute exudativedermatitis Demodectic mange is relativelyuncommon in swine. The caus- upon exposure to sunlight.Initiatingproper husbandry measures ative agent,Demodex phylloides, livesin hair follicles and pro- and in the case ofphotosensitizationor chemical-inducedderma- duces a mild to moderatelysevere dermatitis over the snout, in- titis, removingthe causativeagent leads to an uneventfulrecovery. side the thighs, and over the flanks (Figure 11). Occasionally, whole body involvementcan occur and lead to excessive trimming or condemnationat slaughter.Infestationmayproduce skin Nutritionally induced nodules that resemble swine pox. Nodules contain a mixture of dermatoses cheesyexudateand mites.ll Nutritionally induced dermatoses in swine are rare as optimal Lice diet formulation and feeding practices are becoming standard Clinical signs produced by Haematopinus suis infection in swine procedures in swine production during the course of producing are often confused with mange as both provoke an intense pruri- quality pork at a lower price. Detailed information regarding di- tus. Pediculosis and sarcoptic mange are common concurrent in- etary needs, ingredient quality, and milling procedures are readily fections, but swine herds routinely treated for mange seldom are available to the average producer and have an acceptable margin infected with lice. Observing clinical signs coupled with close ex- of error built into their recommendations. Dietary deficiency is amination of affected swine for lice leads to a definitive diagno- usually only a temporary event that has minimal effect on the ap- sis.u pearance of skin disease. Nevertheless, evaluating nutritional sta- tus and feeding practices should be part of a routine investigation Biting flies of an outbreak of skin disease in a swine herd. Biting flies such as the stable fly (Stomoxys calcitrans) and black flies (familySimulliidae) are important pathogensin swine health management.14Not only are flies a nuisance and a source Summary of annoyance,theyare blood suckers and can produce an intense Afteryou've made a definitivediagnosis of skin disease, you can nonspecific dermatitis that can be confused with other parasitic implement specific treatment or control measures. Whiletreat- skin diseases. Diagnosisis based on observance of clinical signs. ment is ofconcern at the outset, preventionis more important. To Bitingflies have also been incriminated as vectors in the spread avoid a recurrence of the problem, use your knowledgeof swine of eperythrozoonosisand swinepox virus. practice and medicine to review management and husbandry practices. Miscellaneous dermatoses References

Pityriasis rosea 1. Cargill CF, Dobson KJ. Experimental Sarcoptes scabiei infestation in pigs. II. Skin lesions associated with pityriasis rosea may be clinically in- Effects on production. Vet Rec. 1979;104:33-36. distinguishablefromthose causedbyringworm.IS Thecauseof 2. Underdahl NR, Grace OD, Twiehaus MJ. Experimental transmission of exudative pityriasis rosea is unknown but is thought to have a hereditary epidermitis of pigs.jAI0L4. 1963;142:754-762. disposition'in the Landracebreed.16Noinfectious agent has been 3. Harcourt RA. Porcine ulcerative spirochetosis. Vet Rec. 1973;92:647-648. identified and attempts to transmit the condition to susceptible 4. Richardson JA, Morter RL, Rebar AH, Olander HJ. Lesions of porcine necrotic ear animals have been unsuccessful. Lesions consist of small syndrome. Vet Pathol. 1984;21:152-157. erythematouspapuleswhich developon the medialthigh and ven- 5. Vesicular diseases. In: Foreign Animal Diseases. Richmond, Virginia: United tral abdomen (Figure 12). Papules become scaly, expand cen- States Animal Health Association. 1992:368-382. trifugally,and may coalesce to form a mosaic pattern where the 6. Kresse JI, Taylor WD, Stewart WW, Eernisse KA. Parvovirus infection in pigs with centers return to normal. Rarelyare lesions seen on the dorsum necrotic and vesicle-like lesions. Vet Microbiol. 1985;10:525-531. of the body. Diagnosis is made from physical examination and 7. Andrews JJ. Ulcerative glossitis and stomatitis associated with exudative recognition of characteristic lesions. The condition is usually epidermitis in suckling swine. Vet Pathol. 1979;16:432-437. self-limitingand resolveswithin 4 weeks.

260 SwineHealth and Production- November and December, 1995 8. Borst GHA, Kimman TG, Gielkens ALJ, van der Kamp JS. Four sporadic cases of 13. Sheahan BJ. Experimental Sarcoptes scabiei infection in pigs: Clinical signs and congenital swine pox. Vet Rec. 1990;127:61-63. significance of infection. Vet Rec. 94;1974:202-209.

9. Miller RB, Olson LD. Epizootic of concurrent cutaneous streptococcal abscesses 14. Campbell JB, Boxler DJ, Danielson DM, Crenshaw MA. Effects of house and and swine pox in a herd of swine.jAVM4. 1978;172:676-680. stable flies on weight gain and feed efficiency by feeder pigs. S West Entomo!. 1984;9:273-274. 10. Ginther OJ, Bubash GR. Experimental Microsporum nanum infection in swine. jAVM4. 1966;148:1034. 15. Thomson R. Pityriasis rosea in a herd of swine. Can Vet jour. 1960;1:449-451.

11. Dobson KJ, Davies PRo External Parasites. In: Leman AD, Straw BE, Mengeling 16. Corcoran CJ. Pityriasis rosea in pigs. Vet Rec. 1964;76:1407-1409. WL, D'Allaire S, Taylor DJ, eds. Diseases of Swine. 7th ed. Ames, IA:lowa State 17. Straw BE. Skin. In: Leman AD, Straw BE, Mengeling WL, D'Allaire S, Taylor DJ, University Press; 1992:668-679. eds. Diseases of Swine. 7th ed. Ames, IA:lowa State University Press; 1992:196- 12. Hewett GR. Phosmet for the systemic control of pig mange in growing pigs. Vet 222. Parasito!. 1985;18:265-268.

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