D W. S , DVM ANNY COTT Diplomate, American College of Veterinary Dermatology Professor of Medicine Department of Clinical Sciences and Department of Biomedical Sciences College of Veterinary Medicine Cornell University Ithaca, New York W H. M , J ., VMD ILLIAM ILLER R Diplomate, American College of Veterinary Dermatology Professor of Medicine Department of Clinical Sciences and Department of Biomedical Sciences College of Veterinary Medicine Cornell University Ithaca, New York With 900 illustrations AnImprintofElsevierScience 3251RiverportLane MarylandHeights,Missouri63043 EQUINEDERMATOLOGY ISBN9781437709209 Copyright#2011,2003bySaunders,animprintofElsevierInc. 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Notice VeterinaryMedicineisanever-changingfield.Standardsafetyprecautionsmustbefollowed,butas newresearchandclinicalexperiencebroadenourknowledge,changesintreatmentanddrugtherapy maybecomenecessaryorappropriate.Readersareadvisedtocheckthemostcurrentproduct informationprovidedbythemanufacturerofeachdrugtobeadministeredtoverifythe recommendeddose,themethodanddurationofadministration,andcontraindications.Itisthe responsibilityofthetreatingveterinarian,relyingonexperienceandknowledgeofthepatient,to determinedosagesandthebesttreatmentforeachindividualanimal.Neitherthepublishernorthe editorassumesanyliabilityforanyinjuryand/ordamagetoanimalsorpropertyarisingfromthis publication. InternationalStandardBookNumber9781437709209 VicePresidentandPublisher:LindaDuncan Publisher:PennyRudolph ManagingEditor:TeriMerchant PublishingServicesManager:JulieEddy ProjectManager:MarquitaParker Designer:JessicaWilliams PrintedinChina Lastdigitistheprintnumber: 9 8 7 6 5 4 3 2 1 Preface Danny W. Scott and William H. Miller, Jr. We really thought that we only had one edition of to Equine Dermatology I as the stockpile of “everything” EquineDermatologyinus.1ButthenElsevierapproached that came before. us about doing a second edition... in full color. Now, how cool is that? They made us an offer we couldn’t References refuse. Equineskin diseasesare commonand important.In 1. ScottDW,MillerWH:Equinedermatology,St.Louis,2003, SaundersElsevier. fact, skin problems were the second most common 2. KaneenJB,etal:TheMichiganequinemonitoringsystem2. equine disorders recorded by horse owners and veteri- Frequenciesandimpactofselectedhealthproblems,PrevVet narians in a survey conducted in Michigan.2 Increasing Med29:277,1997. interest in equine dermatology is reflected in the num- 3. LloydDH,etal:Practicalequinedermatology,Ames,2003, ber of textbooks,3–5 book chapters,6–9 and continuing BlackwellScience. education articles10–14 devoted to the subject since 4. MuellerRS:Dermatologyfortheequinepractitioner,Jackson,2005, 2003. TetonNewMedia. Having been involved in the genesis of a number of 5. KnottenbeltDC:Pascoe’sprinciplesandpracticeofequine dermatology,Oxford,2009,SaundersElsevier. textbooks,wehavealwaysfoundthatthemostdifficult 6. RobinsonNEeditor:CurrenttherapyinequinemedicineV, challenge (indeed, the “Impossible Dream” of the vet- St.Louis,2009,SaundersElsevier. erinary educator) is to address the student, clinician, 7. ReesCA:Disordersoftheskin.InReedSMetal,editor:Equine pathologist, and researcher alike... all in one groovy internalmedicineII,St.Louis,2004,SaundersElsevier,p667. tome. We have done our best in this regard. 8. RobinsonNE,SprayberryKA,editors:Currenttherapyinequine Flowcharts,conceptmaps,anddrop-downliststend medicineVI,St.Louis,2004,SaundersElsevier. to gag us. We just don’t (to our knowledge) think that 9. WhiteSD:Diseasesoftheskin.InSmithBP,editor:Largeanimal way.However,thereareanumberoftablesinChapter2 internalmedicine,ed4,St.Louis,2009,MosbyElsevier,p1306. that will guide the clinician in terms of breed-disease 10. SchottHC,PetersenAD:Cutaneousmanifestationsofdisorders associations, regional differential diagnoses for non- affectingyounghorses,ClinTechEquinePract4:314,2005. neoplastic and neoplastic/cystic/hamartomatous der- 11. PetersenAD,SchottHC:Cutaneousmarkersofdisorders affectingadulthorses,ClinTechEquinePract43:324,2005. matoses, and differential diagnoses for selected 12. WhiteSD:EquinedermatologyI.Diagnosisandtreatmentofthe cutaneous reaction patterns. pruritichorse,ProcAmAssocEquinePract52:457,2006. We have always had the obsession to provide 13. WhiteSD:EquinedermatologyII.Nodules,lumps,andbumps, exhaustive bibliographies. In an effort to keep page ProcAmAssocEquinePract52:475,2006. numbers down, we have reined-in (pardon the pun!) 14. YuAA:EquinedermatologyIII.Crustingandulcerativelesions, our encyclopedic tendencies for this second edition. ProcAmAssocEquinePract52:490,2006. Forthemostpart,weciteonlynewreferencesandrefer v Acknowledgments Wecannotoverstateourgratitudetothosethathavecontributedtothissecondedition.If we have failed to acknowledge any one, please forgive us and send us your correction. Special“Thanx”toKris(DWS)andKathy(WHM)forsomuchloveandsomuchsupport for so long. And to our Elsevier “boss”... Teri Merchant... you rock! Wereallyhopeyoufindthisbookenjoyableanduseful.Itistrulyanewbookinterms of content and illustrations. Peace be with you. vii Preface and Acknowledgments from the First Edition D.W. Scott and W.H. Miller, Jr. Equine skin disorders are common and important. Interestinequinedermatologyhasresultedinitsbeing After dogs and cats, horses are the most common spe- reviewedinanumberoftextbooks13–36,46andcontinuing cies presented to our Dermatology Service and tele- education articles.37–44 Of particular note is the special phone consultation service for evaluation. In general, issueofVeterinaryDermatologydedicatedtothelateDr. theequinedermatosesseenworldwidearesimilarboth Tony Stannard.45 Skin diseases are a source of animal in nature and frequency.1–8 suffering—through annoyance, irritability, pruritus, dis- Very little information is available concerning the figurement,secondaryinfections,myiasis,andincreased demographics of equine skin disorders. A survey car- susceptibilitytootherdiseases.Inadditiontocompromis- ried out by the British Equine Veterinary Association ing the animal’s comfort and appearance, skin diseases in 1962 and 1963 indicated that 2% of all cases seen caninterferewiththehorse’sabilitytofunctioninriding, by the membership were presented for skin disease.9 working,orshow.Economiclossesthroughthefinancial A 1989 survey of the members of the American burdens of diagnostic, therapeutic, or preventive pro- Association of Equine Practitioners revealed that skin grams can be sizable. Rarely, zoonotic dermatoses may disorders were the fourth most common medical beasourceofhumandiseaseandsuffering. problem encountered (following colic, viral respira- We wholeheartedly echo the conclusion reached by tory tract disease, and endometritis).10 The top 10 the1989surveyofthemembersoftheAmericanAssoci- equine health problems as determined by a survey of ation of Equine Practitioners: “Dermatologic disorders horse owners included skin diseases, which ranked in horses are common problems that need emphasis in number 9.11 veterinary curricula and research endeavors.”8,10 Panel reports of veterinary practitioners in 1975, 1981, and 1986 found that dermatophytosis, dermato- philosis, urticaria, insect hypersensitivities, onchocerci- TABLE1 CommonHorseBreedsPresentedfor Dermatologic Diagnosis12 asis, eosinophilic granulomas (“nodular necrobiosis”), papillomas (“warts”), sarcoids, photodermatitis, and nutritional “seborrheas” were the most commonly Breed Percentage Percentageof encountered equine skin disorders.4–6 In a 21-year ofCases TotalHospital Dermatology Population (1979-2000) retrospective study of equine skin disor- ders at the College of Veterinary Medicine at Cornell Thoroughbred 23.9 22.9 University, 4.1% of all horses examined at the Large QuarterHorse 16.5 14.6 Animal Clinic were evaluated by a dermatologist for Standardbred 15.8 24.2 skin problems (Tables 1 and 2).12 There was no breed Arabian 6.4 5.2 predisposition for skin disease as a whole. Due to the Appaloosa 5.8 5.4 referralnatureofourpractice,thetypesandfrequencies Morgan 4.5 3.0 of the various dermatoses documented would not be Belgian 3.9 2.1 expected to be those seen in general equine practice. American 1.8 1.8 The“Top10”equinedermatosesseenatourclinicwere Paint bacterial folliculitis, dermatophytosis, insect hypersen- Percheron 1.1 0.7 sitivity, dermatophilosis, drug reaction, eosinophilic American 0.9 0.6 granuloma, atopy, vasculitis, chorioptic mange, and Saddle equine sarcoid. In a 16-year (1978-1994) retrospective Horse study of biopsy specimens submitted to the Diagnostic Clydesdale 0.6 0.4 Laboratory, College of Veterinary Medicine, at Cornell Allother 18.8 19.1 University, 23.4% of all equine submissions were skin breeds lesions.12 ix x PREFACE TABLE 2 Dermatologic Diagnoses* for 900 Horses over a 21- Year Period (1979-2000)12 Diagnosis #ofCases %ofCases Bacterial folliculitis 106 11.78 Dermatophytosis 80 8.89 Insect hypersensitivity 57 6.33 Dermatophilosis 50 5.56 Drugreaction 37 4.11 Eosinophilic granuloma 35 3.89 Atopy 35 3.89 Vasculitis 30 3.33 Chorioptic mange 24 2.67 Equine sarcoid 23 2.56 Urticaria, idiopathic 22 2.44 Idiopathic pruritus 19 2.11 Pemphigus foliaceus 17 1.89 Erythemamultiforme 17 1.89 Onchocerciasis 15 1.67 Ear papillomas 13 1.44 Viral papillomatosis 12 1.33 Alopecia areata 12 1.33 Follicular dysplasia 12 1.33 Pediculosis 11 1.22 Idiopathic seborrhea 11 1.22 Unilateralpapular dermatosis 11 1.22 Dermoid cysts 10 1.11 Bacterial pseudomycetoma 10 1.11 Telogen defluxion 10 1.11 Melanoma 9 1.00 Lymphoma 9 1.00 Anagendefluxion 9 1.00 Habronemiasis 9 1.00 Coronary banddysplasia 9 1.00 Ventralmidline dermatitis 8 0.89 Cannonkeratosis 7 0.78 Contact dermatitis{ 7 0.78 Verrucoushemangioma 6 0.67 Linearkeratosis 6 0.67 Trichorrhexis nodosa 6 0.67 Vitiligo 6 0.67 Bacterial cellulitis 6 0.67 Traumaticalopecia 5 0.56 Blackfly bites,pinna 5 0.56 Sterileeosinophilic folliculitis 5 0.56 Secondaryseborrhea,hepatic 5 0.56 Pseudolymphoma 5 0.56 Epidermal nevus 5 0.56 Schwannoma 5 0.56 Sterilepyogranuloma 4 0.44 Sterilepanniculitis 4 0.44 Sarcoidosis 4 0.44 Tickbitegranuloma 4 0.44 Hyperadrenocorticism 4 0.44 Continued Preface and Acknowledgments from the First Edition xi TABLE 2 Dermatologic Diagnoses* for 900 Horses over a 21- Year Period (1979-2000)12—cont’d Diagnosis #ofCases %ofCases Foodhypersensitivity 4 0.44 Behavioral self-mutilation 4 0.44 Maneand tailseborrhea 3 0.33 Idiopathicpastern dermatitis 3 0.33 Discoid lupuserythematosus 3 0.33 Epitrichialsweatglandneoplasm 3 0.33 Spottedleukotrichia 3 0.33 Amyloidosis 3 0.33 Barbering 3 0.33 Burns 2 0.22 Bullouspemphigoid 2 0.22 Lymphangitis, bacterial 2 0.22 Photodermatitis, hepatic 2 0.22 Systemiclupus erythematosus 2 0.22 Epitheliotropic lymphoma 2 0.22 Squamouscell carcinoma 2 0.22 Idiopathicdelayedshedding 2 0.22 Sporotrichosis 2 0.22 Eumycoticmycetoma 2 0.22 Photicheadshaking 2 0.22 Pressuresores 2 0.22 Multisystemic eosinophilic epitheliotropic disease 2 0.22 Aplasiacutiscongenita 1 0.11 Malignantfibroushistiocytoma 1 0.11 Carcinosarcoma 1 0.11 Halicephalobiasis 1 0.11 Phaeohyphomycosis 1 0.11 Cutaneousasthenia 1 0.11 Mastcell tumor 1 0.11 Arsenictoxicosis 1 0.11 Hypotrichosis 1 0.11 Trichoepithelioma 1 0.11 Pilitorti 1 0.11 Strawmitedermatitis 1 0.11 Organoidnevus 1 0.11 Lichenoid keratosis 1 0.11 *Wheremorethanonedermatosiswaspresentatthesametimeinonehorse,onlythemostimportantarelisted. {ContactreactionsassociatedwithtopicalmedicamentsareincludedunderDrugReaction. xii PREFACE We cannot overstate our appreciation for those who 19. PascoeRR:Equinedermatoses.UniversityofSydneyPost- have contributed to this text. We couldn’t have done it GraduateFoundationinVeterinarySciences,VetRev#21,1981. 20. McMullenWC:Theskin.InMansmannRA,etal,editor:Equine without you!Ifwehavefailed toacknowledgeanyone, MedicineandSurgeryIII,volII,SantaBarbara,1982,American please forgive us and send us your correction! Special VeterinaryPublications,p789. thanks go out to Drs. Bill McMullen and Reg Pascoe 21. RobinsonNE,editor:CurrentTherapyinEquineMedicine, for their many years of observation, investigation, and Philadelphia,1983,W.B.SaundersCo. 22. MontesLF,VaughanJT:AtlasofSkinDiseasesoftheHorse, reporting.Werememberandsaluteourgreatestteacher Philadelphia,1983,W.B.SaundersCo. in equine dermatology, the late Tony Stannard. We 23. RobinsonNE,editor:CurrentTherapyinEquineMedicineII, have purposely used many of Tony’s slides that he so Philadelphia,1987,W.B.SaundersCo. 24. ScottDW:LargeAnimalDermatology,Philadelphia,1988,W.B. graciously donated to us over the years. SaundersCo. Heldupforspecialpraiseandrecognitionarethosewho 25. ChatterjeeA:SkinInfectionsinDomesticAnimals,Calcutta,1989, havegivensomuchintermsoflove,patience,andsupport MoitriPublication. during this endeavor: Kris, Travis, and Tracy (DWS) and 26. AckermanLJ:PracticalEquineDermatology,Goleta,1989, AmericanVeterinaryPublications,Inc. Kathy,Steven,Julia,andAndrew(WHM).YoLexi(Alexis 27. PascoeRR:AColourAtlasofEquineDermatology,London,1990, Wenski-Roberts) . . . thanx for your photomicrographic WolfePublishing,Ltd. expertise!AbigkissforDeniseLeMelledo,JenniferFurey, 28. BarbetJL,etal:Diseasesoftheskin.InColahanPT,etal,editor: RayKersey,andthewholeW.B.Saundersgang. EquineMedicineandSurgeryIV,volII,Goleta,1991,American VeterinaryPublications,Inc,p1569. I (DWS) first began working on the idea of an 29. RobinsonNE,editor:CurrentTherapyinEquineMedicineIII, equine dermatology textbook in 1984. It has gone Philadelphia,1992,W.B.SaundersCo. through many starts and stops, ups and downs, and 30. JubbKVF,etal:PathologyofDomesticAnimals,IV,NewYork, incarnations in the subsequent 18 years. In the words 1993,AcademicPress. 31. RadostitsDM,etal:VeterinaryMedicine.ATextbookoftheDiseases of Sam Cooke, “It’s been a long time comin’.” Bill ofCattle,Sheep,Pigs,Goats,andHorsesVIII,Philadelphia,1994, and I hope it’s been worth the wait. Baillie`re-Tindall. 32. KoblukCN,etal,editors:TheHorse.DiseasesandClinical Management,Philadelphia,1995,W.B.SaundersCo. REFERENCES 33. RobinsonNE,editor:CurrentTherapyinEquineMedicineIV, Philadelphia,1997,W.B.SaundersCo. 1. HutchinsDR:SkindiseasesofcattleandhorsesinNewSouth 34. FadokVA,editor:Dermatology,TheVeterinaryClinicsofNorth Wales,NZVetJ8:85,1960. America:EquinePractice,April1995. 2. PascoeRR:Thenatureandtreatmentofskinconditions 35. ReedSM,BaylyWM,editors:EquineInternalMedicine, observedinhorsesinQueensland,AustVetJ49:35,1973. Philadelphia,1998,W.B.SaundersCo. 3. ThomsettLR:Skindiseasesofthehorse,InPract1:16,1979. 36. PascoeRRR,KnottenbeltDC:ManualofEquineDermatology, 4. PanelReport:Skinconditionsinhorses,ModVetPract56:363, Philadelphia,1999,W.B.SaundersCo. 1975. 37. FadokVA,MullowneyPC:DermatologicdiseasesofhorsespartI. 5. PanelReport:Dermatologicproblemsinhorses,ModVetPract Parasiticdermatosesofthehorse,CompContEduc5:S615, 62:75,1981. 1983. 6. PanelReport:Skindiseasesinhorses,ModVetPract67:43,1986. 38. MullowneyPC,FadokVA:Dermatologicdiseasesofhorsespart 7. vonTscharnerC:DiewichtigstenHautkrankheitenbeimPferd, II.Bacterialandviralskindiseases,CompContEduc6:S15,1984. PraktTierheilk69:4,1988. 39. MullowneyPC,FadokVA:Dermatologicdiseasesofhorsespart 8. Halldo´rsdo´ttirS:Hudlidelserhoshest,NorskVeterinaer102:19, III.Fungalskindiseases,CompContEduc6:S324,1984. 1990. 40. MullowneyPC,editor:SymposiumonLargeAnimalDermatology, 9. HopesR:Skindiseasesinhorses,VetDermatolNews1(23):4, TheVeterinaryClinicsofNorthAmerica:LargeAnimalPractice, 1976. March1984. 10. Traub-DargatzJL,etal:Medicalproblemsofadulthorses,asranked 41. MullowneyPC:DermatologicdiseasesofhorsespartIV. byequinepractitioners,JAmVetMedAssoc198:1745,1991. Environmental,congenital,andneoplasticdiseases,CompCont 11. UnderhillLJP,ShowalterTL:Thewellnessmovement,1989,Equus. Educ7:S22,1985. 12. ScottDW,MillerWHJr:Unpublisheddata. 42. MullowneyPC:DermatologicdiseasesofhorsespartV.Allergic, 13. KralF,NovakBJ:VeterinaryDermatology,Philadelphia,1953,J.B. immune-mediated,andmiscellaneousskindiseases,CompCont LippincottCo. Educ7:S217,1985. 14. KralF:CompendiumofVeterinaryDermatology,Exton,1959, 43. VrinsA,etal:Dermatologiee´quine.1e`repartie:lesaffections PfizerLaboratories. alope´ciquesetaffectionsprurigineuses,PratVe´tEquine24:73, 15. BoneJF,etal,editors:EquineMedicineandSurgeryI,Wheaton, 1992. 1963,AmericanVeterinaryPublications,Inc. 44. VrinsA,etal:Dermatologiee´quine2e`mepartie:lesaffections 16. KralF,SchwartzmanRM:VeterinaryandComparative papuleusesetnodulairesetlesboutonsdechair,PratVe´tEquine Dermatology,Philadelphia,1964,J.B.LippincottCo. 24:157,1992. 17. StannardAA:Theskin.InCatcottEJ,SmithcorsJF,editors: 45. vonTscharnerC,etal,editors:Stannard’sIllustratedEquine EquineMedicineandSurgeryII,Wheaton,1972,American DermatologyNotes,2000.VetDermatol,11,p161. VeterinaryPublications,Inc,p381. 46. SloetvanOldruitenborgh-OosterbaanMM,KnottenbeltDC:The 18. PascoeRR:Equinedermatoses.UniversityofSydneyPost- Practitioner’sGuidetoEquineDermatology,Leeuwarden,2001, GraduateFoundationinVeterinaryScience,VetRev#14,1974. UitgeverijLibreBV. 1 C H A P T E R Structure and Function of the Skin The skin is the largest and most visible organ of the 8. Immunoregulation. Keratinocytes, Langerhans bodyandtheanatomicandphysiologicbarrierbetween cells, lymphocytes, and dermal dendrocytes animal and environment. It provides protection from together provide the skin with an physical, chemical, and microbiologic injury, and its immunosurveillance capability that effectively sensory components perceive heat, cold, pain, pruritus, protects against the development of cutaneous touch, and pressure. In addition, the skin is synergistic neoplasms and persistent infections. with internal organ systems and thus reflectspathologic 9. Pigmentation. Processes in the skin (melanin processes that are either primary elsewhere or shared formation, vascularity, and keratinization) help with other tissues. Not only is the skin an organ with determine the color of the coat and skin. its own reaction patterns, it reflects the milieu inte´rieur Pigmentation of the skin helps prevent damage and, at the same time, the capricious world to which it from solar radiation. is exposed. 10. Antimicrobial action. The skin surface has antibacterial and antifungal properties. 11. Sensoryperception.Skinisaprimarysensoryorgan GENERAL FUNCTIONS AND fortouch,pressure,pain,itch,heat,andcold. 12. Secretion. Skin is a secretory organ by virtue of its PROPERTIES OF THE SKIN epitrichial sweat glands and sebaceous glands. Thegeneralfunctionsofanimalskinareasfollows:73,92 13. Excretion.Theskinfunctionsinalimitedwayasan 1. Enclosing barrier. The most important function of excretory organ. skin is to make possible an internal environment for all other organs by maintaining an effective ONTOGENY barrier to the loss of water, electrolytes, and macromolecules. Skin is a complex multicellular organ in which endo- 2. Environmental protection. A corollary function is derm, neural crest, and ectoderm contribute to form a the exclusion of external injurious agents— three-dimensional unit in a spatially and temporally chemical, physical, and microbiologic—from defined manner. Skin morphogenesis involves the entrance into the internal environment. action of multiple genes in a coordinated fashion. 3. Motion and shape. The flexibility, elasticity, and Homeobox genes are a gene family that encode infor- toughness of the skin allow motion and provide mation critical for normal embryologic development shape and form. and that likely play an important role in the develop- 4. Adnexa production. Skin produces glands and ment of skin adnexa, pigment system, and stratified keratinized structures such as hair, hoof, and the epithelium during embryogenesis. horny layer of the epidermis. Epithelial-mesenchymal interactions regulate tissue 5. Temperature regulation. Skin plays a role in the homeostasis,thebalancedregulationofproliferationand regulationofbodytemperaturethroughitssupport differentiation maintaining normal tissue architecture of the hair coat, regulation of cutaneous blood and function. Multiple circuits of reciprocal permissive supply, and sweat gland function. andinstructiveeffectsexistbetweenepithelialandmesen- 6. Storage. The skin is a reservoir of electrolytes, chymalcellsandextracellularmatrices. water, vitamins, fat, carbohydrates, proteins, and To the authors’ knowledge, the ontogeny of equine other materials. skin has not been reported. The following discussion 7. Indicator. The skin may be an important indicator is an amalgamation of information from other domes- of general health, internal disease, and the effects tic mammals and humans.34,36,89,91 of substances applied topically or taken internally. Initially,theembryonicskinconsistsofasinglelayer It contributes to physical and sexual identity. of ectodermal cells and a dermis containing loosely 1