THE HORSE REPORT Vol. 3. No. 1 a publication of the E^quine Research Laboratory, School of Veterinaiy Medicine, University of California, Davis John P. Hughes, D.V.M., Director Radioactive Implants Prove Successful For Treating Skin Tumors Equine sarcoids are the most common type of skin tumor observed in horses, mules and donkeys. These growths occur most frequently on the skin of an animal's head, trunk or legs, often developing at sites of old wounds. Although equine sarcoids are not usually life-threatening, they can be disfiguring when they involve the areas of the eyes, lips or ears. In some cases, they can seriously inter¬ fere with the function of facial structures such as eyelids or lips. Several treatment methods have been used to combat this type of tumor, the most common tDeing surgical removal of the tumor and the surrounding normal tissue. Other methods include cryosurgery (ultra-cold therapy using liquid nitrogen), immunotherapy (vaccines are injected into the tumor tissue to stimulate anti¬ tumor cells), radiotherapy (radiation treatment), and hyperthermia (ultra-heat therapy). This type of tumor, which char¬ acteristically invades the skin and outer layers of tissue, can regrow rapidly after treatment and has proven difficult to successfully and permanently irradicate. Surgical removal has jdelded variable results, the associated rate of recurrence cifter surgery being 33-50%. Cryo¬ surgery has disadvantages in that the recurrence rate is also high, 20- 40%, and cosmetic defects and functional disturbances may occur. Immunotherapy has produced variable results, but is often used in combination with surgery. Equine sarcoids have been reported to have a low sensitivity to radiation and many types of radiation therapy CCD An Equine sarcoid on upper eyelid. Tumor was very extensive and had grown through eyelid to rub on eyeball Buttons hold iridium'192 ribbons firmly in place within tumor. Three months afier irradiation, tumor is gone. Continued on page 3 Hereditary Condition? A question continually asked of veterinarians is, "Should a mare or stallion with confirmed osteo¬ chondrosis be used in a breeding progr£un?" On the basis of current knowledge, sound recommendations regarding treatment, future sound¬ ness, and breeding cannot be made. Osteochondrosis, commonly abbrevi¬ ated "OCD", is a condition which occurs in man and in a variety of domestic animals. Osteochondrosis of the equine stifle ("knee" joint) is a well-recognized disorder in young growing horses. It is characterized by abnormal development of the cartilage-bone junction of an affected joint. Chronic lameness is often the result. The reason or reasons some horses develop OCD are not yet understood. A variety of factors, including growth rate, physical trauma to the leg, heredity, and diet have been suspected as causes. Recently, at the Veterinaiy Medical Teaching Hospital, eight horses were treated for OCD. Of the eight, four were interrelated. This provides circumstantial evidence for familial factors and has given three veteri¬ narians at the School of Veterinaiy Medicine the impetus to explore the question further. These investigators. Dr. John Pascoe of the Department of Surgery and Drs. Susan Stover and Roy Pool of the Department of Pathology, have designed a research project to study the role of heredity in osteochondrosis. Are the off¬ spring of affected mares or stallions bom with the tendency to develop this condition? To make this determination, siblings from the matings of affected stallions and mares will be examined by clinical and radiographic means, from birth to maturity. Continued on page 3
Transcript
THEHORSE
REPORT
Vol. 3. No. 1
a publication of theE^quine Research Laboratory,
School ofVeterinaiy Medicine,University ofCalifornia, Davis
John P. Hughes, D.V.M., Director
Radioactive ImplantsProve Successful ForTreating Skin TumorsEquine sarcoids are the most
common type of skin tumorobserved in horses, mules anddonkeys. These growths occur mostfrequently on the skin of ananimal's head, trunk or legs, oftendeveloping at sites of old wounds.Although equine sarcoids are notusually life-threatening, they can bedisfiguringwhen they involve theareas of the eyes, lips or ears. Insome cases, they can seriously inter¬fere with the function of facialstructures such as eyelids or lips.Several treatment methods have
been used to combat this type oftumor, the most common tDeingsurgical removal of the tumor andthe surrounding normal tissue.Other methods include cryosurgery(ultra-cold therapy using liquidnitrogen), immunotherapy(vaccines are injected into thetumor tissue to stimulate anti¬tumor cells), radiotherapy(radiation treatment), andhyperthermia (ultra-heat therapy).This type of tumor, which char¬
acteristically invades the skin andouter layers of tissue, can regrowrapidly after treatment and hasproven difficult to successfully andpermanently irradicate. Surgicalremoval has jdelded variable results,the associated rate of recurrencecifter surgery being 33-50%. Cryo¬surgery has disadvantages in thatthe recurrence rate is also high, 20-40%, and cosmetic defects andfunctional disturbances may occur.Immunotherapy has producedvariable results, but is often used incombination with surgery. Equinesarcoids have been reported to havea low sensitivity to radiation andmany types of radiation therapy
CCD An
Equine sarcoid on upper eyelid. Tumorwas very extensive and had grownthrough eyelid to rub on eyeball
Buttons hold iridium'192 ribbonsfirmlyin place within tumor.
Three months afier irradiation, tumor isgone.
Continued on page 3
Hereditary Condition?A question continually asked of
veterinarians is, "Should a mare or
stallion with confirmed osteo¬
chondrosis be used in a breedingprogr£un?" On the basis of currentknowledge, sound recommendationsregarding treatment, future sound¬ness, and breeding cannot be made.Osteochondrosis, commonly abbrevi¬ated "OCD", is a condition whichoccurs in man and in a variety ofdomestic animals. Osteochondrosisof the equine stifle ("knee" joint) is awell-recognized disorder in younggrowing horses. It is characterizedby abnormal development of thecartilage-bone junction of anaffected joint. Chronic lameness isoften the result.The reason or reasons some
horses develop OCD are not yetunderstood. A variety of factors,including growth rate, physicaltrauma to the leg, heredity, and diethave been suspected as causes.Recently, at the Veterinaiy MedicalTeaching Hospital, eight horseswere treated for OCD. Of the eight,four were interrelated. This providescircumstantial evidence for familialfactors and has given three veteri¬narians at the School ofVeterinaiyMedicine the impetus to explore thequestion further.These investigators. Dr. John
Pascoe of the Department ofSurgery and Drs. Susan Stover andRoy Pool of the Department ofPathology, have designed a researchproject to study the role of heredityin osteochondrosis. Are the off¬
spring of affected mares or stallionsbom with the tendency to developthis condition? To make thisdetermination, siblings from thematings of affected stallions andmares will be examined by clinicaland radiographic means, from birthto maturity.
Continued on page 3
The Horse Reportt VoL 3, No. 1—2
Profile: John D. Wheat, D.V.MDepartment ofSurgeiy
Dr.Wheat a 1945 graduate of Cornell University School ofVeterinaiy Medicine, has beenon the faculty of the School of Veterinary Medicine at the University of California, Davissince 1950. After receiving his D.V.M. degree, he stayed on at Cornell for three years, serving asassistant veterinarian. In 1948 he took a position as an instructor and assistant professorat the School ofVeterinary Medicine, Kansas State University, Manhattan, Kansas. A
world-renowned surgeon, Dr.Wheat has been a full professorwith the Department of Surgery, School ofVeterinaryMedicine at Davis since 1958.Dr. Wheat was awarded a Fulbright Senior Lecturer Scholarship in 1968 and traveled to the University ofQueensland
in Australia where he studied and taught. He has also served as consultant to the National Thoroughbred Racetrack ofCaracas, Venezuela Dr.Wheat is highly respected for his expertise in the surgical repair of injuries in racing Thorough¬breds and many horses with complex problems are directed to him. Besides his rigorous round of clinic duties. Dr.Wheat teaches in the veterinaiy school curriculum and to graduate students.When away from the Teaching Hospital, Dr.Wheat involves himself in many extracurricular activities. He enjoys
horsepacking in the high Sierra wilderness and packed for seven days last summer with feUow veterinarians and theirfamilies. Another hobby is beekeeping. With an apiaiy in his backyard. Dr. Wheat enjoys observing the habits of bees aswell as consuming the by-products. Bicycling, a popular pasttime in the "flatlands" of Davis, is often his mode oftransportation to and from the UCD campus.
New Techniques For Ehraluating Founder MayLead to ImprovedTreatmentMethods
(4
Most horse owners have eitherhad experience with, or are familiarwith, the serious problemlaminitis", commonly referred to asfounder". Laminitis has long beenrecognized as a frequent cause ofsevere lameness in horses, and can
be potentially life-threatening.Moderate to severe lameness, abounding digital pulse, and warm orhot feet are the most obviousclinical signs of the disease. Thesesigns are most often seen in thefront legs, however, all four feet maybe affected. Laminitis c£in be caused
by a variety of problems; some of themore common predisposing factorsbeing grass or grain overload,abnormal concussion on the foot, ora severe generalized disease ormetabolic disturbance such as colic.The treatment methods pre¬
scribed for horses with acutelaminitis generally attempt to:(1) remove the inciting factors;(2) relieve the pain; (3) correct boththe local (in the foot) and anygeneralized circulatory disturbancesassociated with the disorder;(4) prevent separation or rotation ofthe third phalanx (coffin bone); and(5) prevent infection or othersecondary complications.
Many different treatmentregimens have been utilized forlaminitis, however, no one
treatment has been consistentlysuccessful. The reason for this lackof success is that many of thephysiological mechanisms involvedin the laminitis disease processhave yet to be fully characterized:therefore, it is difficult to prescribea guaranteed treatment method. Itis also currently believed that manyof the changes which occur in thehoofwall during mild founder maybe similar to those which occur in
racing horses with chronic footsoreness related to a problem withthe coffin bone (a condition called"pedal osteitis"). Studying thisproblem may also help to develop abetter treatment program for horsesaffected with acute laminitis.Researchers from the Department
ofRadiological Sciences haverecently developed two new methodsfor evaluating acute laminitis: (1) anon-invasive nuclear imaging pro¬cedure for characterizing bloodflowwithin the foot; and (2) a new tech¬nique for studying microscopicchanges in the blood vessels,laminae and associated tissue inthe hoof wall. Drs. Donald Trout and
WiUiam Homof, working on thenuclear medicine aspect of thisproject, are injecting radioactivepharmaceuticals into the blood¬stream of an awake, standing horse.Using a nuclear medicine gammacamera linked to a computer, theseradioactive isotopes are tracked asthey flow through the foot.With theuse of the computer, the investi¬gators can determine when bloodflow is increasing or decreasing todifferent areas within the foot.Three protocols have been de¬
veloped for this nuclear isotopicevaluation of circulation to the foot.Using several radiopharmaceuticalsand two different injection sites(median artery and jugular vein), anaccurate overall picture of blooddistribution within the foot and theexact vascular changes leading tofounder will be determined. Byusing these techniques on controlanimals, these researchers haveestablished standards for normal,healthy horses. At present, they areperforming similar nuclearmedicine protocols on animalshaving acute laminitis to determinewhat happens to the distribution of
Continued on page 4
The Horse Report* VoL 3, No. 1—3
CCD (cont.) Implants (cont.)Currently, two donated stallions
and two donated mares with con¬
firmed OCD are being housed onERL pastures. The two OCD mareshave been bred to the affectedstallions, and their foals will be bomthis spring. These foals will be thesubjects of the initial study.To gather the data necessary to
form conclusive evidence, a muchgreater number of foals must begenerated. The three investigatorsare collaboratingwith veterinariansinvolved in the Embryo TransferProgram at the School ofVeterinaryMedicine and plan to utilize thismethod to provide the needednumbers of foals. A relatively newtechnique, the nonsurgical transferof embryos (see Spring 1983 issueof The Horse Report "EmbryoCleavage Has Long-Range Po¬tential") makes results from theOCD investigation feasible within areasonable time frame. By breedingthe OCD mares each estrous cycleand then nonsurgically trauisferring
Swelling over thefront of the stifleJoint(arrow) in a horse affected with OCD.
the tiny embryos to healthy,synchronized recipient mares, eachaffected mare can theoretically"produce" six to eight offspring perseason, thus suppl3ring a largernumber of foals for the investi¬
gation of the hereditary aspect ofOCD. These foals will be carefullytended and consistantly examinedfor appeairance ofOCD symptoms asthey grow to adulthood. If, assuspected, the offspring are affectedwith osteochondrosis, the investi¬gators hope to enlarge upon theirstudy. The future goal is to find anearly and successful treatment ofosteochondrosis. In studying thedisease as it develops, rather thanwhen it has become apparent asclinical lameness, there may be anopportunity to devise treatmentwhich can prevent the cripplingeffects ofOCD.
[The ERL would welcome donationsofmares with confirmed OCD foruse in this study.]
A large bone cyst (arrow), oneform ofosteochondrosis, is evident in this radiograph ofa stifleJoint
THE HORSE REPORT
CO-WRITERS/EDITORS:Cherie Frost & Cindee Worland
Contributions may be made payable to: REGENTS, UNIVERSITY OF CALIFORNIA. Please includeyour name and address and speciiy that your donation is for the EQUINE RESE:ARCHLABORATORY.
Dr. Jane Turrel, radiotherapist atthe VeterinaryMedical TeachingHospital, recently completed a studyin which 22 horses with equinesarcoids were treated with iridium-192 interstitial brachytherapy.Fourteen of these horses had been
previously treatedwith surgery, cryo¬surgery, hyperthermia, or immuno¬therapy but without success.Twenty horses had skin tumors onthe head; two on the legs.Simplified, iridium-192 interstitial
brachytherapy is a treatmentwhereby iridium-192 seeds (tinyradioactive particles) sealed inplastic ribbons are implanted intothe tumor tissue. The horse is putunder general anesthesia or issedated and local anesthesia given.The ribbons are then surgicallyplaced in parallel rows approxi¬mately one centimenter apartwithin the tumor tissue permittingdirect radiation to the tumor in a
relatively short period of time,between 7 to 10 days. Once theimplants are removed, the animalcan be sent home. There is often a
mild to moderate inflammatoryreaction as the tumor cells die,which may persist for 1 to 2 monthsafter treatment. Other than keepingthe area clean and fly-free, specialcare is not required.In Dr. Turrefs study, brachy¬
therapy was given alone on 14horses, in conjunctionwith surgeryon 6 horses, and after hyperthermiaon 2 horses. The tumors graduallyregressed within 2 to 4 monthsafter therapy. After an averagefollow-up of 20 months, all of the 20horses with tumors on the head and1 horse with a tumor on the leg hadcomplete response to therapy, thatis, the tumors had not recurred.One horse with a sarcoid on the leghad only partial response with a50% reduction in tumor size. In this
study, the tumor-free incidenceafter one year was 94% showing verysuccessful treatment of the oftenrecurrent and difficult-to-managesarcoid.
According to Dr. Turrel, theprimary advantage of iridium-192interstitial brachytherapy is thatradiation doses can be given directlyto the tumorwhile normal sur-
Continued on page 4
The Horse Report; Vol. 3, No. 1—4
For your generous response! We want to thank each of you who have sent contributions to the Equine ResearchLaboratory.
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New Techniques (cont.)bloodflow during this diseaseprocess.Dr. Robert Linford, also from the
Department of RadiologicalSciences, has developed a methodfor taking biopsy specimens of thehoofwall with minimal discomfortto the horse. Biopsies of the hoofwall and associated connectivetissue (between the hoofwall andthe coffin bone) will be taken dallyfrom laminitis-affected horses. The
biopsy specimens will be examinedunder the microscope to assess thechanges occurring during thedevelopmental stages of thisdisease. At the same time, nuclearimaging protocols will be performed
on the opposite foot of theseanimals to evaluate alterations inbloodflow patterns.With thiscombined information, theresearchers will be able to makecorrelations between the vascular
changes, laminar lesions andclinical signs present duringlaminitis.These new evaluation methods
are relatively easy and harmlessways to study founder. Drs. Trout,Linford and Homof are enthusiasticabout this project's potential andbelieve that by determining themechanisms involved in laminitis,this research will contributesignificantly to improving treatmentmethods and prevention programs.
Implants (cont.)rounding tissues are generallyspared, giving high likelihood oftumor control and yet having a goodcosmetic effect. Also, the tumor isbeing continuously radiated whichmay help to improve cell killingefficiency. An important aspect ofthis type of treatment is that it canbe completed in a relatively shortperiod of time and involves only oneanesthetic procedure.
