278 Journal of Equine Veterinary Science June 2006

Current Research

CANCER

D04EQ-10, University of Missouri-Columbia,Dr. Elizabeth A. Giuliano

“Photodynamic Therapy for the Treatment ofPeriocular Squamous Cell Carcinoma in Horses”

Completed: September 2005

Description:

Squamous cell carcinoma is the most common typeof tumor affecting the eye and surrounding area and thesecond most common tumor affecting horses overall.This type of cancer is usually locally invasive and slowto spread; however, currently no accepted standard oftreatment exists. Current treatments include surgery,cryotherapy (freezing), and radiofrequency hyperther-mia; however, the recurrence rate after all treatments ishigh. Many horses with this type of cancer go blind. Theinvestigators in this study are examining the effective-ness of a novel new treatment called photodynamictherapy (using intense light), which has shown promisein treating squamous cell carcinoma in cats and dogs.

Accomplishment:

Researchers developed a novel approach to thetreatment of equine periocular squamous cell carci-noma using photodynamic therapy. Preliminary studyresults of treating nine horses with photodynamic ther-apy are extremely favorable, suggesting that this treat-ment, when compared with conventional therapies, mayprove more effective, require fewer treatment episodesand shorter hospital stays, and result in the preservationof eyelid function. The clinical benefits of using thistherapy to treat this type of cancer are far reaching, andthe treatment may work for this type of tumor in otherlocations or in other species.

FOAL DISEASE

D02EQ-43, North Carolina State University, Dr.Babetta A. Breuhaus

“Thyroid Function in Premature Foals”

Completed: September 2005

Description:

Foals born prematurely often do not survive, andthose that do face huge challenges, including compli-cations from decreased gastrointestinal, neural, andmusculoskeletal development. For example, immaturelungs can lead to early illness and death, whereas animmature skeletal system affects the foal’s long-termsoundness and athletic potential. Because thyroid hor-mones are essential for the normal growth and matu-ration of these systems, the investigators are studyingfull-term and premature foals to determine whetherfoals born early are hypothyroid at birth, meaningthey have low thyroid hormone production. Once thy-roid function is understood in both full-term and pre-mature foals, veterinarians may be able to treat pre-mature foals with thyroid hormone supplements thatwould improve their rate of survival and preservetheir athletic ability.

Accomplishment:

Researchers determined that premature foals arehypothyroid in comparison with healthy, full-term foals.This information is important for equine veterinariansto know because thyroid hormones are necessary forproper growth and the development of major organ sys-tems, including the lungs, gastrointestinal tract, andmusculoskeletal system. Immaturity of these organ sys-tems makes it difficult to survive and can cause damageearly on that can interfere with eventual soundness orathletic potential. Investigators hope to conduct furtherresearch to determine whether early thyroid hormonesupplementation to premature foals might improve sur-vivability and improve athletic soundness.

Morris Animal FoundationEquine Study Accomplishments – May 1, 2005 to

September 30, 2005

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FOAL DISEASE

D03EQ-34, University of Florida, Dr. SteeveGiguère

“In Vivo-Induced Antigens of Rhodococcus equias Targets for Vaccine Development”

Completed: July 2005

Description:Rhodococcus equi bacteria cause devastating pneu-

monia in foals. Despite the widespread magnitude ofthis problem, the development of a vaccine has been de-layed because scientists do not know enough about themakeup of the bacteria. Although bacteria cause infec-tions in all species, a part of the bacteria—usually theouter wall—also triggers an immune response to whichthe infected animal will create antibodies to ward off in-fection. The investigators are studying R. equi bacteriato identify the parts of the bacteria that would best trig-ger a foal’s immune response. They will use that infor-mation to develop a vaccine that would prevent R. equiinfections and protect foals from the disease.

Accomplishment:

This study provided important insight into diseasedevelopment and immune response to R. equi in foals.Investigators validated a novel, noninvasive approachfor identifying bacterial antigens that are expressed dur-ing an active R. equi infection in foals. In addition, theylearned more about how the immune systems in foalsand adult horses respond to bacterial proteins that playa role in disease development. These bacterial proteinsmay provide good targets for vaccine development.

GASTROINTESTINAL DISORDERS

D02EQ-23, North Carolina State University, Dr.Samuel L. Jones

“Anti-inflammatory Effects of Lipoxins onEquine Neutrophil Activation”

Completed: June 2005

Description:

Many equine diseases, including colic, pneumonia,heaves, arthritis, and endotoxemia, result from damagecaused when the horse’s tissues are inflamed. When in-flammation occurs, blood cells called leukocytes defendthe body against invading bacteria. Unfortunately, thesesame blood cells also produce toxins that can cause tis-

sue damage. The investigators are studying lipoxins,which are natural molecules in the body that control themagnitude of inflammation.Their findings may help de-velop anti-inflammatory therapies, based on lipoxins,that are more potent and specific than the current drugsused in horses.

Accomplishment:

This project identified a new potential class of anti-inflammatory drugs derived from natural anti-inflam-matory compounds called lipoxins. Investigators deter-mined that lipoxins inhibit the adhesion and migrationof white blood cells (neutrophils) at the site of inflam-mation. This information added to the body of knowl-edge about inflammation in horses. Based on the re-sults, the investigators believe lipoxins will be used inthe future to treat inflammation in horses.

MISCELLANEOUS

D03EQ-68, University of California-Davis, Dr.K. Gary Magdesian

“Validation of Multi-Frequency BioelectricalImpedance Analysis in Horses”

Completed: September 2005

Description:Maintaining proper fluid balance is critical for

horses participating in athletic competition because se-vere dehydration may contribute to colic and myopathy,a painful muscular disorder. Currently, however, nopractical and timely techniques exist for accurately mea-suring hydration levels in horses. In a variety of otherspecies, a non-invasive technology called multi-fre-quency bioelectrical impedance analysis is used to assessfluid levels. The investigators are evaluating the abilityof this technology to accurately estimate abnormal fluidgains and losses in horses. Obtaining accurate fluid mea-surements can help determine drug dosing and responseto medical treatment and to help diagnose disease.

Accomplishment:

Investigators determined that multi-frequency bio-electrical impedance analysis can accurately detect ab-normal changes in fluid levels in horses. This type oftechnology will be very useful in monitoring intra-venous fluid therapy in clinically ill horses as well ashorses that are exercising or performing. Aside fromthis method, no objective means exists of detectingacute fluid changes in a rapid and repeatable manner.

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280 Journal of Equine Veterinary Science June 2006

This technique has the potential to benefit horse own-ers and veterinarians by providing a method for earlierdetection of fluid imbalances, enabling them to provideearlier therapeutic intervention.

NEUROLOGICAL DISORDERS

D03EQ-74, Cornell University, Dr. NikolausOsterrieder

“Neurovirulence of Equine Herpesvirus Type 1”

Completed: September 2005

Description:Equine herpesvirus type 1 is a serious problem for

horse populations worldwide. The disease targets therespiratory tract, reproductive organs, and central ner-vous system. Symptoms include respiratory distress,late-term miscarriages in pregnant mares, and neuro-logical disease. The neurological form of the viruscauses paralysis in the hind legs and some internal or-gans, including the bladder. Recent outbreaks of thisform of the disease have been particularly devastating,despite horses receiving regular vaccinations.The inves-tigators are studying how the virus enters the centralnervous system and causes infection and eventualparalysis. They are using this information to test othervaccine candidates that would establish immunity tothis new strain of the virus.

Accomplishment:

Investigators generated and analyzed a number ofmutant equine herpesvirus type 1 (EHV-1) viruses in alaboratory setting and identified the virulence, or abil-ity to evoke disease, of these modified pathogens. Theyalso generated candidate modified-live virus vaccinesthat are being tested for efficacy and ability to inoculateagainst the disease in horses. They hope to continuetheir work and will concentrate on a single-point muta-tion that is significantly associated with neurologicaldisease caused by EHV-1.

PULMONARY DISORDERS

D04EQ-06, Virginia Tech, Dr. VirginiaBuechner-Maxwell

“Nebulized Magnesium as a Treatment forEquine Recurrent Airway Obstruction”

Completed: September 2005

Description:

Equine heaves, also known as recurrent airway ob-struction (RAO), is a debilitating disease that in somecountries affects more than half the horse population.The disorder occurs when horses are exposed to breath-able debris that causes inflammation and contraction ofthe muscles around the airways. Treating asthmatic hu-mans with magnesium inhalers improves their pul-monary function by relaxing muscles in the constrictedairway, but scientists have not tested this substance inhorses with RAO. The goal of this study is to determinewhether inhalant magnesium sulfate will improve respi-ratory function in horses with clinical RAO. The find-ings will serve as a foundation for further studies aimedat better treatment for horses with this disease.

Accomplishment:

This study examined the effect of magnesium sul-fate in vapor form on clinical signs and pulmonary func-tion in horses with heaves. Because this was a pilot study,only five horses were tested, but subjectively they ap-peared to improve clinically after treatment. Analysis ofthe pulmonary function data is under way, and investi-gators anticipate the data will support the subjectiveclinical impression. Further studies are needed to deter-mine the optimal dose of magnesium for treatment;however, the results are the first step toward developingan inexpensive and safer way to treat equine heaves.

Reprinted with the permission of Morris Animal Foundation.

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