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The Modern

Equine Vet

Vol 8 Issue 5 2018

Resistance Fighters

Choosing the best antibiotic The Dental Evolution Continues I'll Be Watching You Technician Update: Photodynamic Dye Therapy for Squamous Cell Carcinoma



Resistance Fighters: 4 Choosing the Best Antibiotic Cover photo: CDC/ James Archer


The Dental Evolution Continues............................................................. 8 TECHNICIAN UPDATE

Photodynamic Dye Therapy for the Treatment of Squamous Cell Carcinoma...................................10 NEWS

Merck Animal Health Introduces Updated Equine Influenza Vaccines........................................................................................ 3 I’ll Be Watching You......................................................................................................................13 Good Plasma Concentrations Seen with IV and IG Levetiracetam..........................13 ON THE COVER: A three-dimensional (3D) computer-generated image of three multidrug-resistant, Pseudomonas aeruginosa bacteria. The artistic recreation was based upon scanning electron microscopic (SEM) imagery. Note the presence of numbers of thin, diaphanous fimbriae emanating from the organisms' cell walls as well as a single, corkscrew-shaped flagellum, which provides the bacteria with a unipolar mode of motility.

ADVERTISERS Merck Animal Health.................................................. 5 Boehringer Ingelheim................................................ 7


The Modern

Equine Vet SALES: Matthew Todd • Lillie Collett • EDITOR: Marie Rosenthal • ART DIRECTOR: Jennifer Barlow • CONTRIBUTING WRITERS: Paul Basillo • Carol Jean Ellis Jason Mazda COPY EDITOR: Patty Wall Published by PO Box 935 • Morrisville, PA 19067 Marie Rosenthal and Jennifer Barlow, Publishers PERCYBO media  publishing


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Merck Animal Health Introduces Updated Equine Influenza Vaccines Merck Animal Health recently introduced new equine influenza vaccines that feature the most recent circulating flu strains. “For the past 10 years, we’ve been monitoring influenza along with other common infectious upper respiratory diseases through the Merck Animal Health Biosurveillance Program, a partnership with the University of California, Davis. It was through this program that we identified and isolated a new highly infectious and relevant equine influenza strain from the 2013 Ocala, Fla. influenza outbreak that impacted a large number of horses from all over the world,” said D. Craig Barnett, DVM, director of equine veterinary professional services, Merck Animal Health. “This strain is now part of our updated line of influenza-containing killed virus vaccines and represents a current, clinically significant strain responsible for a large influenza outbreak in well-vaccinated horses.” Prestige influenza-containing vaccines includes the Florida ‘13 of the clade 1 family and Richmond ‘07 of the clade 2 family, meeting current World Organization for Animal Health (OIE) and American Association of Equine Practitioners (AAEP) guidelines for clade 1 and clade 2 strains. The clade 1 family of equine influenza primarily circulates in the United States, while clade 2 predominantly circulates in Europe. Influenza vaccines are updated periodically to account for antigenic drift in the circulating viruses to ensure the best protection, according to Dr. Barnett. “And while we have not had any outbreaks of clade 2 in the United States to date, U.S. horses competing internationally should have clade 2 protection on board.” Equine influenza is one of the most common causes of equine viral respiratory tract disease. It has been the culprit of some of the largest equine infectious respiratory disease outbreaks worldwide, disrupting major equestrian events and causing significant economic losses. Once the virus begins to circulate, it’s very difficult to control and can spread rapidly. Recovery can

take several weeks to months. Influenza vaccination is recommended at six-month intervals for any performance, show or pleasure horses at risk of exposure, including resident horses exposed to traveling horses. United States Equestrian Federation (USEF) and Federation Equestre Internationale (FEI)-sanctioned events both have six-month influenza vaccination requirements. “A cornerstone of the Merck Animal Health Biosurveillance Program is identifying and monitoring current circulating strains of major equine respiratory pathogens such as influenza,” Dr. Barnett said. Prestige vaccines feature the proprietary Havlogen adjuvant and Antigen Purification System, formulated to maximize protection and minimize adverse reactions. To educate horse owners about the risks of equine influenza and the importance of working with their veterinarian to design a vaccination program, Merck recently introduced the “Perform with PRESTIGE” online sweepstakes. Now through June 30, horse owners can visit for a chance to win a Featherlite horse trailer, a trip to the 2018 World Equestrian Games in North Carolina, as well as many other monthly and weekly prizes. For more information see the ad on page 5, visit or call 800-521-5767. MeV


Featuring the Most Current Clade 1 and Clade 2 Influenza Strains

For more information: Daly JM, MacRae S, et al. Equine influenza: a review of an unpredictable virus. Vet J. 2011;189:7-14 Timoney PJ. Factors influencing the international spread of equine diseases. Vet Clin North Am Equine Pract. 2000;16:537-551. American Association of Equine Practitioners (AAEP) Risk-based vaccination guidelines. Available at | Issue 5/2018



Resistance Fighters: Antimicrobial resis-

Antimicrobial resistance is a serious, but not insurmountable problem in equine medicine. By Paul Basilio

This is an example of an antibiotic sensitivity test on a wet plate culture of Escherichia coli, which had taken place at a pH 7.2. Note that the inhibition zones varied in their magnitude from no inhibition, to a clearly demarcated inhibition perimeter.


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tance is a serious, but not insurmountable problem, in equine medicine. “I want to keep us grounded; resistance is part of the clinical picture,” said J. Scott Weese, DVM, DVSc, DACVIM, professor at the Ontario Veterinary College at the University of Guelph, Canada, at the 63rd AAEP Annual Convention in San Antonio. “We need to know about it, we need to address it, but it doesn’t mean the patient is going to die, and it doesn’t mean we need to freak people out.” Resistance genes are not virulence genes—just because a horse has a resistant infection does not automatically mean a grave prognosis, he said. “If I have a horse with a MRSA [methicillin resistant Staphylococcus aureus] infection and a horse with a susceptible Staphylococcus infection [methicillin susceptible S. aureus] in front of me, and I know which one has MRSA and which one has MSSA, then the outcomes should be exactly the same,” he explained. “MRSA is not more virulent. We just have to treat it differently.”

When encountering a resistant pathogen, focus on the organism, focus on the disease, and then focus on the susceptibilities. One of the pathogens that is coming to the forefront in horse populations is an extended spectrum beta-lactamase (ESBL) producing Escherichia coli that is resistant to most of the beta-lactams. It breaks down penicillins and cephalosporins, which eliminates two routine treatments. Since they accumulate resistance genes over time, these pathogens are becoming a larger problem in human medicine, as well. And animal organisms can pick up the resistance genes from human organisms. “That’s how we got MRSA in the horse population, to a large degree,” Dr. Weese said. E. coli prevalence rates vary by population. In horses that come into referral clinics that have been stressed and exposed to antibiotics, prevalence can be as high as 70%. In a general horse population, the number can be around 20%. Even at the lower numbers, that means a lot of horses exposed to fecal shedding of the organism.

Photo courtesy of the CDC

Choosing the Best Antibiotic

The Science of Significant Introducing updated flu strains, only available in the Prestige vaccine line from Merck Animal Health


FEATHERLITE The Next Generation of FLU Protection


Developed to help protect against influenza viruses threatening horses today, the Prestige line of flu vaccines offers the most encompassing and advanced level of protection against equine influenza. Horses deserve the best protection we can give them. Contact Merck Animal Health or your veterinarian to learn more about the new Prestige line of vaccines.

2 Giralda Farms • Madison, NJ 07940 • • 800-521-5767 Copyright © 2018 Intervet Inc., d/b/a/ Merck Animal Health, a subsidiary of Merck & Co., Inc. All rights reserved. 3643-FLUSTRAIN-ADVERTISEMENT


Enter to win at NO PURCHASE NECESSARY. Open to U.S. residents, at least 18 years of age.


Just as in human medicine, culture and susceptibility testing are good guides for deciding the best antimicrobials when treating resistant or susceptible infections.

CDC/ Janice Haney Carr

This digitally colorized scanning electron microscopic (SEM) image depicted large numbers of gram-positive, Enterococcus sp. bacteria.


“The good thing is that we’ve got a lot of horses shedding ESBLs, but not everyone is seeing a lot of ESBL infections,” he said. “A resistant bug isn’t more likely to cause an infection. What this does tell you, is that over the next few years we’re going to start seeing some resistant E. coli infections. You won’t see more E. coli infections, but the infections will be harder to treat.” Culture and susceptibility testing are good guides for treatment in these infections. They are typically susceptible to aminoglycosides and carbapenems. ESBLs seem to be more susceptible to cephamycins in vitro versus in vivo, and Dr. Weese tends to not use them unless he has no other choice. The beta-lactamase inhibitors, such as ampicillin sulbactam, can work in ESBLs, but it’s not a consistently successful tool. “You’ve got a bacterium that’s producing an enzyme, and the enzyme is trying to break down the antibiotic,” he explains. “It’s a battle between how much enzyme is produced and how much enzyme is being neutralized by the drug. Sometimes it works, but sometimes it doesn’t.” In a case of a life-threatening ESBL infection, Dr. Weese tends to avoid cephalosporins, beta-lactams and beta-lactamase inhibitors. Fluoroquinolones are typically effective for gram-negative

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infections, but by the time the infections are seen as an ESBL, the organism has picked up the genes to become resistant. Carbapenems are an option, but the drugs are expensive. Aminoglycosides are often the first choice. In a less serious infection where time is less of a barrier, beta-lactams/beta-lactamase inhibitors and cefoxitin can be used, but typically they work best when combined with an aminoglycoside. The most common enterococcal infections are caused by Enterococcus faecium and Eneterococcus faecalis, which are both associated with multidrug resistance and are inherentlyresistant to a variety of drug classes. The pathogen is often present as a contaminant or a coinfection, and isolation of an Enterococcus strain is not always an indication for treatment. But in a case where an Enterococcus that is resistant to everything is suspected of causing disease, what can be done? If Dr. Weese is presented with an enterococcal strain at a site where such infections are typical and no other pathogens are isolated, then he’s likely to treat it. However, if he is not convinced that the Enterococcus is relevant, particularly if another pathogen is detected, he’s likely to ignore the Enterococcus. Even in the face of multidrug resistance, ampicillin will often work for enterococcal infections.

If the pathogen is also susceptible to gentamicin, then combining the two is often successful. Pseudomonas is another pathogen that is intrinsically resistant to many antimicrobials, such as most cephalosporins, chloramphenicol and tetracyclines. The organism enjoys slimy surfaces and likes to live in the water. It produces a biofilm, a physical barrier that can make treatment even trickier. In a case of a Pseudomonas infection in a prosthetic implant, Dr. Weese offered some advice. “Good luck,” he said. The implant is likely to have to be removed, as it’s incredibly difficult to treat implant-associated infections to begin with, let alone a stubborn bug covered in biofilm. “Most often, all we can really do is try to keep the infection at bay until we can remove that implant,” he added. Aminoglycosides and fluoroquinolones are fairly useful. Fluoroquinolone as monotherapy can be difficult; however, as the treatment then becomes a battle between the pathogen and resistance during treatment. As a result, combination treatment with another drug is an ideal approach. Piperacillin, ticarcillin and ceftazidime may also be effective. If the owner can afford it, IV administration of ceftazidime and amikacin is a fairly effective combination. MeV

UPDATED GUIDELINES FOR PPID NEW PPID DIAGNOSTIC RECOMMENDATIONS ARE NOW AVAILABLE FROM THE EQUINE ENDOCRINOLOGY GROUP.1 Pituitary pars intermedia dysfunction, or PPID, also called “equine Cushing’s disease,” can sometimes be difficult to diagnose. To help veterinarians identify and test for this disease, the Equine Endocrinology Group (EEG) updated its recommendations to include updated reference ranges for ACTH while also adding additional early and advanced signs of the disease. There are two types of procedures available for PPID testing. TRH stimulation procedure (measuring ACTH at T0 and T10) is used for horses with early signs of PPID or suspected horses with a normal resting ACTH. Resting ACTH is recommended for the suspected PPID horse with moderate or advanced clinical signs. If resting ACTH is normal or equivocal in horses with advanced signs, the follow-up procedure is the TRH stimulation. Seasonal variations in ACTH have been previously documented in the horse. Testing in the fall months has been shown to increase the sensitivity of resting ACTH in horses with signs of early PPID. TRH stimulation testing in the fall is not recommended as sufficient data to establish accurate cutoff values is being further evaluated. It’s important for veterinarians to use seasonally adjusted resting ACTH reference ranges specific for the time of year they’re testing for PPID.

“If a horse is borderline for PPID after a resting ACTH test, veterinarians can then utilize the TRH stimulation procedure, giving a more precise diagnosis,” says Steve Grubbs, DVM, PhD, DACVIM, equine technical manager for Boehringer Ingelheim. “Information from the history, clinical signs and testing results should all be utilized when making the diagnosis of PPID. Each aspect is extremely important for the proper diagnosis.” The new EEG guidelines also updated the clinical presentation of the early and advanced signs of PPID. Additions to early signs include abnormal sweating (increased or decreased), infertility, desmitis and tendonitis. Additions to the advanced signs include dull attitude/altered mentation, exercise intolerance, excessive mammary gland secretions and suspensory ligament laxity. For horses showing signs of PPID, Boehringer Ingelheim offers complimentary testing for up to three horses per veterinarian. This testing is part of a study to identify epidemiological information for horses with PPID at initial diagnosis. This offer continues through June 13, 2018. For more information about complimentary testing and the complete 2017 EEG diagnostic guidelines for PPID, please visit

Recommendations for the Diagnosis and Treatment of Pituitary Pars Intermedia Dysfunction, Equine Endocrinology Group. Available at Accessed February 14, 2018.



™Unbridle Your Potential is a trademark of Boehringer Ingelheim Vetmedica, Inc. ©2018 Boehringer Ingelheim Vetmedica, Inc. All rights reserved. EQU-0598-PRAS0518



Dental Evolution Continues Research and innovation continue in equine dentistry


Despite all the advances in

equine medicine, dentistry remains a developing discipline that some are advancing but not all are taking seriously enough, said Padraic Martin Dixon, MVB, PhD, FRCVS, DEVCC.

Horse with “Slopemouth” (slantmouth” “diagonal bite”). Almost all cases of this disorder are caused by a craniofacial deformity such as “wrynose.” Mechanically leveling the incisors by floating will just give a temporary change to incisors that will soon revert to their original appearance. All such cases should be assessed for facial symmetry to prevent such potentially painful and unnecessary procedures.


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“The main advance over the last couple of years is that we actually know the basic anatomy,” Dr. Dixon said at the American Association of Equine Practitioners meeting and exhibition in San Antonio. “We actually know where




the pulps are. We know the structure of the calcified tissues.” Dr. Dixon reminded veterinarians not to forget the basics. The Triadan System of Dental Nomenclature and the Equine CT Pulp Numbering System are important

Photo courtesy of Dr. Dixon


tools, he said. “Everybody should now be getting familiar with the Triadan System; it’s such an easy way to communicate,” he said. “With the Equine CT Pulp Numbering System,” he added, “We can say, ‘The 09 had a fracture to its first and second pulp.’” Other important developments include effective sedatives, new treatments and new equipment. Imaging equipment, in particular, has vastly improved equine veterinarians’ ability to provide optimal dental care. Dr. Dixon joked that unless the veterinarian has x-ray vision, he or she needs to take radiographs, and he added that computed-tomography (CT) scanning is extremely helpful as well. “Early equine apical abscesses are very difficult to pick up, particularly in the maxillary teeth,” Dr. Dixon said. “(CT scanners) are getting cheaper, and they’re wonderful.” Research continues to provide important insights regarding best practices as well. Dr. Dixon cited recent work by Patricia Schrock showing that the anatomy of incisors is slightly different than previously believed. “A lot of them are curved,” he said. “The canal tapers. There sometimes is possible apical rota-

The Triadan Nomenclature and Equine CT Pulp Numbering System are important tools in equine dentistry. tion. People are beginning to do endodontic treatment on incisors, so it is good to know exactly what we are dealing with.” Other important ongoing studies include several on equine microbiota. Dr. Dixon cited the Equine Microbiome Project by Berg et al; work by two different groups studying gut microbiota dysbiosis, including grain overload; and studies by two other groups on oral microbiota dysbiosis, including peripheral caries and periodontitis. Some practices in equine dentistry, however, must be approached with caution, Dr. Dixon said. “We in Britain have problems

with some lay dental technicians,” he said. Many people take a short course to obtain ... dentist. "Part of thei a certificate that they’re a trained dentist. Part of their two-week professional training means that you’ve got to grind all these ridges down to promote rostral movement of the mandible, which apparently is essential for the horse. Some of us disagree slightly with that. It took 53 million years to evolve, we can’t see how somebody who left high school in Idaho can change this overnight.” In some cases veterinarians should resist the temptation to perform procedures such as correcting wave mouth, which may prevent the dentition from ever regaining proper occlusion, or reducing incisors, which may lead to dangerously exposed pulp. Remember Due to the mastication forces it requires, hay poses more of a risk than oats to the horse’s long-term dental health. Dentistry should not do anything that prevents the horse from being able to properly chew its food. “Sometimes,” he said, “when we imagine that this animal lived in the wild, evading predators … we might be better off just doing areas that are causing soft-tissue damage rather than to do a cosmetic Hollywood job on the horse.” MeV

Advances in Clinical Equine Dentistry in the Last 25 Years Advances in basic anatomy and pathology research to give a scientific basis to this discipline Effective sedatives and new regional nerve blocks allow standing procedures NEW TREATMENTS: • Oral and MTE cheek teeth extractions • Diastema/periodontal treatments • Infundibular and endodontic treatments • Scientific evaluation of old and new procedures

NEW EQUIPMENT: • Motorized dental equipment • Oral endoscopy • Speculums, MTE equipment, diastema pumps • New imaging techniques: Computed tomography • Education and increased awareness of dental disorders

Source: Frank J. Milne State of the Art Lecture by Padraic Martin Dixon, MVB, PhD, FRCVS, DEVCC at the American Association of Equine Practitioners (AAEP) Annual Convention 2017. | Issue 5/2018



Photodynamic Dye Therapy for the Treatment of Squamous Cell Carcinoma By Karen Chapman, RVT

Photo courtesy of Karen Chapman, RVT

Bugs Magic Breese, a 13-yearold American Paint Horse mare, presented to the Texas A&M University Veterinary Medical Teaching Hospital on July 29, 2016, for evaluation of a recurring tumor on her lower left eyelid. The tumor had been resected previously and injected with cisplatin 45 days earlier. Regrowth was noted (Figure 1) and Breese was referred for a second opinion. Breese was sedated with 10 mg detomidine administered IV to keep her comfortable and sedated during the procedure. An auriculopalpebral nerve block was performed using carbocaine to facilitate manipulation of the lid. A local block using carbocaine was used to desensitize the left lower eyelid. The tumor was resected using sharp dissection and the resultant wound bed was injected with 3.75 mg verteporfin (Visudyne; Novartis.) using a 5-mL syringe and a 25-gauge needle. Immediately following the dye infiltration, the area was exposed with a 690 nm wavelength, non-thermal laser red light source (LumaCare) for eight minutes. During this procedure, the globe was protected with a Styrofoam shield covered in duct tape. After treatment, bacitracin-neomycin-polymyxin veterinary ophthalmic ointment was applied on the eye and flunixin meglumine along with dexamethasone-

SP were administered IV for pain and inflammation. Side effects of the PDT treatment are usually minimal. Breese’s owner was encouraged to leave her in a stall for 48 hours following treatment and told the treated area would be sensitive to sunlight for five to seven days. She was encouraged to use a UV protective fly mask while the wound healed. Oral administration of flunixin meglumine by mouth once to twice daily for three to four days as needed was advised. Some patients do tend to have excessive pruritus immediately following and up to three to four days after treatment. Swelling often occurs as does the presence of a thick mucopurulent discharge, but these symptoms usually resolve within a week. Breese returned to the Texas A&M Medical Teaching Hospital on Sept. 29, 2016, and upon examination, her SCC appeared to be resolved. No other treatments were performed. She returned one more time on June 7, 2017, to evaluate a small mass in the lateral aspect of her left lower eyelid that occasionally scabbed over without a consistent frequency. She was sedated with 1-mL detomidine to allow for examination and mass removal. An auriculopalpebral block using carbocaine and a local infiltration using carbocaine were performed to allow for examination and mass removal on the left lower eyelid. The lower eyelid mass was removed using sharp dissection and fixed to allow for histopathology. Following the removal, cryotherapy using liquid nitro-

FIGURE 1: Lesion at admission on July 29, 2016


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FIGURE 2: Lesion at recheck on Sept. 29, 2016

AAEV T M E M b E r s h i p Membership in the AAEVT is open to all veterinary technicians, assistants, support staff and those employed in the veterinary health care industry worldwide. Student membership is open to those currently enrolled in an AVMA/CVMA accredited veterinary technology program.

AAEVT Membership • • • • • • • • • • •

Bi-Annual Newsletter Weekly “HoofBeats” Email Newsblast Full access to, including the Career Center and the Library Up-to-date information on the AAEVT Discounted registration for AAEVT Regional Meetings and the annual AAEP/AAEVT Convention NTRA, Working Advantage and Platinum Performance Benefits The opportunity to participate in the AAEVT Online Certification Program or to become a member of the AEVNT Academy-Specialty in Equine Veterinary Nursing Scholarship opportunities. AAEVT’s Equine Manual for Veterinary Technicians (Blackwell Publishing 20% discount on purchase price) Opportunity to attend Purina’s Annual Equine Veterinary Technician Conference - All Expenses paid!

AAEVT Objectives • • • •

Provide opportunities for CE, training, communication, and networking Educate the equine veterinary community and the public about our profession Inform Members of issues affecting our profession Assist in providing the best medical care to improve the health and welfare of the horse

AAEVT Online Equine Certification Program

• A three course, 10 module, equine-only online program offered through ACT • Geared toward Credentialed Veterinary Technicians, Assistants, Support staff, & Students • Areas of study include: equine medical terminology, anatomy and physiology, parasitology, laboratory, diagnostics, equine basics (breeds, wellness, husbandry,) diagnostic procedures, emergency medicine, restraint, pharmacology, surgical assistance and anesthesia, equine office procedures • A certificate of completion is awarded to those who: Successfully complete required courses Complete the list of required skills (per a supervising DVM who is an AAEP member) Attend an AAEVT regional CE symposium and participate in the we labs • Those individuals who successfully complete the programs will be recognized as AAEVT Certified Equine Veterinary Technicians / AAEVT Certified Equine Veterinary Assistants depending on their current designation. The certificate is recognized by the AAEVT and the AAEP but does not grant the credentialed status by the AVMA • For more information go to or call 800-357-3182

AAEVT Mission Statement: To promote the health and welfare of the horse through the education and professional enrichment of the equine veterinary technician and assistant.

Fo r m o re i n f o r m a t ion v ist w w w.a ae vt.or g

*American Association of Equine Veterinary Technicians and Assistants


Horses in Texas and other sunny southern states are susceptible to developing squamous cell carcinoma (SCC). This tumor is the most common neoplasm of the eye and surrounding tissue. Most frequently seen in Appaloosas and American Paint Horses because of the lack of pigmentation of the mucocutaneous tissue of the eyelids, this tumor is locally invasive and can result in loss of the eye. These tumors are often treated with cryotherapy and injectable chemotherapies, with a high recurrence rate. Surgical procedures, such as H-plasty, are performed in some cases to help maintain proper eyelid function after tumor excision. This procedure is not always successful because it often results in excessive scarring of the eyelids. Improved treatments were needed to fight this common tumor, which lead investigation into the use of photodynamic dye therapy (PDT). The first body of research looking at PDT in horses was performed at the University of Missouri between 2006 and 2010 by Elizabeth Giuliano, DVM, MS, DAVO. This pilot study involved the use of nine horses with SCC that were treated by surgical resection and local PDT. The average disease-free interval was 45 months (with a range of 25–68 months) as of January 2008. In a follow-up study, two groups of horses were used to compare the efficacy of cryotherapy to PDT. Horses in the first group were treated by surgical excision followed by cryotherapy. Horses in the second group were treated by surgical excision followed by PDT. In group 1, 11 out of 14 horses showed regrowth with a median time to recurrence of 10 months. Group 2 had no regrowth at 50 months after one treatment with surgical excision and PDT. Leslie Easterwood, DVM, MA, from Texas A&M University Veterinary Medical Teaching Hospital, began using PDT to treat periocular SCC in November 2015. Because of the inherent problems associated with repeated eyelid excision when treating periocular SCC, a new modality was needed. Horses can’t spare much of the skin making up the eyelids; therefore, removal of any of the eyelid can potentially cause problems with lid closure. Loss of vision can occur when the eye is not able to be fully lubricated. This lack of proper lubrication leads to exposure keratitis and possible removal of the globe. Dr. Easterwood has now treated approximately 80 cases of periocular SCC using PDT with positive results.

gen in 3 freeze cycles was used on the left lower eyelid. Additionally, 5-fluorouracil was injected intralesionally into the left lower eyelid. Interestingly, the histopathology report revealed no evidence of squamous cell carcinoma and indicated that the proliferative changes were consistent with excessive exposure to UV radiation/solar keratosis. Photodynamic dye therapy has proven to be an effective therapy in the fight against periocular SCC. Owners have been very pleased with the results and have all told us they would not hesitate to consider PDT in the future. The procedure costs around $900; most of that of that cost for the verteporfin dye. Usually only one treatment of PDT is necessary but this depends on the size of the tumor. It is not uncommon to treat larger SCC

tumors with PDT and then follow up at 30-day intervals with minor surgical excisions of remaining cancerous tissue followed by cryotherapy and injectable 5-fluorouracil. Client compliance is important to stay ahead of any remaining cancerous tissue which will continue to proliferate if not completely removed. At this time, photodynamic dye therapy remains one of our most successful therapies in the fight against periocular squamous cell carcinoma. MeV

About the author

Karen Chapman, RVT, is an equine technician at the Texas A&M University Veterinary Medical Teaching Hospital, College Station, Texas.

For more information: Giuliano El, et al. Local photodynamic therapy delays recurrence of equine periocular squamous cell carcinoma compared to cryotherapy. Veterinary Ophthalmology (2014) 17, Supplement 1, 37-45. Giuliano E, et al. Photodynamic therapy for the treatment of periocular squamous cell carcinoma in horses: a pilot study. Veterinary Ophthalmology (2008) 11, Supplement 1, 27-34. 12

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Teaching Points


Horses appear to be able to read people’s emotional expressions—and remember them—enabling them to identify people who could pose a threat. The horses were shown a photograph of an angry or happy human face and several hours later saw the actual person, who did not show emotion. The shortterm exposure to the photograph of a person's facial expression was enough to generate clear differences in the horses' responses to the actual person. Despite the people being in a neutral state during the live meeting, the horses' gaze direction revealed that they perceived the person more negatively if they had previously seen them looking angry in the photograph rather than happy. “What's very striking is that this happened after just briefly viewing a photograph of the person with a particular emotional expression—they did not have a strongly positive or negative experience with the person,” said Leanne Proops, BSc(Hons), MSc, PhD, of the University of Portsmouth in the United Kingdom. Previous research has shown that animals tend to view negative events with their left eye due to the right brain hemisphere's specialization for processing threat-

ening stimuli (information from the left eye is processed in the right hemisphere). To avoid any risk of behaving differently, the people did not know which photographs the horses had seen. Also the reactions were just to the people they had seen in photographs, not to other people to whom they were introduced. “What we've found is that horses can not only read human facial expressions but they can also remember a person's previous emotional state when they meet them later that day—and, crucially, that they adapt their behavior accordingly,” said Karen McComb, PhD, of the University of Sussex in Great Britain, one of the co-leaders of the study. This ability to remember emotional experiences could have clear benefits for social bonding and aggression avoidance, they said. MeV

Universities of Sussex and Portsmouth

I’ll Be Watching You

The research is in a neutral state.

For more information: Proops L, Grounds K, Victoria Smith A, McComb K. Animals remember previous facial expressions that specific humans have exhibited. Current Biology. 2018;28(9): 1428–1432.e4.

Good Plasma Concentrations Seen with IV and IG Levetiracetam in Foals Giving levetiracetam to neonatal foals at a dose of 32 mg/kg IV or orally twice daily is likely to maintain therapeutic plasma concentrations. This randomized crossover study looked at the pharmacokinetics of levetiracetam in neonatal foals. Six healthy Quarter Horse foals, who were 3 days old or younger, were administered a single 32 mg/ kg dose of levetiracetam either intravenously (IV) or intragastrically (IG); the dose of which was extrapolated from pharmacokinetic data reported for adult horses. To determine plasma levetiracetam concentra-

tions blood was taken from all the foals at 0, 5, 10, 15, 20, 35, 45, 60 and 90 minutes and 2, 3, 4, 6, 8, 10, 12, 24, 36 and 48 hours after administration. The levetiracetam and plasma concentrations remained within the proposed therapeutic range (5–45 mg/L) and above the proposed target concentration (35 mg/L) for at least 12 hours for both IV and IG administration and there were no adverse events. Bioavailability for IG administration was excellent, and there was no significant difference in the pharmacokinetic variables between IV and IG administration. MeV

For more information: MacDonald, Hart KA, Davis JL, et al. Pharmacokinetics of the anticonvulsant levetiracetam in neonatal foals. Equine Vet J. 2017 Dec 1 (Epub ahead of print). | Issue 5/2018


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