The Modern Equine Vet November 2016

The Modern

Equine Vet www.modernequinevet.com

Vol 6 Issue 11 2016

Endocrine Abnormalities in brood mares Which Diets are Better for Omeprazole Treatment?

Antibiotic Use in Horses Where Rules Matter Most Technician Update:

Caring for Infected Wounds

Table of Contents

reproduction

Endocrine Abnormalities

4 in Problem Brood Mares Cover photo: Shutterstock/Julie Landrieu

Infectious Diseases

Antimicrobial Prescribing Habits for Horses.....................................................................10 FDA Issues Antibiotic Resistance Monitoring Report....................................................12 technician update

Caring for an Infected Wound..................................................................................................14 News

Which Diets Are Better for Omeprazole Treatment? ................................................................. 3 Where Medication Matters Most...................... 9 Guarantee Might Help You Convince Folks to Vaccinate...................................................13

advertisers Merck Animal Health.................................................. 5 Henry Schein/ImproMed............................................ 7

AAEVT............................................................................15

The Modern

Equine Vet Sales: Matthew Todd • ModernEquineVet@gmail.com Editor: Marie Rosenthal • mrosenthal@percybo.com Art Director: Jennifer Barlow • jbarlow@percybo.com contributing writerS: Paul Basillo • Kathleen Ogle 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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Issue 11/2016 | ModernEquineVet.com

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News notes

Shutterstock/acceptphoto

Which Diets Are Better for Omeprazole Treatment?

Omeprazole may be more effective at increasing gastric pH if horses are on a high grain, low fiber diet, according to a recent study.

The effects of two doses of omeprazole and two diets on the pharmacodynamics of the drug were studied in six horses fitted with percutaneous gastrotomy tubes. A hay only diet was compared with a high grain, low fiber diet designed to replicate that of a racehorse in training. Once adapted to the diet, the intragastric pH of each horse was monitored for six consecutive days and measurements were taken from two locations within the stomach 5 cm apart.

The percentage of time that pH exceeded 4 was considered to be the conditions under which squamous ulceration healing occurs and a 1 mg/kg bodyweight dose of omeprazole (GastroGard paste, Merial) was compared with a 4 mg/kg dose once daily.

The effect of both diet and dose was evident with pH values typically higher at the upper (4 mg/kg bwt) dose and in high grain, low fiber diets. The overall efficacy of omeprazole in raising intragastric pH was good under the high grain, low fiber conditions but relatively poor with the hay diet. When comparing Day 5 to Day 1 of treatment, the pH values were

higher at location 2 at both doses and on both diets.

Based on these results the researchers recommend that on a roughage-only diet, omeprazole should be used at 4 mg/kg in horses and that a period of fasting before administration of omeprazole may be beneficial in these horses.

The differences in results obtained at two different sampling locations within the stomach may be attributable to regional pocketing of acid, and future studies investigating acid suppression should involve sampling at multiple locations, they said.

The use of singular dosing recommendations that encompass all horse types and management conditions may not be appropriate and dosing recommendations that consider the diet of the horse are needed, they added.

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For more information: Sykes BW, Underwood C, Greer CR, et al. The effects of dose and diet on the pharmacodynamics of omeprazole in the horse.

Equine Vet J. 2016 Oct. 3 [Epub ahead of print]). http://onlinelibrary.wiley.com/doi/10.1111/evj.12630/full

Omeprezole dosing should consider the horse's diet.

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reproduction

Endocrine Abnormalities Although metabolic diseases are likely to affect reproduction, a review of the literature is likely to show scattered individual case reports specifically relating to metabolic disease and thyroid function, rather than evidence-based studies.

However, a more focused look at the specific abnormalities associated with these diseases, such as an increase in glucocorticoid production and insulin resistance, sheds a bit more light on the role of these abnormalities in folliculogenesis, ovulation, pregnancy, the neonatal foal and the horse later in life.

“My instinct is that yes, metabolic disease can affect reproduction,” said Jennie Henderson, BVSc, DECEIM, MRCVS, here at the British Equine Veterinary Association (BEVA) Congress in Birmingham, England. “I have had fat mares, thin mares, chronically laminitic mares, and mares that have been diagnosed with subclinical Cushing’s disease that have been challenging to get into foal.”

B y

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Issue 11/2016 | ModernEquineVet.com

P a u l

Shutterstock/Callipso

in Problem Brood Mares

B a s i l i o

The Science of Trusted Regu-Mate® (altrenogest) is the name veterinarians and their clients depend on for estrus control (suppression, management).

From the broodmare to the performance horse, properly managing your mare’s hormones is critical. Rely on the product that’s trusted most.

• More than 30 years of practical use in the field by veterinarians 1 • More than 200 clinical trials to determine efficacy, duration and safety1 • More than 20 million doses sold to veterinarians, trainers and horse owners 1 Now that’s trusted.

Ask your veterinarian for Regu-Mate®. Visit us online at merck-animal-health-equine.com to learn more about Merck Animal Health and the equine products and programs that help keep horses healthy.

Talk to your veterinarian about proper use and safe handling of Regu-Mate®. Avoid skin contact. Always wear protective gloves when administering Regu-Mate®. This product is contraindicated for use in mares with a previous or current history of uterine inflammation. Pregnant women, or women who suspect they are pregnant, should not handle this product. For complete product information, see accompanying product insert.

The Science of Healthier Animals 2 Giralda Farms • Madison, NJ 07940 • merck-animal-health-usa.com • 800-521-5767 Copyright © 2016 Intervet Inc., d/b/a/ Merck Animal Health, a subsidiary of Merck & Co., Inc. All rights reserved. 3290 EQ-FP AD Regu-Mate®

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Data on file, Merck Animal Heath

reproduction Regu-Mate® (altrenogest) Solution 0.22% (2.2 mg/mL) CAUTION: Federal law restricts this drug to use by or on the order of a licensed veterinarian.

DESCRIPTION: Regu-Mate® (altrenogest) Solution 0.22% contains the active synthetic progestin, altrenogest. The chemical name is 17α-allyl-17ß-hydroxyestra-4,9,11-trien-3-one.

The CAS Registry Number is 850-52-2. The chemical structure is: Each mL of Regu-Mate® (altrenogest) Solution 0.22% contains 2.2 mg of altrenogest in an oil solution.

ACTIONS: Regu-Mate® (altrenogest) Solution 0.22% produces a progestational effect in mares.

INDICATIONS: Regu-Mate® (altrenogest) Solution 0.22% is indicated to suppress estrus in mares. Suppression of estrus allows for a predictable occurrence of estrus following drug withdrawal. This facilitates the attainment of regular cyclicity during the transition from winter anestrus to the physiological breeding season. Suppression of estrus will also facilitate management of prolonged estrus conditions. Suppression of estrus may be used to facilitate scheduled breeding during the physiological breeding season.

CONTRAINDICATIONS: Regu-Mate® (altrenogest) Solution 0.22% is contraindicated for use in mares having a previous or current history of uterine inflammation (i.e., acute, subacute, or chronic endometritis). Natural or synthetic gestagen therapy may exacerbate existing low-grade or “smoldering” uterine inflammation into a fulminating uterine infection in some instances.

PRECAUTIONS: Various synthetic progestins, including altrenogest, when administered to rats during the embryogenic stage of pregnancy at doses manyfold greater than the recommended equine dose caused fetal anomalies, specifically masculinization of the female genitalia.

DOSAGE AND ADMINISTRATION: While wearing protective gloves, remove shipping cap and seal; replace with enclosed plastic dispensing cap. Remove cover from bottle dispensing tip and connect luer lock syringe (without needle). Draw out appropriate volume of Regu-Mate solution.

(Note: Do not remove syringe while bottle is inverted as spillage may result.) Detach syringe and administer solution orally at the rate of 1 mL per 110 pounds body weight (0.044 mg/kg) once daily for 15 consecutive days. Administer solution directly on the base of the mare’s tongue or on the mare’s usual grain ration. Replace cover on bottle dispensing tip to prevent leakage.

Excessive use of a syringe may cause the syringe to stick; therefore, replace syringe as necessary.

WHICH MARES WILL RESPOND TO REGU-MATE® (altrenogest) SOLUTION 0.22%: Extensive clinical trials have demonstrated that estrus will be suppressed in approximately 95% of the mares within three days; however, the post-treatment response depended on the level of ovarian activity when treatment was initiated. Estrus in mares exhibiting regular estrus cycles during the breeding season will be suppressed during treatment; these mares return to estrus four to five days following treatment and continue to cycle normally. Mares in winter anestrus with small follicles continued in anestrus and failed to exhibit normal estrus following withdrawal.

Response in mares in the transition phase between winter anestrus and the summer breeding season depended on the degree of follicular activity. Mares with inactive ovaries and small follicles failed to respond with normal cycles post-treatment, whereas a higher proportion of mares with ovarian follicles 20 mm or greater in diameter exhibited normal estrus cycles posttreatment. Regu-Mate® (altrenogest) Solution 0.22% was very effective for suppressing the prolonged estrus behavior frequently observed in mares during the transition period (February, March and April). In addition, a high proportion of these mares responded with regular estrus cycles post-treatment.

SPECIFIC USES FOR REGU-MATE® (altrenogest) SOLUTION 0.22%: SUPPRESSION OF ESTRUS TO: 1. Facilitate attainment of regular cycles during the transition period from winter anestrus to the physiological breeding season. To facilitate attainment of regular cycles during the transition phase, mares should be examined to determine the degree of ovarian activity. Estrus in mares with inactive ovaries (no follicles greater than 20 mm in diameter) will be suppressed but these mares may not begin regular cycles following treatment. However, mares with active ovaries (follicles greater than 20 mm in diameter) frequently respond with regular post-treatment estrus cycles.

2. Facilitate management of the mare exhibiting prolonged DOSAGE CHART: estrus during the transition period. Estrus will be suppressed in mares exhibiting prolonged behavioral estrus either early Approximate Weight Dose or late during the transition period. Again, the posttreatment in Pounds in mL response depends on the level of ovarian activity. The 770 7 mares with greater ovarian activity initiate regular cycles 880 8 and conceive sooner than the inactive mares. Regu-Mate® 990 9 (altrenogest) Solution 0.22% may be administered early in 1100 10 the transition period to suppress estrus in mares with inactive 1210 11 ovaries to aid in the management of these mares or to mares 1320 12 later in the transition period with active ovaries to prepare and schedule the mare for breeding.

3. Permit scheduled breeding of mares during the physiological breeding season. To permit scheduled breeding, mares which are regularly cycling or which have active ovarian function should be given Regu-Mate® (altrenogest) Solution 0.22% daily for 15 consecutive days beginning 20 days before the date of the planned estrus. Ovulation will occur 5 to 7 days following the onset of estrus as expected for nontreated mares. Breeding should follow usual procedures for mares in estrus. Mares may be regulated and scheduled either individually or in groups.

ADDITIONAL INFORMATION: A 3-year well controlled reproductive safety study was conducted in 27 pregnant mares, and compared with 24 untreated control mares. Treated mares received 2 mL Regu-Mate® (altrenogest) Solution 0.22% /110 lb body weight (2x dosage recommended for estrus suppression) from day 20 to day 325 of gestation. This study provided the following data: 1. In filly offspring (all ages) of treated mares, clitoral size was increased.

2. Filly offspring from treated mares had shorter interval from Feb. 1 to first ovulation than fillies from their untreated mare counterparts.

3. There were no significant differences in reproductive performance between treated and untreated animals (mares & their respective offspring) measuring the following parameters: • •

• • • • • • •

interval from Feb. 1 to first ovulation, in mares only. mean interovulatory interval from first to second cycle and second to third cycle, mares only. follicle size, mares only. at 50 days gestation, pregnancy rate in treated mares was 81.8% (9/11) and untreated mares was 100% (4/4). after 3 cycles, 11/12 treated mares were pregnant (91.7%) and 4/4 untreated mares were pregnant (100%). colt offspring of treated and control mares reached puberty at approximately the same age (82 & 84 weeks respectively). stallion offspring from treated and control mares showed no differences in seminal volume, spermatozoal concentration, spermatozoal motility, and total sperm per ejaculate. stallion offspring from treated and control mares showed no difference in sexual behavior. testicular characteristics (scrotal width, testis weight, parenchymal weight, epididymal weight and height, testicular height, width & length) were the same between stallion offspring of treated and control mares.

Dr. Henderson also noted that while there certainly are implications for metabolic disease in problem mares, there is little published evidence linking metabolic disease or thyroid function to specific effects on reproduction. She talked about some of the possible implications.

PPID

Approximately 20% of horses older than 15 have some evidence of pituitary pars intermedia dysfunction (PPID), which can be a confounding factor when considering reproductive health, and it can be difficult to separate the two.

“Increased glucocorticoid production can have adverse effects on ovarian function directly,” said Dr. Henderson, associate veterinarian at the Newmarket Equine Hospital in Suffolk, England. “Mares with PPID may also be prone to endometritis due to the potential for immune suppression.”

Insulin resistance, laminitis and pain are also seen in horses with PPID, and their management could affect the pregnancy. Evidence has shown that NSAIDs can inhibit ovulation and increase the risk of anovulatory hemorrhagic follicles. Pros-

taglandin function has also been known to be inhibited by NSAIDs.

Glucocorticoids

Early studies have shown that glucocorticoids can affect estrus behavior, inhibit ovulation and inhibit follicular development when used in the early estrous period.

A 2010 study revealed that dexamethasone caused a reduction in the ovulation rate to 40%. Prednisolone saw a smaller reduction, but the results were still significant when compared with controls.

Insulin resistance in mares has also been shown to increase the estrous cycle length from 20 to 26 days and increase progesterone concentrations.

“Approximately one-third of horses with PPID have insulin resistance,” Dr. Henderson said. “The stress response to glucocorticoids is to liberate energy resources. In humans, chronic exposure such as you would see in a horse with PPID has been associated with visceral adipose tissue expansion and inflammatory cytokine production.”

Hypothyroidism

Evidence is fairly limited on the effect of

Stallions In human literature, approximately 70% of cases of PPID are women, and it is associated with decreased fertility in men.

“We used to think PPID was more prevalent in mares than in geldings and stallions, but current data say that there is no sex predilection in horses,” Dr. Jennie Henderson said.

Not much has been written about metabolic syndrome in stallions, but obesity is associated with secondary hypogonadism in men. Insulin resistance can affect testosterone production, and therefore, semen production.

In stallions, hypothyroidism has potentially been associated with decreased libido and sperm count.

REFERENCES: Shoemaker, C.F., E.L. Squires, and R.K. Shideler. 1989.Safety of Altrenogest in Pregnant Mares and on Health and Development of Offspring. Eq. Vet. Sci. (9); No. 2: 69-72.

Squires, E.L., R.K. Shideler, and A.O. McKinnon. 1989.Reproductive Performance of Offspring from Mares Administered Altrenogest During Gestation. Eq. Vet. Sci. (9); No. 2: 73-76.

WARNING: Do not use in horses intended for food.

HUMAN WARNINGS: Skin contact must be avoided as Regu-Mate® (altrenogest) Solution 0.22% is readily absorbed through unbroken skin. Protective gloves must be worn by all persons handling this product. Pregnant women or women who suspect they are pregnant should not handle Regu-Mate® (altrenogest) Solution 0.22%. Women of child bearing age should exercise extreme caution when handling this product. Accidental absorption could lead to a disruption of the menstrual cycle or prolongation of pregnancy. Direct contact with the skin should therefore be avoided. Accidental spillage on the skin should be washed off immediately with soap and water.

INFORMATION FOR HANDLERS: WARNING: Regu-Mate® (altrenogest) Solution 0.22% is readily absorbed by the skin. Skin contact must be avoided; protective gloves must be worn when handling this product.

Effects of Overexposure: There has been no human use of this specific product. The information contained in this section is extrapolated from data available on other products of the same pharmacological class that have been used in humans. Effects anticipated are due to the progestational activity of altrenogest. Acute effects after a single exposure are possible; however, continued daily exposure has the potential for more untoward effects such as disruption of the menstrual cycle, uterine or abdominal cramping, increased or decreased uterine bleeding, prolongation of pregnancy and headaches. The oil base may also cause complications if swallowed. In addition, the list of people who should not handle this product (see below) is based upon the known effects of progestins used in humans on a chronic basis.

PEOPLE WHO SHOULD NOT HANDLE THIS PRODUCT. 1.

2.

3.

4.

5.

6.

7.

8.

Women who are or suspect they are pregnant.

Anyone with thrombophlebitis or thromboembolic disorders or with a history of these events.

Anyone with cerebral-vascular or coronary artery disease.

Women with known or suspected carcinoma of the breast.

People with known or suspected estrogen-dependent neoplasia.

Women with undiagnosed vaginal bleeding.

People with benign or malignant tumors which developed during the use of oral contraceptives or other estrogen-containing products.

Anyone with liver dysfunction or disease.

Shutterstock/Raymond Llewellyn

ACCIDENTAL EXPOSURE: Altrenogest is readily absorbed from contact with the skin. In addition, this oil based product can penetrate porous gloves. Altrenogest should not penetrate intact rubber or impervious gloves; however, if there is leakage (i.e., pinhole, spillage, etc.), the contaminated area covered by such occlusive materials may have increased absorption. The following measures are recommended in case of accidental exposure.

Skin Exposure: Wash immediately with soap and water.

Eye Exposure: Immediately flush with plenty of water for 15 minutes. Get medical attention.

If Swallowed: Do not induce vomiting. Regu-Mate® (altrenogest) Solution 0.22% contains an oil. Call a physician. Vomiting should be supervised by a physician because of possible pulmonary damage via aspiration of the oil base. If possible, bring the container and labeling to the physician.

CAUTION: For oral use in horses only. Keep this and all medication out of the reach of children.

Store at or below 25°C (77°F).

NADA# 131-310, Approved by FDA. HOW SUPPLIED: Regu-Mate® (altrenogest) Solution 0.22% (2.2 mg/mL).

Each mL contains 2.2 mg altrenogest in an oil solution.

Available in 1000 mL plastic bottles. * US Patents 3,453,267; 3,478,067; 3,484,462 Manufactured by: DPT Laboratories, San Antonio, TX 78215 Distributed by: Intervet Inc., Millsboro, DE 19966

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Issue 11/2016 | ModernEquineVet.com

For Dr. Megan Hays, equine veterinarian at B.W. Furlong & Associates, it didn’t take long to notice the benefits of running ImproMed’s Equine practice management software. Her work is remarkably efficient, whether in the hospital or in the field. By having all the information and tools at her fingertips through a complete mobile edition, treatment plans and easy-to-use cloud-based apps, she is able to provide better patient care with maximized profitability. Plus, with ImproMed’s best-in-class support and training, she can focus on what Imp matters - practicing better medicine.

reproduction

thyroid dysfunction on pregnancy in mares. It can be quite hard to diagnose, as multiple factors can cause variations in resting T3 and T4 concentrations. Some reports have suggested that hypothyroid mares may have irregular or absent estrous cycles.

“However, thyroidectomy did not have an effect on estrous cycles or fertility in experimental cases,” Dr. Henderson noted. “Supplementing broodmares who had low resting T4 concentrations was common for some time on stud farms, but when the practice was evaluated there had not been significant associations between pregnancy rates in supplemented vs non-supplemented mares.”

Dr. Henderson feels that there may be some role for thyroid supplementation for barren mares prior to covering. However, the potential role may be a result of horses that are assumed to be hypothyroid but who actually have metabolic syndrome. Supplementation with thyroid hormones has been suggested as a treatment for metabolic syndrome to reduce obesity and to increase insulin sensitivity, which can increase the chance for successful pregnancy.

BCS

Mares are naturally more insulin resistant while pregnant, but obe-

Time Management Studies have shown that obesity can affect the cyclicity of mares, which can result in marked seasonal anovulatory periods and prolonged interovulatory intervals.

When scheduling obese mares for cover that are receiving treatment, be aware that the mares might come back into season faster than expected. sity and diet may have more of a detrimental effect than they would in a nonpregnant animal.

“Feeding a diet higher in starch compared with a fat and fiber-based diet has been associated with a significantly higher glycemic response in pregnant mares vs nonpregnant horses,” Dr. Henderson said. “We tend to focus on obesity and overnutrition, but undernutrition can also have a significant effect on

pregnancy and the neonatal foal.”

One study from 2008 noted that acute maternal nutrient restriction during mid-gestation resulted in foals with enhance beta cell responsiveness, exaggerated HPA activity, and reduced birthweight. A more recent study looked at mares maintaining a low body condition during pregnancy found reduced insulin sensitivity and a reduced beta cell response in mares, which is a feature of diabetes mellitus.

“We don’t detect much diabetes mellitus in horses, but features of the condition in humans, such as some the hormones produced during pregnancy, can decrease insulin sensitivity,” she explained.

“Progesterone has been suggested to antagonize insulin, and women with gestational diabetes tend to have a lower prepregnancy insulin sensitivity. That may be something we see in our mares who have decreased insulin sensitivity before becoming pregnant.”

Dr. Henderson believes that metabolic disease should be in the back of the veterinarian’s mind when evaluating a problem mare. The potential for metabolic disease to cause adverse effects on the fetus, neonate and foal later in life is coming into focus. Control and/or management may be indicated throughout breedMeV ing season and pregnancy.

For more information: McGowan TW, et al. Prevalence, risk factors and clinical signs predictive for equine pituitary pars intermedia dysfunction in aged horses.

Equine Vet J. 2013;45(1):74-79.

Lima, et al. Does clinical treatment with phenylbutazone and meloxicam in the pre-ovulatory period influence the ovulation rate in mares? Reprod Domest Anim. 2015;50(5):771-775.

Ferris RA, McCue PM. The effects of dexamethasone and prednisolone on pituitary and ovarian function in the mare. Equine Vet J. 2010;42(5):438-443.

Sessions DR, et al. Development of a model for inducing transient insulin resistance in the mare: Preliminary implications regarding the estrous cycle. J Anim Sci. 2004; 82:2321-2328.

Ousey, et al. The effects of maternal health and body condition on the endocrine responses of neonatal foals. Equine Vet J. 2008;40(7):673-679.

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News notes

Where Rules Matter Most: Managing Horse's Medication Blood levels of NSAIDs in competition horses would have to meet certain standards.

Click here to download a free owner handout. stay in compliance, she explained.

As with any prescription medication, prior to use, a veterinarian should perform a physical examination and review the horse’s medical history. A veterinarian should advise horse owners to look for signs of potential drug toxicity. As a class, NSAIDs may be associated with gastrointestinal, hepatic and renal toxicity. Use with other NSAIDs, corticosteroids or nephrotoxic medication should be avoided. EQUIOXX has not been tested in horses less than 1 year of age or in breeding horses, or pregnant or lactating mares. For additional information, please refer to the prescribing information or visit www.equioxx.com.

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Shutterstock/AsyaPozniak

Although prohibited substances should be avoided in equestrian competition, there can be confusion about allowed therapies, such as non-steroidal antiinflammatory drugs (NSAIDs).

Timing and dosage can vary between what is allowed for a particular show and common barn and at home or hospital. Before giving a horse any medication, check the rule book for the show where the horse will compete. Most associations use the U.S. Equestrian Federation (USEF) Equine Drugs and Medication Rules.

For example, NSAIDs, used to treat conditions such as the pain and inflammation associated with equine osteoarthritis, usually have restricted doses based on allowed blood levels at the time of competition as well as withdrawal time recommendations.

“Managing joint health is often an ongoing process — and it doesn’t stop just because you have a show or competition,” said Hoyt Cheramie, DVM, MS, DACVS, Senior Manager, Merial Large Animal Veterinary Services. “Veterinarians may suggest an NSAID, but it’s important to give the correct dose, especially when showing.”

With the recent edition of a tablet formulation, there might be confusion about when firocoxib (Equioxx, Merial), can be given to assure compliance with each association’s rules. “While Equioxx Tablets are a great option for routine use in non-competition settings, equestrians need to be aware that they are labeled for 800 to 1,300 lbs. This may mean they aren’t the best option for some competition horses,” she said. “The approved dose and withdrawal time of oral firocoxib to ensure accepted blood level requirements for showing is 0.1 mg/kg given a minimum 12 hours before showing. Thus, for the purposes of competition drug testing, any horse weighing less than 1,254 lbs receiving the 57 mg tablet is receiving a higher dosage than competition rules allow.”

When giving any NSAID, an accurate body-weight assessment is necessary for proper dosage. Over dosing can cause overages of allowed levels, while under dosing can result in a less than effective result.

When showing, the paste or injection formulations of Equioxx offer the most accurate dosing to

For more information: United States Equestrian Federation. Drugs and Medications Guidelines. 2015:2‐3. Available at: https://www.usef.org/documents/drugsMeds/2016/2016Guidelines.pdf

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infectious disease

Antimicrobial Prescribing Habits f o r

The decision to use reserved anti-

biotics is rarely informed by a culture and sensitivity results, according to a new study. The researchers recommended that equine veterinarians modify their prescribing

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H o r s e s

habits to use fewer reserved antimicrobials, according to a recent study.

In a retrospective cohort study, Dr. Claire Welsh of the Equine Clinical Sciences Division, School of Veterinary Medicine, University

of Glasgow, United Kingdom, and her colleagues wanted to determine how often veterinarians prescribed the reserved antimicrobials: enrofloxacin (Baytril, Bayer), ceftiofur (Excede, Zoetis) and clarithromy-

Editorial Credit: thomas koch / Shutterstock.com

cin. The researchers said that they did the study because there have not been many studies that looked at this important issue: Inappropriate use of antimicrobials is known to be a strong driver of resistance, they said. However, “what constitutes inappropriate use in equine medicine is not well defined,” they wrote.

They hoped that their study would help veterinarians and public health officials understand what is being done today to identify areas of improvement and help the industry adopt best practices.

“Links between antimicrobial resistance in companion animals and man have been postulated, with some evidence to support them,” the researchers wrote. “Given the frequency of close contact between horses and people, understanding the threat posed to each species from the transfer of bacterial resistance (genes or organisms) from the other is essential.”

The researchers analyzed the electronic medical records of 116,600 horses treated in nine first opinion equine practices in the United States and Canada between 2006 and 2012.

Some veterinary surgeons were more likely to prescribe reserved antimicrobials than others.

Antibiotics were prescribed in 207,325 cases, of which 7.5% were for reserved antimicrobials. Of these, 9,856 (4.8%) were for ceftiofur, 5,016 (2.4%) were for enrofloxacin and 664 (0.3%) were for clarithromycin.

Of all antimicrobials prescribed, 44.7% were done during a period of hospitalization, and 46.6% of reserved antimicrobials were prescribed during hospitalization.

Ceftiofur and enrofloxacin were both significantly associated with hospitalization. Only 3.3% of anti-

microbial prescriptions were associated with a culture and sensitivity result, with only slightly higher percentage of reserved antimicrobials being informed by culture and sensitivity (5.2%).

There were fluctuations in the use of individual antimicrobials with enrofloxacin and clarithromycin prescriptions apparently on the rise. A strong seasonal association between clarithromycin and summer months was found, thought to be due to its use for Rhodococcus equi infections in foals. The increasing use of this drug in the latter years of the study may indicate that it is superseding erythromycin as the macrolide of choice in these foals.

Veterinary surgeons in certain practices were more likely to prescribe reserved antimicrobials than in other practices. The low uptake of culture and sensitivity testing may be due to a desire to avoid additional expense for the client and the delay in obtaining results; however, this is especially important in new infections and where use of reserved antimicrobials is being considered.

MeV

For more information: Welsh CE, Parkin TDH, Marshall JF. Use of large-scale veterinary data for the investigation of antimicrobial prescribing practices in equine medicine. Equine Vet J. 2016 Oct. 5 [Epub ahead of print]). http://onlinelibrary.wiley.com/doi/10.1111/evj.12638/full

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ModernEquineVet.com | Issue 11/2016

11

Infectious diseases

FDA Issues

Antibiotic Resistance Monitoring Report B y

M a r i e

R o s e n t h a l ,

M S

Shutterstock/aboikis

Overall antimicrobial resistance to organisms

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found in food animals continues to remain low for most human infections, and there have been measurable improvements in resistance levels in some important areas, according to the recently released 2014 National Antimicrobial Resistance Monitoring System (NARMS) Integrated Report.

NARMS monitors foodborne bacteria to determine whether they are resistant to various antibiotics used in human and veterinary medicine. Specifically, NARMS screens nontyphoidal Salmonella, Campylobacter, Escherichia coli and Enterococcus.

The FDA, the CDC and the Department of Agriculture established NARMS in 1996 to track antibiotic resistance in foodborne bacteria and monitor trends in antimicrobial resistance among foodborne bacteria collected from humans, retail meats and food-producing animals. This helps the FDA to make data-driven decisions on the approval of safe and effective antimicrobial drugs for animals.

The prevalence of Salmonella in both retail chicken meat (9.1%) and retail ground turkey (5.5%) was at its lowest level since retail meat testing began in 2002, according to the report. The prevalence of Campylobacter in retail chicken meat samples has declined over time to 33%, also the lowest level since testing began.

Salmonella and Campylobacter are the leading bacterial causes of food-

borne illness in humans. About 80% of human Salmonella isolates are not resistant to any of the tested antibiotics. Resistance for ceftriaxone, azithromycin and ciprofloxacin in human nontyphoidal Salmonella isolates remained below 3%.

Overall, ceftriaxone resistance continued to decline in nontyphoidal Salmonella from all NARMS sources, with the exception of retail turkey meat isolates, where it rose slightly. This was paralleled by a decline in ceftriaxoneresistant E. coli from retail chicken meat and Salmonella isolates from cattle carcasses collected at processing plants.

Among all Salmonella serotypes, the percentage of human

isolates resistant to at least ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracyclines continued a steady decline to 3.1%, the lowest since testing began in 1996 (8.7%). Similarly, resistance in cattle PR/HACCP Salmonella typhimurium isolates declined sharply from 67% in 2009 to 7% in 2014, the lowest level since this testing began in 1997.

With the exception of five isolates in the past 10 years, no resistance has been detected in Enterococcus bacteria isolates to three important drugs: daptomycin, linezolid and vancomycin.

The picture isn't all rosy: • Decreased susceptibility to ciprofloxacin has increased in human and cattle Salmonella

serotype Dublin isolates since 2003, with slight declines since 2012. Although the incidence of human Salmonella Dublin infections is relatively low, it can cause invasive disease and ranks among the top four serotypes isolated from retail ground beef and cattle.

• Multidrug-resistant Salmonella from turkey samples has increased from 27% to 41% over the past 10 years.

• High and increasing levels of ciprofloxacin resistance were detected in Campylobacter jejuni from human (6.7%) and chicken samples (28%) in 2014, and remained above 35% in Campylobacter coli from humans.

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Click here to watch video ModernEquineVet.com | Issue 11/2016

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technician update

Caring for an Infected Wound

By Heather R. Hopkinson, RVT VTS-EVN

Courtesy of Ms. Hopkinson, NCS-VTH

On June 13 2010, an 8-year-old Holsteiner mare was admitted to the North Carolina State’s Veterinary Teaching Hospital. The mare, who weighed 593 kgs, presented with a penetrating wound of one week duration over her caudal thoracic spine.

The wound was first noted on June 6, when the mare came in from turnout overnight. The wound was located on the caudal thoracic spine and initially appeared fresh with clean edges. The origin of the injury was unknown but the owner suspected an overhanging tree branch. The referring veterinarian cleaned and flushed the wound and placed five simple interrupted

Top: Ultrasound of wound before wound cleaning. Bottom: Looking for draining tracts post wound cleaning

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Issue 11/2016 | ModernEquineVet.com

sutures on June 6. The mare was administered 1 g of phenylbutazone twice daily for three days and then 1 g/ day until admission and trimethoprim sulfamethoxazole orally for five days. Silver sulfadiazine ointment was applied to the wound daily. The wound appeared to be healing until June 11, when it was noted that there was circumferential swelling and a malodorous, purulent discharge draining from the wound. At that time, the referring veterinarian administered one IV dose of gentamicin and flushed the wound with saline and gentamicin. The owner began flushing the wound with betadine solution and administered naxcel intramuscular once daily. The wound had not improved by June 13, and had a foul odor. It was at this time that mare was referred to NCSU-VTH. A fourth-year student, intern and senior clinician performed a complete physical exam, which was normal with a rectal temperature of 100.2° F, heartbeat of 48 beats per minute (bpm), 28 respirations per minute (rpm), mucous membranes were pink with a capillary refill time of less than 2 seconds. No murmurs or arrhythmias were auscultated, and the lungs were clear bilaterally. Normal borborygmi was auscultate in all four quadrants.

The wound measured approximately 6X3 cm and was located on the caudal thoracic spine. There was a purulent, malodorous discharge oozing from the wound, and the edges were necrotic. The five sutures were removed, and the wound was cleaned using a betadine solution. Blood work was performed with a few abnormalities noted including a fibrinogen 500 mg/dL and a white cell count (WBC) of 14.20 x 10^3/UL. The complete blood cell count (CBC) findings of increased WBC and fibrinogen are both consistent with chronic inflammation.

An ultrasound examination revealed an abscess 3 cm cranial to the wound, measuring 3.5 cm deep with an associated drain-

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

ModernEquineVet.com | Issue 11/2016

*American Association of Equine Veterinary Technicians and Assistants

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Courtesy of Ms. Hopkinson, NCS-VTH

technician update

ing tract that can be followed to the hemorrhage was noted during the wound. Adjacent to the focal hyprocedure. The wound was packed poechoic area, an irregular border of and a stent bandage was applied. the dorsal spinous process was notThe mare recovered from sedation ed. Due to the irregular border of the and was walked backed to her stall. dorsal spinous process, radiographs Pre-surgery, the mare was startwere recommended, which showed ed on IV antibiotics, which consistan open, comminuted short oblique ed of penicillin and gentamicin. She fracture of a caudal thoracic spinous was also started on oral phenylbutaStanding debridement of sequestrum process of thoracic vertebrae #16 zone for pain. Post-surgery, she was necrotic bone that was removed by (T16). Surgery was recommended to also started on oral metronidazole standing surgery. remove the sequestrum. and continued on her normal dose At this time a 14-gauge 5.25 inch over the needle IV of oral Regu-Mate (Merck). catheter was placed in the mare’s left jugular vein, and On the morning of June 14, the mare appeared to secured in place with suture (2-0 Ethilon on a straight be bright and alert. She did not seem to be in any pain needle). The mare was sedated using detomidine and and was eating and drinking normally. Her physical exbutorphanol intravenously. A constant rate infusion of amination was within normal limits. The bandage was detomidine and butorphanol in a 250 mL bag of saline changed and the wound appeared clean and with no was administered, dosed to effect. The skin around the odor associated with the wound of the bandage. The wound was clipped and then prepped and draped uswound was dÊbrided with dilute betadine soaked gauze ing sterile technique. The original wound, measuring and then flushed with 1 L of dilute betadine. A diluted 6 cm, was extended cranially 4 cm using a #10 scalpel betadine-soaked gauze was placed into the deep pocket blade. The epaxial muscles were visualized and sharp where the fractured bone was removed and a wet to dissection with Mezenbaum scissors was performed dry bandage was placed. to isolate the dorsal spinous process of T16. The bony On the morning of June 15, the mare appeared to be sequestrum of the dorsal spinous process was isolated bright and alert. She did not seem to be in any pain and and extracted using sharp dissection. The necrotic was eating and drinking normally. Her physical examipiece of bone measured approximately 3.5 cm in height nation was within normal limits. Lateral radiographs and 2 cm wide at its dorsal base and was triangularly were repeated on the wound. She was sedated at 11:30 shaped. The remaining necrotic bone on the dorsal am using xylazine and detomidine. The radiographs spinous process was dÊbrided using Ronguers. The epshowed that the remaining portion of T16 showed no axial muscle and dorsal spinous ligament adjacent to signs of fractures or bone lysis. A small crest of bone the bony seqestrum was necrotic and debrided using extended from the cranial aspect of the remaining porsharp dissection with Mezenbaum scissors. Moderate tion of T16. She was redosed with xylazine. Her wound 16

Issue 11/2016 | ModernEquineVet.com

Teaching Points This case required many nursing skills. For all cases admitted to the NCSU-VTH, baseline vital signs and a history are obtained. All patients that are admitted to the NCSUVTH receive a physical examination and are assigned a pain score at least twice a day.

I was present when this patient was admitted to the NCSU-VTH, and the advanced skills I performed were essential. I placed the IV catheter, clipped and cleaned around the wound, maintained a sterile field and assisted with the surgery, and performed multiple physical examinations. I also assisted with radiographs and administered intramuscular, IV and oral medications.

Shutterstock/nelelena

was palpated, and additional bone was removed with Rongeurs. 11 pieces of 1-2 mL size were removed from the dorsal process. The wound was flushed with copious amounts of 1% betadine solution and then packed with saline soaked gauze covered by lap sponges formed into a stent bandage. All of her medications remained the same except her penicillin was reduced.

On the morning of June 16, the mare had no significant changes overnight. She did seem to be reluctant to eat her grain but was eating her Timothy hay well.

She also produced less manure than previous days. Her physical examination was within normal limits. A bandage change was also performed. The lap sponges and gauze were removed, and the entire wound was flushed with dilute betadine solution. It appeared to be making progress, and the caudal (more superficial) aspect of the wound appeared to have a good amount of healthy granulation tissue forming, and the deep pocket just dorsal to the dorsal spinous process of T16 speared to be filling in. The tissue looked healthy and no foul odor was noticed. The deep pocket was débrided using a curette. A single saline soaked gauze was packed into the deep pocket and the wet to dry tent bandage was replaced over the wound. All of her medications remained the same except oral ranitidine was added to prevent ulcer formation and her metronidazole dose was discontinued because there were no signs of infection and the mare had been reluctant to eat.

Over the next several days the mare’s wound was lavaged and a bandage change was performed. The wound had a moderate amount of exudative cream to yellow color material attached to the removed bandage. It had a slight foul odor. A small amount of yellow necrotic tissue associated with the dorsal spinous ligament was trimmed away using a curette and a scalpel. The wound was measured and was 13 cm long by 5 cm wide by 4 cm deep. The wound surface on the shallow aspect of the wound is covered with dark pink to red granulation tissue. The deep pocket over the remaining portion of the dorsal process of T16 appears to be granulating in from the sides but appears to be the same depth. Small vessel growth can be seen throughout the superficial tissue. Overall the wound appeared to be improving. One week post-surgery, culture results from the necrotic bone revealed a growth of three different bacterial organisms, a multidrug resistant Enterobacter cloacae, Escherichia coli and a Bacteroides sp. However, based on the theory that all necrotic and infected tissue were removed at surgery, and how well the wound looked at the time of culture results (clean, non-odorous, no excessive discharge) it was decided to place the mare on an oral broad-spectrum antibiotic, TMP-SMX.

Salt paste given orally every six hours was also added to her regimen to promote water intake. Eleven days post-surgery, the phenylbutazone was discontinued but the mare’s pain level was closely monitored. The bandage was changed daily and the wound continued to improve as granulation tissue gradually filled in the deep pocket where the fractured bone had been removed. The wound was débrided as needed to stimulate growth of granulation tissue and to remove any areas that started to look necrotic.

The mare was discharged on June 28 with continued TMP-SMX, as well as instructions on how to care for the bandage and what to look for if the wound became infected. She was continue on a normal diet and placed on stall rest until her wound has filled in with granulation tissue. The prognosis for her recovery was good.

Epithelization of the wound would likely take 2-3 months, and further maturing of the wound will be necessary after this time for increased strength before it is able to handle the pressure of a saddle and rider. It was possible that back soreness will be a concern. MeV

About the author

Heather, who is an equine veterinary technician at the North Carolina State University College of Veterinary Medicine, received her VTS in Equine Veterinary Nursing in 2011 and is the current president of the Academy of Equine Veterinary Nursing Technicians. She is also the current vice president of the North Carolina Association of Veterinary Technicians.

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