The Horse

MAR 2019

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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A9 The Horse | AAEP Wrap-Up March 2019 YOUR GUIDE TO THE 2018 AAEP CONVENTION Doppler Ultrasonography to Evaluate Suspensory Ligament Branches Scientists tested if power Doppler ultra- sonography (which is more powerful and sensitive than traditional color Doppler) could help diagnose suspensory ligament branch (SLB) abnormalities in horses. They evaluated eight horses with lameness localized to the SLBs and five nonlame horses with SLB lesions using power Doppler ultrasonography. Two independent readers found that power Doppler effectively detected abnormal le- sions in SLBs in both lame and nonlame horses. However, Sutter said, grading scores were higher in lame limbs. He said this suggests power Doppler could help vets determine the significance of SLB abnormalities. Compression and Nerve Blocks Using nerve blocks to find the source of pain in lame horses comes with caveats: The analgesic can spread following injec- tion, numbing nerves farther up the limb. In these cases the lameness might resolve because other structures were numbed inadvertently, leading to inaccurate diagnoses. University of Copenhagen researchers examined whether applying a compres- sion bandage to the pastern before ad- ministering a palmar digital nerve (PDN) block to numb the rear portion of the foot would solve this problem. They injected radiodense contrast material in the areas they'd given anes- thetic for a PDN to nine horses on two occasions—once with a 5-centimeter-wide compression bandage on the pastern and once with no bandage (controls). They took radiographs post-injection to moni- tor how far the contrast material spread. They found that the compression ban- dage reduced upward diffusion and kept the contrast material at the injection site. Visual Lameness Exam Accuracy Researchers from Belgium and the U.K. explored how reliable vets are at seeing lameness. They created 3D anima- tions of a horse trotting with 0 to 60% movement asymmetry and asked 89 vets with varying expertise to determine if the horse was lame and in which limb. They found that: ■ Experience did not impact accuracy; ■ Caseload did not significantly impact if vets correctly identified lame or sound horses, except with forelimb lameness; the higher the caseload, the more likely they were to identify it correctly; ■ Vets were significantly more likely to correctly classify horses as sound in the forelimb (average 72% correct) than sound in the hind limbs (average 28% correct), meaning participants often saw hind-limb lameness where there was none; and ■ In subtle lameness cases vets often missed forelimb lameness and classi- fied the incorrect hind limb as lame. Sutter said the software used could be a possible future model for veterinarian self- evaluation and systematic training for low-grade lameness detection. PNAG Vaccine for Pregnant Mares Protects Foals From R. Equi The first study MacKay presented focused on Rhodococcus equi, one of the leading causes of pneumonia in young foals. In seeking a vaccination option, a multi-institution research team found that vaccinating mares against a specific and common surface antigen, poly-N- acetyl glucosamine (PNAG), prior to foaling offered protection to their foals. MacKay said the results are promising for prevent- ing R. equi, as well as other diseases, in horses, humans, and other species. Ice Boot Therapy: Method Matters In two studies investigators from Penn Vet, Cornell University, and North Carolina State University looked at how commercial cryotherapy (cold therapy) sleeves are used (Study 1) and whether they could overcool tissues (2). In Study 1 researchers found that horses' foot temperature dropped to 10 degrees Celsius (14 degrees Fahrenheit) in about 45 minutes using ice sleeves. In Study 2 investigators found soft tissue injury from overcooling in 7% (20/285) of horses treated with cryotherapy using an ice boot. Overcooling results from leaving the boot on for too long, MacKay said. He said the studies show that ice therapy sleeves are effective for cooling the laminae. However, careful observa- tion is important to prevent side effects caused by making the horse's tissue too cold for too long, MacKay said. Parvovirus Found in Vaccine Serum A Cornell-led research team identified a new liver-disease-causing virus after a Nebraska horse died 65 days after routine vaccination. The team found equine parvovirus-hepatitis (EqPV-H) in both the deceased horse's liver and the tetanus antitoxin he had received. The researchers tested serum samples of 100 horses submitted to the New York State Animal Health Diagnostic Center for nonclinical reasons. Thirteen tested positive for the virus, meaning apparently healthy horses had contracted it at some point and "subclinical (without clinical signs) cases are common," MacKay said. EqPV-H is the most recent addition to the list of viruses found to cause liver dis- ease in horses. Parvoviruses are relatively resistant to heat treatment, said MacKay, which might explain how they occasion- ally survive in tetanus antitoxin. Can SAA, CRP Testing Identify EPM? A Penn Vet team investigated whether blood testing for inflammatory markers such as serum amyloid A (SAA) and C- reactive protein (CRP) could offer another avenue to help identify equine protozoal myeloencephalitis (EPM) cases. These two acute phase proteins increase or decrease in response to inflammation in the body, helping vets detect certain infections and differentiate between infectious and non- infectious causes of some diseases. The scientists compared SAA and CRP levels in EPM and wobbler syndrome horses and found no differences. "So far, acute phase proteins have no value in differentiating among equine central nervous system diseases," MacKay said. Eastern U.S. Protozoal Coinfection Concurrent infection by multiple proto- zoa is unlikely the cause of EPM cases in the Eastern United States, reported one Oregon State University researcher. Sarcocystis neurona and Neospora hughesi are known to cause EPM. How- ever, not all horses exposed to these parasites develop EPM. Researchers theorized that another protozoon, Toxo- plasma gondii, might play a role in EPM by increasing S. neurona and N. hughesi infection severity. In their study of horses diagnosed with

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