Medicine

Pituitary Pars Intermedia Dysfunction (PPID), otherwise known as Equine Cushing’s Disease and Equine Metabolic Syndrome (EMS or insulin resistance) are common endocrinopathic diseases of horses. Clinical symptoms of PPID include abnormal hair coat shedding patterns (hypertrichosis), laminitis, weight loss or loss of topline muscle mass, recurrent common infections including foot abscesses, tooth root abscesses or dermatitis, abnormal sweating patterns and fertility issues in mares. While PPID may effect up to 30% of horses of 15 years of age, EMS often presents in younger horses. These horses tend to be easy keepers,” overweight (either generalized obesity or regional fat deposits) and may suffer from pasture associated episodes of laminitis. Testing for both PPID involves measuring plasma ACTH concentrations. These measurements can be measured as baseline values or after administration of a TRH (thyrotropin releasing hormone) test. Testing for EMS requires measuring blood insulin, glucose and sometimes leptin concentrations after an overnight fasting. Additionally, an oral sugar test can be utilized to detect this disease.

– Gastrointestinal diseases that commonly affect horses include choke (or esophageal obstruction), acute colic, gastric ulcers and diarrhea. Choke is considered a medical emergency as these horses are unable to swallow food appropriately and at risk for aspiration pneumonia. Horses with choke will show signs of distress, drooling and nasal discharge consisting of saliva and feed material. An esophageal obstruction is typically relieved by sedation, passing a nasogastric tube and gentle lavage until the obstruction is cleared. More serious forms of choke may require hospitalization and treatment with intravenous fluids, and antibiotics.

– Colic is the term given to horses showing signs of abdominal pain, most commonly related to problems associated with the gastrointestinal tract. Causes of acute colic include gas colic, intestinal obstruction (such as an impaction or displacement), strangulating lesions (where the blood supply to the bowel is compromised) and inflammatory conditions such as enteritis, colitis or peritonitis. In order to diagnose the cause of colic and determine the correct course of therapy, a thorough physical examination is performed along with rectal palpation, routine blood testing (CBC and blood biochemistry), abdominal ultrasound and an abdominocentesis. Most forms of colic typically respond to medical management; however, some forms may require surgery.

– Equine Gastric Ulcer Syndrome (EGUS) can be associated with low grade, chronic colic where episodes of colic are frequently noted in association with feeding. Other symptoms of EGUS include poor performance, behavioral issues (aggression, “girthy” behavior or cribbing), weight loss and poor coat. A definitive diagnosis of equine gastric ulcer syndrome can ONLY be made with gastroscopy, an endoscopic examination that allows visualization of the interior lining of the stomach and pylorus.

– Inflammatory conditions such as enteritis, colitis or peritonitis can also cause colic. These conditions can be associated with infectious diseases such as parasitism, Equine Coronavirus, Salmonellosis or Clostridium difficile or perfringens infections. Diagnostic evaluation of inflammatory GI diseases includes a thorough physical examination, rectal palpation, abdominal ultrasound, routine blood work and specific fecal testing to identify enteric (GI) pathogens. Horses with inflammatory GI diseases may require intensive medical care including intravenous fluid therapy, plasma transfusions and therapies aimed to limit endotoxemia or prevent laminitis.

Liver disease in horses can be caused by ingestion of toxic plants, viral infections associated with administration of blood products, bacterial infection, hepatobiliary stones (bile stones), inappropriate fat accumulation (hepatic lipidosis) and cancer. Horses with liver disease may show signs of weight loss, low grade colic, decreased appetite, jaundiced mucous membranes or eyes and abnormal behavior. Evaluation for a horse with suspected liver disease includes a complete physical examination, routine blood work and additional blood tests to evaluate liver function, ultrasound examination of the liver and liver biopsy.

Disease of the urinary system in horses include lower and upper urinary tract infections, bladder stones (cystic calculi) and renal disease. Horses with diseases of the urinary system may present with signs of straining when urinating, urine dribbling (or dysuria), colic signs, blood tinged urine or hemorrhage noted during urination, decreased appetite, lethargy and excessive drinking and urination. Diagnostic evaluation of a horse with a suspected problem of the lower urinary system may include rectal palpation and trans-rectal ultrasound of the bladder, catheterization of the bladder to collect urine for analysis and endoscopic evaluation to view the inside of the bladder (cystoscopy). If renal disease is suspected, diagnostics may include routine blood work and urinalysis, ultrasound examination of the kidneys and in some instances, renal biopsy.

Disease of the respiratory system in horses can range from sinusitis, upper airway dysfunction, guttural pouch disease, bacterial pneumonia, viral respiratory infections and allergic lower airway diseases (such as heaves or inflammatory airway disease). Diagnostic evaluation of the respiratory system may include a thorough physical examination with a rebreathing exam, upper airway and guttural pouch endoscopy and imaging including ultrasound or radiography. Additionally, samples may be collected through a tracheal wash for microscopic examination and culture or a bronchoalveolar lavage to characterize cell populations.

Neurologic diseases in horses may have a wide range of presentations depending on the causative agent. Clinical signs associated with neurologic diseases in horses include ataxia or incoordination, tripping or stumbling, falling or circling to one direction, weakeness, asymmetrical muscle atrophy, dysphagia (difficulty eating and swallowing), incontinence or urine dribbling, head shaking, behavioral changes, inability to stand and even seizures. Sometimes mild neurologic deficits may even be confused with lameness. Evaluation of a horse with neurologic disease should always begin with a thorough neurologic examination, evaluating the horse’s deficits in mentation, cranial nerve function and gait. Once the lesion is localized, additional diagnostics may include collection and examination of cerebral spinal fluid, testing for infectious diseases and diagnostic imaging including cervical radiography, CT and MRI.

Infectious diseases in horses may cause symptoms including fever, lethargy and decreased appetite, purulent (snotty) nasal discharge, coughing, increased respiratory effort or respiratory distress, diarrhea and neurologic abnormalities. In efforts identify an infectious disease, a thorough physical examination is performed along with routine blood testing to identify the body systems affected. At this point, additional testing for specific pathogens may be performed. Horses with suspected infectious diseases may be isolated from other horses and even kept in limited to contact to people as some infectious disease are zoonotic (contagious to people).

Certain medical conditions may negatively impact performance. Evaluation of the horse at rest, during exercise and after exercise may be necessary to determine the source of poor performance. Medical causes of poor performance in horses can include anhydrosis (failure to sweat), inflammatory airway disease (an allergic airway disease), cardiac abnormalities such as murmurs or arrhythmias, and muscle diseases including Polysaccharide Storage Myopathy. Diagnostic testing for exercise intolerance may include a terbutaline sweat test, bronchoalveolar lavage, echocardiogram, an ECG at rest and under exercising conditions and evaluations of plasma muscle enzyme activities before and after exercise.