Chapter Equine
Introduction
Horses in Australia face a range of health challenges due to environmental factors, management practices, and genetic predispositions. This paper provides an overview of the most prevalent equine diseases and disorders in Australia, focusing on infectious diseases, genetic disorders, and environmental conditions. By understanding these conditions and their management, veterinarians and horse owners can better safeguard equine health.
Common Equine Diseases and Disorders
1. Infectious Diseases
Equine Influenza:
- Etiology: Equine influenza virus (EIV), an Orthomyxovirus.
- Clinical Signs: Fever, nasal discharge, cough, lethargy, anorexia.
- Diagnosis: PCR, ELISA, virus isolation, clinical signs.
- Treatment: Supportive care, rest, anti-inflammatories, antibiotics for secondary infections, vaccination for prevention.
Strangles:
- Etiology: Streptococcus equi subsp. equi.
- Clinical Signs: Fever, nasal discharge, swollen and abscessed lymph nodes, difficulty swallowing, anorexia.
- Diagnosis: PCR, culture of nasal or lymph node discharge, clinical signs.
- Treatment: Antibiotics (controversial), supportive care, hot packing of abscesses, isolation to prevent spread, vaccination for prevention.
Hendra Virus:
- Etiology: Hendra virus (HeV), a Paramyxovirus.
- Clinical Signs: Fever, respiratory distress, neurological signs, lethargy, sudden death.
- Diagnosis: PCR, virus isolation, serology.
- Treatment: None specific; strict biosecurity measures, supportive care, vaccination for prevention.
Equine Herpesvirus (EHV):
- Etiology: Equine herpesvirus types 1 and 4.
- Clinical Signs: Fever, nasal discharge, cough, abortion in pregnant mares, neurological signs.
- Diagnosis: PCR, virus isolation, serology.
- Treatment: Supportive care, antiviral medications (acyclovir, valacyclovir), isolation, vaccination for prevention.
2. Genetic Disorders
Hyperkalemic Periodic Paralysis (HYPP):
- Etiology: Genetic mutation affecting sodium channels in muscle cells.
- Clinical Signs: Muscle twitching, weakness, paralysis, respiratory distress.
- Diagnosis: Genetic testing, clinical signs.
- Treatment: Low-potassium diet, medications (acetazolamide, hydrochlorothiazide), regular exercise.
Polysaccharide Storage Myopathy (PSSM):
- Etiology: Genetic mutation causing abnormal glycogen storage.
- Clinical Signs: Muscle stiffness, reluctance to move, sweating, muscle atrophy.
- Diagnosis: Genetic testing, muscle biopsy, clinical signs.
- Treatment: Low-starch, high-fat diet, regular exercise, management of stress.
Recurrent Exertional Rhabdomyolysis (RER):
- Etiology: Genetic predisposition, often associated with stress and excitement.
- Clinical Signs: Muscle pain, stiffness, sweating, dark urine, reluctance to move.
- Diagnosis: Clinical signs, elevated muscle enzymes (CK, AST), muscle biopsy.
- Treatment: Dietary management, regular exercise, medications (dantrolene, phenytoin).
3. Environmental Conditions
Laminitis:
- Etiology: Multifactorial, including excessive intake of soluble carbohydrates, obesity, endocrine disorders (e.g., PPID, EMS).
- Clinical Signs: Lameness, heat in hooves, digital pulse, reluctance to move.
- Diagnosis: Clinical signs, radiography, hoof testing.
- Treatment: Dietary management, pain relief (NSAIDs), hoof care, corrective trimming/shoeing, management of underlying conditions.
Colic:
- Etiology: Various causes, including gastrointestinal impaction, gas accumulation, torsion, enteritis.
- Clinical Signs: Abdominal pain, rolling, pawing, sweating, anorexia, decreased fecal output.
- Diagnosis: Clinical signs, rectal examination, ultrasound, blood tests, abdominal tap.
- Treatment: Pain relief (NSAIDs, opioids), fluid therapy, nasogastric intubation, surgical intervention if necessary.
Equine Gastric Ulcer Syndrome (EGUS):
- Etiology: Stress, high-grain diets, prolonged fasting, NSAID use.
- Clinical Signs: Poor appetite, weight loss, colic, poor performance, behavioral changes.
- Diagnosis: Gastroscopy, clinical signs.
- Treatment: Proton pump inhibitors (omeprazole), histamine receptor antagonists (ranitidine), dietary management, reducing stress.
Diagnostic Approaches
1. History and Physical Examination:
- Detailed history taking, including vaccination status, management practices, and environmental exposures.
- Thorough physical examination to identify clinical signs.
2. Laboratory Tests:
- Complete Blood Count (CBC) and Biochemistry Panel: To assess overall health and organ function.
- Serology and PCR: To confirm infectious diseases.
- Urinalysis: To evaluate kidney function and detect urinary tract issues.
3. Imaging Studies:
- Radiography and Ultrasound: For diagnosing musculoskeletal and internal organ conditions.
- Endoscopy: For diagnosing gastric ulcers and respiratory issues.
4. Specialized Tests:
- Genetic Testing: For hereditary disorders.
- Muscle Biopsy: For diagnosing muscle disorders.
Treatment Strategies
1. Supportive Care:
- IV fluids for hydration and electrolyte balance.
- Pain management using NSAIDs and opioids.
- Nutritional support and dietary management.
2. Specific Treatments:
- Antibiotics and Antivirals: For bacterial and viral infections.
- Antitoxins and Antivenoms: For toxin exposures.
- Surgical Interventions: For severe gastrointestinal and musculoskeletal disorders.
3. Preventive Measures:
- Regular vaccinations and parasite control.
- Genetic screening for breeding programs.
- Owner education on environmental hazards and preventive care.
Conclusion
The health of horses in Australia is impacted by a variety of infectious diseases, genetic disorders, and environmental conditions. Effective management requires a comprehensive understanding of these common health issues, including their diagnosis and treatment. By adopting preventive measures and ensuring timely medical intervention, veterinarians and horse owners can significantly improve the health and well-being of horses in the region.
References
1. Robinson, N. E., & Sprayberry, K. A. (2009). *Current Therapy in Equine Medicine*. Elsevier.
2. Mair, T. S., Love, S., Schumacher, J., & Smith, R. K. (2013). *Equine Medicine, Surgery and Reproduction*. Elsevier.
3. Australian Veterinary Association (AVA). (2024). [Equine Health Guidelines](https://www.ava.com.au/).