Ionophore diagnostics
Matt Sturos, DVMUniversity of Minnesota-Veterinary
Diagnostic Laboratory
Outline
• Diagnosis• Gross findings• Histological findings• Diagnostic samples• Testing
Diagnosis
• Clinical signs in groups of pigs• Gross and/or histological findings• Ionophore in feed– At toxic levels– At an otherwise safe levels with concurrent
potentiators• Exclusion of differential diagnoses
Expected gross findings
Acute – • Often mild or absent
• Pale pink to white areas of necrosis in skeletal muscle
• Red-brown urine due to myoglobinuria• +/- hemorrhage in skeletal or cardiac muscle
Gross findings
Chronic – • Often no residual gross lesions
• Firm, fibrotic, hard cutting muscles• White, gritty foci of mineralization within
skeletal muscles
Histopathology
Acute• Skeletal muscle necrosis• +/- Myocardial necrosis• +/- Pigmentary tubular nephrosis
Histopathology
Sub-acute and Chronic• Macrophage infiltrate to remove necrotic
tissue• Regenerative myofibers• +/- Fibrosis, mineralization
Diagnostic samples to collect
• Feed/medication history• Multiple feed samples from feeders in affected
pens/barns• Fresh and formalin-fixed tissues• +/- Blood
Feed/medication history
• New feed?• Source of feed?– Company owned mill• Does mill use ionophores (narasin is swine labeled)?
– Purchased feed• Does mill provide feed to ruminants or poultry?
• Is feed supposed to contain ionophores?• Introduction of new medications?– Tiamulin
Feed samples
Multiple representative feed samples– Distribution in feed most likely not homogeneous– Transition between bins may result in two
formulations present within a barn• Quantitative ionophore testing– Need to demonstrate toxic level
• Mineral/vitamin analysis– Rule out nutritional diseases
Ionophore testing
Liquid chromatography– AOAC-approved method– Qualitative identification of multiple compounds• Retention time• Parent ion identification (LC/MS)• Daughter ion identification (LC/MS/MS)
– Quantitative identification• Requires standard curve• Not all labs will offer
Fresh samples• Liver –
– GC/MS screening for other toxic organic compounds– Mineral/vitamin analysis
• Limbs/joint swabs –– Rule out infectious arthritis
• Rib – – Rule out metabolic bone diseases
• Bone ash, bone density, mineral composition
• Lung – – Rule out other causes of respiratory distress
• Culture, PCR
• Brain/spinal cord or head/section of spine – – Rule out meningitis/encephalomyeltis
Fresh samples
• Blood – – PCV and bilirubin – rule out hemoglobinuria– Serum chemistry:• Creatine (phospho)kinase = CK or CPK• Aspartate transferase = AST
– Electrolytes: Potassium
Fixed tissues
Skeletal muscle – muscle groups are not equal• Diaphragm• Proximal esophagus• Major muscle groups– Shoulder– Ham– Flank– Loin
Diaphragm EsophagusInner Outer
Semimembranosus – Ham Longissiumus – Loin
Fixed tissues
Cardiac muscle – • Atria – – Affected more frequently than ventricle– Left > right
• Ventricles– Rarely affected– Rule out nutritional myopathy
Fixed tissue
Major organs – rule out differentials– Lung– Liver– Kidney– Brain/head– Spinal cord/section of spine
Rule out differentials
Clinical– Lame or painful pigs
• Infectious arthritis• Metabolic bone disease
– Pigs unable to rise• Selenium toxicosis• Meningitis or
encephalomyelitis
– Respiratory distress• Pneumonia• Heart disease
– Not eating/refusing feed• Sick pig• Feed contamination
Rule out differentials
Gross/histopathology– Skeletal muscle and/or cardiac necrosis and
hemorrhage• Vitamin E/Selenium deficiency• Porcine stress syndrome• Gossypol toxicity
– Red/brown urine and pigmentary nephrosis• Hemoglobinuria due to hemolysis
Review
• Diagnosis• Lesions• Sample collection• Testing• Differential diagnoses
Acknowledgements
• Dr. Stephanie Rossow• Dr. Steve Ensley
Questions?
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