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?