Zearalenone_and_Fumonisins-2__1_

Introduction to Fumonisins

  • Fumonisins (B1 and B2) are naturally occurring mycotoxins produced by the fungus Fusarium verticillioides.

  • Commonly found in corn, they are implicated in conditions such as porcine pulmonary edema (PPE) and equine leukoencephalomalacia (ELEM).

Learning Objectives

  • Understand the characteristics, sources, and exposure modes of fumonisins.

  • Study the toxicokinetics and mechanism of action.

  • Review toxicity, clinical pathology findings, signs, and lesions.

  • Learn about diagnosis protocols and therapeutic measures.

Characteristics and Sources of Fumonisins

  • Fumonisins are water-soluble and heat-stable mycotoxins.

  • Detected primarily in corn and corn-based foods.

  • Associated with consumption of moldy corn, affecting livestock worldwide.

Toxicokinetics of Fumonisins

  • Low bioavailability following oral dosing; eliminated via feces and urine.

  • Residues in meat, milk, or eggs do not pose a food safety hazard.

Mechanism of Action

  • Fumonisins alter sphingolipid metabolism, as they are structurally similar to sphingosine.

  • They inhibit sphinganine and sphingosine N-acyltransferase, essential enzymes in sphingolipid biosynthesis.

Effects on Sphingolipid Pathways

  • Disruption of pathways leads to impaired cell membrane structure and function.

  • Blockage of sphingolipid biosynthesis affects critical cellular processes.

Toxicity and Clinical Signs

  • Fumonisins induce specific target organ toxicity: lungs in pigs and brains in horses.

  • Accumulation of sphinganine and sphingosine causes significant cardiovascular effects, leading to acute left-sided heart failure in pigs.

  • Major clinical signs in pigs: dyspnea, cyanosis, inactivity, sudden death.

Clinical Signs in Pigs

  • Chronic exposure may cause hepatic disease with signs such as anorexia and icterus.

Clinical Signs in Horses

  • ELEM presents with neurotoxic signs like aimless circling and paralysis, linked to acute exposure.

Lesions Induced by Fumonisins

  • Pigs: Pulmonary edema and potential long-term fibrosis in lungs and liver.

  • Horses: Liquefactive necrosis in cerebral hemispheres and distinct liver damage with irregular nodules.

Clinical Pathology Findings

  • Elevated protein and IgG concentrations in cerebrospinal fluid (CSF) indicating vasogenic edema.

  • Increased liver enzyme activities noted in affected animals.

Diagnosis Protocol

  • Diagnosis confirmed through clinical signs, pathological findings, and detection of fumonisin in feed using HPLC and ELISA methods.

  • Fungal culture offers little diagnostic value.

Treatment and Prevention

  • No specific treatments for ELEM or PPE; primary management involves removing contaminated feed.

  • Options include discarding contaminated corn or diluting it with safer feed options.

  • Preventive measures focus on proper grain storage and moisture control.

Summary of References

  • Various studies and sources support the findings on fumonisins and their impact on animal health.