ISSN 2398-2993      

Mycotoxicosis

obovis
Contributor(s):

Mike Reynolds

Nicola Bates

Synonym(s): Mycotoxin poisoning, Ryegrass staggers, Aflatoxicosis, Ergotism, Facial eczema, Slobbers, Fescue foot


Introduction

  • Mycotoxicoses are diseases caused by secondary toxic metabolites produced by molds.
  • Cause: important mycotoxin-producing molds, include Penicillium spp, Claviceps spp, Phomopsis leptostromiformis, Rhizoctonia leguminicola.
  • Signs: vary depending on toxin and species. Mycotoxins affect almost all organ systems. Ergot and some Penicillium spp produce indole tremorgens which affect the nervous system.
  • Diagnosis: difficult. Mycotoxin isolation from feed, clinical signs and history, feeding trials.
  • Treatment: removal of toxin source; supportive therapy.
  • Prognosis: depends on toxin, dose and clinical course.

Pathogenesis

Etiology

  • Mycotoxins are diverse, secondary toxic metabolites produced by molds, especially Aspergillus spp, Penicillium spp (aflatoxins, ochratoxins) and Fusarium spp (fumonisins).
  • Clinical signs are due to the action of these mycotoxins and not fungal growth or allergic reactions to foreign proteins within the affected animal.

Predisposing factors

General

  • Spoilage of feedstuff by fungi.
  • Depends on moisture content, viability, physical state of grain and insect activity.
  • Seasonal.
  • Climatic conditions.
  • TMR feeding may precipitate mycotoxins being widely disseminated to a greater number of animals.

Specific

  • Field fungi: grow under conditions prior to harvest, eg Fusarium spp, require relative humidity above 90%.
  • Storage fungi, eg Aspergillus spp, especially in leaky containers or after long periods of storage.
  • Note that this division of field and storage molds is not distinct, and some fungal species can affect feed under both field and storage conditions.

Pathophysiology

  • Ruminants are relatively resistant to mycotoxins but detoxification by rumen bacteria may be overwhelmed, and the risk of toxic effects is increased if multiple mycotoxins with synergistic effects are involved. 
  • Mycotoxins affect metabolic and anabolic processes in various organ systems.
  • Four general mechanisms affect carbohydrate metabolism, mitochondrial function, lipid metabolism or nucleic acid function and protein biosynthesis.
  • Mycotoxins may affect a variety of cellular processes.
  • May require activation by biotransformation.

Disruption of mitochondrial function

  • Aflatoxins, ochratoxins, rubratoxin.
  • Inhibit electron transport and uncouple oxidative phosphorylation.

Altered lipid metabolism

  • Reduced fatty acid and cholesterol biosynthesis.
  • Impaired lipid transport.
  • Disruption of sphingolipid metabolism (fumonisins).

Altered nucleic acid function and protein synthesis

  • Aflatoxin, trichothecenes.
  • Modification of DNA, inhibition of RNA polymerase, increased RNA breakdown.

Affect on carbohydrate metabolism

  • Aflatoxins, ochratoxin A, rubratoxin B, cyclochlorotine and citreoviridin.
  • Inhibit biosynthetic enzymes such as glycogen synthetase and increasing the activity of enzymes metabolizing glycogen precursors resulting in reduced hepatic glycogen and increased blood glucose concentrations.

Other mechanisms

  • Ergotism Ergotism and fescue foot Distal limb necrosis: the ergopeptine alkaloids inhibit D1-dopaminergic receptors and are partial agonists of alpha-1 adrenergic and serotonin receptors, resulting in vasoconstriction.
  • Slaframine: acts as a parasympathomimetic agent and stimulates exocrine and endocrine glands, particularly the salivary glands and pancreas.
  • Sporidesmin: undergoes cyclic reduction/auto-oxidation to produce superoxide radicals which cause tissue damage.

Timecourse

  • May be acute or chronic.

Epidemiology

  • Not transmissible between animals.
  • Common source outbreaks.
  • Association with a particular feedstuff or spoilage of a particular feed source.
  • Field outbreaks seasonal and associated with particular climatic patterns.
  • May be difficult or impossible to identify cause.

Diagnosis

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Becker-Algeri T A, Castagnaro D, de Bortoli K, de Souza C, Drunkler D A & Badiale-Furlong E (2016) Mycotoxins in bovine milk and dairy products: A review. J Food Sci 81 (3), R544-52 PubMed.
  • Rodrigues I (2014) A review of the effects of mycotoxins in dairy ruminants. Animal Prod Sci 54 (9), 1155-1165 VetMedResource.
  • Johnstone L K, Mayhew I G & Fletcher L R (2012) Clinical expression of loitrem B (perennial ryegrass) intoxication in horses. Equine Vet J 44 (3), 304-309 PubMed.
  • Fink-Gremmels J (2008) Mycotoxins in cattle feeds and carry-over to dairy milk: a review. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 25 (2), 172-80 PubMed.
  • Hasso S A (2003) Non-fatal aflatoxicosis in Arabian horses in Iraq. Vet Rec 24 (152), 657-658 PubMed.
  • Lebars J & Lebars P (1996) Recent acute and subacute mycotoxicoses recognized in France. Vet Res 27 (4-5), 383-394 PubMed.
  • Diaz G J & Boermans H J (1994) Fumonisin toxicosis in domestic animals - a review. Vet Human Toxicol 36 (6), 548-555 PubMed.

Other sources of information

  • Kolosova A & Stroka J (2012) Evaluation of the Effect of Mycotoxin Binders in Animal Feed on the Analytical Performance of Standardised Methods for the Determination of Mycotocins in Feed. In: Food Additives & Contaminants: Part AResearchgate.
  • Plumlee K H (2004) Ed. Mycotoxins. In: Clinical Veterinary Toxicology. Mosby, USA. pp 231-281.
  • Willey T D & Morehouse L G (1978) Eds. Mycotoxicoses in Cattle. In: Mycotoxic Fungi, Mycotoxins and Mycotoxicosis. An Encyclopedic Handbook. Volume 2. Marcel Dekker Inc, USA. pp 9-171.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!

 
 
 
 

To show you are not a Bot please can you enter the number showing adjacent to this field

 Security code