Deon van der Merwe BVSc, PhD KSVDL Toxicology Section
[email protected] 785 532 4333
All conceivable habitats Incredible genetic diversity Over 1-
1.5 million species Only about 70 000 species have been described
Many more
genotypes/ecotypes/chemotypes
http://herbarium.usu.edu/fungi/FunFacts/Kingfact.htm
Mostly multicellular Mycelium (mold) consists of branching
hiphae (filaments) Yeasts are exceptions Usually chitin cell walls
Aerobic Asexual/sexual reproduction Spore-forming Sexual
reproductive structures/fruiting bodies are called
mushrooms/puffballs/truffles etc.
Spore formation is key to reproductive success Imparts genetic
variation through sexual reproduction Increases adverse condition
survivability Small and light - easily spreads by wind/air
currents
Aspergillus flavus (green) growing on a corn grain
A. flavus viewed under a microscope
Photos: Stella Marie M. Doyungan
Mostly saprophytic (eat dead stuff) Good at breaking down plant
material Often symbiotic with plants/insects Mycorrhizae
Endophytes
Can be commensal/infectious/parasitic
(eg Candida spp.) But mostly COMPETITIVE
Specialize in chemical warfare Antibiotics eg penicillin
Mycotoxins Human/animal poisoning is collateral
damage!
Signs of mold HeatC6H12O6 + 6O2
www.exploratorium.edu/.../Turkey_cooking_c.gif
6CO2 + 6H2O + energy
(Carbohydrate)
Smell
www.squirrelldesigns.co.uk/smelly.jpg
Discoloration
www.ipm.iastate.edu/.../images/aspercorn.jpg
www.ent.iastate.edu/.../diplodia_ear_rot.jpg
Caking or clumping
Photo: Stella Marie M. Doyungan
Slow movement out of bins
Photo: Stella Marie M. Doyungan
Economic loss Production loss Spoilage Waste Feed refusal Health
risks
Acute/chronic organ toxicities Neurotoxicity Cancer Reproductive
failure Allergens/irritants Immunosuppression
Genetic potential Environmental conditions Aerobic conditions
Temperature and
relativewww.geomatics.uottawa.ca/copland/AylesIceShel...
weathersavvy.com/desert2_OPT.jpg
humidity Generally warm and humid
Available water Accessible nutrients Crop
damage!lh6.ggpht.com/.../rdXiSi1bZNA/DSC03623.JPG
Growth stage/proliferation
www.abc.net.au/reslib/200710/r190166_714313.jpgwww.ces.ncsu.edu/.../notes/Corn/aflatoxin2.jpg
Resistant to decomposition by cooking freezing digestion May end
up in milk (eg Aflatoxin M)
Breakdown is often slow Contaminated crops/food/feed
tendwww.exploratorium.edu/.../Turkey_cooking_c.gif
to remain contaminated
Aflatoxins Aspergillus spp.
Ochratoxins Penicillium/Aspergillus spp.
Fumonisins Fusarium
spp.www.moldinspectionsinny.com/MOLD12.JPG
Trichothecenes Fusarium/Stachybotrys spp. and many
others
Zearalenone Fusarium spp. and others
AB1
Seed crops; oilseeds; spices; nuts A. flavus, A. paraciticus, A.
nominus and others
Rapid contamination High levels within 2-7 days of inoculation
Persistent survives processing Many potential sources of
human/animal
exposure
Types AB1, AB2 AG1, AG2 AM1, AM2 Metabolites of B1 and B2
Associated with milk
Potent carcinogens; Hepatotoxic Metabolized to reactive epoxides
in the liver Causes DNA alkylation Trout are particularly sensitive
(0.4 ppb) Tightly regulated due to health risks
www.robertsreview.com/images/cancer_px/Liver_...
www.brown.edu/.../HepatitisC/cirrhosis.jpg
Mostly cereals, but also beans
(including coffee), dried fruit, wine etc. Aspergillus spp. and
Penicillium spp.
Ochratoxin A most common Carcinogenic; Teratogenic;
Nephrotoxic Chronic renal failure typical Evidence for human
carcinogenicity
weak
z.hubpages.com/u/46516_f260.jpg
FB1
Mostly in corn (maize) Fusarium
spp.wikimedia.org/.../200px-FumonisinB1.png
Fumonisin B1 most common Also FB2; FB3
Hepatotoxic and nephrotoxic at
relatively high doses in all species Increases apoptosis
www.ipm.iastate.edu/.../fusarium_ear_rot.jpg
Leucoencephalomalacia (LEM) in horses
and pulmonary edema in pigs Affects lipid metabolism and
cardiac
function
Associated with grains in cool, wet
bugs.bio.usyd.edu.au/.../Vomitoxin.gif
weather (optimal temp 59F/15C) Late-harvested/overwintered grain
Fusarium spp. and others
Mostly deoxynivalenol (DON or vomitoxin) Also diacetoxyscirpenol
(DAS) and T2 Radiomimetic (bone marrow
suppression)www.ars.usda.gov/.../9765_9959/scab-image2.jpg Triggers
vomiting through effects on
chemoreceptors in CNS Decreased feed consumption and feed
refusal in animalsPhoto: Andrew Schneider
Mostly corn (maize); also other grains Fusarium spp.
Estrogenic False heat; infertility; abortion Pigs most
susceptible
www.engormix.com/.../agranco_vulvarcomp03.jpg
Action Levels Must be reported to FDA Agencies such as GIPSA
(Grain Inspection, Packers and Stockyards Administration part of
the USDA) has to report violative levels to the FDA if Action
Levels are exceeded. Lots are subject to FDA seizure
Guidance or Advisory Levels Provide an adequate margin of safety
Not subject to enforcement by FDA
United States (regulated by the FDA) 20 parts per billion (ppb)
- For corn and other grains intended for immature animals
(including immature poultry) and for dairy animals, or when its
destination is not known; 100 ppb - For corn and other grains
intended for breeding beef cattle, breeding swine, or mature
poultry; 200 ppb - For corn and other grains intended for finishing
swine of 100 pounds or greater 300 ppb - For corn and other grains
intended for finishing (i.e., feedlot) beef cattle and for
cottonseed meal intended for beef cattle, swine or poultry. 20 ppb
All other animal feeds
AM1 in milk: 0.50 ppb Expected when AB1 in dairy cattle feed
exceeds 40 ppb
Other food: 20 ppb total Action levels in Europe are lower (but
controversial) 5 ppb for AB1 4-10 ppb total depending on type of
food 0.05 ppb AM1 in milk
Product Animal Feeds
Total Fumonisins (FB1+FB2+FB3)
Corn and corn by-products intended for: Equids and rabbits 5 ppm
(no more than 20% of diet)** Swine and catfish 20 ppm (no more than
50% of diet)** Breeding ruminants, breeding poultry and breeding
mink* 30 ppm (no more than 50% of diet)** Ruminants > 3 months
old being raised for slaughter and mink being raised 60 ppm (no
more than 50% of diet)** for pelt production Poultry being raised
for slaughter 100 ppm (no more than 50% of diet)** All other
species or classes of livestock and pet animals 10 ppm (no more
than 50% of diet)**
----------------------------------------------------------------------------------------------------------------*Includes
lactating dairy cattle and hens laying eggs for human consumption
**Dry weight basis
------------------------------------------------------------------------------------------------------------------
Class of animalHumans
Portion of dietFinished wheat products
Max. DON level1 ppm 10 ppm 10 ppm 5 ppm 5 ppm
-----------------------------------------------------------------------------------------------------------------
Beef and feedlot cattle older than 4 mos. Grain and grain
by-products not to exceed 50% of diet Chickens Grain and grain
by-products not to exceed 50% of diet Swine Grain and grain
by-products not to exceed 20% of diet All other animals Grain and
grain by-products not to exceed 40% of diet
---------------------------------------------------------------------------------------------------------------
No action, guidance or advisory levels for ochratoxin A or
zearalenone have been established by the FDA in animal feeds These
mycotoxins are handled on a case-bycase basis.
In the field Prevent insect damage/plant stress Crop rotation
Use clean seed Plant fungus-resistant varieties Harvest when grain
moisture is low Avoid harvesting at high rainfall periods Deep
plowing to bury spores
www.altenergyinvestor.org/images/cornfield.jpg
In storage Moisture control Dry grain if wet Monitor moisture
and maintain dry conditions
www.grainbinsupply.com/images/bins.jpg
Limit mechanical and insect damage Clean containers and
equipment Mold inhibitors can be considered
Physical methods Removal Separation, density segregation Thermal
breakdown Wet/dry milling Other types of thermal processing
Ammoniation Ammonia gas at high temperature and pressure for 30
mins Commercial facilities available for specific products
Cottonseed, corn, groundnut products Has not been formally approved
by FDA
Hydrated Sodium Calcium Aluminosilicate (HSCAS) clay Feed
additive (Novasil) Reduces caking; improves feed flow properties
Feed supplement to increase egg shell hardness Mixed with feed;
adsorbs aflatoxin in GIT Adsorbs aflatoxin, but NOT effective for
other mycotoxins)
Aim for reliability and efficiency Sampling points Weighing
towers, conveyor belts, trucks, barges, storage
containers etc. Distribution in bulk material is highly variable
Requires a systematic collection strategy 50-100 increments,
depending on bulk mixing status
Sample size should increase with particle size Eg groundnuts: 20
kg; corn: 10 kg; rice: 5 kg
Murphys Rules of Thumb Toxic fungi does not indicate presence of
toxin Mold-free appearance does not indicate absence of toxin
Is mold present? Heat, appearance, smell etc. Microscopy
Fluorescence under UV (not reliable!) Mold count (serial dilution
and plating) Fair indicator of feed refusal1: 102 1: 103
1:104Photo: Stella Marie M. Doyungan
Toxin quantitation No safety assumptions should be
made without toxin quantitation Chemical analyses Chromatography
TLC (qualitative), HPLC, GC etc. Requires well trained technicians
Equipment Immunoassay (ELISA) Commercial kits available Relatively
easy Cheaper?
