aflatoxins; Sources and hazardous health effects.ppt

Aflatoxins

1. Want to understand:
(1) How does the scientific process
helps us solve health problems?
(2) What are aflatoxins? Are they
relevant to human and animal health?
(3) How do organisms’ interactions with
each other and their environment
influence disease?

2. http://www.oardc.ohio-state.edu/ohiofieldcropdisease/Mycotoxins/aspergillus1.jpg

3. 4 spp. shown to produce toxins:
A. flavus
A. parasiticus
A. nomius A. niger

4. 4 major
aflatoxins
M
2
2 metabolic
products

5. Aflatoxin distribution
•Exposure mainly from:
–A. flavus: global distribution,
produces B classes of aflatoxins
–A. parasiticus: Africa and the
Americas, produces B and G classes
of aflatoxins

6. Partial list of foods:
•Cereals
–maize, sorghum, millet, rice, wheat
•Oil seeds
–groundnut, soybean, sunflower, cotton
•Tree nuts
–pistachio, almond, walnut, coconut
•Spices
–paprika, chile, black pepper, coriander,
turmeric, ginger
•Figs
•Milk, cheese,
meat, eggs

7. Pre-harvest risk factors:
–High temperatures
–Chronic drought
–Heavy rains
–Crop insect damage
–Poor fertility
–Weed competition
–High crop densities

8. Post-harvest risk factors:
–High temperatures
–Humidity

9. Liver function
•One of the largest internal organs
•Produces bile used to digest food
•Metabolizes carbohydrates and lipids
•Stores glycogen (for energy), key nutrients
•Breaks down toxic substances
http://digilander.libero.it/BodyMindCare/kapil/moremedi.htm

10. Cytochrome P450 oxidase:
•Found in high densities in liver
•Oxidative enzymes that modify and degrade toxins
•Absorb light at 450 nm
http://www.biochem.ucl.ac.uk/bsm/proLig/pdbEntries/1pha/

11. Bioactivation:
•Enzymes can convert a chemical into something
even more reactive or toxic
•Ex.: Ethanol via Alcohol dehydrogenase 
Acetaldehyde
http://www.gps.caltech.edu/~fry/winter2003/winter2003.html

12. Williams, J.H., T.D Phillips, P.E. Jolly, J.K Stiles and D. Agga. 2004. Human aflatoxicosis in
developing countries: a review of toxicology, exposure, potential health consequences, and
interventions. Am. J. Clin. Nutr.Nov;80(5):1106-1122.

13. No aflatoxin
Highest dose
Rat livers
http://www.ansci.cornell.edu/plants/toxicagents/aflatoxin/image9.html

14. Toxicology
•Acute aflatoxicosis
–high dosage over short time
–hemorrhage
–acute liver damage
–edema
–altered digestion,
absorption, and metabolism
–death

15. Toxicology
•Chronic aflatoxicosis
–impaired food
conversion
–slower growth
–immunity problems
–cirrhosis
–liver cancer

16. Documented outbreaks
•1974, rural NW India: 397 ill, 108 dead
•High fever, jaundice, ascites
•Preceded by same symptoms in dogs
•Traced to maize w/ major A. flavus
infestation
•Chronic drought, unseasonable rain, poor
storage, ignorance of dangers of moldy
food

17. Documented outbreaks
•1981, rural Kenya: 20
hospitalizations, 12 deaths
•Abdominal discomfort, anorexia,
malaise, fever, jaundice, dark
urine
•Doves died, then dogs ill, then
people ill
•Contaminated maize
•Heavy rains, drought, and protein-
deficient diets thought to contribute

18. 1) The scientific process is investigative
and helps us solve health problems
(2) Aflatoxins are fungal toxins that
pose serious risks to human and animal
health
(3) Organisms’ interactions with each
other and their environment determine
whether or not disease outbreak occurs