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?

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

4 spp. shown to produce toxins:

A. flavus

A. parasiticus

A. nomius

A. niger

4 major aflatoxins

M22

metabolic products

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

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

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

Post-harvest risk factors:

–High temperatures

–Humidity

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

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/

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

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.

No aflatoxin

Highest dose

Rat livers

http://www.ansci.cornell.edu/plants/toxicagents/aflatoxin/image9.html

Toxicology

• Acute aflatoxicosis– high dosage over short

time – hemorrhage– acute liver damage– edema– altered digestion,

absorption, and metabolism

– death

Toxicology

• Chronic aflatoxicosis– impaired food

conversion– slower growth– immunity problems– cirrhosis– liver cancer

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

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

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