• Caused by a common mold, Aspergillus flavus
• It produces a mycotoxin (aflatoxin)
• Grows on many foods, particularly peanuts and corn
• May contribute to liver cancer and cirrhosis

Taenia spp.

• A helminth (Cestodes)
• Travels to muscle of the intermediate host
• Has three stages:

1. Adult worm in intestines of humans lays eggs and are excreted in feces
2. Eggs are ingested by grazers (intermediate host) and hatch into larvae
3. Humans eat undercooked meat and larvae develop into adults that attach to walls of SI

Enterobius vermicularis

• A helminth
• Migrates out of anus to lay eggs
• If ingested, larvae hatch in SI
• Best detected by the "Graham Sticky Tape Method"

Necator americanus

• A helminth
• It makes its way into the host by burrowing through the skin
• Once it is in the host, it has a similar life-cycle as Ascaris lumbricoides
• Hookworm attaches to intestinal wall, feeding on blood and tissues
• Eventually, the host can becomes anemic

Ascaris lumbricoides

• A helminth
• Roundworm infection
• Spread via a fecal/oral route
• Adult worms migrate
• Usually not severe symptoms but can cause duct blockage

1. If someone has nematode eggs, they are passed into the environment
2. The A. lumbricoides eggs begin to develop into the larval form with an egg casing
3. The larval form with the egg casing becomes ingested by another person
4. It begins to mature in the small intestine
5. It can then go to the lungs, where it migrates up the trachea to the pharynx
6. It will then be swallowed to the stomach, make its way to the small intestine, and undergo further maturation there
7. The adult forms will mate, make unfertilized eggs, and the cycle is repeated

Giardia lamblia

• A protozoan
• Like Entamoeba, mild to severe diarrhea
• Cysts and Trophozoite forms
• Adhere to microvilli of the SI
• Most commonly diagnosed intestinal parasite in the US
• It is hard to detect
• It comes from beavers

Entamoeba histolytica

• Causes amoebic dysentery (amoebiasis): mild to severe diarrhea, with blood, mucus, pus in stools
• It can become systemic
• Food or water contaminated with cysts; stomach acids do not affect cysts
• Found worldwide but more common in tropical countries

Picornaviridae

• Hepatovirus
• Single stranded RNA that can be cultured
• Spread by fecally contaminated food, water, hands, or by anal intercourse
• Multiplies in the intestinal epithelium, spreads to liver, kidneys, spleen
• It can damage kupffer cells that are fixed macrophages in the liver
• Usually no liver damage

Salmonella

• Gram negative bacillus
• Facultative Anaerobe
• Pathogen not found in animals; only spread by human fecal/oral route
• Pathogens multiply in phagocytic cells, spread to liver, spleen, and lyse, becoming blood-borne
• Frequent cause of death in parts of the world with poor santitation
• Can become chronic carriers

Helicobacter pylori

• Gram negative spiral
• Microaerophilic
• Involved in the majority of gastric and duodenal ulcers
• Adhesins, urease, cytotoxins disrupt stomach and SI mucosa
• Urease is responsible for the formation of NH₄⁺ that makes the stomach pH basic