Infectious Diseases of the Digestive System

1. Infectious Diseases of the Digestive System

2. GI Tract

3. U.S. Foodborne-Disease Outbreaks

5. Typhoid Mary • Human carrier (and reservoir) of Salmonella typhi

6. Typhoid Fever and Salmonellosis

7. Salmonella enterica serovars • Infect domestic animals • Eggs and contaminated meat • One of the most prevalent causes of food-borne illnesses • Transmission dose as few as 10 organisms • Attachment is key virulence factor

8. Salmonella enterica serovars. • Gram negative bacillus • Classification based on serology and phage susceptibility assays

9. Salmonellosis • 40,000 cases annually in US • Invades intestinal epithelial cells • Nausea, cramps, diarrhea • Recovery in a few days but may shed organism for 6 months

12. Campylobacter jejuni • Small curved Gram negative rod • Lives in large intestine of birds and mammals • Fecal contamination of water and foods

13. Campylobacteriosis • Leading bacterial cause of human gastroenteritis in the world • 2.4 million U.S. cases/year • Undercooked poultry, shellfish, unpasteurized dairy products, contaminated water • Waterybloody diarrhea • Treated with antibiotics

14. Rotavirus • virus • Primary cause of diarrhea morbidity and mortality • 1 million cases per year; 70,000 hospitalizations • Fecal-oral transmission • Most serious in infants 6-24 months

15. Hepatitis • Inflammation of the liver • Multiple viruses

16. Hepatitis A Virus • “Infectious” hepatitis • Small RNA virus • Transmitted by fecal-oral route • New effective vaccine

17. Hepatitis A in US

18. Hepatitis A Worldwide

19. Hepatitis B Virus • “Serum” hepatitis • Enveloped DNA virus • Can result in chronic infection and liver cancer • Recombinant vaccine

21. Hepatitis C Virus • “Serum” hepatitis • More likely than HBV to become chronic • Also causes liver cancer • No vaccine

22. Hepatitis C • Treated with Interferon alpha and ribavirin • No cure but slows liver damage

23. Giardia lamblia • Protozoan • Cysts survive in environment • Insensitive to chlorine • Contaminated water source of infection

24. Giardiasis • Shed by wild animals into water supply as well as by infected humans • G. lamblia attaches to human intestinal wall • Diarrhea lasting for weeks • Treated with anti-parasitic drugs

25. HELMINTHES Flat worms and Round worms

27. Hermaphroditic Flukes

34. FLAT WORMS Phylum Platyhelminthes = Flat worms Class Cestoda = Tape worms Scolex contained in egg holdfast structure with hooks and suckers Proglottids major body of tapeworm contains both ovaries and testes = hermaphroditic Eggs can penetrate intestine of host and form hydatid cysts in tissues

36. FIGURE 13-57Taenia solium scolex (X64). The Taenia solium scolex has two rings of hooks and four suckers.

43. Hookworms • Ancylostoma duodenali and Necator americanus Old world and new world hookworms differ only in their geographic location. Human phase of this worm begins with a filaform larvae penetrating the skin, enters circulation, carried to the lungs, coughed up and swallowed, develops to adulthood in small intestine. Adult worms lay between 10,000 and 20,000 eggs per day. Daily blood loss 0.2ml/adult/day. Microcytic hypochromic anemia develops.

45. Biblical worm • Trichinella spiralis etiological agent of trichinosis. Infectious larva is present in the striated muscle of carnivorous and omnivorous mammals. Swine most common organism to transmit to humans. Encysted larvae live for many years. Polar bears and walruses are accounting for new human infestations in our Alaskan artic regions.

47. FIGURE 13-68Trichinella spiralis larva in skeletal muscle (W.M., X260). The spiral juvenile and its nurse cell are visible in this preparation.

48. Pin worms or Seat worms • Enterobius vermicularis most common helminthic infestation in America, 500 million cases annually globally second globally to Ascaris infestations. Eggs are ingested mainly fecal-oral.Egg laden dust can be inhaled. Autoinfection occurs frequently. “Scotch Tape Test” from perianal folds of diagnostic value.