Welcome to Parasitology

1. Welcome to Parasitology Ugra S. Singh, Ph.D. Pathology, Immunology, and Virology USC School of Medicine Columbia, SC 29209 Contact information- Tel. 803-253-5851 Email: Ugra.Singh@uscmed.sc.edu Office: Building, 1. B-30

2. Some definitions… Parasite: An organism that obtains food and shelter from another organism and derives all the benefits from this association Obligate: When the parasite can live only in host Facultative: When the parasite can live in the host as well as in free form Endoparasites: When the parasite lives inside the body Ectoparasites: When the parasite survives on the body surface 2

3. Some definitions… Continued….. Pathogenic: When the parasite causes harm to the host Commensals: Those parasites which benefit from the host without causing harm Host: The organism that harbors the parasite and suffers a loss caused by the parasite Primary host or definitive host: In which the parasite reaches its maturity or if applicable reproduces sexually Secondary host or intermediate host: Where the parasite lives its asexual stage for a short period 3

4. Some definitions… Continued….. Dead-end host is an intermediate host that does not allow the transmission to the definite host, thereby preventing the parasite from completing its development Reservoir: Hosts other than humans that harbor the parasite, ensure the continuity of the life cycle, and act as additional sources of infection Vector: An organism (usually an insect) that is responsible for transmitting the parasite infection 4

5. DISEASE CASES/YEAR DEATHS Ascariasis 1,000,000,000 <20,000 Hookworm 60,000 800,000,000 Trichuriasis 500,000,000 low Amebiasis 500,000,000 100,000 Schistosomiasis >500,000 300,000,000 200,000,000 low Filariasis PREVALENCE OF PARASITIC DISEASES I 5

6. Giardiasis 200,000,000 low Malaria 177,000,000 >100,000 Strongyloidiasis 35,000,000 low Trypanosomiasis (Am) 25,000,000 low Onchocerciasis 20,000,000 60,000 >1,000,000 Leishmaniasis ?5,000 PREVALENCE OF PARASITIC DISEASES II Continued-- Estimates of the prevalence of parasitic diseases are at best extremely rough, as morbidity reporting is nonexistent or very inaccurate in many of the areas in which these diseases occur. 6

7. Some characteristics of parasitic diseases • Prevalence in underdeveloped countries specially in the lower income group of population • Low mortality and morbidity • Limited drug development • No vaccines 7

8. Year Giardia Entamoeba 74-77 2,787 227 90-94 1,402 340 Parasitic infections in South Carolina Number of specimen positive for parasites in South Carolina 8

9. Organism Disease Epidemiology Dysentery, liver & brain abscess Entamoeba histolytica 500 x 106 cases worldwide 200 x 106 cases world-wide Diarrhea Giardia lamblia Farm associated: world-wide Dysentery Balantidium coli Intestinal and uro-genital protozoa of man 9

10. Organism Disease Epidemiology Cryptosporidium parvum Diarrhea Sporadic epidemics: world-wide Isospora belli Diarrhea Rare, opportunistic Frequent, common among prostitutes: world-wide Trichomonasvaginalis Sexual Intestinal and uro-genital protozoa of man 10

11. What you need to know? • Morphology • Geographic distribution • Life cycle • Symptoms • Pathogenesis and immunity • Diagnosis • Treatment and prevention 11

12. Amebiasis • Etiologic agent: Entamoeba histolytica • Disease: Amoebic dysentery Liver, lung, brain and other abscesses 12

13. Amebiasis Although anyone can have this disease, it is most common in the people who live in developing countries that have poor sanitation conditions. In parts of Africa, Latin America, India and South East Asia amebiasis is endemic. In US up to 4% population probably carries the parasite, mostly found in immigrants from developing countries. 13

14. Amebiasis A 37 years old businessman complains of central abdominal pain, diarrhea and flatulence of 10-days duration which started 2 days after returning from a trip to Central-South America. His wife and children who did not travel with him have no GI complaints. He has no fever and the physical examination is otherwise normal. The stool contains mucus and blood (leucocytes and monocytes). 14

15. E. histolytica: morphology 15-30 mm 10-15 mm The active trophozoite stage exists only in the host and in the fresh loose stool. Cysts often found in the stool survive outside of the host, in water, soil and on foods. 15

16. Fecal-oral life cycle Excystation Trophozoite Cyst Encystment • Passed in feces • Non motile • Resistant to hostile environment • Does not multiply • Metabolically active • Motile • Multiplies by replication 16

17. E. histolytica: life cycle Ingestion of cyst in the contaminated water and food Excystation occurs in the small intestine. Eight trophozoites produced from one cyst. Trophozoites migrate to large intestine where they multiply or may encyst for excretion Cysts exit hosts in the stool 17

18. Symptoms of acute amebiasis Organ involved Symptoms Abdominal pain; frequent bloody dysentery with necrotic mucosa Small and large intestine 18

19. Symptoms of chronic amebiasis Organ involved Symptoms Recurrent bloody and mucoid dysentery with intervening constipation; appendicitis; pseudopolyps; perforation Small and large intestine Abscess; hepatitis Liver Abscess; pneumonia Lung Abscess; encephalitis Brain 19

20. Chronic amebiasis:mucosal erosion and crater formation 20

21. Chronic amebiasis:drainage of a liver abscess 21

22. Chronic amebiasis:drainage of a lung abscess 22

23. Chronic amebiasis:brain abscess 23

24. E. Histolytica:pathology and Immunology Pathology Invasiveness and abscess formation are due to amoebic proteolytic enzymes Immunology • Antibodies are detectable in chronic infections but they are of questionable protective value 24

25. Amebiasis:Differential diagnosis Amebiasis is different from giardiasis and bacterial dysentery Mucus and blood in stool No granulocytosis No high fever 25

26. E. Histolytica:the diagnostic features When amebic dysentery is suspected, a fresh fecal sample or a swab should be examined under microscope. If examined quickly the colorless motile trophozoite can be seen. The motile trophozoite has one nucleus H/E stained Staining- Lugol staining --- General morphology Iodine staining --- Glycogen Iron/Haematoxylin staining –Chromatoidal bodies Fresh sample 26

27. E. Histolyticaprevention and treatment • Prevention • Better hygiene • Efficient sewage treatment and disposal • Treatment • Iodoquinol for acute amebiasis • Metronidazole for chronic amebiasis 27

28. Giardiasis • Etiologic agent: Giardialamblia • Disease: Giardia affects humans, but is also one of the most common parasites infecting cats, dogs and birds. • Diarrhea, lipid and vitamin B12 and other nutrient mal-absorption 28

29. Giardiasis A 37 year old businessman complains of central abdominal pain, diarrhea and flatulence of 10-days duration which started the day after returning from a trip to Leningrad. His wife and children who did not travel with him have no GI complaints. He has no fever and the physical examination is otherwise normal. Milk consumption makes the symptoms worse. The stool is bulky, foul smelling and floats on the water surface. It contains no mucus or blood. 29

30. Giardiasis HIV positive cases mostly affected 2.5 million cases each year in US 30

31. Giardialamblia:morphology The active trophozoite attaches to the lining of small intestine with a ‘sucker’ responsible for causing the signs and symptoms of giardiasis. Giardia do not have mitochondria 31

32. Giardialamblia:life cycle 32

33. Giardiasis: symptoms organ involved symptoms stage Acute Small and large intestine Flatulence; foul-smelling, bulky light diarrhea; malabsorption, lactose intolerance Chronic Small and large Intestine Asymptomatic or symptoms described above 33

34. Giardiasis: pathology and Immunology Pathology • Covering of the epithelium by trophozoites and flattening of the mucosal surface (no invasiveness) Immunology Some protective role for IgA and IgM Increased incidence in immunodeficiency 34

35. Giardiasis: Differential diagnosis Giardiasis is different from amebiasis and bacterial dysentery: No mucus, blood No granulocytosis and no fever 35

36. Giardiasis: diagnosis The mainstay of diagnosis of Giardia is stool microscopy, this can be for distinctive oval cyst and motile trophozoite 36

37. Giardiasis prevention and treatment • Prevention • Better hygiene • Efficient sewage treatment and disposal • Treatment • Iodoquinol • Metronidazole 37