1. PARASITIC DISEASES OF GIT
Assistant Professor Dr.
Syed Yousaf Kazmi

2. OBJECTIVES
Major Parasites that cause GIT disease, their epidemiology, etiology, life cycle and pathogenesis
Mechanism of transmission. Enlist clinical conditions
Discuss the laboratory diagnosis of these infections

3. INTRODUCTION TO BASIC PARASITOLOGY
Parasites are Eukaryotes
Two major groups
Protozoa (unicellular)
Metozoa/Helminth (Multicellular)- worms
Trophozoite -trophē=nourishment, zōon=animal (active feeding stage of a protozoal parasite)
Cyst/ oocyst -inactive and infective form
Protozoa-motility via pseudopods, flagella, cilia etc

4. INTRODUCTION TO BASIC PARASITOLOGY
Helminths-worms
Definitive host-which harbor sexual phase of parasite
Intermediate host-which harbor asexual phase of parasite

5. LIST OF MAJOR PARASITES OF GIT
PROTOZOA
HELMINTHS
Entamoeba histolytica
Hookworms(Ankylostoma duodenale, Necator americanis)
Giardia lamblia
Ascaris lumbricoides
Cryptosporidium parvum
Strongyloides stercoralis
Tinea saginata, Tinea solium
Hymenolepsis nana
Trichuris trichiura
Diphylobothrium latum

6. Entamoeba histolytica
Worldwide-common infection
Trophozoites attach large gut
Flask shape ulcers
Mucus, epith cells, pus cells, amoeba pass in stool
Acute-Extreme abd tenderness, dysentery, dehydration, incapacitation
Subacute-Diarrhea, abd cramps, vomiting, desire to defecate, weight loss, general malaise
Asymptomatic cyst passers
E histolytica/dispar trophozoites
E histolytic/dispar cyst

7. E histolytica-LIFE CYCLE & EPIDEMIOLOGY
Feco-oral route
Poor sanitation & hygiene
Cyst ingested-contaminated water, veg, fruits, flies

8. Giardia lamblia Common pathogen of duodenum & jejunum
Trophozoite heart shaped sucking disc-attachment to villi
Does not invade, but attachment cause irritation, inflammation of duodenum/ jejunum
Crypt hypertrophy, villous atrophy/ flattening, epith cell damage
Giardia lamblia trophozoite
Giardia lamblia cyst

9. Giardia lamblia-Pathogenesis
Asymptomatic- if light infection
Acute/ chronic diarrhea- in heavy infection
Stool bulky, watery, semisolid, greasy, foul smelling- Mal-absorption
Fatigue, weakness, weight loss, abd cramps, distention, flatulence-long period
Symptoms intermittent in many cases
Nutritional def e.g. iron def, folate def etc

10. Giardia lamblia- Pathogenesis
Ingestion of cyst contaminated water, food
Direct fecal oral route
Cysts can survive for 3 months
Drinking stream water during camping

11. Cryptosporidium parvum
Protozoa of small intestine
Immuno-compromised e.g. HIV inf- serious life threatening diarrhea
Pathogen of rodents, monkeys, cattle, etc.
Unrecognized cause of self limiting diarrhea in healthy
Oocyst infective form
Contaminated food/ water source of infection
High vol stool like cholera
Oocysts of C parvum modified ZN stain

12. Cryptosporidium parvum-Pathogenesis
Oocysts- excystation of sporozoites-infect epith cells-released-infect other epith cells
Whole life cycle within host
Incubation period 1-12 d
Diarrhea-large volume stool
Cholera like pic in HIV, severe dehydration, shock and death
Self limiting diarrhea in healthy
Life cycle of C parvum

13. Ascaris lumbricoides Large worm, ♂&♀ Ingestion of eggs
Larva hatch, heart lung cycle, reenters intestine-mature into adults
Eggs passed in stool
Eggs infective after 1 month till many months
Very common world wide
Poor sanitation & hygiene

14. Ascaris lumbricoides-Pathogenesis
Pathogenesis is due to larval migration in lung-irritation, mucus production, wheeze (Loeffler’s syndrome)
Adults-mechanical obstruction of gut, appendicitis, pancreatitis,
Abdominal pain, vomiting,
Anemia

15. HOOKWORM INFECTION Ankylostoma duodenale, Necator americanus
Small 10 mm, ♂&♀
Female release up to 10,000 eggs/day
Larva hatch in day or two, survive for several weeks in moist environment
Penetrate intact skin of barefoot person, enter blood and undergoes heart lung cycle like Ascaris
Adult reach intestine and attach to small intestine mucosa

16. HOOKWORM INFECTION-PATHOGENESIS
Adult worm attach intestinal villi-buccal teeth
Secrete anticoagulant and feed on blood
Few hundred worms –blood loss and anemia
Abdominal discomfort, diarrheoa,
Ground itch
Adult hookworm
Ground itch

17. Strongyloides stercoralis
Adult ♀ 2mm- parthenogenic
Eggs passed in feces, larva develop into either infective or free living form
Infective larva penetrate skin, heart lung cycle like Ascaris
Adult form reach intestine
In immuno-compromised-serious fulminant hyper-infection
Severe diarrhea, abd pain, GI bleeding, nausea, vomiting
Wheezing, hemoptysis, cough
Chronic infection-many years
Adult Strongyloides stercoralis with larva

18. Strongyloides stercoralis

19. TAENIA SAGINATA & TAENIA SOLIUM-Beef & Pork Tapeworm
Humans eat "measly beef" or "measly pork" containing the bladder-like larvae called cysticerci- inf of T saginata and T solium, respectively
Cysticerci develop in to adult-intestine
May reach many meters
Few problems, most asymptomatic
Diarrhea and abdominal pain
Egg-filled terminal segments break off-pass out with human feces-infective for cattle/pigs

20. Enterobius vermicularis
Female pinworms about 10 mm in length
Worldwide, mostly children
perianal pruritus, especially at night
female worms migrate down from the colon at night & lays egg-severe itch
Scratching the anal region promotes transmission
eggs are highly infectious within hours of being laid (hand-to-mouth transmission
Irritability and fatigue from loss of sleep
Ova of Enterobius vermicularis

21. Diphyllobothrium latum
Fish tapeworm
Enormous size, sometimes exceeding 10 m in length
Eat improperly cooked or raw fish that is infected with the infective larvae known as plerocercoids
Worm > 1 million eggs per day released
Vague abdominal discomfort and loss of appetite
Unusual capacity to absorb vitamin B12-deficiency leading to anemia

22. Hymenolepsis nana Dwarf tapeworm of humans
Worldwide & one of the most common tapeworm infections in humans
Direct human to human cycle
Autoinfection common
Massive infections, mostly in children
Abdominal discomfort
Most infections are asymptomatic
Hymenolepsis nana ovum

23. LAB DIAGNOSIS OF PARASITIC INFESTATION OF GIT
STOOL MICROSCOPY
Most important and very cheap method of diagnosing parasitic infestation of GIT
Naked eye examination-worm in stool e.g. Ascaris lumbricoides, Taenia saginata/solium etc. Blood, mucus in dysentery
Wet film examination-motile trophozoites and cysts of Giardia lamblia, Entamoeba histolytica, RBCs, WBCs, ovum of hookworm, Ascaris , Taenia spp, etc
Iodine stained examination-better visualization of cysts of Giardia, Entamoeba
Modified ZN stain- Oocysts of Cryptosporidium

24. Tapeworm
Hookworm ovum
Taenia ovum
E histolytica/dispar trophozoite
Ascaris ovum
Giradia lamblia trophozoite

25. LAB DIAGNOSIS OF PARASITIC INFESTATION OF GIT
Upper GI Endoscopy
Biopsy examination for Giardia, Cryptosporidium
“Scotch tape” test for Enterobius vermicularis ovum
Serological Tests ELISA for Giardia lamblia, Entamoeba histolytica etc. antigen detection