2. GIARDIASIS (lambliasis) Etiology: Giardia lamblia (flagellate) Epidemiology: It has worldwide distribution. It is the most frequent protozoan intestinal disease in the US and the most common identified cause of water-borne disease associated with breakdown of water purification systems, outdoors man ship, travel to endemic areas (Russia, India, and middle east, etc.)

3. Morphology: Trophozoite: It is12-15 µ, half pear shaped with 8 flagella and, 2 axostyles arranged in a bilateral symmetry. There are two anteriorly located large suction discs. The cytoplasm contains two 2 nuclei and two parabasal bodies Cyst: Giardia cysts are 9-12 µ ellipsoidal body with smooth well-defined wall. The cytoplasm contains 4 nuclei and many structures of the trophozoite.

7. Giardia lamblia trophozoite

8. Giardia lamblia cyst

9. Giardia lamblia trophozoite

10. Life cycle (Figure 6): Infection occurs by ingestion of cysts, usually in contaminated water. Decystation occurs in duodenum and trophozoites (trophs) colonize the upper small intestine where they may swim freely or attach to the sub-mucosal epithelium via the ventral suction disc. The free trophozoites encyst as they move down stream and mitosis takes place during the encystment. The cysts are passed in the stool. Man is the primary host although beavers, pigs and monkeys are also infected and serve as reservoirs.

11. Life cycle of Giardia lamblia
Life cycle of Giardia lamblia. Infection occurs by the ingestion of cysts in contaminated water or food. In the small intestine, excystation releases trophozoites that multiply by longitudinal binary fission. The trophozoites remain in the lumen of the proximal small bowel where they can be freeor attached to the mucosa by a ventral sucking disk. Encystation occurs when the parasites transit toward the colon, and cysts are he stage found in normal (non diarrheal) feces. The cysts are hardy, can survive several months in cold water, and are responsible or transmission. Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible. While animals are infected with Giardia, their importance as a reservoir is unclear

12. Symptoms: The early symptoms include flatulence, abdominal distension, nausea and foul-smelling bulky, explosive, often watery, diarrhea. The stool contains excessive lipids but very rarely any blood or necrotic tissue. The more chronic stage is associated with vitamin B12 malabsorption, disaccharidase deficiency and lactose intolerance. Pathology: Covering of the epithelium by the trophozoite and flattening of the mucosal surface results in malabsorption of nutrients. Immunology: Some role for IgA and IgM. Increased incidence in immunodeficiency (e.g. AIDS). Diagnosis: Symptoms, history, epidemiology. Distinct from other dysentery due to lack of mucus, and blood in the stool, lack of increased PMN leukocytes in the stool and lack of high fever. Cysts in the stool and trophs (Figure 7) in duodenal content obtained using a string device (EnterotestR). Trophs must be distinguished from the nonpathogenic flagellate Trichomona hominis, an asymmetrical flagellate with an undulating membrane.

14. Giardia lamblia cyst. Chlorazol black. CDC/Dr. George R. Healy
Figure 7 - Cysts of Giardia lamblia,stained with iron- hematoxylin (A, B) and in a wet mount (C; from a patient seen in Haiti). Size: 8-12 µm in length. These cysts have two nuclei each (more mature ones will have four). CDC

15. Giardia  trophozoites in section of intestine (H&E)  Queensland University of Technology clinical parasitology collection. Used with permission

16. Treatment: Metronidazole is effective drugs .

17. 203pp Treatment of Giardia infection in adults and children Dosing
Drug Adult Dose in Children* Comments
Metronidazole 250 mg tid x 5 mg/kg tid x
5 -10 days days
Tinidazole 2 gm single 50 mg/kg Only recently available
dose single dose in the United States
Nitazoxanide 500 mg bid x 1-3 year-old: 100 A recent addition to the
3 days mg bid x 3 days anti-Giardia arsenal
4-11 yrs: 200 mg
bid x 3 days
Albendazole 400 mg qd x 15 mg/kg/d x
5d 5-7 d
Paromomycin 500 mg tid x 10 mg/kg tid x Used primarily in
5-10 days 5-10 days pregnant women
Quinacrine 100 mg tid x 2 mg/kg tid x Used primarily in
5 - 7 days days refractory cases in
combination with
a nitroimidazole

18. OTHER INTESTINAL PROTOZOA Blanatidium coli and Cryptosporidium (parvum) are both zoonotic protozoan intestinal infections with some health significance. Isospora belli is an opportunistic human parasite. B. coli: This is a parasite primarily of cows, pigs and horses. The organism is a large (100x60 µ) ciliate with a macro and a micronucleus (Figure 8). The infection occurs primarily in farm workers and other rural dwellers by ingestion of cysts in fecal material of farm animals. Man to man transmission is rare but possible. Symptoms and pathogenesis of balantidiasis are similar to those seen in entamebiasis, including intestinal epithelial erosion. However, liver, lung and brain abscesses are not seen. Metronidazole and iodoquinol are effective.

19. Figure 8 - Balantidium coli trophozoites
Figure 8 - Balantidium coli trophozoites. These are characterized by: their large size (40 µm to more than 70 µm)  the presence of cilia on the cell surface - particularly visible in (B) a cytostome (arrows)  a bean shaped macronucleus which is often visible - see (A), and a smaller, less conspicuous micronucleus CDC

21. Balantidium coli trophozoites in section of intestine (H&E) , Queensland University of Technology clinical parasitology collection. Used with permissionC. parvum

22. Atrial PROTOZOA TRICHOMONIASIS Trichomonas vaginalis (flagellate) Epidemiology: It has a world-wide distribution; as low as 5% in normal females and as high as 70% among prostitutes and prison inmates. Morphology: Trophozoite: µ, half pear shaped with a single nucleus, 4 anterior flagella and a lateral flagellum attached by an undulating membrane, 2 axostyles arranged asymmetrically The organism does not encyst

25. Life cycle: T. vaginalis colonizes the vagina of women and the urethra (sometimes prostate) of men. Infection occurs primarily via sexual contact, although non-venereal infections are possible. The organism does not encyst and divides by binary fission which is favored by low acidity (pH>5.9; normal: ). No non-human reservoir. Symptoms: T. vaginalis infection is rarely symptomatic in men, although it may cause mild urethritis or occasionally prostatitis. In women, it is often asymptomatic, but heavy infections in high pH environment may cause mild to severe vaginitis with copious foul-smelling yellowish, sometimes frothy discharge.

26. Figure 14 - Trichomonas - Stained vaginal secretion CDC

27. Trichomonas vaginalis trophozoite, Pap stain, Queensland University of Technology clinical parasitology collection. Used with permission

28. Diagnosis

29. Treatment: Metronidazole (although teratogenic) is effective in both males and females. Vinegar douche may be useful. Personal hygiene and use of condom are helpful.

31. Isospora belli is a rare infection of normal humans, although it is being seen in increasing numbers in AIDS patients. The infection occurs via the oro-fecal route. The infective stage of the organism is an oval oocyst (Figure 11) which, upon ingestion, follows the same course as C. parvum. The disease produces symptoms similar to those of giardiasis. In normal individuals, mild infections resolve themselves with rest and mild diet and heavier infections can be treated with sulpha drugs. The treatment may have to be for a prolonged period in AIDS patients.

32. Figure 11 - Oocysts of Isospora belli
Figure 11 - Oocysts of Isospora belli. The oocysts are large (25 to 30 µm) and have a typical ellipsoidal shape. When excreted, they are immature and contain one sporoblast (A, B). The oocyst matures after excretion: the single sporoblast divides in two sporoblasts (C), which develop cyst walls, becoming sporocysts, which eventually contain four sporozoites each. Images contributed by Georgia Division of Public Health/CDC 

33. Isospora