1 Parasitology Faculty: AGUAZIM SAMUEL M.D. Lange chapter 51

Introduction A parasite is either a protozoa or helminth that lives on or in a host and gets its food from or at the expense of its host. less The definitive or primary host is a host in which the parasite reaches maturity and sexually reproduces within. A secondary host or intermediate host is a host that harbors the parasite only for a short transition period, usually allowing for the completion of a developmental stage. A reservoir host is a host in which the parasite can live in indefinitely with no harmful effects. Dead-end host or incidental host is an intermediate host that does not allow transmission to the definitive host, preventing the parasite from completing its development. An example of this can be seen in Echinococcus. 2

3 Intestinal and Urogenital Protozoa

4 Parasites occur in two distinct forms: Single-cell called protozoa Multicellular metazoa called helminths or worms.

5 Protozoa can be subdivided into four groups: Sarcodina (amebas), Sporozoa (sporozoans), Mastigophora (flagellates), Ciliata (ciliates)

6 Metazoa are subdivided into two phyla: Platyhelminthes (flatworms) Nemathelminthes(roundworms, nematodes). Platyhelminthes contains two medically important classes: Cestoda (tapeworms) (swimming in a cespool of tapeworms) Trematoda (flukes). (It is a fluke that you won a million dollars and you are trembling with excitement)

7 Intestinal Protozoa Within the intestinal tract, three organisms: - The ameba (Entamoeba histolytica) - The flagellate (Giardia lamblia) - The sporozoan (Cryptosporidium parvum)

8 Urogenital Protozoa In the urogenital tract, one organism: - The flagellate (Trichomonas vaginalis).

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CASE 33 year old man, presenting with right upper quadrant pain and fever of 4 days duration; slight yellowing of skin. 1 week before, he had bloody stools, about 3 or 4 times per day, but it resolved 10

Case: 5 cm hypoechoic liver mass 11

CASE Metronidazole Significant improvement after 7 days Repeat UTZ: smaller mass 12

CASE Impression: Amebic liver abscess, secondary to Entamoeba histolytica 13

14 Intestinal Protozoa Entamoeba histolytica Diseases:Amebic dysentery and liver abscess.

15 Entamoeba histolytica Characteristics: Intestinal protozoan. The life cycle consists of two stages: (1) Motile ameba (trophozoite) consists of one ingested red blood cell and one nucleus (2) Non-motile cysts with four nuclei with no internal fiber.

16 Trophozoite: one ingested red blood cell and one nucleus

17 Cysts: four nuclei with no internal fiber Cysts: four nuclei with no internal fiber

18 Entamoeba histolytica trophozoites in section of intestine (H&E)

19 Entamoeba histolytica cyst and trophozoite, haematoxylin stained

20 Entamoeba histolytica Life cycle: Humans ingest cysts, which form excystation in small intestine, which form trophozoites. Trophozoites pass to the colon and multiply. Cyst form in the colon. Transmission and Epidemiology: Fecal-oral transmission of cysts via water, fresh fruit and vegetables. Human reservoir. Occurs worldwide, especially in tropics. Also: ano-genital or oro-anal sexual contact Pathogenesis: Trophozoites invade colon epithelium and produce “teardrop” ulcer. Can spread to liver and lungs and cause abscess. Excystation: the action of an encysted organism in escaping from its envelope

21 Life cycle of Entamoeba histolytica

22 Histopathology of a typical flask-shaped ulcer of intestinal amebiasis. CDC

Amebic dysentery  Acute amebiasis presents frequent dysenteric stools(ie, bloody, mucus- containing diarrhea) accompanied by lower abdominal discomfort, flatulence, and tenemus  Chronic amebiasis: recurrent episodes of dysentery intervening GIT disturbances, constipation  Invasive disease: liver, lung and brain 23

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AMEBOMA proliferative granulomatous response at an ulcer site (cecal or rectosigmoid area of the colon) infectious pseudo tumor Lesion can resemble an adenocarcinoma of the colon 26

Ameboma 27 leading point of an intussusception or may cause intestinal obstruction

Amebic liver abscess Most common extraintestinal form metastasis from intestinal infection Symptomatic intestinal infection need not be present right upper quadrant pain right shoulder pain presses on the common bile duct : jaundice Lung atelectasis, consolidation, pleural effusion 28

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30 Gross pathology of liver containing amebic abscessGross. CDC

31 Gross pathology of amebic abscess of liver. Tube of "chocolate" pus from abscess. CDC RUPTURED AMEBIC LIVER ABSCESS WITH “ANCHOVY PASTE”

Amebiasis cutis 32

Brain abscess 33

34 Entamoeba histolytica Laboratory Diagnosis: 1. Trophozoites or cysts visible in stool. 2. Serologic testing (indirect hemagglutination test positive with invasive disease). Treatment: - Metronidazole plus iodoquinol. GET BAC on the Metro (Giardia, Entamoeba, Trichomonas, Bacterial vaginitis, amoebic infection, C. difficile) Prevention: 1- Proper disposal of human waste. 2- Water purification. 3- Hand washing.

35 Giardia lamblia Most prevalence enteric parasite in the us Leading in infectious agent in water borne outbreaking diarrhea Disease: Giardiasis, especially diarrhea -Characteristics: Intestinal protozoan. The life cycle consists of two stages: (1) Trophozoite, Pear-shaped with two nuclei and four pairs of flagella and a suction disk. (2) The oval cyst with four nuclei and several internal fibers.

36 Trophozoite: Pear-shaped with two nuclei and four pairs of flagella

37 Oval cyst: four nuclei and several internal fibers.

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39 Giardia lamblia Life cycle: Humans ingest cysts – form trophozoites in duodenum which encyst and are passed in feces. Transmission and Epidemiology: Fecal-oral transmission of cysts. Human and animal reservoir. Occurs worldwide. Pathogenesis: Trophozoite attach to wall with no invasion. The trophozoite causes inflammation of the duodenal mucosal, leading to malabsorption of proteins and fat. IgA deficiency greatly predisposes to symptomatic infection. Giardiasis is common in male homosexual as a result of oral- anal contact Incidence is high among children in day-care centers and among patients in mental hospitals

Giardiasis  Early symptoms: flatulence abdominal distension nausea foul-smelling bulky, often watery, diarrhea explosive!!!  chronic stage vitamin B12 malabsorption disaccharides deficiency lactose intolerance 40

Diagnosis 41  Definitive tests: trophozoites or cysts or both in diarrheal stool  (Enterotest®)- string test  Endoscopy  Treatment Metronidazole(flagyl) or quinacrine hydrochloride Prevention: Water purification. Hand- washing. 4-6 hours Bile-stained

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44 Cryptosporidium parvum Disease: Cryptosporidiosis, especially diarrhea. Characteristics: Intestinal protozoan. Life cycle: Oocysts release sporozoites; they form trophozoites. After schizonts and merozoites form, microgametes and macrogametes are produced; they unite to form a zygote and then an oocyst.

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47 Cryptosporidium parvum Transmission and Epidemiology: Fecal-oral transmission of cysts from undercook meat and contaminated water. Human and animal reservoir. Occurs worldwide. Pathogenesis: Trophozoites attach to wall of small intestine but do not invade. Laboratory Diagnosis: (round) Oocysts visible in stool with acid-fast stain.*** Treatment and Prevention :None. Children should be treated with nitazoxanide, a drug that inhibits the growth of sporozoites and oocysts.

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CASE 23 year old female, with pain during sexual contact, copious, malodorous vaginal discharge of 3 days duration. Mild hypogastric pain, no vaginal bleeding Regular periods Multiple sexual partners, uses OCP 49

Case: Strawberry cervix, frothy discharge, 50

Case: vaginal smear 51

Case: vaginal smear Impression: Trichomoniasis, secondary to Trichomonas vaginalis 52

53 Urogenital Protozoa Trichomonas vaginalis Disease: Trichomoniasis. Characteristics: Urogenital protozoan. Pear-shaped,with a central nucleus and four anterior flagella. It exists only as a trophozoites. No cysts or other forms. Mot : trophozoites, sexual, formites Laboratory Diagnosis: motile Trophozoites visible in vaginal and prostate secretions. Clinical Finding: A watery, foul-smelling, yellow- greenish vaginal discharge accompanied by itching and burning occurs.

54 Trophozoites: pear-shaped, a central nucleus and four flagella. Trophozoites: pear-shaped, a central nucleus and four flagella.

55 Trichomonas - Stained vaginal secretion

56 Trichomonas vaginalis Trichomoniasis

Men: asymptomatic OR urethritis, prostatitis Women: asymptomatic OR mild to severe vaginitis copious yellowish, frothy discharge strawberry cervix “colpitis macularis” 57

Trichomoniasis Risk factors –Infection with other STDs, especially gonorrhea –Four or more lifetime sex partners –Sexual contact with an infected partner –Not using barrier contraception –Trading sex for money or drugs 58

59 T. vaginalis - Vaginal discharge

60 Trichomonas vaginalis Treatment: Metronidazole for both sexual partners. Prevention: Condoms limit transmission

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Isospora belli 62 ISOSPORIASIS Transient diarrhea in healthy pts and severe in IC Forms and transmission Fecal oral ingestion of oocysts. Pathogenesis: The oocysts excyst in the upper small intestine and invade the mucosa, causing destruction of the brush border. Dx: ACID FAST & ELLIPTICAL OOCYSTS RX: TMP-SMX OR PYRIMETHAMINE/SULFADIAZINE Note: causes malabsoption similar to giardia

CYCLOSPORA CAYETANENSIS MILD WATERY DIARRHEA IN HEALTHY AND SEVERE IN IC Member of coccida(subtype of sporozoa) TRANSMISSION: fecal oral(via contaminated water) Dx;spherical oocysts in modified acid fast stain of a stool sample Rx:trimethoprim sulfamethoxazole. 63

MICROSPORIDIA Characterized by obligate intracellular replication and spore formation Persistent diarrhea in AIDS pts(Enterocytozoon bieneusi and Septata intestinalis) Tx: fecal oral Dx: spores in stool Rx: albendazole Others: no proven treatment 64

Balantidium coli only ciliated protozoan that causes human disease, ie, diarrhea. hosts: cows, pigs and horses farm work, rural dwellers. MOT: ingestion of cysts similar to entamebiasis (extraintestinal lesions do not occur) liver, lung and brain abscesses are not seen. Diagnosis is made by finding large ciliated trophozoites or large cysts with a characteristic V-shaped nucleus in the stool. The treatment of choice is tetracycline. Prevention consists of avoiding contamination of food and water by domestic-animal feces. 65

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