Parasitology - Protozoa

Front 1

T/F: Most protozoa are benign

Back 1

True. Most protozoa are neither pathogenic nor parasitic

Front 2

T/F: Parasitic protozoa are intracellular.

Back 2

False. Some parasitic protozoa are intracellular, and some multiply in extracellular fluids (eg, blood). In some species, certain stages are extracellular while others are intracellular.

Front 3

How do protozoa differ from worms, pathogenically?

Back 3

All protozoa that cause disease in humans must be capable of multiplying in humans (not true of worms)

Eosinophilia is not a usual sign of protozoal infection

Front 4

Metronidazole is useful against these types of parasitic infections

Back 4

Infection by anaerobic protozoa

Front 5

These three protozoa are anaerobes

Back 5

Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis

Front 6

Cause of amebiasis

Back 6

Entamoeba histolytica

Front 7

This parasite is an extracellular protozoan that grows anaerobically

Back 7

Entamoeba histolytica

Front 8

The simple life cylce of this protozoa involves only humans

Back 8

Entamoeba histolytica

Front 9

Transmission of Entamoeba histolytica

Back 9

Oral-fecal. Human ingests CYSTS (human fecal contamination)

Front 10

Life cycle of Entamoeba histolytica and Giardia

Back 10

Ingestion of cyst --> cyst opens in intestine releasing parasites --> parasites multiply as trophozoite in large intestine and can then either invade colon wall and multiply or … --> trophozoite changes to cyst --> cysts are excreted in stool

Front 11

Surivival time of Entamoeba histolytica cysts

Back 11

Weeks

Front 12

Trophozoite

Back 12

General term for actively multiplying stage of parasitic protozoa

Front 13

Infective stage of Entamoeba histolytica

Back 13

Mature cyst

Front 14

Pathogenic stage of Entamoeba histolytica

Back 14

Trophozoites

Front 15

Diagnostic stage of Entamoeba histolytica

Back 15

Cyst in stool, trophozoite in diarrhea

Front 16

Appearance of Entamoeba histolytica cyst

Back 16

4 nuclei and chromatoidal bodies which are linear structures

Front 17

Dystenteric stool vs diarrhea

Back 17

Dystenteric stool contains blood and mucus

Front 18

This parasite is morphologically identical to E. histolytica but is nonpathogenic

Back 18

Entamoeba dispar

Front 19

Ingested RBC's can be seen in these protozoa

Back 19

Entamoeba histolytica

Front 20

Signs and symptoms of Entamoeba histolytica infection

Back 20

Dysentery (blood, mucous stools), invasion of colon mucosa, pain

Front 21

Flask shaped ulcers are seen on colonoscopy in this infection

Back 21

Entamoeba histolytica

Front 22

Common cause of death in E. histolytical infection

Back 22

Bowel perforation, liver abscess

Front 23

T/F: Most patients with amebic dysentery will have cysts or trophozoites in stool

Back 23

True.

Front 24

Amebic abscess

Back 24

Feature of E. histolytica infection. Most commonly in liver but can also appear in brain or lung. It is uniformly fatal in the brain

Front 25

Hepatosplenomegaly can be impressive and hard to diagnose in the setting of infection by this parasite

Back 25

Entamoeba histolytica

Front 26

T/F: The liver abscess seen in E. histolytica accompanies dysentery and excretion of cysts and trophozoites.

Back 26

False. Only 10% of liver abscess patients continue to excrete cysts or trophozoites, and only 50% have a hx of dysentery

Front 27

Diagnosis of amebic abscess

Back 27

(1) serology (anti-parasite Ab)
(2) liver scan
(3)trophozoites in aspirate

Front 28

This parasite has a substantial mortality rate associated with colonic perforation that, even following colectomy, can be fatal

Back 28

Entamoeba histolytica

Front 29

Cause of Amebic meningoencephalitis

Back 29

Naegleria (an emeba)

Front 30

This disease is contracted by swimming in warm, shallow, stagnant water

Back 30

Amebic meningoencephalitis (Naegleria)

Front 31

These are three amebic presentations

Back 31

Dysentery, abscess, meningoencephalitis

Front 32

These ameba reach brain by a neural route via penetration of the cribiform plate

Back 32

Naegleria

Front 33

This disease is usually not diagnosed until autopsy because it is misdiagnosed as bacterial or viral disease

Back 33

Amebic meningoencephalitis (Naegleria)

Front 34

Two ways to disinfect water

Back 34

Boil (best)
Halogen treatment

Front 35

T/F: Compared to water, carbonated water is generally safe

Back 35

True.

Front 36

T/F: Carbonation disinfects water

Back 36

False. It is useful because the companies that bottle carbonated beverages do not use contaminated water.

Front 37

T/F: In the 3rd world, canned foods are generally safe

Back 37

True.

Front 38

These extracellular protozoa parasites are flagellated

Back 38

Giardia lamblia, Trichomonas vaginalis

Front 39

Diagnostic stage of Giardia

Back 39

Trophozoites and cysts in feces

Front 40

Infective stage of Giardia

Back 40

Cyst

Front 41

Transmission of Giardia

Back 41

Oral-fecal. Human ingests CYSTS (human fecal contamination)

Front 42

The cysts of this protozoa opens in the small intestine, releasing parasites that multiply as trophozoites in the duodenum and jejunum

Back 42

Giardia lamblia

Front 43

Trophozoites become encysted and excreted in feces when this happens

Back 43

Dehydration of stool mass

Front 44

Incubation period of Giardia

Back 44

1-3 weeks

Front 45

This protozoa produces diarrhea, foul smelling greasy stools, abd discomfort and nausea

Back 45

Giardia

Front 46

This protozoa can cause wt loss due to malabsorption

Back 46

Giardia

Front 47

Higher incidents of chronic infection with this protozoa is seen in patients with congenital defects in IgA

Back 47

Giardia

Front 48

This protozoa spreads from the GI tract

Back 48

Entamoeba histolytica

Front 49

What is the difference in pathogenesis between E. histolytica and Giardia

Back 49

E. histolytica is invasive; Giardia is not

Front 50

This protozoa has caused substantial epidemics from municipal water supplies in cities and towns worldwide

Back 50

Giardia lamblia

Front 51

T/F: Chlorination kills cysts of Giardia lamblia

Back 51

False. Chlorination does not kill cysts

Front 52

This is the best way to prevent Giardia epidemics

Back 52

Filtration of water supply

Front 53

Treatment of Giardia

Back 53

Metronidazole

Front 54

Beavers are a common cause of municipal water supply contamination with this parasite

Back 54

Giardia lamblia

Front 55

This protozoa has no cyst stage

Back 55

Trichomonas vaginalis

Front 56

Transmission of Trichomonas vaginalis

Back 56

STD. Trophozoites in vagina or urethra/prostate transmitted by sexual contact or poor hygiene

Front 57

The trophozoites of this species of protozoa are relatively hardy

Back 57

Trichomonas vaginalis

Front 58

Diagnostic stage of Trichomonas vaginalis

Back 58

Trophozoites in vaginal and prostatic secretions and urine

Front 59

Infective stage of Trichomonas vaginalis

Back 59

Trophozoite

Front 60

This protozoa has a posterior flagellum, and four anterior flagella

Back 60

Trichomonas vaginalis

Front 61

Most infected males are asymptomatic, whereas 10-20% of infected females will have symptoms

Back 61

Trichomonas vaginalis

Front 62

Signs and symptoms of Trichomonas vaginalis infection

Back 62

Inflammation, burning, itching, purulent discharge in 10-20% of women. A few men might have nonspecific urethritis.

Front 63

Treatment of Trichomonas vaginalis

Back 63

Metronidazole (must include sexual partner)

Front 64

Prevention of Trichomonas vaginalis

Back 64

Mechanical barriers (condoms)

Front 65

This protozoa is an obligate intracellular parasite

Back 65

Toxoplasma gondii

Front 66

T/F: Humans are the definitive host of Toxoplasma gondii

Back 66

False. Humans are an accidental intermediate host.

Front 67

Definitive host of Toxoplasma

Back 67

Cat

Front 68

Intermediate host of Toxoplasma

Back 68

Mammals (eg, mice), birds

Front 69

Cysts that contain dormant parasites of this protozoa are found in muscle and brain

Back 69

Toxoplasma gondii

Front 70

Infective stage of Toxoplasma

Back 70

Fecal cysts from cat feces (and *only* cat feces; non-felines who ingest infectious cysts can develop tissue cysts but these are different than the fecal cysts excreted by infected cats)

Front 71

Life cycle of Toxoplasma gondii

Back 71

Cat consumes tissue cysts --> parasite grows intracellularly in intestinal mucosa to produce male and female gametes --> gametes fuse to form ZYGOTE --> zygote is excreted from feces as noninfectious fecal cyst --> fecal cyst becomes infectious at ambient temperature for 2 days

Front 72

Transmission of Toxoplasma gondii

Back 72

(1) eating undercooked or raw meat with tissue cysts (pork, beef,)
(2) ingestion of fecal cysts from feline contamination

Front 73

This protozoa causes an often asymptomatic acute infection, followed by chronic infection with cysts in muscle and brain

Back 73

Toxoplasma gondii

Front 74

Diagnostic stage of Toxoplasma gondii

Back 74

No diagnostic stage. Dx is serological--look for rise in antibodies, anti-toxo IgM. In AIDS patients, diagnosis can be confirmed by therapeutic trial (pyrimethamine-sulfadiazine)

Front 75

Serological tests of Toxomplasma

Back 75

(1) Sabin-Feldman dye test: complement-mediated lysis of parasites in presence of anti-toxoplasma antibody
(2) ELISE or fluorescent antibody test
(3) PCR for toxoplasma DNA

Front 76

Treatment of Toxoplasmosis

Back 76

Pyrimethamine (blocks dihydrofolate reductase) plus sulfadiazine (blocks dihydrofolate synthesis) which act synergistically

Front 77

T/F: Most protozoa are benign

Back 77

True. Most protozoa are neither pathogenic nor parasitic

Front 78

T/F: Parasitic protozoa are intracellular.

Back 78

False. Some parasitic protozoa are intracellular, and some multiply in extracellular fluids (eg, blood). In some species, certain stages are extracellular while others are intracellular.

Front 79

How do protozoa differ from worms, pathogenically?

Back 79

All protozoa that cause disease in humans must be capable of multiplying in humans (not true of worms)

Eosinophilia is not a usual sign of protozoal infection

Front 80

Metronidazole is useful against these types of parasitic infections

Back 80

Infection by anaerobic protozoa

Front 81

These three protozoa are anaerobes

Back 81

Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis

Front 82

Cause of amebiasis

Back 82

Entamoeba histolytica

Front 83

This parasite is an extracellular protozoan that grows anaerobically

Back 83

Entamoeba histolytica

Front 84

The simple life cylce of this protozoa involves only humans

Back 84

Entamoeba histolytica

Front 85

Transmission of Entamoeba histolytica

Back 85

Oral-fecal. Human ingests CYSTS (human fecal contamination)

Front 86

Life cycle of Entamoeba histolytica and Giardia

Back 86

Ingestion of cyst --> cyst opens in intestine releasing parasites --> parasites multiply as trophozoite in large intestine and can then either invade colon wall and multiply or … --> trophozoite changes to cyst --> cysts are excreted in stool

Front 87

Surivival time of Entamoeba histolytica cysts

Back 87

Weeks

Front 88

Trophozoite

Back 88

General term for actively multiplying stage of parasitic protozoa

Front 89

Infective stage of Entamoeba histolytica

Back 89

Mature cyst

Front 90

Pathogenic stage of Entamoeba histolytica

Back 90

Trophozoites

Front 91

Diagnostic stage of Entamoeba histolytica

Back 91

Cyst in stool, trophozoite in diarrhea

Front 92

Appearance of Entamoeba histolytica cyst

Back 92

4 nuclei and chromatoidal bodies which are linear structures

Front 93

Dystenteric stool vs diarrhea

Back 93

Dystenteric stool contains blood and mucus

Front 94

This parasite is morphologically identical to E. histolytica but is nonpathogenic

Back 94

Entamoeba dispar

Front 95

Ingested RBC's can be seen in these protozoa

Back 95

Entamoeba histolytica

Front 96

Signs and symptoms of Entamoeba histolytica infection

Back 96

Dysentery (blood, mucous stools), invasion of colon mucosa, pain

Front 97

Flask shaped ulcers are seen on colonoscopy in this infection

Back 97

Entamoeba histolytica

Front 98

Common cause of death in E. histolytical infection

Back 98

Bowel perforation, liver abscess

Front 99

T/F: Most patients with amebic dysentery will have cysts or trophozoites in stool

Back 99

True.

Front 100

Amebic abscess

Back 100

Feature of E. histolytica infection. Most commonly in liver but can also appear in brain or lung. It is uniformly fatal in the brain

Front 101

Hepatosplenomegaly can be impressive and hard to diagnose in the setting of infection by this parasite

Back 101

Entamoeba histolytica

Front 102

T/F: The liver abscess seen in E. histolytica accompanies dysentery and excretion of cysts and trophozoites.

Back 102

False. Only 10% of liver abscess patients continue to excrete cysts or trophozoites, and only 50% have a hx of dysentery

Front 103

Diagnosis of amebic abscess

Back 103

(1) serology (anti-parasite Ab)
(2) liver scan
(3)trophozoites in aspirate

Front 104

This parasite has a substantial mortality rate associated with colonic perforation that, even following colectomy, can be fatal

Back 104

Entamoeba histolytica

Front 105

Cause of Amebic meningoencephalitis

Back 105

Naegleria (an emeba)

Front 106

This disease is contracted by swimming in warm, shallow, stagnant water

Back 106

Amebic meningoencephalitis (Naegleria)

Front 107

These are three amebic presentations

Back 107

Dysentery, abscess, meningoencephalitis

Front 108

These ameba reach brain by a neural route via penetration of the cribiform plate

Back 108

Naegleria

Front 109

This disease is usually not diagnosed until autopsy because it is misdiagnosed as bacterial or viral disease

Back 109

Amebic meningoencephalitis (Naegleria)

Front 110

Two ways to disinfect water

Back 110

Boil (best)
Halogen treatment

Front 111

T/F: Compared to water, carbonated water is generally safe

Back 111

True.

Front 112

T/F: Carbonation disinfects water

Back 112

False. It is useful because the companies that bottle carbonated beverages do not use contaminated water.

Front 113

T/F: In the 3rd world, canned foods are generally safe

Back 113

True.

Front 114

These extracellular protozoa parasites are flagellated

Back 114

Giardia lamblia, Trichomonas vaginalis

Front 115

Diagnostic stage of Giardia

Back 115

Trophozoites and cysts in feces

Front 116

Infective stage of Giardia

Back 116

Cyst

Front 117

Transmission of Giardia

Back 117

Oral-fecal. Human ingests CYSTS (human fecal contamination)

Front 118

The cysts of this protozoa opens in the small intestine, releasing parasites that multiply as trophozoites in the duodenum and jejunum

Back 118

Giardia lamblia

Front 119

Trophozoites become encysted and excreted in feces when this happens

Back 119

Dehydration of stool mass

Front 120

Incubation period of Giardia

Back 120

1-3 weeks

Front 121

This protozoa produces diarrhea, foul smelling greasy stools, abd discomfort and nausea

Back 121

Giardia

Front 122

This protozoa can cause wt loss due to malabsorption

Back 122

Giardia

Front 123

Higher incidents of chronic infection with this protozoa is seen in patients with congenital defects in IgA

Back 123

Giardia

Front 124

This protozoa spreads from the GI tract

Back 124

Entamoeba histolytica

Front 125

What is the difference in pathogenesis between E. histolytica and Giardia

Back 125

E. histolytica is invasive; Giardia is not

Front 126

This protozoa has caused substantial epidemics from municipal water supplies in cities and towns worldwide

Back 126

Giardia lamblia

Front 127

T/F: Chlorination kills cysts of Giardia lamblia

Back 127

False. Chlorination does not kill cysts

Front 128

This is the best way to prevent Giardia epidemics

Back 128

Filtration of water supply

Front 129

Treatment of Giardia

Back 129

Metronidazole

Front 130

Beavers are a common cause of municipal water supply contamination with this parasite

Back 130

Giardia lamblia

Front 131

This protozoa has no cyst stage

Back 131

Trichomonas vaginalis

Front 132

Transmission of Trichomonas vaginalis

Back 132

STD. Trophozoites in vagina or urethra/prostate transmitted by sexual contact or poor hygiene

Front 133

The trophozoites of this species of protozoa are relatively hardy

Back 133

Trichomonas vaginalis

Front 134

Diagnostic stage of Trichomonas vaginalis

Back 134

Trophozoites in vaginal and prostatic secretions and urine

Front 135

Infective stage of Trichomonas vaginalis

Back 135

Trophozoite

Front 136

This protozoa has a posterior flagellum, and four anterior flagella

Back 136

Trichomonas vaginalis

Front 137

Most infected males are asymptomatic, whereas 10-20% of infected females will have symptoms

Back 137

Trichomonas vaginalis

Front 138

Signs and symptoms of Trichomonas vaginalis infection

Back 138

Inflammation, burning, itching, purulent discharge in 10-20% of women. A few men might have nonspecific urethritis.

Front 139

Treatment of Trichomonas vaginalis

Back 139

Metronidazole (must include sexual partner)

Front 140

Prevention of Trichomonas vaginalis

Back 140

Mechanical barriers (condoms)

Front 141

This protozoa is an obligate intracellular parasite

Back 141

Toxoplasma gondii, "Spor" protozoa

Front 142

T/F: Humans are the definitive host of Toxoplasma gondii

Back 142

False. Humans are an accidental intermediate host.

Front 143

Definitive host of Toxoplasma

Back 143

Cat

Front 144

Intermediate host of Toxoplasma

Back 144

Mammals (eg, mice), birds

Front 145

Cysts that contain dormant parasites of this protozoa are found in muscle and brain

Back 145

Toxoplasma gondii

Front 146

Infective stage of Toxoplasma

Back 146

Fecal cysts from cat feces (and *only* cat feces; non-felines who ingest infectious cysts can develop tissue cysts but these are different than the fecal cysts excreted by infected cats)

Front 147

Life cycle of Toxoplasma gondii

Back 147

Cat consumes tissue cysts --> parasite grows intracellularly in intestinal mucosa to produce male and female gametes --> gametes fuse to form ZYGOTE --> zygote is excreted from feces as noninfectious fecal cyst --> fecal cyst becomes infectious at ambient temperature for 2 days

Front 148

Transmission of Toxoplasma gondii

Back 148

(1) eating undercooked or raw meat with tissue cysts (pork, beef,)
(2) ingestion of fecal cysts from feline contamination

Front 149

This protozoa causes an often asymptomatic acute infection, followed by chronic infection with cysts in muscle and brain

Back 149

Toxoplasma gondii

Front 150

Diagnostic stage of Toxoplasma gondii

Back 150

No diagnostic stage. Dx is serological--look for rise in antibodies, anti-toxo IgM. In AIDS patients, diagnosis can be confirmed by therapeutic trial (pyrimethamine-sulfadiazine)

Front 151

Serological tests of Toxomplasma

Back 151

(1) Sabin-Feldman dye test: complement-mediated lysis of parasites in presence of anti-toxoplasma antibody
(2) ELISE or fluorescent antibody test
(3) PCR for toxoplasma DNA

Front 152

Treatment of Toxoplasmosis

Back 152

Pyrimethamine (blocks dihydrofolate reductase) plus sulfadiazine (blocks dihydrofolate synthesis) which act synergistically

Front 153

One-eight of the US population is infected sometime in life with this protozoa

Back 153

Toxoplasma gondii

Front 154

Infections by this protozoa in immunocompetent people are asymptomatic, but result in encysted parasites.

Back 154

Toxoplasma gondii

Front 155

Signs and symptoms of Toxoplasma gondii infection

Back 155

Only a few primary infections are sympomatic. Lymphadenitis, myalgia, headache, fatigue, fever; in more severe cases, encephalitis, myocarditis, hepatitis, pneumonia

Front 156

Infection by this is seen in HIV infection with a CD4 count < 100

Back 156

Toxoplasma gondii

Front 157

Serologic diagnosis is not possible in this infection in this type of person

Back 157

Toxoplasmosis in AIDS patients--since disease is almost due to reactivation rather than primary infection, so the patient will already be seropositie (unless they are late in their disease and immune system is shot, wherein they will be seronegative)

Front 158

This protozoa causes transplacental infection in primary infection of the mother

Back 158

Toxoplasma gondii. Improve outcome by giving chemotherapy during pregnancy.

Front 159

Manifestations of congenital disease due to Toxoplasma

Back 159

Microcephaly, hydrocephalus, mental retardation, blindness, recurrent chorioretinitis (visual defects)

Front 160

Cats should be avoided in pregnancy for this reason

Back 160

Toxoplasma gondii can infect transplacentally and cause congenital defects

Front 161

These are the four "spor" intestinal parasites

Back 161

Cryptosporidium, cyclospora, isospora, microsporidia

Front 162

What do the four "spor" intestinal parasites have in common?

Back 162

(1) obligate intracellular
(2) diarrhea (mild-to-moderate, self-limiting)
(3) severe, protracted diarrhea in immunosuppressed (eg, AIDS)
(4) fecal-oral transmission
(5) diagnostic stage is fecal cyst
(6) cysts are resistant to chlorination

Front 163

Food-borne epidemics cause by this parasite from imported produce (eg, raspberries) are regularly seen in the US

Back 163

Cyclospora (Cyclosporidiosis)

Front 164

Diagnostic stage of cyclospora and cryptosporidium

Back 164

Acid-fast (red stained) cysts in feces

Front 165

This protozoa forms lumps protruding from the plasma membrane of the intestinal epithelium

Back 165

Cryptosporidium

Front 166

This "spor" intestinal parasite is zoonotic

Back 166

Cryptosporidium

Front 167

T/F: Chronic latent infection can occur in cryptosporidium

Back 167

False. Chronic latent infection does not occur. The implication of this is that AIDS patients acquire it as an exogenous infection (vs. toxoplasma encephalitis, which is a reactivation)

Front 168

This extracellular organism was mistaken as a protozoan but now known to be a fungus

Back 168

Pneumocystis jirovecii

Front 169

Clinical presentation of PCP

Back 169

Sudden onset, fever, cough, dyspnea

Front 170

Nearly all adults are seropositive for this

Back 170

Pneumocystis

Front 171

Diagnostic stage of pneumocystis

Back 171

Cyst in stained bronchoscopy specimen, lung bx, transtracheal aspirate, or induced sputum

Front 172

This organism grows in the alveolus, and its life cycle is poorly understood

Back 172

Pneumocystis

Front 173

Infection by this is seen in HIV infection with a CD4 count < 200

Back 173

Pneumocystis jirovecii

Front 174

AIDS, organ transplants, cancer chemotherapy, leukemia, infants with severe malnutrition all predispose to disease caused by this infection

Back 174

Pneumocystis jirovecii

Front 175

Untreated cases of this disease are 50-100% fatal

Back 175

Pneumocystis pneumonia (PCP)

Front 176

Treatment of PCP

Back 176

Bactrim (Trimethoprim/Sulfadioxide)

Front 177

Diseases in AIDS that are primary infections, and reactivation of latent infections.

Back 177

Toxo is reactivation. Cryptosporidum is new infection (no latent stage). PCP is unknown.