Other Important Protozoan Parasites (Franco Falcone) Flashcards by My Revision

What kind of infection can be caused by Trichomonas vaginalis?

Urogenital

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What kind of infection can be caused by Giardia lambia?

Intestinal

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What kind of infection is caused by Entamoeba histolytica?

Intestinal

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What is Trichomonas vaginalis classed as?

An STI

The most commonly treatable STI with a worldwide prevalence

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Does Trichomonas vaginalis only affect women?

No men too - resides in the urethra and the prostate gland

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How is Trichomonas vaginalis transmitted?

Unprotected sexual intercourse

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Describe the life cycle of Trichomonas vaginalis

Trophozoites reside in vaginal or prostatic secretions and or urine
The protozoa multiplies by longitudinal binary fission
Trophozoite is found in the vagina or urethra orifice

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What is the structure and function of the Trichomonas vaginalis?

4 anterior flagella are free, one is attached to the membrane on opposite site of the protozoa.
Cape = costa
Peto at tip of the flagella that are free
Axosyte like the spine

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What are the symptoms associated with Trichomonas vaginalis?

Irritation, strawberry cervix, malodorous vaginal discharge, itching, pH increases to 5 or higher (normally 4)

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What are the complications in Trichomonas vaginalis in pregnant women?

Can result in premature or low birth weight babies

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What is the difference in symptoms between men and women?

Men are normally asymptomatic ( but can still transmit the parasite)
Women are symptomatic ( or are within 6 months of infection)

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What is a consequence of men being infected with Trichomonas vaginalis?

Can reduce sperm counts and motility (fertility) cause prostatitis or urethritis
Increases risk of HIV and HSV2 acquisition and transmission (Herpes)

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How can Trichomonas vaginalis be diagnosed?

Wet mount; (microscopy) in both men and women, but not very sensitive
Culture more sensitive - the gold standard, but more expensive and time consuming (2-7 days of growth)
Polymerase chain reaction (PCR) - expensive
Point-of-care tests (dipsticks) available, results in less than 1 hour

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What is the treatment for Trichomonas vaginalis?

Metronidazole (Flagyl)

Either 2g dose or 400mg od for 7 days

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What is tried if Metronidazole is not effective for Trichomonas vaginalis?

Tinidazole

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Who else should be treated when a patient has Trichomonas vaginalis?

Sexual partners

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How can Trichomonas vaginalis be prevented?

Treatment of sexual partners by partner referral or patient delivered partner treatment

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Why is repeat infection common in Trichomonas vaginalis?

Reinfection from untreated partner

Resistance to drug

What is Nonoxynol-9?

Used as a spermicide in condoms and has anti-Trichomonal activity which may help prevent infections

How do Trichomonads get energy?

Possess a unique organelle called the hydrogenosome which is used to metabolise Pyruvate to gain energy (releasing hydrogen, hence the name).

Where does metronidazole act?

Activated in the hydrogenosome leading to nitroso (NO) free radical

What is the life cycle of Giardia lamblia?

Contaminated water, food or hands with infective cysts
Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the faeces (diagnostic stages).
Protozoa multiply and proliferate in man and then pass out in faeces leading to further contamination.

What are the cysts of Giardia lamblia like?

Hardy; can survive very cold water for months

The cysts are not destructed by stomach acid

What are the other names given to Giardia lamblia?

G. duodenalis or G. intestinalis

Where do Giardia lamblia reside?

Small intestine; most common protozoan isolated from faeces

What are the symptoms of Giardia lamblia?

Often asymptomatic because does not penetrate the epithelium

What symptoms can Giardia lamblia cause?

Chronic or acute diarrhoea, flatulence, bloating, abdominal cramps

Is Giardia lamblia specific to humans?

No can infect other animals

How is Giardia lamblia diagnosed?

Stool examination: detection of cysts by microscopy (wet mounts or stains) - not always reliable, as intensity of cyst output varies greatly, hence three stools need to be taken with intervals of at least 2 days

What is Enterotest?

Gelatin capsule containing a nylon string taped to patient face and swallowed. Retrieve after 4 hours to overnight, distal string section scraped and used for wet mount and permanent slide staining. Capsule dissolves in stomach lines small intestine remove and examine distal end - parasite attach)

What is a common misunderstanding of Giardia?

Associated with travel abroad / traveller's disease

What is the treatment for Giadia lamblia?

Metronidazole given over multiple days Tinidazole (single dose) Quinacrine (anit-malarial) Paramomycin (broad spectrum aminoglycoside antibiotic - is not absorbed so can be used during pregnancy; remains in gut with parasite).

What is the causative agent of Amebiasis (amebic dysentery)?

Entamoeba histolytica

Which organisms are the hosts of Entamoeba histolytica?

Humans are the only hosts

How is Entamoeba transmitted?

Faecal-oral route

Where do Entamoeba histolytica reside?

In the colon | Can be fatal if spread to other organs

What are the symptoms of Entamoeba histolytica?

Generally asymptomatic or mild symptoms but can be fatal if spread to other organs

What is the life cycle of Entamoeba histolytica?

Cysts can survive days to weeks in the external environment and are responsible for transmission. Trophozoites passed in the stool are rapidly destroyed once out of the body and do not survive gastric passage. In some individuals the protozoa can invade intestinal mucosa or pass through blood infecting other organs such as brain liver lungs.

What is the difference between E. histolytica and E. dispar?

E. dispar is the non invasive form of E. histolytica

What are the different stages of the Entamoeba life cycle?

Trophozoites, precyst, cyst, metacyst.

How is Entamoeba histolytica diagnosed?

Microscopic detection of the trophozoite in the faeces E. histolytica have an amorphous shape The two types (invasive and non-invasive) are morphologically indistinguishable unless E.histolytica is observed with ingested red blood cells.

Which of the Entamoeba's are able to perform erythrophagocytosis?

E. histolytica (invasive)

How is amoebiasis treated?

Two treatments available 1. Luminal amoebicides are used for infections confined to the intesstinal lumen; diloxanide furoate, paramomycin. Tetracycline might be used 2. Tissue amoebiasis (extraintestinal amoebiasis) is treated with metronidazole, tinidazole and related drugs. less effective against treatment of parasites in the gut lumen and not effective against cysts. Treatment should then be followed with a luminal agent.

Which protozoan parasites have we not learned about?

African Trypanosmiasis (sleeping sickness) caused by brucei, rhodesiense and transmitted by tse tse fly. American Tryanosmiasis (chagas disease) caused by cruzi and transmitted by 'kissing bug' Triatana infestans Leishmaniasis (visceral, cutaneous, mucocutaneal) transmitted by sandflies Worse pathophysiology but less common in UK