Protozoa

Flashcards covering key concepts from the lecture notes on protozoa, including definitions, properties, life cycles, epidemiology, pathogenesis, diseases, laboratory diagnosis, treatment, and prevention of various protozoan infections.

What is the infective stage of a parasite?

The stage of the parasite that enters the host or is present in the parasite's source of infection.

What is the pathogenic stage of a parasite?

The stage of the parasite responsible for producing organ damage in the host, leading to clinical manifestations.

What is Encystation?

The process by which trophozoites differentiate into cyst forms.

What is Excystation?

The process by which cysts differentiate into trophozoite forms.

How are protozoa classified?

Mainly based on the organ of locomotion utilized (e.g., flagellates, ciliates, amebae).

How do flagellates, ciliates, and amebae reproduce?

Binary fission

How are protozoan infections typically diagnosed?

Through microscopic examination of body fluids, tissue specimens, or feces, often with special stains.

What are the two forms of parasitic protozoa that are often diagnosed?

Trophozoite (motile, feeding, dividing stage) and cyst (dormant, non-motile form).

Which form of a protozoan is the pathogenic stage?

Trophozoite

Which form of a protozoan is the infective stage for intestinal protozoan parasites?

Cyst (except for Trichomonas vaginalis)

What is the only known pathogenic intestinal ameba?

Entamoeba histolytica.

What are the two stages in the life cycle of Entamoeba histolytica?

Non-motile cyst (infective stage) and motile trophozoite (pathogenic stage).

Where are trophozoites of Entamoeba histolytica found?

Within intestinal and extraintestinal lesions and in diarrheal stools.

Where are cysts of Entamoeba histolytica usually found?

Non-diarrheal, formed stools.

How is Entamoeba histolytica primarily transmitted?

By the fecal-oral route through ingestion of cysts from contaminated food and water.

What happens after ingestion of cysts of Entamoeba histolytica?

Excystation occurs in the ileum, differentiating into trophozoites, which colonize the cecum and colon.

Which stool type contain cysts of Entamoeba histolytica?

Formed, non-diarrheic stools

What is the term for the disease caused by Entamoeba histolytica?

Amoebiasis

What is acute intestinal amoebiasis characterized by?

Bloody, mucus-containing diarrhea (dysentery), lower abdominal discomfort, flatulence, and tenesmus.

What is the most common extraintestinal form of amoebiasis?

Amoebic liver abscess.

How is intestinal amoebiasis diagnosed?

By finding trophozoites in diarrheic stools or cysts in formed stools.

What is the drug of choice for symptomatic intestinal amoebiasis or hepatic abscess?

Metronidazole.

What preventive measures can be taken to avoid amoebiasis

Observance of good personal hygiene, proper handwashing, waste disposal, and adequate washing/cooking of vegetables.

What is an alternative name for Giardia lamblia?

Giardia intestinalis or Giardia duodenale.

What is the motility of Giardia lamblia trophozoite likened to?

Falling leaf

What structure does Giardia lamblia use to attach itself to the intestinal villi?

Sucking disc.

How does Giardia lamblia divide?

Binary fission.

How is Giardia lamblia primarily transmitted?

Through ingestion of the cyst from fecally contaminated water and food.

Where does excystation of Giardia lamblia occur and gets stimulated by what?

In the duodenum and they get stimulated by the gastric acid.

How does Giardia lamblia cause damage to the intestines?

Inflammation of the duodenal mucosa, leading to diarrhea with malabsorption of fat and proteins.

What is the treatment of choice for Giardia lamblia infection?

Metronidazole, tinidazole, and nitazoxanide (as per CDC recommendations).

What preventive measures can be taken to avoid Giardia lamblia infection?

Avoidance of fecal contamination of water supplies, boiling/filtering/iodine treating drinking water, and improvement of personal hygiene.

Does Trichomonas vaginalis has a cyst form?

No, it exists only in the trophozoite form (infective and pathogenic).

How is Trichomonas vaginalis transmitted?

Through sexual intercourse.

Where has Trichomonas vaginalis been isolated from in infected women?

Urethra and vagina

Where has Trichomonas vaginalis been isolated from in infected men?

Urethra and prostate gland

How is trichomoniasis diagnosed?

By finding the characteristic trophozoite in a wet mount of vaginal or prostatic secretions, urine, and urethral discharges.

What is the drug of choice for treatment of trichomoniasis?

Metronidazole.

How can trichomoniasis be prevented?

Practicing safe sex and the use of condoms.

What is the largest protozoan known to infect humans?

Balantidium coli.

Where does Balantidium coli invade?

The mucosal lining of the terminal ileum, cecum, and colon.

Which animal is the most common and important reservoir for Balantidium coli?

Pig.

What happens after Balantidium coli cysts is ingested?

It undergoes excystation in the small intestines, then the trophozoites travel to the large intestines where they produce ulcers.

How is balantidiasis diagnosed?

Based on the finding of trophozoites and cysts in the stool specimen.

What is the current recommended treatment for patients with balantidiasis?

Oxytetracycline and iodoquinol.

Which free-living amoebae can cause severe illness when they gain entrance into the central nervous system or the eyes?

Acanthamoeba and Naegleria

For Acanthamoeba, what are the infective and pathogenic stages?

The infective stage is the cyst while the pathogenic stage is the trophozoite.

How do people acquire Acanthamoeba infection?

Usually while swimming in contaminated water or through inhalation of cysts from dust.

What eye infection do Acanthamoeba cause, and in whom?

Keratitis, primarily in patients who wear contact lenses.

What is the primary characteristic of Naegleria fowleri?

It is the only amoeba with three identified morphologic forms—trophozoite, flagellate, and cyst forms.

How is Naegleria infection usually acquired?

Transnasally when swimming in contaminated water.

What is the disease caused by Naegleria infection and symptoms it present?

Primary amoebic meningoencephalitis (PAM). Patients initially complain of sore throat, nausea, vomiting, fever, and headache. Patients eventually develop signs of meningeal irritation.

For Leishmania spp, what are the vector and infective stage?

Vector: the female sandfly / Infective stage: promastigote.

What forms does Leishmania spp. have?

Amastigote, promastigote, and epimastigote

Which organs are severely affected by L. donovani?

Organs of the reticuloendothelial system (liver, spleen, and bone marrow).

What is the screening test for Visceral Leishmaniasis (Kala azar, Dumdum Fever) and the test for definite diagnosis?

Montenegro skin test for screening and demonstration of the amastigote from Giemsa stained slides for definitive diagnosis

What is the most common drug of choice for Visceral Leishmaniasis (Kala azar, Dumdum Fever)?

liposomal amphotericin B (Ambisome)

How is mucocutaneous leishmaniasis transmitted?

By sandflies (Lutzomyia and Psychodopigus) through skin bite.

Where does promastigotes invade in humans and what happens next in infection with L. braziliensis?

promastigotes invade the reticuloendothelial cells where they transform into amastigotes (diagnostic stage). Reproduction of the amastigotes result in tissue destruction.

What are three members of Leishmania tropica complex?

L. tropica, L. aethiopica, and L. major

What is the disease caused by the Leishmania tropica complex, called?

Old World Cutaneous Leishmaniasis or orientalsore, and Baghdad or Delhi boil

What is the major difference between Leishmania, and the trypanosomes diagnostic stages?

Leishmania is the amastigote and trypomastigote for the trypanosomes.

What is the vector and infective stage of Trypanosoma cruzi?

vector, reduviid or triatomid bugs and Infective stage, the trypomastigotes

What two species are similar in morphology and involves the tsetse fly (Glossina) as the vector

Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense

What is the main diagnostic sign of Trypanosomabrucei gambiense?

Enlargementof the posterior cervical lymph nodes (Winterbottom’s sign).

How is P. vivax and P. ovale different from other palmodium?

P. vivax and P. ovale produce a latent form(called hypnozoite or sleeping form)in the liver,which is the cause of the relapse or recrudescenceseen in vivax and ovale malaria

During malaria paroxysms, why should the greatest number of intracellular organisms are present midway between paroxysmsor before the onset of fever?

This is the best time to take blood films since the greatest number of intracellular organisms are present.

Parenteralquinine is the drug of choice for _?

acute malaria infection

Which species of plasmodium do not affect hypnozoites?

chloroquine for acute malaria infection, but does not affect hypnozoites of P. vivax and P. ovale infection, Primaquine will given for that issue

What are the definitive and intermediate hosts for Toxoplasma gondii?

the domestic cat or other felines as the definitive host / humans and other mammals as intermediate hosts.

What are the two forms of Toxoplasmagondii?

Tachyzoites are the rapidly multiplying forms responsible for the initial infection while bradyzoites are shorter,slow growing forms seen in chronic infections.

Describe conditions to perform treatment of election of immunocompetent patients, and pregnant woman with the conditions of pregnancy

Immunocompetent : not require specific therapy / Immunocompromised, pyrimethamine plus sulfadiazine for especially those with AIDS / Pregnant women, clindamycin or spiramycinmay be given