Protozoan & Helminthic Parasites – Lecture Review

These flashcards cover definitions, life cycles, transmission routes, clinical manifestations, laboratory features, and treatments for the major protozoan and related parasites discussed in the lecture notes. They are structured in a question-and-answer format to aid active recall while studying.

What is a single-celled protozoan called?

Protozoa

What is a multi-celled parasitic organism called?

Helminth

Which protozoan group moves by pseudopods?

Amoebas

What is the infective stage of most intestinal amoebas?

Cyst

What is the primary mode of transmission for amoebic cysts?

Ingestion of contaminated food or water

Where does encystation of amoebas usually occur in humans?

The intestine

Which amoebic life-stage is fragile, motile, and divides by binary fission?

Trophozoite

Which stool consistency is most likely to contain trophozoites?

Liquid or soft stool

Which laboratory technique lets you view living trophozoites in fresh stool?

Wet mount (plus permanent stain for confirmation)

Why can amoebic cysts remain infectious for long periods in feces?

They are environmentally resistant and viable outside the host

Which parasite causes intestinal amoebiasis and extra-intestinal disease?

Entamoeba histolytica

Name the two main life-stages of Entamoeba histolytica and their roles.

Cyst – infective, dormant, resistant; Trophozoite – motile, feeding, tissue-damaging

How does Entamoeba histolytica reproduce inside the host?

By binary fission in the trophozoite stage

State two modes of transmission for Entamoeba histolytica.

Ingesting mature cysts in food/water or hand-to-mouth contact with feces

What is excystation in E. histolytica?

Conversion of an ingested cyst into eight trophozoites in the small intestine

List four common symptoms of intestinal amoebiasis.

Diarrhea, abdominal pain, weight loss, fatigue (severe: bloody dysentery)

What is extra-intestinal amoebiasis?

Spread of E. histolytica beyond the gut, especially to the liver, causing abscesses

Which drugs are recommended for asymptomatic E. histolytica infection?

Paromomycin or Diloxanide furoate

Why is boiling water preferred over chlorination against E. histolytica?

Cysts are chlorine-resistant; boiling or iodine treatment kills them

What two microscopic structures are seen in young E. histolytica cysts?

Chromatoidal bars and a glycogen mass

Define venereal amoebiasis.

Sexual transmission of E. histolytica, e.g., penile infection from vaginal amoebiasis

Which non-pathogenic amoeba is morphologically identical to E. histolytica?

Entamoeba dispar

What distinguishes Entamoeba hartmanni from E. histolytica?

Smaller size, nonpathogenic, non-progressive motility, no ingested RBCs

Describe the motility of Entamoeba hartmanni trophozoites.

Slow, non-progressive movement using finger-shaped pseudopodia

Why is finding Entamoeba coli in stool clinically useful?

Indicates fecal contamination and poor sanitation though nonpathogenic

Which amoeba is linked to pig exposure and common in Papua New Guinea?

Entamoeba polecki

What drug combination treats Entamoeba polecki infection if required?

Metronidazole plus Diloxanide furoate

What identifying feature is typical of Endolimax nana cysts?

Four nuclei in the mature cyst

How is Iodamoeba bütschlii recognized microscopically?

A single nucleus and large glycogen vacuole in the cyst

Which amoeba lacks a cyst stage and may ingest WBCs?

Entamoeba gingivalis

How is Entamoeba gingivalis most often transmitted?

Mouth-to-mouth contact, droplets, or shared utensils

What free-living amoeba causes Primary Amoebic Meningoencephalitis (PAM)?

Naegleria fowleri

How does Naegleria fowleri enter the human body?

Through the nose during water activities in warm, contaminated water

Name two early symptoms of PAM.

Fever and headache (plus sore throat, nausea, vomiting)

What is the effective drug for PAM?

Amphotericin B (often with Miconazole)

Which amoeba causes Acanthamoeba keratitis and GAE?

Acanthamoeba spp.

What is a typical symptom of Acanthamoeba keratitis?

Severe eye pain, redness, and potential vision loss

What medication is preferred for Acanthamoeba infections?

Propamidine (Brolene)

What distinctive structures help Acanthamoeba move?

Acanthopodia (spiny pseudopods)

Which stain aids laboratory detection of Acanthamoeba cysts?

Calcofluor white

What flagellate causes giardiasis?

Giardia intestinalis (G. lamblia)

How is Giardia intestinalis transmitted?

Ingestion of water or food containing cysts

Where does excystation of Giardia occur?

Duodenum (small intestine)

What organelle allows Giardia trophozoites to adhere to the gut lining?

Sucking (adhesive) disk

Give two classic symptoms of giardiasis.

Steatorrhea and abdominal cramps (plus diarrhea, malabsorption)

Which drugs effectively treat giardiasis?

Tinidazole or Nitazoxanide

Why are Giardia cysts resistant to chlorine?

Their tough outer wall protects against normal chlorination levels

What is the transmission route of Chilomastix mesnili?

Ingesting contaminated food, water, or hand-to-mouth contact

Where does Chilomastix mesnili encyst?

In the large intestine

What phenomenon in Dientamoeba fragilis shows granules in Brownian motion?

Hakansson phenomenon

Which drug treats Dientamoeba fragilis infection?

Iodoquinol

Name one preventive measure against Dientamoeba fragilis.

Good personal hygiene (others: proper sanitation, safe sex)

Which Trichomonas species infects the intestine?

Trichomonas hominis

How is Trichomonas hominis transmitted?

Fecal-oral route or ingestion of contaminated milk

Which Trichomonas species inhabits the mouth?

Trichomonas tenax

Which Trichomonas causes sexually transmitted vaginitis/urethritis?

Trichomonas vaginalis

List two symptoms of T. vaginalis infection in women.

Foul-smelling green-yellow discharge and itching/burning

What drug is standard therapy for Trichomonas vaginalis?

Metronidazole (Flagyl)

What are hemoflagellates?

Flagellated protozoa (Leishmania, Trypanosoma) that infect blood/tissues

Name the four morphological forms of hemoflagellates.

Amastigote, Promastigote, Epimastigote, Trypomastigote

Which form of Leishmania is infective to humans?

Promastigote (in sandfly bite)

Which diagnostic stage of Leishmania is found in human tissue?

Amastigote inside macrophages

What disease is produced by the Leishmania braziliensis complex?

Mucocutaneous leishmaniasis (espundia)

Which sandfly genera transmit L. braziliensis complex parasites?

Lutzomyia and Psychodopygus

What is the key symptom of mucocutaneous leishmaniasis?

Large destructive ulcers of nose, mouth, or throat

What antimonial drug treats cutaneous and mucocutaneous leishmaniasis?

Sodium stibogluconate (Pentostam)

Which Leishmania complex causes visceral leishmaniasis (Kala-azar)?

Leishmania donovani complex

What screening test is used for visceral leishmaniasis in populations?

Montenegro skin test

Which drug is first-line for visceral leishmaniasis?

Amphotericin B (liposomal)

What disease does the Leishmania mexicana complex produce?

New World cutaneous leishmaniasis (Chiclero ulcer)

Which Leishmania complex causes Old World cutaneous lesions called Oriental sores?

Leishmania tropica complex

What insect transmits Trypanosoma brucei gambiense?

Tsetse fly (Glossina palpalis or G. tachinoides)

What disease is caused by T. b. gambiense?

West African Sleeping Sickness

What symptom is called Winterbottom’s sign?

Posterior cervical lymph node enlargement in T. b. gambiense

Which drug treats late-stage African trypanosomiasis with CNS involvement?

Melarsoprol (others: Eflornithine, Suramin, Pentamidine)

What disease does Trypanosoma brucei rhodesiense cause?

East African Sleeping Sickness

Which insect transmits Trypanosoma cruzi?

Reduviid (kissing) bugs

Name two hallmark signs of acute Chagas disease.

Chagoma at bite site and Romana’s sign (periorbital swelling)

What medication is used for Chagas disease?

Nifurtimox

Which protozoan genera infect red blood cells?

Plasmodium and Babesia

What is the infective stage of Plasmodium to humans?

Sporozoite injected by Anopheles mosquito

During which fever phase should blood be drawn for malaria diagnosis?

During paroxysms (cold, hot, or sweating stage)

Which Plasmodium species causes quartan malaria?

Plasmodium malariae

Which Plasmodium species is most dangerous due to cerebral involvement?

Plasmodium falciparum

What malaria complication is known as Blackwater fever?

Hemoglobinuria and renal failure in P. falciparum infection

Which drug class is first-line for Plasmodium knowlesi infection?

Artemisinin-based therapy

What tick-borne protozoan causes babesiosis?

Babesia spp.

Which diagnostic clue in blood smear suggests Babesia?

Maltese-cross arrangement of merozoites without malarial pigment

Which Babesia species is severe in splenectomised patients in Europe?

Babesia divergens

What is the standard treatment for human babesiosis?

Clindamycin plus Quinine or Atovaquone plus Azithromycin

What ciliate parasite causes balantidiasis?

Balantidium coli

What is the main reservoir animal for Balantidium coli?

Pigs

Which coccidian parasite causes chronic diarrhea diagnosed by acid-fast oocysts?

Isospora (Cystoisospora) belli

What drug combination treats isosporiasis?

Trimethoprim-Sulfamethoxazole (SXT)

How do humans acquire Sarcocystis hominis as definitive hosts?

Eating undercooked beef or pork containing sarcocysts

Which protozoan causes self-limiting watery diarrhea and has oocysts lacking sporocysts?

Cryptosporidium parvum

How is Cyclospora cayetanensis usually transmitted?

Consumption of contaminated fresh produce (e.g., lettuce, berries)

What is the definitive host of Toxoplasma gondii?

Cats

Name the rapidly dividing stage of Toxoplasma gondii responsible for acute disease.

Tachyzoite

Which drug combination treats toxoplasmosis?

Pyrimethamine plus Sulfadiazine with folinic acid