BtBio 413 · Infectious & Parasitic Diseases · Midterm

Lecture 1 & 2: what will be asked, and how

Built from your two lecture PDFs, the 2022 and 2023 midterms, Quiz 1 (this year), Quizzes 2a/2b, the two T/F quizzes, your notes.docx and the Final Revision sheet. Questions from Lectures 3 to 5 (malaria, Toxoplasma, flukes) are left out.

REPEATED ×nMUST KNOWPROF'S ANSWER KEYTRAPEXTRA / LOW YIELDOUTSIDE SLIDES

Tap any slide image to enlarge it.

Tonight's plan

About 4 hours of study tonight, sleep by 5:30, one hour of practice after you wake at 3 pm. Tick blocks off as you go (ticks stay in this browser).

Tonight · 1:25 to 5:30 am

1:25-1:45Warm up on what repeatsRead Exam brief and the 12 Repeated questions. Say each answer out loud. These are the free marks.
1:45-2:30Lecture 1 basics + E. histolyticaSections 1.1 to 1.4: definitions, protozoa stages, motility, taxonomy, hosts, the transmission table, then E. histolytica with its images (invasion steps, diagnosis, drugs).
2:30-2:40BreakStand up, water, no phone scrolling.
2:40-3:20Lecture 1: Giardia, Trichomonas, B. coliSections 1.5 to 1.7. Learn the labelled diagrams (AD, MB, Ax; axostyle, hydrogenosome; macro/micro nucleus). Finish with the Lecture 1 comparison table.
3:20-4:15All of Lecture 2Leishmania forms, NNN, life cycle, kala-azar, PKDL, oriental sore, mucosal; then T. brucei and T. cruzi with their life cycles. End on the Lecture 2 comparison table and the 3-line insect summary under it. This lecture is under-tested in past papers, so it is where the new questions will come from.
4:15-4:25Break
4:25-5:05Past-paper bankDo every question in the Past-paper bank by tapping answers, not reading them. Write down the numbers you get wrong.
5:05-5:25Traps + redo your wrong onesRead Traps, then redo only the bank questions you missed.
5:30SleepStop here even if it feels unfinished. Sleep is when tonight's facts get stored; an extra hour awake at 6 am is worth less than the sleep it costs.

After you wake · 3:00 to 4:15 pm

3:00-3:15Wake up properlyWash, eat something, no studying in bed.
3:15-4:00Timed mock examOpen the 40-question mock midterm and take it in one go, 45 minutes, no notes. It is in your Para folder as BtBio413_Mock_Midterm.html.
4:00-4:15Fix the gaps, then stopRead the explanation for every wrong answer, then the Last 30 minutes sheet once. Nothing new after this.

If the exam is earlier than about 5 pm, swap the mock exam for the Last 30 minutes sheet + Repeated questions only.

Exam brief

~20 marksLikely shape for 45 min: 10 MCQ + 5 True/False + 5 Matching (the 2023 midterm layout)

59 vs 10Past-paper items on Lecture 1 vs Lecture 2. Lecture 2 is under-tested, so expect more of it this time

12 questionsappeared in two or more papers, mostly word for word. They are the ranked list below

How this professor writes questions

MCQ "ONE BEST answer", often with "all EXCEPT", "respectively", or a short clinical case ("A 23-year-old male had dysentery…", "A soldier serving in Iraq…").
True/False: "underline the wrong part". The false ones swap a single word: multicellular for unicellular, non-feeding for feeding, mutualism for symbiosis, promastigote for amastigote. Read each noun and ask "is this the exact word on the slide?"
Matching: 5 items, 7 to 8 options, with distractors that recur every year (multicellular, metastasis, hydrocephaly, feeding, cyst).
Options use the slide's own wording ("contact-dependent", "hematophagous", "falling leaf"). Learn the slide words, not textbook paraphrases.

Where the past papers came from

M22: Midterm 29 Nov 2022, 10 marks, 20 min (T/F 5, MCQ 5, Matching 5). Lecture 1 + 2. Official key included in para midterm.pdf.
M23: Midterm 2023, 20 marks (MCQ 10, T/F 5, Matching 5). Lecture 1 only. Graded copy, scored full marks, so the circled answers are the accepted key.
Q1-26: Quiz 1 this year, 10 MCQ in 10 min. Q2a / Q2b: Quizzes 26 Oct 2023. TF-A / TF-B: Lecture 1 T/F quizzes. TF-L2: Lecture 2 T/F quiz (handwritten answers on it are a student's, three of them are wrong, see bank).

The repeated questions

Ranked by how many papers asked them. If you only have one hour, learn this list and the Traps section.

×5PAPERS
Trichomonas vaginalis: diagnostic stage = trophozoite. It has ONE stage only, no cyst.Asked as MCQ (M22, Q2a), matching (Q2b), "only one stage in its life cycle" (M23), and again in the Final Revision.M22 · Q2a · Q2b · M23 · FR
×4PAPERS
Balantidium coli: ciliate, macro + micro nucleus, conjugation, pigs (swine) are the reservoir, cyst is infective, causes dysentery.Every paper has at least one B. coli item.M22 · M23 (×4 items) · Q2a/2b · Q1-26
×3PAPERS
"Facultative and commensal respectively" = Giardia lamblia, Balantidium coli.Same 4 options every time. Option A (E. histolytica, T. vaginalis) is the bait.M22 · Q2a · Q2b version
×3PAPERS
Giardia lamblia is a typical example of fecal-oral transmission (TRUE); giardiasis ↔ water-borne epidemics.M22 T/F · M23 T/F · M23 matching
×3PAPERS
Protozoa = eukaryotic, unicellular (never "multicellular", never "prokaryotic").M22 matching · TF-A · Q1-26
×3PAPERS
Entamoeba histolytica ↔ metastasis / extra-intestinal amebiasis; dysentery with mucus and blood."Extra-intestinal amoebiasis is defined as oral infection" is FALSE (it is metastasis).M22 · M23 T/F · Q2a
×2PAPERS
Reservoir host = continuous source of infection.Identical wording both times.M23 · Q1-26
×2PAPERS
Propagative transmission = changes in NUMBERS only (multiplies, no change of form).M23 T/F · Q1-26
×2PAPERS
Axostyle = support. Hydrogenosome = ATP production.Q2a · Q2b · M23 matching
×2PAPERS
Trichomoniasis ↔ dysuria or pruritus; discharge is greenish, frothy.M22 · Q2b · Q2a
×2PAPERS
Symbiosis = close association of two different organisms (NOT mutualism).M23 · TF-B
L2DUE
Lecture 2 favourites: sand fly + painless face sores (Iraq) · Glossina morsitans → nagana · T. cruzi = muscular & nervous tissue · promastigote → amastigote inside macrophages · amastigote is the diagnostic form · kala-azar ↔ hepatomegaly · NNN medium is for Leishmania.M22 · TF-L2

Lecture 1 · Intro + intestinal & urogenital protozoa

1.1 Animal associations

Slide: symbiosis, mutualism, commensalism, parasitism, pathogen definitions — LECTURE 1 · SLIDE 2Five definitions. Learn the exact wording; every past paper used at least one.

Must know ×4

Symbiosis = close association of two different organisms. (The umbrella word. "Mutualism is a close association" = FALSE.)
Mutualism = beneficial to both. Example from Quiz 1: protozoa in the termite gut → mutualistic.
Commensalism = one benefits, the other neither benefited nor harmed. (B. coli is "usually non-pathogenic commensal".)
Parasitism = one organism (the parasite) living at the expense of the other (the host). TF-A swapped host and parasite → FALSE.
Pathogen = parasites that injure their host.

Parasitology: science of organisms that seek shelter and nourishment on or within other living organisms. Branches: Medical Protozoology (protozoa), Helminthology (worms), Entomology (arthropods that cause or transmit disease).

Tree: pathogenic parasites split into protozoa and metazoa — LECTURE 1 · SLIDE 4Protozoa = simple **unicellular**; Metazoa = complex **multicellular** (helminths). Protozoa groups: Rhizopoda (amoeba), Mastigophora (flagellates), Sporozoa, Ciliates.

1.2 Protozoa: definition, stages, motility

Must know ×3

Protozoa: unicellular, microscopic, eukaryotic ("eukaryotic unicellular protist" in Q1-26). All parasitic organisms are eukaryotes.
Infective stage = cysts, oocysts, sporozoites, spores → non-feeding, non-motile, no reproduction.
Vegetative stage = trophozoite → feeding, motility, reproduction; invasive, causes pathology. ("The vegetative form is non-feeding" = FALSE, TF-A.)

Protozoan motility table — LECTURE 1 · SLIDE 7Motility defines the groups.
flagella
flagellates (Giardia, Trichomonas, Leishmania, Trypanosoma)
cilia
ciliates (Balantidium coli)
ameboid
amebas, by **pseudopodia** (also used for phagocytosis, Q1-26)
gliding
sporozoa (Plasmodium, Toxoplasma)
**Cilia and flagella = same structure, different shape** (M23).

Taxonomy (Quiz 1 this year asked it)

Monophyletic (one common ancestor): kinetoplastids, apicomplexa, ciliates.
Polyphyletic (multiple ancestors): amebas and flagellates. Q1-26 answer: Amebas.
Taxonomy was originally based on motility (light microscope), EM since the 1960s, now molecular data.

Classification of protozoa — LECTURE 1 · SLIDE 10Classification: Phylum Sarcomastigophora (subphyla Sarcodina = amebae, e.g. E. histolytica; Mastigophora = flagellates, e.g. Giardia, T. vaginalis, Trypanosoma) · Phylum Ciliata (B. coli) · Phylum Apicomplexa (Plasmodium, Toxoplasma, Cryptosporidium).

Lifestyles and reproduction (M23 matching + TF-B)

Osmotrophy = absorb solutes · Phagotrophy = ingest particulates = predation on bacteria or other protozoa ("phagotrophy is a parasitism…" = FALSE) · Pinocytosis = fluid uptake · Autotrophy = photosynthetic · Heterotrophy = combinations.
Asexual: binary fission, multiple fission, budding. Sexual: fusion of gametes, conjugation (conjugation ↔ sexual reproduction, M23).

Extra / low yield: sizes, diversity, Euglena cartoon, study outline

>200,000 named species, ~10,000 parasites, ~20 human pathogens. Sizes: Plasmodium merozoites 2-5 µm; Paramecium 200-500 µm; Spirostomum 3 mm; Nummulites (fossil) 7-13 cm. µm = 10^-6 m. Euglena: "it's green, alga" (phycologist) vs "it moves, protozoan" (protozoologist). Study outline per parasite: nomenclature (Genus species), epidemiology, morphology, life cycle, symptoms, pathology, diagnosis, treatment, prevention.

TF-B: "Protozoa are classified according to body shapes" → FALSE. A student wrote "body size" as the fix, but the slides say classification is based on motility. If asked, underline "body shapes" and write "motility (locomotion)". Medium confidence.

1.3 Types of parasites, hosts, transmission

Type of parasite	Meaning	Exam hook
Ectoparasite	lives on the body surface
Endoparasite	lives inside the body
Facultative	can live free OR as a parasite	×3 Giardia (answer key); E. histolytica = "facultative pathogen"
Obligatory	cannot survive without a host	"Obligatory parasites able to live free life" = FALSE
Opportunistic	causes disease when host defences are low	M23 key: B. coli see note below
Coprozoic	found in feces, cannot infect man	M23: "no ability to infect the human"
Accidental	infects an unusual host

Professor's key: opportunistic parasite

M23 Q7 "typical example of an opportunistic parasite": the graded paper (10/10) accepted Balantidium coli; Toxoplasma was crossed out by the student. Logic that fits the slides: B. coli is "usually non-pathogenic commensal" but "can invade intestinal epithelium". If the same options return, choose B. coli.

Outside slides: textbooks define opportunistic parasites as those that cause disease mainly in immunocompromised hosts. The Final Revision sheet's "infect immunocompetent people" is likely a typo. The T/F quiz version ("Opportunistic parasite infect immunocompetent or immunodeficien[t] peop[le]") is cut off at the right edge of the photo, and the student's answer is [illegible], so it gives no key. Low confidence on how a T/F version would be keyed.

Types of hosts slide — LECTURE 1 · SLIDE 17
Intermediate
developmental stages; may/may not reproduce asexually; never adult or sexual
Final (definitive)
parasite reaches **maturity + sexual reproduction**
Reservoir
harbors it, no ill effects, **source of infection** ×2

Types and modes of transmission — LECTURE 1 · SLIDE 18The slide only lists the names; the definitions below come from your notes and match the answer keys.

Transmission	Numbers change?	Form changes?	Hook
Mechanical	No	No	vector just carries it on its body ("dirty needle")
Biological · Propagative	Yes	No	×2 "changes in numbers only"
Biological · Cyclo-developmental	No	Yes	changes in form only
Biological · Cyclo-propagative	Yes	Yes	both (e.g. Plasmodium in mosquito, Leishmania in sand fly)

Mosquito bite → malaria = biological vector transmission (Q1-26). Sources of exposure: water, food, blood transfusion, blood-sucking insects, environment.

1.4 Entamoeba histolytica (amebiasis)

E. histolytica key facts — LECTURE 1 · SLIDE 20Phylum Rhizopoda (Sarcomastigophora), subphylum Sarcodina. **Cosmopolitan, no animal reservoirs, facultative pathogen.** Most clear spontaneously in 6-12 months. ~10% of world infected, 50 million invasive cases/yr, 100,000 deaths/yr.

E. histolytica life cycle cyst and trophozoite — SLIDE 21 · LIFE CYCLECyst: passed in feces, resistant, infective. **Trophozoite**: feeding, motile, replication.

Excystation — SLIDE 22 · EXCYSTATIONSmall intestine · nuclear division **4 → 8** · 8 amebulae · trophozoites migrate to **large** intestine.

Encystation with immature and mature cysts — SLIDE 24 · ENCYSTATIONRounds up, secretes cyst wall, ribosomes aggregate = **chromatoid bodies**, 2 nuclear divisions **1 → 4 nuclei**; survives weeks to months.

Trophozoite in large intestine — SLIDE 23Trophozoites colonize the **large intestine**, feed on bacteria and debris, binary fission.

Pathogenesis of amebiasis — SLIDE 25 · PATHOGENESISNon-invasive: asymptomatic cyst passer, non-dysenteric diarrhea. Invasive: necrosis → ulcers, dysentery → colitis, peritonitis → **metastasis → extraintestinal amebiasis**.

Disease manifestations with body diagram — SLIDE 27Spread via **portal vein** to liver. **Ameboma** = inflammatory thickening around abscess, can be confused with a tumor. Cyst production stops in invasive disease.

Invasion steps diagram: lumen, mucus layer, epithelial cells, ECM, neutrophil, metastasis via portal vein — LECTURE 1 · SLIDE 30 · HOW IT INVADES
①
penetration of the mucus layer
②
contact-dependent killing of epithelial cells
③
breakdown of tissue (extracellular matrix, ECM)
④
contact-dependent killing of neutrophils / leukocytes
⑤
metastasis via portal vein
"Hematophagous" trophozoites = they ingest red blood cells (slide 26).

Must know: E. histolytica

Routes (Q1-26): sexual transmission, contaminated water, contact with amebic skin lesion. NOT inhalation of spores in dust.
Cysts are never found in the tissues = TRUE (M22). Tissue has trophozoites only (they invade; cyst production stops).
Trophozoites typically identified by stool examination (Q1-26).
Dysentery (stool with mucus + blood) in a young man → E. histolytica (M22). If E. histolytica is not an option → B. coli (Q2a).
Extra-intestinal: liver abscess (RUQ pain, enlarged liver, reddish-brown "anchovy" pus, trophozoites at the abscess wall), pulmonary (rarely primary, usually liver abscess rupturing through the diaphragm), cutaneous (perianal, urogenital ulcers via fistula).

Diagnosis of amebiasis — LECTURE 1 · SLIDE 31 · DIAGNOSISIntestinal: stool (cysts and/or trophozoites), sigmoidoscopy, antigen detection (*histolytica* vs *dispar*; E. dispar is the non-pathogenic look-alike). Hepatic: symptoms, serology, imaging (CT, MRI, US), abscess aspiration in selected cases only.

Treatment and control — LECTURE 1 · SLIDE 32 · TREATMENT
Asymptomatic
**iodoquinol or paromomycin** (lumenal agents)
Symptomatic
**metronidazole or tinidazole**, then a lumenal agent
Liver abscess
drain **only** if high probability of rupture
Control: avoid fecal-oral spread; mass drug treatment has little effect.

Extra / low yield: list of intestinal protozoa, epidemiology numbers

Flagellates: Giardia lamblia, Dientamoeba fragilis, Chilomastix mesnili, Trichomonas hominis, Enteromonas hominis, Retortamonas intestinalis. Amebas: E. histolytica, E. dispar, E. coli, E. hartmanni, Endolimax nana, Iodamoeba bütschlii. Apicomplexa: Cryptosporidium, Cyclospora, Isospora. Microsporidia: Enterocytozoon, Encephalitozoon. Other: Blastocystis, Balantidium coli. Lumen-dwellers elsewhere: T. vaginalis (urogenital), T. tenax (oral), E. gingivalis (oral). Homosexual men 40-50% infected in NYC/SF in the late 70s.

1.5 Giardia lamblia (giardiasis)

Subphylum Mastigophora, class Zoomastigophora. Also called G. duodenalis, G. intestinalis. Worldwide; most common protozoa in stools (~200 million cases/yr). Zoonosis: Entamoeba = no, Cryptosporidium = yes, Giardia = controversial; person-to-person is most common.

Giardia life cycle cyst and trophozoite labelled — LECTURE 1 · SLIDE 36 · LIFE CYCLECyst = infective stage passed in feces. **Trophozoite** = replicative stage inhabiting the **small intestine**.

Giardia cyst labelled — SLIDE 37 · CYSTOval, 11-14 × 6-10 µm, **4 nuclei** at anterior end Q2b
Nu
nucleus (×4)
k
karyosome (large; no peripheral chromatin)
Ax
axonemes (fibrils)
MB
median bodies
CW
cyst wall, set apart from cytoplasm

Giardia trophozoite labelled — SLIDE 38 · TROPHOZOITEPear shape, 12-15 × 5-10 µm, **2 nuclei**, bilateral symmetry, **4 pairs of flagella**, "falling leaf" motility
AD
adhesive disk (sticks to small-intestine wall)
k
karyosome
Nu
nucleus (×2)
MB
pair of median bodies
Ax
axonemes
Fg
flagella

Tested: Giardia trophozoite "all EXCEPT" (M23)

Has 2 nuclei ✓ · replicates by binary fission ✓ · can cause diarrhea ✓ · colonizes large intestine ✗ (it is the small intestine).

Giardia clinical features — LECTURE 1 · SLIDE 41 · CLINICALIncubation 1-2 weeks. Sudden explosive watery diarrhea; **bulky, frothy, greasy, foul-smelling** stool, **no blood or mucus**. Bloating, belching (sulfuric), cramps, nausea. Chronic: weight loss, failure to thrive.

Must know: Giardia diagnosis, treatment, control

Stools on 3 non-consecutive days (excretion is inconsistent, infection patchy); wet mount or stained; IFA, copro-antigens.
Duodenal aspirate / biopsy; Enterotest (string test).
Drug of choice: metronidazole (Flagyl) 750 mg tid × 5 d, >90% cure. Alternatives: tinidazole (single dose), paromomycin (pregnancy), quinacrine, furazolidone.
Water: boiling or iodine, not chlorine.
Risk: children in day care, food handlers, travelers' diarrhea, water-borne epidemics, oral-anal contact.

Extra / low yield: history, in-vitro culture

1681 van Leeuwenhoek observed; 1859 Lambl documented; 1954 Rendtorff fulfilled Koch's postulates. Excystation in vitro: brief acid pH ~2, flagella active 5-10 min after return to neutral pH, cytokinesis within 30 min. Encystation: pH 7.8 with high bile; loss of disk and flagella.

1.6 Trichomonads and Trichomonas vaginalis

Trichomonad labelled drawing and human Trichomonas species — LECTURE 1 · SLIDE 443-5 anterior flagella, one undulating membrane, axostyle, hydrogenosome.
fg
flagella
bb
basal bodies
nu
nucleus (single)
um
undulating membrane
cs
costa (rod under the membrane)
cy
cytostome
ax
**axostyle = support** ×2
label decoding is outside the slides
Species: **T. tenax** = oral cavity · **T. hominis** (Pentatrichomonas) = intestine · **T. vaginalis** = urogenital. **Hydrogenosome = ATP production** (M23 matching).

T. vaginalis transmission — SLIDE 46Trophozoite transmitted during sexual intercourse (non-sexual possible). Females: vagina; males: urethra, prostate, epididymis. Both sexes equally susceptible; symptoms more common in females.

Trichomoniasis symptoms — SLIDE 47Females: discharge **frothy, yellowish or greenish** (50-75%), pruritus, painful coitus; worse with menstruation/pregnancy. Males: 50-90% asymptomatic, mild **dysuria or pruritus**.

Repeated ×5: T. vaginalis has only one stage

No cyst → no excystation → transmitted directly by sex (trophozoite cannot survive long outside). So the diagnostic stage = trophozoite, and it is "the parasite with only one stage in its life cycle".

Diagnosis: direct observation or in-vitro culture of vaginal discharge, urine sediment, prostatic secretion. Treatment: metronidazole 250 mg 3/d for 5-7 d or single 2 g dose + simultaneous treatment of the partner (85-90% cure). Prevention: limit partners, condoms.

1.7 Ciliates and Balantidium coli

Ciliates SEM and characteristics — SLIDE 49 · CILIATESB. coli is the only ciliate infecting humans. Covered with rows of cilia. Defining feature: **nuclear dimorphism**: micronucleus (genetic) + macronucleus (somatic). Sexual reproduction by **conjugation**.

Balantidium coli trophozoite and cyst labelled — SLIDE 52 · B. COLITrophozoite ~70 × 45 µm (up to 200) · cyst ~55 µm
cytostome
cell mouth = **feeding** (M23)
contractile vacuole
expels excess water (osmoregulation). "Function is respiration" = FALSE (M23)
macronucleus
large, kidney shaped, somatic
micronucleus
small, genetic
cilia
locomotion
cyst wall
cyst = infective stage

Repeated ×4: B. coli in one box

Swine (pigs) = primary reservoir; also rodents, nonhuman primates. "Communities living near… → pigs" (M23); "Swine are the primary host for the commensal parasite → B. coli" (Q1-26).
Usually non-pathogenic commensal in large intestine; can invade epithelium → ulceration, dysentery-like (acute diarrhea with mucus and blood).
Infective stage: cyst (M23). Diagnosis: cyst or trophozoite in feces.
Not sexually transmitted (M22 T/F = FALSE); fecal-oral.
Treatment: tetracycline or iodoquinol. World-wide, tropics, rarely exceeds 1%.
Ciliates are unique because they have macro and micro nuclei (M23).

Lecture 2 · Blood & tissue flagellates

Why Lecture 2 matters more than its past-paper count

Only 10 past items touched Lecture 2 (the 2023 midterm had none), but your exam covers both lectures. Expect at least 5-8 marks from here. The professor likes vectors, forms (amastigote/promastigote/trypomastigote), habitat and culture medium.

2.1 Leishmania: classification and forms

Four forms: trypomastigote, amastigote, promastigote, epimastigote — LECTURE 2 · SLIDE 5 · THE FOUR FORMSTell them apart by where the **kinetoplast** sits relative to the nucleus and whether there is a flagellum / undulating membrane.
Amastigote
round/oval, **no free flagellum**, intracellular (in man)
Promastigote
kinetoplast at **anterior** end, free flagellum, no undulating membrane (sand fly + culture)
Epimastigote
kinetoplast just **in front of the nucleus**, short undulating membrane (insect)
Trypomastigote
kinetoplast at **posterior** end, long undulating membrane (blood of man)
epimastigote/promastigote kinetoplast positions are standard textbook detail, not stated on the slides

Amastigote stage — SLIDE 4 · AMASTIGOTE (aflagellate)Formerly "Leishmanial form". Inside **reticuloendothelial (RE) cells** (macrophages) of man, dog, hamster. Round/oval **2-4 µm**, nucleus 1 µm, kinetoplast at right angles to nucleus, axoneme, vacuole.

Cultivation NNN — SLIDE 7 · CULTIVATIONNNN medium (Novy, MacNeal, Nicolle): **2 parts salt agar + 1 part defibrinated rabbit blood**; inoculate at **22-24 °C**; ascorbic acid + hematin favour growth. Grows as **promastigotes**. Susceptible animal: dog.

Promastigote (formerly Leptomonad): sand fly gut + culture. Early: short oval/pear 5-10 × 2-3 µm; fully developed: long spindle 5-20 × 1-2 µm; kinetoplast transverse near anterior end; flagellum same length as body or longer.

Reservoir: dog (Mediterranean, China, Brazil). Transmission: man → man by sand fly of genera Phlebotomus (Old World) & Lutzomyia (New World).

2.2 Leishmania life cycle

CDC Leishmania life cycle — LECTURE 2 · SLIDE 8 · CDC LIFE CYCLE
1
Sand fly bites, injects **promastigotes** (infective stage, ▲i)
2
Promastigotes are phagocytized by **macrophages**
3
Promastigotes **transform into amastigotes** inside macrophages
4
Amastigotes multiply in cells of various tissues (**diagnostic stage**, ▲d)
5-6
Sand fly ingests macrophages containing amastigotes
7
Amastigotes → promastigotes in the fly's **midgut**
8
Divide in midgut, migrate to **proboscis**

Tested T/F (M22, TF-L2)

"Promastigotes transform into trypomastigotes in macrophages" = FALSE → amastigotes.
"Diagnostic form in human leishmaniasis is a promastigote form" = FALSE → amastigote.

2.3 Visceral leishmaniasis: kala-azar

Kala-azar names — SLIDE 10First described in India. Names: **Kala-azar (black sickness)**, Dum Dum fever, Burdwan fever, tropical splenomegaly. **Incubation 3-6 months.**

Kala-azar clinical features — SLIDE 12Pyrexia · **splenic enlargement** · **liver enlargement (hepatomegaly, M22 matching)** · lymphadenopathy. Untreated: **75-90% die within 2 years** (dysentery, TB, pneumonia, cancrum oris).

Lab diagnosis of kala-azar flow chart — LECTURE 2 · SLIDE 14 · LAB DIAGNOSIS
Direct
demonstrate L. donovani: peripheral blood (**amastigote**) · blood culture (**promastigote**) · biopsy (lymph node, sternal/iliac crest marrow, splenic puncture)
Indirect
**aldehyde test, antimony test, complement fixation test**
Prophylaxis: attack parasite, attack vector, personal prophylaxis.

SLIDE 16 · PKDLPost kala-azar dermal leishmaniasis (dermal leishmanoid): **non-ulcerative** skin lesion in endemic India (Bengal, Madras, Assam). Deep pigmented macules, erythematous patches (**butterfly erythema**), yellow-pink nodules. Diagnosis: **biopsy**. African kala-azar may show warty skin eruption.

2.4 Cutaneous & mucosal leishmaniasis

Oriental sore clinical features — SLIDE 20 · L. TROPICAOriental sore / tropical sore / Delhi boil: slow-healing ulcer, clean-cut margin, raised indurated edge, red areola; heals spontaneously in ~6 months leaving a depressed white scar. Habitat: **clasmatocytes** (RE cells) of skin. Pathology: chronic granuloma with fibrosis; nodules/ulcers after 1-3 months.

Must know: L. tropica & the Iraq soldier

Leishmanin (skin) test is positive in oriental sore.
Mice: intraperitoneal inoculation produces visceral infection.
Prophylaxis: eliminate reservoir hosts, control sand flies, personal protection, prophylactic immunisation with a culture of L. tropica.
Old World CL is common in Algeria, Iran, Iraq, Saudi Arabia, Syria, Afghanistan → "soldier in Iraq with large painless sores on head and face" → vector = sand fly (M22).

Cutaneous leishmaniasis new and old world — SLIDE 22New World: L. mexicana complex, L. braziliensis, L. panamensis. Old World: L. tropica, L. major.

Mucosal leishmaniasis — SLIDE 23 · MUCOSALRare; destructive oral/nasal/pharyngeal lesions, usually **L. braziliensis**. Epistaxis + erythema/edema of nasal mucosa → ulceration → **naso-oropharyngeal destruction**.

2.5 Trypanosomes: general

General characters of trypanosomes — LECTURE 2 · SLIDE 26Exist as **trypomastigotes** in vertebrates. Two hosts: vertebrate + insect. In the insect: amastigote, promastigote, epimastigote, metacyclic trypomastigote. Multiplication can happen in any stage. Transmitted by **blood-sucking insects**. Two species: **T. brucei** and **T. cruzi**.

2.6 Trypanosoma brucei: African trypanosomiasis

T. brucei habitat and morphology — SLIDE 28Causes **African trypanosomiasis** in man and **nagana** in domestic animals. Subspecies: *T. b. gambiense*, *T. b. rhodesiense*. Habitat: **connective tissue** → lymph nodes → blood (parasitaemia) → finally **brain**.

Labelled drawing of trypomastigote — SLIDE 29 · TRYPOMASTIGOTE (50 µm scale)
flagellum
starts near posterior end, runs along body, free at anterior end
nucleus
large, oval, **central**
kinetoplast
**small, posterior**
undulating membrane
along the body
Shape: elongated, flattened spindle; blunt posterior, pointed anterior.

Staining (same for T. brucei and T. cruzi): Leishman / Romanowsky

Cytoplasm + undulating membrane = pale blue · nucleus = reddish purple · kinetoplast + flagellum = dark red.

Culture (T. brucei): Ringer's solution with NaCl, Tyrode's solution, citrated human blood. Not NNN. Animal inoculation: mice, rats, guinea pigs (when parasites are scanty in blood).

CDC T. brucei life cycle — LECTURE 2 · SLIDE 31 · CDC LIFE CYCLE
1
Tsetse fly (*Glossina*) injects **metacyclic trypomastigotes** (▲i) with saliva
2-3
Become bloodstream trypomastigotes; **multiply by binary fission in blood, lymph, spinal fluid**
4
Trypomastigotes in blood (▲d diagnostic)
5-6
Fly ingests them → **procyclic trypomastigotes** in fly **midgut**
7
Leave midgut → **epimastigotes**
8
Multiply in **salivary gland** → metacyclic trypomastigotes

T. brucei: pathogenesis and diagnosis

Animal strain transmitted by Glossina morsitans among wild game and domestic animals → nagana (M22).
Host response: large amounts of non-specific immunoglobulin + macrophages; neutrophils take little interest.
Lesions: damage to perivascular connective tissue, mainly in lymph nodes and CNS.
Diagnosis: peripheral blood, sternal marrow, lymph node juice, CSF by lumbar puncture.

2.7 Trypanosoma cruzi: Chagas disease

T. cruzi morphology C shaped — SLIDE 35Central & South America. Habitat: **muscular & nervous tissue** and RE system (M22 T/F = TRUE). Vector: **triatomine bug** (*Triatoma*, *Reduvius*). Two forms in man: **trypomastigote, C or U shaped**, 20 µm, central nucleus, **large oval posterior kinetoplast**; and **amastigote** 2-4 µm.

Reservoir hosts armadillo and opossum — SLIDE 38Reservoirs: **armadillos & opossum**. **Man is the secondary host.** Diagnosis: stained blood film, **guinea pig inoculation**, specific complement fixation test.

CDC T. cruzi life cycle — LECTURE 2 · SLIDE 37 · CDC LIFE CYCLE
1
Bug takes a blood meal and passes **metacyclic trypomastigotes in its feces** near the wound (▲i)
2
They enter cells at the bite site and become **amastigotes**
3
Amastigotes **multiply inside cells** by binary fission
4
Become trypomastigotes, burst out into blood (▲d). **These do NOT multiply in blood**
5-6
Bug ingests them → **epimastigotes in midgut**
7
Multiply in midgut
8
Metacyclic trypomastigotes in **hindgut** → out with feces

Comparison tables

Lecture 1 protozoa side by side

	E. histolytica	Giardia lamblia	T. vaginalis	B. coli
Group / motility	Ameba · pseudopodia	Flagellate · 4 pairs flagella, falling leaf	Flagellate · 3-5 flagella + undulating membrane	Ciliate · cilia
Habitat	Large intestine (+ liver, lung, skin)	Small intestine	Urogenital tract	Large intestine
Stages	Cyst + trophozoite	Cyst + trophozoite	Trophozoite only	Cyst + trophozoite
Infective stage	Cyst (4 nuclei)	Cyst (4 nuclei)	Trophozoite	Cyst
Nuclei	Cyst 1→4; excyst 4→8	Cyst 4 · troph 2	1	Macro + micro
Transmission	Fecal-oral, sexual, skin lesion contact	Fecal-oral, water-borne	Sexual	Fecal-oral (pigs)
Reservoir	None (no animal reservoir)	Controversial zoonosis	Humans	Swine
Status (keys)	Facultative pathogen	Facultative	Pathogenic	Commensal; "opportunistic" in M23 key
Stool	Dysentery: mucus + blood	Greasy, frothy, no blood/mucus	Frothy greenish discharge	Diarrhea with mucus + blood
Key diagnosis	Stool, sigmoidoscopy, antigen (vs dispar), serology, imaging	Stool ×3 non-consecutive days, string test, duodenal aspirate	Discharge, urine sediment, prostatic secretion	Cyst/troph in feces
Drug	Metronidazole/tinidazole; iodoquinol/paromomycin if asymptomatic	Metronidazole; paromomycin in pregnancy	Metronidazole + treat partner	Tetracycline or iodoquinol

Blood & tissue flagellates side by side

	L. donovani	L. tropica	T. brucei	T. cruzi
Disease	Kala-azar (VL)	Oriental sore (CL)	African trypanosomiasis; nagana in animals	Chagas disease (American)
Vector	Sand fly (Phlebotomus, Lutzomyia)	Sand fly	Tsetse fly (Glossina)	Triatomine bug (Triatoma, Reduvius)
Form in man	Amastigote (in RE cells)	Amastigote (clasmatocytes of skin)	Trypomastigote	Trypomastigote (C/U) + amastigote
Form in insect	Promastigote	Promastigote	Procyclic trypo → epimastigote → metacyclic	Epimastigote → metacyclic
Insect site → exit	Midgut → proboscis (bite)	Midgut → proboscis (bite)	Midgut → salivary glands (bite)	Midgut → hindgut → feces
Multiplies in human blood?	No (inside macrophages)	No	Yes	No (inside cells as amastigote)
Habitat	Liver, spleen, bone marrow	Skin	Connective tissue → lymph nodes → blood → brain	Muscle, nervous tissue, RE system
Kinetoplast	Right angle to nucleus	Right angle to nucleus	Small, posterior	Large, oval, posterior
Reservoir	Dog	Reservoir hosts (eliminate)	Wild game, domestic animals	Armadillo, opossum (man = secondary host)
Culture	NNN (22-24 °C), grows as promastigote		Ringer's + Tyrode's + citrated human blood	Culture antigen for CFT
Animal	Dog / hamster susceptible	Mice (IP → visceral)	Mice, rats, guinea pigs	Guinea pig
Diagnosis	Blood, marrow, spleen, node; aldehyde, antimony, CFT	Leishmanin test, biopsy	Blood, marrow, node juice, CSF	Blood film, guinea pig, CFT

T. brucei in fly: bloodstream trypo → procyclic trypo (midgut) → epimastigote (salivary gland) → metacyclic trypo (saliva)
T. cruzi in bug: trypo → epimastigote (midgut) → metacyclic trypo (hindgut, feces)
Leishmania in sand fly: amastigote → promastigote (midgut) → metacyclic promastigote (proboscis)

Traps the distractors are built on

Three insects, three diseases. Sand fly = Leishmania · Tsetse (Glossina) = T. brucei / nagana · Triatomine (assassin, kissing, reduviid) bug = T. cruzi. "African trypanosomiasis via feces of assassin bugs" = FALSE. "Tsetse flies inject which stage of malaria?" = none of the above (malaria is mosquito).
NNN is for Leishmania, not trypanosomes.
Amastigote is what you find in human tissue (diagnostic) for Leishmania; promastigote is in the fly and culture.
T. cruzi vs T. brucei and the brain. T. brucei "finally localises in the brain" (sleeping sickness: coma, death). T. cruzi = muscle and nervous tissue (TRUE as written in M22). A statement linking T. cruzi to "CNS, coma and death" is most likely FALSE (the fix is T. brucei). Medium confidence.
American sleeping sickness is not a real option: sleeping sickness is African (T. brucei); American = Chagas.
Large vs small intestine: Giardia = small; E. histolytica + B. coli = large.
Nuclei numbers: Giardia cyst 4, troph 2; E. histolytica cyst 4, excystation 4 → 8; encystation 1 → 4.
Symbiosis is the "close association"; mutualism is "both benefit".
Propagative = numbers; cyclo-developmental = form; cyclo-propagative = both; mechanical = neither.
Coprozoic cannot infect; accidental infects an unusual host; obligatory cannot live free.
Intestinal parasites are diagnosed by stool, not blood film (TF-A).
Giardia water: iodine or boiling, not chlorine. Pregnancy: paromomycin.
Drugs: metronidazole for amebiasis, giardiasis, trichomoniasis; tetracycline only for B. coli.

Past-paper bank (Lectures 1-2 only)

Every in-scope question from your papers, with the accepted answer. Tap an option to check yourself.

0 / 0 correct

True / False (underline the wrong part)

Matching sets

Practice questions for tomorrow

New questions in the professor's style, aimed at slide facts that have not been asked yet (mostly Lecture 2). Confidence tags say how likely the topic is.

0 / 0 correct

True / False practice

Matching practice

Last 30 minutes before the exam

Definitions

Symbiosis = close association · mutualism = both benefit · commensalism = one benefits, other unaffected · parasitism = parasite at expense of host · pathogen = injures host.

Protozoa

Unicellular, microscopic, eukaryotic. Infective stage: non-feeding, non-motile, no reproduction. Trophozoite: feeding, motile, reproducing, invasive.

Motility

Flagella/flagellates · cilia/ciliates · pseudopodia/amebas · gliding/sporozoa. Cilia + flagella = same structure, different shape.

Taxonomy

Monophyletic: kinetoplastids, apicomplexa, ciliates. Polyphyletic: amebas, flagellates.

Hosts

Definitive = sexual/mature · intermediate = developmental · reservoir = source of infection, no ill effects.

Transmission

Propagative = numbers · cyclo-developmental = form · cyclo-propagative = both · mechanical = carried only.

E. histolytica

Large intestine · no animal reservoir · facultative pathogen · cyst 4 nuclei, chromatoid bodies · cysts never in tissue · dysentery · metastasis (liver via portal vein) · ameboma · metronidazole; iodoquinol/paromomycin if no symptoms.

Giardia

Small intestine · facultative · cyst 4 nuclei, troph 2 nuclei, 4 pairs flagella, adhesive disk, falling leaf · fecal-oral, water-borne · greasy stool, no blood · 3 stools, string test · metronidazole; paromomycin in pregnancy; iodine not chlorine.

T. vaginalis

Trophozoite only (diagnostic) · sexual · axostyle = support · hydrogenosome = ATP · greenish frothy discharge · dysuria/pruritus · metronidazole + partner.

B. coli

Only human ciliate · macro + micro nucleus · conjugation · swine · commensal · cyst infective · dysentery · cytostome feeding · tetracycline/iodoquinol.

Leishmania

Amastigote in man (RE cells, 2-4 µm, diagnostic) · promastigote in sand fly + NNN (2 salt agar : 1 rabbit blood, 22-24 °C) · promastigote → amastigote in macrophage · dog reservoir · Phlebotomus/Lutzomyia.

Kala-azar

L. donovani · liver, spleen, marrow · fever, splenomegaly, hepatomegaly, lymph nodes · incubation 3-6 months · 75-90% die in 2 yrs · aldehyde, antimony, CFT · PKDL non-ulcerative, biopsy.

CL / ML

L. tropica = oriental sore / Delhi boil, clasmatocytes, leishmanin +, heals in 6 months with white scar · Iraq soldier → sand fly · L. braziliensis = mucosal, naso-oropharyngeal destruction.

T. brucei

Tsetse (Glossina) · nagana · connective tissue → nodes → blood → brain · small posterior kinetoplast · multiplies in blood · Ringer's/Tyrode's culture · CSF diagnosis.

T. cruzi

Triatomine bug, feces · Chagas · muscle + nerve · C/U-shaped trypo, large posterior kinetoplast · amastigote multiplies in cells · armadillo, opossum · guinea pig.

Stain

Cytoplasm + undulating membrane pale blue · nucleus reddish purple · kinetoplast + flagellum dark red.

Help me improve this guide

Did the doctor say anything in class like "this is important" or "this will come"? Those are the strongest signal I don't have.
Is the exam pure MCQ, or the usual MCQ + True/False + Matching mix? Do you know the exact marks (10 or 20)?
Were any slides skipped or added in class? Lecture 2 has no treatment slides; if the doctor gave drugs for leishmaniasis or trypanosomiasis verbally, tell me.
Is there a Lecture 2 quiz with the official key? The TF-L2 sheet has student answers, and three disagree with the slides.
Do you want a shorter printable version, or a 40-question timed mock exam?