Parasitology - T. cruzi, T. brucei, B.coli, Leishmania, , G lamblia, T vaginalis,

Parasitology - T. cruzi, T. brucei, B.coli, Leishmania, , G lamblia, T vaginalis,

Trypanosoma cruzi

Intracellular parasite. consist of All four stages: amastigote, promastigote, epimastigote, trypomastigote.

Metacyclic trypomastigotes invade host → engulfed by macrophages → convert to amastigotes (by binary fission) multiply → become trypomastigotes → cell ruptures (4–5 days).

What is the life cycle of the T. cruzi?

(spleen, liver), muscles, skin, gonads, intestine, placenta.

What cells do T. cruzi invade?

• Trypomastigotes:

• Similar to T. brucei complex

• C-shaped (also U or S) in stained smears.

• Pointed posterior.

Amastigotes:

• Found in muscle and tissues.
  

• Round/ovoid, 1.5–4 µm, appear in cyst-like groups.

Chagas (Chagoma)

small painful reddish nodule caused by T. cruzi

T.cruzi

Fever, lymphadenopathy, enter conjunctive of the eye and cause edema of eyelid and conjunctive, Romana’s sign (periorbital swelling).

megacolon

Chronic: Cardiospasm, Cardiomyopathy / CHF, Megaesophagus

blood cultures (xenodiagnosis)

parasite concentration methods (probability of parasitemia)

serologica methods (IFA, IHA)

ELISA - demonstrate antibodies

how is T Cruzi diagnosed

T cruzi

maybe suspected when general and cardiac symptoms are presents from patients coming from endemic regions

Nifurtimox and Benznidazole:

Partially effective in acute phase of T. cruzi

Trypanosoma brucei complex

Only epimastigote and trypomastigote forms.

blood, lymph, csf

where is T. brucei complex found

tsetse fly (glossina spp)

what is the vector of t. brucei

metacyclic trypomastigotes

what is the infective of T brucei?

• Stumpy trypomastigotes → posterior gut → foregut → salivary gland.
  
  

Develop into epimastigotes → metacyclic trypomastigotes (infective). (15-35 complete life cycle)

what is the life cycle of t brucei?

Gambian (West African, T. b. gambiense):

Chancre at bite site

fever headache, tachycardia, dizziness rashes (RHODESIENSE)

Winterbottom's sign (posterior cervical lymph nodes are enlarged, non tender). (GAMBIAN)

blood, lymph node aspirate, CSF

thick and thin blood films

buffy coat concentration method

multiple blood examinations

serologic techniques, IHA ELISA IFA

Diagnosis of Trypanosoma is through

Antigenic variation:

• Trypomastigotes change surface coat → evade host antibodies → recurrent parasitemia.

T. brucei Gambian

• Mental dullness, sleep disturbances, tremors. severe headaches , lacks interest, hyperesthesia (CNS)

Rhodesian (East African, T. b. rhodesiense):

• Acute, more fatal.

• Rapid CNS involvement.

• Death within weeks/months.

• Early stage: Pentamidine, Suramin (don’t cross blood-brain barrier).
  
  

• CNS stage: Melarsoprol, Tryarsamide.
  
  

DFMO (eflornithine): Effective for Gambian form, not Rhodesian.

Treatment for T. brucei

b coli

• Has cytostome, cytopyge, micronucleus, and macronucleus (bean-shaped).
  
  

Balantidium coli

• Largest protozoan infecting humans.
  
  

• Ciliated, with trophozoite and cyst stages.
  
  

B. coli

• Tissue invasion, produces ulcers with wide neck and round base.
  
  

• Secretes hyaluronidase → bloody/mucoid diarrhea.
  
  

• Asymptomatic in many; severe cases: 6–15 episodes/day of diarrhea.

• From pigs or contaminated water/food with B. coli cysts.

Transmission of B coli

• Fecal-oral transmission.
  
  

Ingested cysts → excyst in small intestine → trophozoites → colonize large intestine (cecum).

encystation occurs during intestinal transport or evacuation of semi formed stools

Life Cycle of B coli

B coli

Multiply by binary fission.

Encystation in colon or after passage in stool.

metronidazole

tetracycline

rectal biopsy

treatment for b coli

• Quadrinucleated infective cyst stages

infective stage of G. lamblia

• Flagellate that lives in the duodenum, jejunum, and upper ileum

• Has a simple asexual life cycle

where fo g lamblia live?

• Pyriform or tear-drop shaped, pointed posteriorly

• Pair of ovoidal nuclei, one on each side of the midline

• Dorsal side is convex

• Ventral side is concave with a large sucking disc for attachment

• Bilaterally symmetrical, with a distinct medial line called axostyle

• Propelled by 4 pairs of flagella into erratic tumbling motion

Trophozoites of G lamblia

• Characterized by flagella retracted into axonemes, a median body, and deeply stained curved fibrils

• Surrounded by tough hyaline cyst wall secreted from condensed cytoplasm

• young cyst 2 nuclei; mature 4

Cyst of G lamblia

• Demonstration of Giardia lamblia trophozoites and/or cysts in stool specimens

• Direct examination and concentration techniques

• Duodenal aspiration or biopsy if parasite is not found in feces

• Rectal biopsy may also be done to document the presence of the organism

• In patients with protracted diarrhea, giardiasis must be considered

• Entero-test may demonstrate Giardia trophozoites

• ELISA (using Giardia antigen) in stool is a more sensitive method

Diagnosis: of G. Lamblia

incubation: avrge of 9 days; 1 to 4 weeks

cramping & diarrheic stools

excessive flatus (rotten eggs odor)

nausea, anorexia

malabsorption

Pathogenesis of G LAMBLIA

Giardiasis

Gay Bowel SYndrome

• Metronidazole: 250 mg 3x/day for 5–10 days (Pediatric dose: 15 mg/kg in three doses)

  • Cure rate over 90%

  • May produce metallic taste, nausea, and vomiting

• Metronidazole: 750 mg 3x daily for 5 days (contraindicated in early pregnancy)

• Tinidazole: Single dose of 2 g for adults or 50 mg/kg in children

• Furazolidone: 100 mg 4x daily for 7–10 days

• Tetracycline: 500 mg 4x daily for 10 days (for adults and older children)

  • Contraindicated for children <8 years and pregnant women

Treatment for G Lamblia

Trichomonas Vaginalis

• Exists only in the trophozoite stage

• Pyriform shape, measuring 7–20 μm

• Four free anterior flagella arising from a simple stalk

Trichomonas vaginalis

• Fifth flagellum embedded in the undulating membrane

• Undulating membrane extends about half the organism’s length

• Has a median axostyle and a single nucleus

T. vaginalis

• Found in the urogenital tract

• Trophozoites multiply by binary fission

• Transmitted via sexual intercourse

how do T vaginalis reproduce

T. Vaginalis

• Inflammation of vaginal mucosa several days after inoculation

• Degeneration and desquamation of vaginal epithelium

• Leukocytic inflammation follows

Acute stage of T Vaginalis

greenish/yellow liquid vaginal secretions, itchiness, burning sensation

Chronic Stage of T vaginalis

secretion loses purulent appearance

T. vaginalis

• "strawberry cervix" (punctate hemorrhages, 2% cases)

• In males: may be latent and symptomless

  • Can cause recurrent urethritis and prostatitis

• Giemsa

• Papanicolaou

• Romanowsky

• Acridine orange

• Culture methods:

  • Diamond’s modified medium

  • Whittington culture medium

• Staining methods: T vaginalis

Metronidazole, sexual intercourse discouraged

Treatment to T vaginalis

Leishmaniasis

• Caused by three large species complexes of Leishmania

• Differ in clinical manifestations, geographic distribution, and sandfly vectors

William Boog Leishman & Charles Donovan (1900–1903)

: Discovered Leishman-Donovan bodies in spleen macrophages

Leonard Rogers (1904) & Charles Nicolle (1908):

Cultured promastigotes, revealing extracellular form

John Sinton (1924)

: Linked incidence of visceral leishmaniasis in eastern India to distribution of silvery sandfly

Knowles (1928)

: Detected Leishmania in sandflies

Swaminath (1942):

Demonstrated sandflies could transmit Leishmania to humans

David Sacks (1984–1985)

: Differentiated promastigotes into complement-resistant metacyclic promastigotes in sandfly midgut

Amastigote of Leishmania

• Ovoid/rounded, 2–3 μm

• Intracellular in monocytes, PMNs, and endothelial cells

• Large nucleus, axoneme from kinetoplast

Promastigotes of Leishmania

• 15–20 μm long, 1.5–3.5 μm wide

• Single free flagellum from kinetoplast at anterior end

• Found in midgut and proboscis of sandfly

• congenitally, via blood transfusion, contaminated bite wounds, and direct contact

• Bite of infected sandfly (Phlebotomus spp)

Transmission of Leishmania

Leishmania

• Promastigotes injected during feeding, transform into amastigotes inside host

1. Cutaneous Leishmaniasis (L. tropica):

Incubation: 2 weeks to several months

• Skin ulcers: elevated, indurated margins, painless, no lymphadenopathy

• Subcutaneous nodules may occur

• Systemic symptoms usually absent

• Amastigotes reside in lymphoid tissue of the skin

• Diffuse cutaneous form: widespread skin thickening, resistant to healing, relapses common

• New World form more severe/chronic than Old World

2. Mucocutaneous Leishmaniasis (L. braziliensis):

• Initially resembles cutaneous leishmaniasis

• May spread after years to oronasal/pharyngeal mucosa

2. Mucocutaneous Leishmaniasis (L. braziliensis):

• Causes disfiguring destruction and swelling ("Tapir nose")

• Chiclero ulcer: pinna erosion in forest workers

 Visceral Leishmaniasis / Kala-azar (L. donovani):

• Incubation: 1–3 months

• Major symptoms: bi-daily fever spikes, splenomegaly, cachexia

• Other signs: skin darkening, hepatomegaly, lymphadenopathy, malaise, weight loss, cough, diarrhea, anemia

•  Pentavalent antimonials

  • Sodium stibogluconate

  • N-methyl-glucamine antimonate

Primary/ first line treatment of leishmania

• Amphotericin B

• Pentamidine (especially for kala-azar)

• Metronidazole

• Nifurtimox

second line treatment of leishmania

• Microscopic demonstration of amastigotes in:

  • Skin biopsies for cutaneous form

  • Bone marrow, spleen, or lymph nodes for visceral form

• Serologic tests: aldehyde test, complement fixation, immunofluorescence, counter-current electrophoresis

DIagnosis for Leishmania