University of SulaimaniUniversity of SulaimaniCollege of ScienceCollege of Science

Department of BiologyDepartment of Biology

University of SulaimaniUniversity of SulaimaniCollege of ScienceCollege of Science

Department of BiologyDepartment of Biology

PracticalPractical ParasitologyParasitology22ndnd stage stage

Lab 9 : ToxoplasmosisLab 9 : Toxoplasmosis

Apicomplexa: Tissue Apicomplexa

Toxoplasma gondii

Toxoplasma gondii

Objectives: STUDENT SHOULD BE ABLE TO:• Desacribe tachyzoid, bradyzoid and oocyst stages of Toxoplasma gondii• Identify T. gondii•List methods of transmission and diagnosis.

Toxoplasma gondii

Toxoplasma (Toxo = arc ; plasma = cell)Toxoplasma gondii was first discovered & isolated by Nicolle & Manceaux, in 1908 in an African rodent, Ctenodactylus gundi.

Toxoplasma gondii

Toxoplasma is an apicomplexan protozoa

Its an Obligate intracellular parasite.

In the fetal life, the parasite infection can lead to

death

Morphology

1. tachyzoites (trophozoites).2. tissue cysts (bradyzoites).3. oocyst.

Oocyst

Tachyzoites

Bradyzoites

Toxoplasma gondii exists in three forms:_

Toxoplasma gondii FORMS1.TACHYZOITES2.BRADYZOITES (TISSUE CYSTS)1.OOCYSTS

1.TachyzoiteThe tachyzoite is often crescent or arc shaped, 2 by 6 μm, with a pointed anterior end and a rounded posterior end.Has prominent, centrally placed nucleus.Rapid replicative form during initial acute infection Multiplies asexually within the host cell by repeated endodyogeny.It can infect phagocytic and non-phagocytic, nucleated cells.

(TEM)

1.Tachyzoite

TEM of an intracellular tachyzoite. Note a parasitophorous vacuole (PV) around the tachyzoite. Parasite organelles visible in this picture include a conoid (c), micronemes (m), dense granules (dg), nucleus (n) and rhoptries (r).

Intracellular in cell culture. Note a group arranged in a rosette (arrow) and vacuole (arrowhead) around a tachyzoite.

1.Tachyzoite

2.Bradyzoite

Encysted slow replicative form, marks the beginning of the chronic phase of infection. Also multiplies asexually by endodyogeny.Bradyzoites infect tissue and transform into tachyzoitess.

Tissue cysts

Tissue cysts of Toxoplasma gondii filled with bradyzoites

Toxoplasmosis: brain cyst at low magnification

Toxoplasmosis: brain cyst at high magnification

3.The Oocyst

The oocyst measure 10 by 12 µm. its noninfectious before sporulation

Sporulation occurs outside the body (1 to 5 days).

Sporulated oocysts has two ellipsoidal sporocysts.

Each Sporocyst contains four sporozoites.

3.The Oocyst

TEM of a sporulated oocyst.

Note thin oocyst wall

(arrow),

2 sporocysts (arrowheads)

and 4 sporozoites (double

arrowheads) in sporocysts.

G.D. CosmopolitanHabitat:- Macrophage and most nucleated cells, toxoplasmosis favored host cells are the muscle and brain cells. Disease Toxoplasmosis

Intermediate Host most mammals and most birds are susceptible to infection.  Definitive Host Cat

Toxoplasma gondii

Toxoplasma gondiiTransmission

Contaminated water or food by oocystsUndercooked meat.Mother to fetus.Organ transplant (rare).Blood transfusion (rare).

Toxoplasma gondii

Tissue phase (intermediate hosts).

infected by ingesting sporulated oocysts.

Intermediate host

Human, cattle, birds, rodents, pigs, and sheep.

1 to 5 days

3-10

Toxoplasma gondii

Cat’s intestinal enterocytes

Bradyzoites infect cells and become tachyozoites.

Tissue cyst

Multiplication

Merozoites

Gametocytes

Zygote

Oocyst

Encapsulation of zygote within a rigid wall: oocyst

Toxoplasma gondii

Diagnosis

1 -Microscopic examination * Tissue biopsy

* CSF 2 -Serological diagnosis

* ELISA * IFAT

* Latex agglutination Test

References•Cox FEG, Wakelin D, Gillespie SH, &

Despommier DD. TOPLEY & WILSON'S MICROBIOLOGY& MICROBIAL I NFECTIONS:

PARASITOLOY. (2005). 10th ed. Flodder Arnold.

•Satoskar AR, Simon GL, Hotez PJ, & Tsuji, M. (2009). Medical Parasitology. LANDES,

Bioscince. Boston.•Gillespie S, & Pearson RD. (2001)

Principles and Practice of Clinical Parasitology. John Wiley & Sons Ltd.

Chichester.

References

•http://www.dpd.cdc.gov/dpdx/

•http://www.cdfound.to.it/

•http://www.stanford.edu/group/parasites/

ParaSites2006/

Next Lab

Enteric Apicomplexa:Enteric Apicomplexa:Cryptosporidium parvumCryptosporidium parvum