Toxoplasma gondii, isospoa, cryptosporidium

ClassificationClassification Phylum: ApicomplexaClass: SporozoeaSubclass: CoccidiaOrder: EucoccidiaSuborder: EimeriinaGenus: ToxoplasmaSpecies: gondii

Toxoplasma gondiiToxoplasma gondii Worldwide Zoonotic parasite; Toxoplasma is an opportunistic

pathogen. Infects animals, cattle, birds, rodents, pigs, and sheep. and humans. Causes the disease Toxoplasmosis. Toxoplasmosis is leading cause of abortion in sheep and

goats. Intracellular parasite. Final host (Felidae family, cat) Intermediate host (mammals ) Toxoplasmosis1. All parasite stages are infectious.2. Risking group: Pregnant women, meat handlers (food

preparation) or anyone who eats the raw meat

Definitive (final) host. Domestic cats, who pick up the organism from eating infected rodents.

Asexual and sexual division is intracellular.Oocysts in feces.

• Intermediate host..• Asexual tissue cycle.• Motile, disease producing phase = tachyzoites.• Non-motile “slow” phase in tissue cyst =

bradyzoites.

Humans (Mammals)

Cats (Mainly domestic and wild cats)

Toxoplasma gondiiToxoplasma gondii exists in three forms exists in three forms All parasite stages are infectiousAll parasite stages are infectious..

1. Tachyzoites 2. Tissue cysts (bradyzoit)

3- Oocysts

Tachyzoite stageTachyzoite stage Rapidly growing stage observed in the early stage of

infection.(Acute phase) habits in the body fluid.

Crescent-shaped. One end is more pointed than the other subterminal placed nucleus.

Asexual form. Multiplies by endodyogeny. It can infect phagocytic and non-phagocytic, cells.

BradyzoitesBradyzoitesAre slow-growing stage inside the tissue cysts.Bradyzoites mark the chronic phase of infection.Bradyzoites are resistant to low pH and digestive

enzymes during stomach passage.Protective cyst wall is finally dissolved and

bradyzoites infect tissue and transform into tachyzoites.

Bradyzoites are released in the intestine and are highly infective if ingested.

Oocysts in the feces of catOocysts in the feces of catCat ingests tissue cysts containing bradyzoites. Gametocytes develop in the small intestine. Sexual cycle produces the oocyst which is excreted in

the feces.Oocysts appear in the cat’s feces 3-5 days after

infection by cysts.Oocysts require oxygen and they sporulate in 1- 5

days.

The Oocyst• The oocyst is noninfectious before sporulation.• Unsporulated oocysts are subspherical to spherical. • Sporulated oocysts are subspherical to ellipsoidal.• Each oocyst has two ellipsoidal sporocysts. • Each Sporocyst contains four sporozoites .• Shedding occurs 3-5 days after ingestion of tissue cysts • Sporulated oocyst remain infective for months .

Life cycle of T. gondii

Sources of infection :Contaminated water or food by oocystsIngestion of tachyzoites and bradyzoites (cysts) in flesh of infected host.Undercooked meat.Mother to fetus. Organ transplant (rare).Blood transfusion (rare).

Toxoplasma Transmission

Disease: ToxoplasmosisDisease: ToxoplasmosisA- Acquired toxoplasmosis(Mild

lymphatic inflammation).B- Congenital toxoplasmosis:1-Intracerebral calcification.

Congenital ToxoplasmosisCongenital Toxoplasmosis2- Chorioretinitis . 3-Hydrocephaly.

4- Microcephaly . 5- Convulsions.6- Mental retardation .7- Cardiomegaly .

Prophylaxis

1- Individuals at risk, particularly pregnant women,children, and immunocompromised persons should avoid contact with cat and its feces.2- Proper cooking of meal.3- Proper washing of hands and washing of vegetablesand fruits before eating.4-Blood or blood products from seropositive persons5- should not be given and screening for T. gondii antibody6- should be done in all blood banks.

controlIt is difficult to control toxoplasmosis because of wide range of animal reservoirs. Currently, there is no effective vaccnine available for humans. A genetically engineered vaccine is under development for use in cats.

Treatment Congenital infection is treated with pyrimethamine and sulfadiazine. For primary prophylaxis Trimethoprimsulfamethoxazole is the drug of choice

ClassificationClassification Phylum: ApicomplexaClass: SporozoeaSubclass: CoccidiaOrder: EucoccidiaSuborder: EimeriinaGenus:IsosporaSpecies: belli

MorphologyOocysts of I. belli are elongatedovoid and measure 25 μm × 15 μm.Each oocyst is surrounded by a thin smooth 2 layered cyst wallImmature oocyst seen in the feces of patients contain two sporoblasts.The oocysts mature outside the body.

On maturation, the sporoblast convert into sporocysts.Each sporocyst contain 4 crescentshapedsporozoitesThe sporulated oocyst containing 8 sporozoites is the infective stage of the parasite.

A B

Oocysts of Isospora belli. A. Immature cyst; B. Mature cyst

Life CycleI. belli completes its life cycle in one host.Man gets infection by ingestion of food and watercontaminated with sporulated oocyst.When a sporulated oocyst is swallowed, 8 sporozoitesare released from the 2 sporocysts in the small intestineand invade the intestinal epithelial cells.In the epithelium, the sporozoites transform intotrophozoites, which multiply asexually (schizogony)to produce a number of (merozoites). The merozoitesinvade adjacent epilhelial cells to repeat asexual cycle.

Some of the trophozoites undergo sexual cycle (gametogony) in the cytoplasm of enterocytes and transforminto macrogametocytes and microgametocytes.

After fertilization, a zygote is formed, which secretes acyst wall and develops into an immature oocyst.

These immature oocysts are excreted with feces andmature in the soil.

Incubation period: 1–4 days.

Life Cycle of Isospora belli

Clinical FeaturesInfection is usually asymptomatic.Clinical illness includes abdominal discomfort, mild fever, diarrohea, and malabsorption.The diarrohea is usually watery and does not contain blood or pus and is selflimiting.However, protracted diarrohea, lasting for several years can be seen in immunocompromised persons, particularly in the human immunodefi ciency virus (HIV) infected.

Indirect evidenceHigh fecal fat content.Presence of fatty acid crystals in stool.Presence of CharcotLeyden crystals in stool.Direct evidenceIt may be diffi cult to demonstrate the transparent oocyst in saline preparation of stool.Stool concentration techniques may be required whendirect wet mount of stools are negative.The staining technique used are Modified ZiehlNeelsen stain or Kinyoun acid fast staining of stool smear. In these methods, pink colored acid fast large oocyst (>25 μm) can be demonstrated. The stool smear can also be stained by auramine rhodamine and Giemsa stains.

Laboratory Diagnosis1-Stool Examination

2- Duodenal AspiratesAfter repeatedly negative stood examinations, duodenalaspirate examination or enterotest can be performed todemonstrate oocyst.3- Intestinal BiopsyUpper gastrointestinal endoscopy may provide biopsy specimens for demonstration of oocysts.4-OthersEosinophilia, which is generally not seen with other entericprotozoan infections, is detectable in case of isosporoloasis

TreatmentNo treatment is indicated in self limiting infection in immunocompetent persons.Immunodefecient patients with diarrhea and excreting oocysts in the feces should be treated with cotrimoxazole (trimethoprimsulfamethoxazole)in a dose of 2 tablet, 4 times a day for 10 days followed by 2 tablets 2 times a day for 3 weeks.For patients intolerant to sulfonamides, pyrimethamine50–75 mg/day is given.Relapses can occur in persons with AIDS and necessitate maitainance therapy with cotrimoxazole 1 tablet thrice a week.

Classification•Phylum: Apicomplexa•Class: Sporozoea•Subclass: Coccidia•Order: Eucoccidia•Suborder: Eimeriina•Genus:Isospora•Species: belli

MorphologyThe infective form of the parasite is oocyst.The oocyst is spherical or oval and measures about 5 μmin diameter. Oocysts does not stain with iodine and is acid fast.The wall of the oocysts is thick, but in 20% cases, wallmay be thin. These thin walled oocysts are responsiblefor autoinfection. Both thin walled and thick walled oocyst contain 4crescent shaped. Oocyst can remain viable in the environment forlong periods, as it is very hard and resistant to mostdisinfectants and temperature upto 60°C. It can survive chlrorinated water, but sequentialapplication of ozone and chlorine has been foundeffective in eliminating the cysts.

The parasite complete its life cycle, sexual and asexualphases in a single host (monoxenous)Suitable host: Man.Reservoirs: Man, cattle, cat, and dog.Mode of transmission:Man acquires infection by:€ Ingestion of food and water contaminated withfeces containing oocysts€Autoinfection.Infective form: Sporulated oocysts.The oocyst contains 4 sporozoites, which are released inthe intestine.

Life Cycle

Pathogenicity and Clinical FeaturesClinical manifestations of c. parvum infection varydepending upon the immune status of the host.� Infection in healthy immunocompetent personsmay be asymptomatic or cause a selflimiting febrileillness, with watery diarrhea in conjunction withabodminal pain, nausea, and weight loss. It can alsocause childhood and traveller’s diarrhea, as well aswaterborne outbreaks.

In immunocompromised hosts, especially those withAIDS and CD4+ T cell counts below 100/uL, diarrheacan be chronic, persistent, and remarkably profuse,causing significant fl uid and electrolyte depletion,weight loss, emaciation, and abdominal pain. Stoolvolume may range from 1 to 25 L/day. Billary tractinvolvement can manifest as right upper quadrantpain, sclerosing cholangitis, or cholecystitis.

Laboratory DiagnosisStool ExaminationDiagnosis is made by demonstration of the oocysts in feces.A direct wet mount reveals colorless, spherical oocyst of 4–5 μm, containing large and small granule. The oocysts are diffi cult to visualize in unstained wet preparations. Modifi ed acid fast staining is the method ofchoice and by this method oocysts appear as red acidfastspheres, gainst a blue background . Yeast closely resembles oocysts of c. parvum in shape and sizebut can be differentiated by using acidfast stain, as theyare not acidfast and appear blue in color. The stainingcan also be used for demonstration of oocysts in otherspecimens like sputum, bronchial washing, etc.

If oocysts load is less and cannot be demonstrated even after examination of 3 wet mounts of stoolspecimen, concentration techniques like Sheather'ssugar floatation technique and zinc sulfate floatationtechnique can be applied.Fluroscent staining with auraminephenol or acridine orange has also been reported to be a useful technique.Definitive identification can be made by indirectimmunofl uroscence microscopy using specific antibody.

Histopathological Examination:Cryptosporidia can also be identified by light and electronmicroscopy at the apical surface of intestinal epitheliumfrom biopsy specimen of the small bowel (jejunum beingthe preferred site).Serodiagnosis:Antibody persists for at least an year and can bedemonstrated by ELISA or immunofl uroscence.An ELISA for detection of cryptosporidium antigensin stools using monoclonal antibody has also beendeveloped and is highly sensitive and specifi c.Molecular DiagnosisFor seroepidemiological study, western blot techniqueis employed by using a 17KDA and 27KDA sporozoiteantigen.PCR technique has also been applied to detect viablecysts

Supportive therapy with electrolytes and fluids and early antiretroviral therapy in AIDS patients.