T

MER0ZQ1T£S RELEASED REENTER MUCOSAL CELLS

DEVELOP TO MATURE TROPHOZOITES

UNDERGOES SCHIZOGONY THEN MATURE SCHIZONT RUPTURES FREEING MEROZOITES

MERDZOITES REENTER HOST CELLS TO BECOME

GAMETOCYTES (MALE I FEMALE)

GAMETES RUPTURE FROM

HOST CELLS AND UNITE TO FORM ZYGOTE

ZYGOTE BECOMES IMMATURE OOCYST WITH SINGLE SPQRQBLAST

SPQRQBLASTS FiECDME SPORQCYSTS WITHIN OOCYST

AS CYSTIC MEMBRANE FORMS

UNDERGOES SPOROGÛNY AS (TWO SPOROELASTS DEVELOP WITHIN OOCYST

Figure 2-6. Life cycle of Isospora belli.

IMMATURE OOCYST

THIN CYST WALL OVOID

12 x 30 mcm

ONE OR TWO SPOROBLASTS

MATURE OOCYST

TWO SPOROCYSTS: 8 x 12 mcm

EACH SPOROCYST CONTAINS FOUR SPOROZOITES

Figure 2-7. Stages of I. belli.

PARASITES OF BIRDS, REPTILES, AND MAMMALS OTHER THAN MAN

OOCYST

Similar to Isospora belli except for four sporocysts with two sporozoites in each. SPECIMEN OF CHOICE: Fecal specimen, looking for oocyst.

Figure 2-8. Eimeria species. ORGANISM 3--Cryptosporidium species GENERAL CHARACTERISTICS

IMMATURE OOCYST MATURE OOCYST

Figure 2-8. Eimeria species. ORGANISM 3--Cryptosporidium species GENERAL CHARACTERISTICS

COMMON NAME: None.

GEOGRAPHICAL DISTRIBUTION: Cosmopolitan.

PATHOGENESIS: Normally a parasite in the intestines of reptiles, birds, and mammals other than man; increasing number of human cases, causing severe diarrhea mostly in immunosuppressed persons. HABITAT: Intestines. INTERMEDIATE HOST: None. RESERVOIR HOST: Mammals. INFECTIVE FORM: Mature oocyst. MODE OF INFECTION: Ingestion. LABORATORY IDENTIFICATION: SPECIMEN OF CHOICE: Feces.

Figure 2-9. Life cycle of Cryptosporidium species.

MATURE OOCYST

SIZE: 2 to 4 mcm. SHAPE: Spherical. CONTENTS: Four sporozoites. Visible cyst wall.

Figure 2-10. Oocyst of Cryptosporidium.

GENERAL CHARACTERISTICS

COMMON NAME: None.

GEOGRAPHICAL DISTRIBUTION: Worldwide.

PATHOGENESIS: 30 to 90 percent human infection; acquired: asymptomatic, rarely a severe systemic disease; congenital: acute or chronic; implicated as one of the leading causes of birth defects; primarily diagnosed serologically.

HABITAT: Intracellular parasite; infects any nucleated cell of the body; intestinal epithelium (initially) in felines only: predominance in brain and retina.

INTERMEDIATE HOST: Humans and many other mammals; cats and other felines are definitive hosts.

RESERVOIR HOST: Cats and other domestic animals (reservoirs for human infection).

INFECTIVE FORM: Infective oocysts from cat feces; or tissue trophozoites or cysts.

MODE OF INFECTION: Ingestion of oocysts; spread by the blood; placental penetration; ingestion of raw or poorly cooked meat.

LABORATORY IDENTIFICATION:

SPECIMEN OF CHOICE: Blood, tissue biopsy.

Figure 2-11. Life cycle of Toxoplasma gondii.

TACHYZOITES

ACUTE STAGES (GROUPS): Contains 8-16 tachyzoites (Giemsa stain) per infected cell.

SIZE: 3 x 6 mcm; crescent-shaped. RED, Central nucleus.

GROSS nOfiPHOlOGY FKEE ORGAN/SMS

(crescentie ship») (3* stsintd hoe/tf ffolds)

CYST

SIZE: 200 to 1000 mcm.

BRADYZOITES: thousands per cyst; size--6 mcm.

Figure 2-12. Stages of Toxoplasma gondii.

ORGANISM 5--Sarcocystis hominis (Mndermanii)

GENERAL CHARACTERISTICS

(Proposed from comparable species in laboratory animals) COMMON NAME: None.

GEOGRAPHICAL DISTRIBUTION: Cosmopolitan. PATHOGENESIS: Usually a mild disease. HABITAT: Muscle; intestinal tract. INTERMEDIATE HOST: Usually herbivores. RESERVOIR HOST: Carnivores. INFECTIVE FORM: Cystozoites or sporozoites. MODE OF INFECTION: Ingestion. LABORATION IDENTIFICATION: SPECIMEN OF CHOICE: Tissue biopsies.

Figure 2-13. Life cycle of Sarcocystis hominis.

Sarcocystis hominis (Mndermanii) (continued)

ZOITOCYST (SARCOCYST)

SIZE: Usually 1 to 2 mm; may be as big as 1 cm. SHAPE: Elongate; cylindrical; spindle-shape. CONTENTS: Internal septae and compartments full or cystozoites. LIMITING MEMBRANE: With radial striations.

Figure 2-14. Zoitocyst S. hominis.

GENERAL CHARACTERISTICS

COMMON NAME: None.

GEOGRAPHICAL DISTRIBUTION: Cosmopolitan.

PATHOGENESIS: Causes interstitial plasma cell pneumonia usually in infants and immunocompromised persons. HABITAT: Lungs. INTERMEDIATE HOST: None. RESERVOIR HOSTS: Rodents, a variety of animals. INFECTIVE FORM: Mature cyst.

MODE OF INFECTION: Air-borne sputum particles inhaled, transplacental. LABORATORY IDENTIFICATION:

SPECIMEN SOURCE: Pulmonary material; bronchial washings; biopsies. SPECIAL TECHNIQUES: Giemsa's stain; methenamine silver nitrate, Gram-Weigert.

LIFE CYCLE (Not well defined)

trophozoites multiply in hilar areas of lung tissue in rodents, man, other animals attach to cells of the tracheobronchial mucosa and alveolus trophozoites develop into immature

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